TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance

*Marzena Małgorzata Kurowska*

#### **Abstract**

Tonoplast Intrinsic Proteins (TIP) are one of five subfamilies of aquaporins in higher plants. Plants typically contain a large number of TIP genes, ranging from 6 to 35 compared to humans. The molecular weight of the TIP subfamily members ranges from 25 to 28 kDa. Despite their sequence diversity, all TIP monomers have the same structure, which consists of six transmembrane helices and five interhelical loops that form an hourglass shape with a central pore. Four monomers form tetramers, which are functional units in the membrane. TIPs form channels in the tonoplast that basically function as regulators of the intracellular water flow, which implies that they have a role in regulating cell turgor. TIPs are responsible for precisely regulating the movement of not only water, but also some small neutral molecules such as glycerol, urea, ammonia, hydrogen peroxide and formamide. The expression of TIPs may be affected by different environmental stresses, including drought, salinity and cold. TIPs expression is also altered by phytohormones and the appropriate *cis*-regulatory motifs are identified in the promotor region of the genes encoding TIPs in different plant species. It was shown that manipulating TIP-encoding genes expression in plants could have the potential to improve abiotic stress tolerance.

**Keywords:** aquaporins, tonoplast intrinsic proteins, abiotic stress, drought, salinity, cold, phytohormones, gene expression analysis, *cis*-regulatory motifs, plants

#### **1. Introduction**

Aquaporins (aqua-pore, AQP), which are members of the major intrinsic proteins (MIPs) superfamily, facilitate the bidirectional flux of water and non-aqua substrates across the cell membranes [1–4]. These transmembrane proteins form pores in the lipid bilayers of archaea, bacteria, fungi, plants, non-mammalian metazoans and mammals including humans. In plants, the first AQP Noduline-26 (GmNOD26) was identified in soybean (*Glycina max* L.) [5], whereas their ability to conduct water in plants was demonstrated for the first time for an Arabidopsis tonoplast intrinsic protein homologue (AtTIP1; 1, gamma-TIP) *via* its heterologous expression in *Xenopus* oocytes [6]. In higher plants, MIPs are divided into five evolutionarily distinct subfamilies in terms of the similarities of their amino acid sequence and intercellular localisation: plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), nodulin-26 like intrinsic proteins (NIPs), small basic intrinsic proteins (SIPs) and X intrinsic proteins / uncharacterised-intrinsic proteins (XIPs) [7]. In turn, the TIP subfamily can be further divided into different

subgroups. In Arabidopsis (*Arabidopsis thaliana*), the TIP subfamily has been divided into five subgroups from TIP1 to TIP5. Each subgroup is then again divided into different isoforms. In Arabidopsis, the TIP subfamily consists of 11 isoforms. Some of these have synonymous name such as TIP1;1 (gamma-TIP, γ-TIP, RB7), TIP1;2 (gamma-TIP2, γ-TIP2), TIP2;1 (delta-TIP, δ-TIP), TIP3;1 (alpha-TIP, α-TIP) and TIP3;2 (beta-TIP, β-TIP) [8].

Water, whose transport is facilitated by aquaporins and, among them TIPs, is their most important substrate. TIPs are responsible for precisely regulating the movement of not only water, but also some small neutral molecules that have great physiological significance such as glycerol, urea, ammonia, hydrogen peroxide (H2O2) and formamide [7]. The transport of these substrates was predicted using a bioinformatic analysis and some of them have also been proven experimentally by using their *in vitro* expression in yeast or in a *Xenopus* oocyte system in which the expression of gene of interest led to, for example, an increase water permeability (**Table 1**).


#### **Table 1.**

*The transport of different substrates by TIPs, which was demonstrated via their in vitro expression in yeast or oocytes.*

**425**

**Figure 1.**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

The central vacuole occupies most of the intracellular space of most mature plant cells [25]. The plant vacuole plays important roles not only in space filling, but also in osmotic adjustment, storage and digestion [26, 27]. TIPs form channels in the vacuolar membrane (tonoplast) that basically function as regulators of the intracellular water flow, which implies that they have a role in regulating cell turgor. It has been proposed that the presence of a specific TIP isoform may define the function of the vacuole and that specific TIP proteins could be used as markers for the different types of vacuoles that occur in different tissue types or in response to developmental and environmental stimuli [28, 29]. Vacuoles whose tonoplast contains TIP2;1 (delta-TIP, δ-TIP) are used by plant cells to store pigments and vegetative storage proteins (VSPs) [28]. Moreover, in vegetative tissues, the lytic or degradative vacuoles (LVs) are marked by the presence of TIP1;2 (gamma-TIP, γ-TIP) [26, 28, 30]. TIP1;2 may be expressed primarily at the time when the large central vacuoles are being formed during cell enlargement [30], while the protein storage vacuoles (PSVs) in mature seeds are marked by the presence of TIP3;1

TIP proteins are most abundant in the tonoplast, but some isoforms have also been detected in the chloroplast, e.g. on the luminal site of the thylakoid, the chloroplast membranes or the envelope fraction using mass-spectrometrybased proteomics. Such a location was detected for TIP1;1, TIP1;2 and TIP2;1 in

Although it has been suggested that AQPs and, among them, TIPs are multifunctional proteins, their structure is unique across all kingdoms of life. Despite their sequence diversity, all TIPs have a similar structure that consists of six transmembrane helices (TM1 to TM6) with five connecting inter-helical loops (LA to LE) and two half helices that contain one highly conserved Asn-Pro-Ala (NPA) motif each of which forms its functional pore (**Figure 1**). The hydrophobic NPA motif is located at the first intracellular (loop B) and the third extracellular loop (loop E) and the overlap in the middle of the lipid bilayer ('hourglass' model) and forms two hemipores that generate a narrow part of the channel [7, 36]. A second filter region is the aromatic/Arginine (ar/R) selectivity filter, which includes four amino acids (aa), which are located at the non-cytosolic end of the pore [37]. These two constriction regions are very important for the transport selectivity of the channel, which have been predicted based on structural knowledge combined with

*The structure of aquaporin as represented by the crystal structure of spinach SoPIP2;1 (PDB 1Z98). The view from different sides of the holoprotein, which consists of four monomers. (a) the side view, (b) the tetrameric* 

*assembly from the cytoplasmic side. Each monomer functions as a single channel pore.*

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

(alpha-TIP, α-TIP) [26, 31, 32].

**2. Structure and diversity of TIPs**

Arabidopsis [33–35].

*Abiotic Stress in Plants*

(**Table 1**).

Arabidopsis (*Arabidopsis thaliana*)

Barley (*Hordeum vulgare* L*.*)

Bread wheat (*Triticum aestivum* L*.*)

Maize (*Zea mays* L.)

Rice (*Oryza sativa* L.)

Radish (*Raphanus sativus*)

Sunflower (*Helianthus annuus* L.)

Tobacco (*Nicotiana tabacum* L.)

and TIP3;2 (beta-TIP, β-TIP) [8].

AtTIP1;1 AtTIP1;2 AtTIP2;1 AtTIP2;3 AtTIP4;1 AtTIP5;1

HvTIP1;1 HvTIP1;2 HvTIP2;3

TaTIP2;1 TaTIP2;2

ZmTIP1;1 ZmTIP1;2 ZmTIP2;3 ZmTIP4;4

OsTIP1;2 OsTIP2;2 OsTIP3;2 OsTIP4;1 OsTIP5;1

RsTIP1;1 RsTIP2;1

TIP7 TIP20

subgroups. In Arabidopsis (*Arabidopsis thaliana*), the TIP subfamily has been divided into five subgroups from TIP1 to TIP5. Each subgroup is then again divided into different isoforms. In Arabidopsis, the TIP subfamily consists of 11 isoforms. Some of these have synonymous name such as TIP1;1 (gamma-TIP, γ-TIP, RB7), TIP1;2 (gamma-TIP2, γ-TIP2), TIP2;1 (delta-TIP, δ-TIP), TIP3;1 (alpha-TIP, α-TIP)

Water, whose transport is facilitated by aquaporins and, among them TIPs, is their most important substrate. TIPs are responsible for precisely regulating the movement of not only water, but also some small neutral molecules that have great physiological significance such as glycerol, urea, ammonia, hydrogen peroxide (H2O2) and formamide [7]. The transport of these substrates was predicted using a bioinformatic analysis and some of them have also been proven experimentally by using their *in vitro* expression in yeast or in a *Xenopus* oocyte system in which the expression of gene of interest led to, for example, an increase water permeability

**Species TIP name Substrate References**

+ + + +

+ + +

NtTIPa + + + [24]

**Urea Ammonia (NH3)**

> + +

> + +

> + +


+ + +

**Glycerol (GLY)**

[6, 9–13]

[14]

[15–17]

[18–20]

[21]

[22]

[23]

**Hydrogen peroxide (H2O2)**

+ +

+ +

**Water (H2O)**

+ + +

+ + +

+ + +

+ + + +

+ +

+ +

*+ transport of the substrate has been confirmed,* − *transport of the substrate has been excluded.*

*The transport of different substrates by TIPs, which was demonstrated via their in vitro expression in yeast or* 

**424**

**Table 1.**

*oocytes.*

The central vacuole occupies most of the intracellular space of most mature plant cells [25]. The plant vacuole plays important roles not only in space filling, but also in osmotic adjustment, storage and digestion [26, 27]. TIPs form channels in the vacuolar membrane (tonoplast) that basically function as regulators of the intracellular water flow, which implies that they have a role in regulating cell turgor. It has been proposed that the presence of a specific TIP isoform may define the function of the vacuole and that specific TIP proteins could be used as markers for the different types of vacuoles that occur in different tissue types or in response to developmental and environmental stimuli [28, 29]. Vacuoles whose tonoplast contains TIP2;1 (delta-TIP, δ-TIP) are used by plant cells to store pigments and vegetative storage proteins (VSPs) [28]. Moreover, in vegetative tissues, the lytic or degradative vacuoles (LVs) are marked by the presence of TIP1;2 (gamma-TIP, γ-TIP) [26, 28, 30]. TIP1;2 may be expressed primarily at the time when the large central vacuoles are being formed during cell enlargement [30], while the protein storage vacuoles (PSVs) in mature seeds are marked by the presence of TIP3;1 (alpha-TIP, α-TIP) [26, 31, 32].

TIP proteins are most abundant in the tonoplast, but some isoforms have also been detected in the chloroplast, e.g. on the luminal site of the thylakoid, the chloroplast membranes or the envelope fraction using mass-spectrometrybased proteomics. Such a location was detected for TIP1;1, TIP1;2 and TIP2;1 in Arabidopsis [33–35].

#### **2. Structure and diversity of TIPs**

Although it has been suggested that AQPs and, among them, TIPs are multifunctional proteins, their structure is unique across all kingdoms of life. Despite their sequence diversity, all TIPs have a similar structure that consists of six transmembrane helices (TM1 to TM6) with five connecting inter-helical loops (LA to LE) and two half helices that contain one highly conserved Asn-Pro-Ala (NPA) motif each of which forms its functional pore (**Figure 1**). The hydrophobic NPA motif is located at the first intracellular (loop B) and the third extracellular loop (loop E) and the overlap in the middle of the lipid bilayer ('hourglass' model) and forms two hemipores that generate a narrow part of the channel [7, 36]. A second filter region is the aromatic/Arginine (ar/R) selectivity filter, which includes four amino acids (aa), which are located at the non-cytosolic end of the pore [37]. These two constriction regions are very important for the transport selectivity of the channel, which have been predicted based on structural knowledge combined with

#### **Figure 1.**

*The structure of aquaporin as represented by the crystal structure of spinach SoPIP2;1 (PDB 1Z98). The view from different sides of the holoprotein, which consists of four monomers. (a) the side view, (b) the tetrameric assembly from the cytoplasmic side. Each monomer functions as a single channel pore.*


*\*Based on the Ensemble Plants Database.*

*The number of Tonoplast Intrinsic Proteins (TIP) has been marked in bold.*

#### **Table 2.**

*The number of AQP isoforms in the selected plant species.*

simulation studies [38, 39]. Both filters at the pore "mouth" constitute barriers to the passage of inorganic cations (such as Na+ and K+ ) and protons [39]. The NPA motif not only plays a role in regulating membrane transport but also in protein localisation [40]. The substrate selectivity of AQPs is controlled by the amino acid residues of the NPA and ar/R filters as well as another conserved region, which is known as the Froger's residues, which consist of five conserved residues [41]. This region enables the aquaglyceroporins that transport glycerol from the AQPs that facilitate the transport of water to be distinguished [39].

All MIP sequences take on a typical hour-glass MIP helical fold with six transmembrane helices and two half-helices [42]. This fold has been maintained during evolution via its conservation around 40 positions within the transmembrane region [42]. The stability of the functionally important half-helix is modulated by a stabilising intra-helical salt-bridge interaction and/or two helix destabilising residues, glycine and proline, which was demonstrated by an analysis of the loop E region of 1468 MIP sequences and their structural models from six different groups of organisms [43]. In the cell membrane, MIPs are grouped as homotetramers that are located in the lipid bilayer (**Figure 1**). Each monomer functions independently as a single channel pore [44]. In plants, the only the crystal structure of the MIPs for two species is currently available in the Protein Data Bank (PDB: http://www.pdb.org), the spinach (*Spinacia oleracea*) aquaporin SoPIP2;1 was in its closed confirmation at a 2.1 Å resolution and its open confirmation at a 3.9 Å resolution [45] and the Arabidopsis aquaporins

**427**

Arabidopsis (*Arabidopsis thaliana*)

Barley (*Hordeum vulgare* L.)

Bread wheat (*Triticum aestivum*

Eucalyptus (*Eucalyptus grandis*

L*.*)

L*.*)

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

TIP subfamily members ranges from 25 to 28 kDa [47].

expression was connected with cell elongation [22] (**Table 3**).

*HvTIP1;1, HvTIP2;3, HvTIP1;2, HvTIP3;1*

*HvTIP1;1, HvTIP2;3,* 

*EgTIP1;1, EgTIP1;4, EgTIP2;1, EgTIP2;2*

*EgTIP1;1, EgTIP1;2,* 

*EgTIP4;1*

*EgTIP1;4* Root

*EgTIP1;3* Cambium *EgTIP1;2, EgTIP3;2* Leaf *EgTIP3;1, EgTIP3;2* Fruit

*HvTIP1;2*

AtPIP2;4 at a 3.7 Å resolution [46] all of which were determined using X-ray diffraction, which showed their structural identity. However, the functions and regulation of the majority of the MIP channels have not yet been fully characterised [42].

A large number of *MIP* genes and, among them *TIP* genes, have been identified in the genomes of different plant species. In plants, the MIP family contains around 2008 members while the TIP subfamily contains 585 members from different plant species, which have been deposited in the MIPDB [47, 48]. The length of the TIP sequences ranges from 55 to 780 aa. Plants typically contain a large number of *AQPs* genes and among them the *TIP* genes, when are compared with for example humans, ranges from 6 to 35 in moso bamboo (*Phyllostachys edulis*) and oilseed rape (*Brassica napus* L.), respectively [49, 50] (**Table 2**). The molecular weights of the

**3. Study of the tissue- and developmental-dependent expression of TIPs**

Aquaporins are postulated to be the main water transporter protein in plants. However their presence and expression may vary among plant species, tissues and time during development. In plants, AQPs are present in almost all organs, including the roots, leaves, stems, flowers, fruits, seeds, dry seeds [60], pollen [13, 61–63], anther and specific cells such as the guard cells [64, 65]. Moreover, some *TIPs* are expressed in specific tissues, e.g. *AtTIP5;1* was localised in the pollen mitochondria, which are probably involved in the remobilisation of N via the transport of mitochondrial urea to the cytoplasm [61] as well as in a time-specific manner, e.g. the *RsTip1;1* (*gamma-VM23*) gene expression was high not only in the hypocotyls but also in the developing tap roots and young growing leaves and the pattern of its

**Species TIP name Organ/tissue/process References**

*AtTIP2;1* Developing vascular tissue, primary shoot

Root

Flower

Stem

*TaTIP1;12* Root-specific [52]

*EgTIP1;1, EgTIP2;1* Flower bud [68]

*AtTIP3;2* Senescence *AtTIP3;1* Seed-specific *AtTIP1;1* Entire vegetative body

*TaTIP2;22* Root-specific

*AtTIP1;3, AtTIP5;1* Pollen mitochondria [61, 66, 67]

Leaf [14]

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

*Abiotic Stress in Plants*

Arabidopsis (*Arabidopsis* 

Barley (*Hordeum vulgare*

Bread wheat (*Triticum aestivum* L.)

Cucumber (*Cucumis* 

Foxtail millet (*Setaria* 

Potato (*Solanum tuberosum* L.)

Rice Japonica (*Oryza* 

Sorghum (*Sorghum* 

(*Solanum lycopersicum*

*\*Based on the Ensemble Plants Database.*

*sativus* L.)

*italica* L.)

*sativa* L.)

*bicolor*)

Tomato

L.)

**Table 2.**

Maize (*Zea mays* L.)

*thaliana*)

L*.*)

**Species Genome size/**

**ploidy x/no. of chromosomes\***

> ~135 Mbp 2n = 2x = 10

> ~5.3 Gbp; 2n = 2x = 14

~17 Gb 2n = 6x = 42, AABBDD, hexaploid

~350 Mbp 2n = 2x = 14

~490 Mb 2n = 2x = 18

2.4 Gb 2n = 2x = 20

~840 Mb 2n = 4x = 48

500 Mb 2n = 2x = 24

~730 Mb 2n = 2x = 20

~828 Mb 2n = 2x = 24

*The number of Tonoplast Intrinsic Proteins (TIP) has been marked in bold.*

113 (65-A, 42-B, 36-D)

simulation studies [38, 39]. Both filters at the pore "mouth" constitute barriers to

motif not only plays a role in regulating membrane transport but also in protein localisation [40]. The substrate selectivity of AQPs is controlled by the amino acid residues of the NPA and ar/R filters as well as another conserved region, which is known as the Froger's residues, which consist of five conserved residues [41]. This region enables the aquaglyceroporins that transport glycerol from the AQPs that

All MIP sequences take on a typical hour-glass MIP helical fold with six transmembrane helices and two half-helices [42]. This fold has been maintained during evolution via its conservation around 40 positions within the transmembrane region [42]. The stability of the functionally important half-helix is modulated by a stabilising intra-helical salt-bridge interaction and/or two helix destabilising residues, glycine and proline, which was demonstrated by an analysis of the loop E region of 1468 MIP sequences and their structural models from six different groups of organisms [43]. In the cell membrane, MIPs are grouped as homotetramers that are located in the lipid bilayer (**Figure 1**). Each monomer functions independently as a single channel pore [44]. In plants, the only the crystal structure of the MIPs for two species is currently available in the Protein Data Bank (PDB: http://www.pdb.org), the spinach (*Spinacia oleracea*) aquaporin SoPIP2;1 was in its closed confirmation at a 2.1 Å resolution and its open confirmation at a 3.9 Å resolution [45] and the Arabidopsis aquaporins

and K+

) and protons [39]. The NPA

**AQP PIP TIP NIP SIP XIP References**

38 13 **11** 11 3 0 [8]

39 18 **11** 8 2 0 [51]

39 19 **8** 9 2 1 [53]

39 12 **11** 13 3 0 [54]

41 12 **18** 8 3 0 [55]

41 15 **11** 10 3 8 [56]

33 11 **10** 10 2 0 [57]

37 13 **11** 11 2 0 [58]

47 14 11 12 4 6 [59]

51 **29** 29 4 0 [52]

the passage of inorganic cations (such as Na+

*The number of AQP isoforms in the selected plant species.*

facilitate the transport of water to be distinguished [39].

**426**

AtPIP2;4 at a 3.7 Å resolution [46] all of which were determined using X-ray diffraction, which showed their structural identity. However, the functions and regulation of the majority of the MIP channels have not yet been fully characterised [42].

A large number of *MIP* genes and, among them *TIP* genes, have been identified in the genomes of different plant species. In plants, the MIP family contains around 2008 members while the TIP subfamily contains 585 members from different plant species, which have been deposited in the MIPDB [47, 48]. The length of the TIP sequences ranges from 55 to 780 aa. Plants typically contain a large number of *AQPs* genes and among them the *TIP* genes, when are compared with for example humans, ranges from 6 to 35 in moso bamboo (*Phyllostachys edulis*) and oilseed rape (*Brassica napus* L.), respectively [49, 50] (**Table 2**). The molecular weights of the TIP subfamily members ranges from 25 to 28 kDa [47].

#### **3. Study of the tissue- and developmental-dependent expression of TIPs**

Aquaporins are postulated to be the main water transporter protein in plants. However their presence and expression may vary among plant species, tissues and time during development. In plants, AQPs are present in almost all organs, including the roots, leaves, stems, flowers, fruits, seeds, dry seeds [60], pollen [13, 61–63], anther and specific cells such as the guard cells [64, 65]. Moreover, some *TIPs* are expressed in specific tissues, e.g. *AtTIP5;1* was localised in the pollen mitochondria, which are probably involved in the remobilisation of N via the transport of mitochondrial urea to the cytoplasm [61] as well as in a time-specific manner, e.g. the *RsTip1;1* (*gamma-VM23*) gene expression was high not only in the hypocotyls but also in the developing tap roots and young growing leaves and the pattern of its expression was connected with cell elongation [22] (**Table 3**).



#### **Table 3.**

*The expression of the selected TIP genes in different plant tissues.*

#### **4. Study of the expression of** *TIPs* **under abiotic stress or phytohormone treatment, and their role in maintaining cell homeostasis under stress conditions**

The gene expression is the process in which gene information is converted into a protein [7]. Analysing the gene expression profiles is a prerequisite for determining the physiological function of a gene [71]. The function of AQPs can generally be modified in two ways: by regulating the gene expression, which leads to changes in protein abundance or by changing its permeability – gating. However, it should be kept in mind that changes in the mRNA expression level often reflect the protein abundance, but that this is not necessarily strictly connected in any cell or tissue [37]. In term, AQP trafficking and activity could be affected by the post-translational modifications (PTMs), like deamination, phosphorylation, methylation, ubiquitination and acetylation [37]. Water homeostasis is fundamental for cell survival [72]. AQP facilitate the transport of water and play roles in response to abiotic stress conditions during which the cell homeostasis is disturbed. Different studies have suggested that a low abundance of the AQP proteins reduces the water permeability of membranes and that a high abundance of them increases it. Although it can be assumed that all AQPs are able to transport water, an experimental study was performed for only a few members of the TIP subfamily in different plant species (**Table 1**). The expression of TIPs may be affected by different environmental conditions, including drought, salinity and cold and this has been investigated in many plant species. Comparative transcriptome studies using RNA sequencing (RNA-seq), which is a next generation sequencing technology, could lead to the discovery of a differential expression of multiple aquaporin homologues in different tissues and/or in different conditions of growth, e.g. under abiotic stress. The transcriptome defines as a set of coding and non-coding RNA molecules that are present in a single cell or a population of cells [73]. Nowadays, RNA-seq technology is used more and more frequently [74, 75]. On the other hand, the reverse-transcription quantitative PCR (RT-qPCR) technique still serves as the method of choice to perform the expression analysis of specific genes in many researches.

Abiotic stresses, which have a significant impact on the plants, are involved in changes at the transcriptome, cellular and physiological levels. When the stress is

**429**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

prolonged, plant growth and productivity are severely diminished [76, 77]. The response of plants is very complicated and many mechanisms are initiated simultaneously to restore cellular homeostasis and promote survival [78]. Aquaporins are thought to be responsive to the stress signalling pathways and are also thought to be involved in the stress-coping mechanisms such as altering the tissue hydraulic conductivity [79, 80]. Drought and salinity are two major factors that significantly limit plant growth and productivity [81, 82]. The huge yield losses caused by drought stress ranging 45–92 (%) have been reported in major field crops like maize (*Zea mays* L.), wheat (*Triticum aestivum* L.), rice (*Oryza sativa* L.), chickpea (*Cicer arietinum* L.), soybean (*Glycine max* L.), sunflower (*Helianthus annuus* L.) [83]. Cold is also often associated with climate change [84]. Drought, salinity and freezing stresses cause a changing water status in plant cells and all of these result in cellular dehydration [85]. In order to improve the tolerance of crop plants to unfavourable environmental conditions, a detailed understanding of their stress

Aquaporins are responsible for precisely regulating the movement of water and therefore may play a crucial role in the drought-stress response as well as in drought-stress tolerance [78]. A transcriptome analysis of the leaf and root tissues in plant species revealed significant changes in the expression of the *TIP* genes in response to drought stress. Under drought stress, when water is limited, the downregulation of the *TIP* genes can lead to a decrease in the water permeability of the tonoplast in order to avoid water loss and to minimise the water flow through the cell membranes in order to prevent the further loss of leaf turgor. This expression pattern has been shown in many studies. In *Nicotiana glauca*, the *NgMIP2* and *NgMIP3* genes, which are homologous to *TIP*, were down-regulated in leaves under drought stress when the leaves were wilting, usually three to four days after water was withheld [86] and in Arabidopsis, the levels of *AtTIP1;1, AtTIP1;2, AtTIP2;1* and *AtTIP2;2* were more than four-fold down-regulated after 12 days of drought [87]. In contrast to these results, the expression level of *AtTIP1;1* and *AtTIP2;1* under drought treatment was up-regulated, but the time that the stress was applied was only 24 hours [88]. Moreover, in barley (*Hordeum vulgare* L.), the expression of five *HvTIP* aquaporins in leaves: *HvTIP1;1, HvTIP1;2, HvTIP2;1, HvTIP2;2* and *HvTIP2;3* was down-regulated after ten days of severe drought treatment [89]. In turn, in *Festuca* species, the transcript level of the *TIP1;1* aquaporin decreased in leaves after 11 days of a water deficit [90]. The possible functional role of coffee (*Coffea arabica* L.) TIPs in in regulating the water balance has been explored by measuring the *TIP* gene expression in leaf and root tissues that had been subjected to drought [91]. In root tissue, the expression of three *CsTIP* genes (*CaTIP1;1, CsTIP2;1, CsTIP4;1*) decreased as the severity of the drought stress increased. In the leaf, a similar expression profile of their expression was obtained only for of *CaTIP1;1* [91]. By contrast, the level of *TIP* expression increased in response to drought in some plant species. In soybean (*Glycine max*), transcriptome analysis data revealed that under dehydration stress, the expression of *GmTIP2;1, GmTIP1;7* and *GmTIP1;8* was up-regulated. The authors suggested that these three genes are

probably the major AQPs that are involved in the stress response [75].

Interestingly, the expression profile of *TIP* genes can be compared for cultivars that have contrasting responses to drought stress under control and stress conditions. In two cultivars of strawberry (*Fragaria* x *ananassa*) that have contrasting drought stress phenotypes, the gene expression of *FaTIPs* in the roots was analysed [79]. During severe drought stress, the *FaTIPs* were only up-regulated in the

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

responses is required.

**4.1 Drought, salinity and cold stress**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

*Abiotic Stress in Plants*

Radish (*Raphanus* 

(*Oryza sativa* L*.*)

Sunflower (*Helianthus annuus*

Tobacco (*Nicotiana tabacum* *RsTip1;1 (gamma-VM23)*

*RsTIP2;1 (delta-VM23)*

*The expression of the selected TIP genes in different plant tissues.*

Maize (*Zea mays* L*.*)

*sativus*)

Rice

L*.*)

L*.*)

**Table 3.**

**conditions**

**4. Study of the expression of** *TIPs* **under abiotic stress or phytohormone treatment, and their role in maintaining cell homeostasis under stress** 

*OsTIP1;1* Shoots, roots

*TIP27 (delta-TIP)* Guard cells

**Species TIP name Organ/tissue/process References**

*ZmTIP2;3* Root-specific [20]

*OsTIP3;2* Mature seed, spikelet, callus [21, 69]

*TIP7 (delta-TIP)* Guard cells [23]

*NtTIP1;1 (TobRB7)* Root-specific [70]

mesophyll

Hypocotyl of seedlings, developing tap roots and young growing leaves

Not expressed in young roots or leaf

[22]

The gene expression is the process in which gene information is converted into a protein [7]. Analysing the gene expression profiles is a prerequisite for determining the physiological function of a gene [71]. The function of AQPs can generally be modified in two ways: by regulating the gene expression, which leads to changes in protein abundance or by changing its permeability – gating. However, it should be kept in mind that changes in the mRNA expression level often reflect the protein abundance, but that this is not necessarily strictly connected in any cell or tissue [37]. In term, AQP trafficking and activity could be affected by the post-translational modifications (PTMs), like deamination, phosphorylation, methylation, ubiquitination and acetylation [37]. Water homeostasis is fundamental for cell survival [72]. AQP facilitate the transport of water and play roles in response to abiotic stress conditions during which the cell homeostasis is disturbed. Different studies have suggested that a low abundance of the AQP proteins reduces the water permeability of membranes and that a high abundance of them increases it. Although it can be assumed that all AQPs are able to transport water, an experimental study was performed for only a few members of the TIP subfamily in different plant species (**Table 1**). The expression of TIPs may be affected by different environmental conditions, including drought, salinity and cold and this has been investigated in many plant species. Comparative transcriptome studies using RNA sequencing (RNA-seq), which is a next generation sequencing technology, could lead to the discovery of a differential expression of multiple aquaporin homologues in different tissues and/or in different conditions of growth, e.g. under abiotic stress. The transcriptome defines as a set of coding and non-coding RNA molecules that are present in a single cell or a population of cells [73]. Nowadays, RNA-seq technology is used more and more frequently [74, 75]. On the other hand, the reverse-transcription quantitative PCR (RT-qPCR) technique still serves as the method of choice to

perform the expression analysis of specific genes in many researches.

Abiotic stresses, which have a significant impact on the plants, are involved in changes at the transcriptome, cellular and physiological levels. When the stress is

**428**

prolonged, plant growth and productivity are severely diminished [76, 77]. The response of plants is very complicated and many mechanisms are initiated simultaneously to restore cellular homeostasis and promote survival [78]. Aquaporins are thought to be responsive to the stress signalling pathways and are also thought to be involved in the stress-coping mechanisms such as altering the tissue hydraulic conductivity [79, 80]. Drought and salinity are two major factors that significantly limit plant growth and productivity [81, 82]. The huge yield losses caused by drought stress ranging 45–92 (%) have been reported in major field crops like maize (*Zea mays* L.), wheat (*Triticum aestivum* L.), rice (*Oryza sativa* L.), chickpea (*Cicer arietinum* L.), soybean (*Glycine max* L.), sunflower (*Helianthus annuus* L.) [83]. Cold is also often associated with climate change [84]. Drought, salinity and freezing stresses cause a changing water status in plant cells and all of these result in cellular dehydration [85]. In order to improve the tolerance of crop plants to unfavourable environmental conditions, a detailed understanding of their stress responses is required.

#### **4.1 Drought, salinity and cold stress**

Aquaporins are responsible for precisely regulating the movement of water and therefore may play a crucial role in the drought-stress response as well as in drought-stress tolerance [78]. A transcriptome analysis of the leaf and root tissues in plant species revealed significant changes in the expression of the *TIP* genes in response to drought stress. Under drought stress, when water is limited, the downregulation of the *TIP* genes can lead to a decrease in the water permeability of the tonoplast in order to avoid water loss and to minimise the water flow through the cell membranes in order to prevent the further loss of leaf turgor. This expression pattern has been shown in many studies. In *Nicotiana glauca*, the *NgMIP2* and *NgMIP3* genes, which are homologous to *TIP*, were down-regulated in leaves under drought stress when the leaves were wilting, usually three to four days after water was withheld [86] and in Arabidopsis, the levels of *AtTIP1;1, AtTIP1;2, AtTIP2;1* and *AtTIP2;2* were more than four-fold down-regulated after 12 days of drought [87]. In contrast to these results, the expression level of *AtTIP1;1* and *AtTIP2;1* under drought treatment was up-regulated, but the time that the stress was applied was only 24 hours [88]. Moreover, in barley (*Hordeum vulgare* L.), the expression of five *HvTIP* aquaporins in leaves: *HvTIP1;1, HvTIP1;2, HvTIP2;1, HvTIP2;2* and *HvTIP2;3* was down-regulated after ten days of severe drought treatment [89]. In turn, in *Festuca* species, the transcript level of the *TIP1;1* aquaporin decreased in leaves after 11 days of a water deficit [90]. The possible functional role of coffee (*Coffea arabica* L.) TIPs in in regulating the water balance has been explored by measuring the *TIP* gene expression in leaf and root tissues that had been subjected to drought [91]. In root tissue, the expression of three *CsTIP* genes (*CaTIP1;1, CsTIP2;1, CsTIP4;1*) decreased as the severity of the drought stress increased. In the leaf, a similar expression profile of their expression was obtained only for of *CaTIP1;1* [91]. By contrast, the level of *TIP* expression increased in response to drought in some plant species. In soybean (*Glycine max*), transcriptome analysis data revealed that under dehydration stress, the expression of *GmTIP2;1, GmTIP1;7* and *GmTIP1;8* was up-regulated. The authors suggested that these three genes are probably the major AQPs that are involved in the stress response [75].

Interestingly, the expression profile of *TIP* genes can be compared for cultivars that have contrasting responses to drought stress under control and stress conditions. In two cultivars of strawberry (*Fragaria* x *ananassa*) that have contrasting drought stress phenotypes, the gene expression of *FaTIPs* in the roots was analysed [79]. During severe drought stress, the *FaTIPs* were only up-regulated in the

drought-tolerant cultivar. This was connected with a gradual stomatal closure in this cultivar, which was further associated with conservative water use [79]. In turn, in soybean (*Glycine max*), the difference in gene expression was investigated using RNA-seq and it was found that the expression level of seven *TIP* genes (*GmTIP2;1, 2;2, 2;3, 2;4, 2;5, 3;2* and *5;1*) in the leaves was lower in the slow-wilting soybean lines, but that it increased in the fast-wilting soybean lines after drought stress [74]. Slow wilting is an important physiological parameter that is used in stress tolerance studies of plants. A cultivar-specific *TIP* expression under drought has also been observed in the common bean (*Phaseolus vulgaris* L.) [92]. In this study, the expression of *PvTIP1;1* and *PvTIP4;1* decreased under drought compared to the control conditions in two cultivars, which has different phenotypes in terms of their tolerance to drought and yield at harvest, which were determined by time that was required for the plants to wilt after withholding water. Interestingly, the gene expression of *PvTIP4;1* during drought was cultivar specific with greater downregulation of these gene in the drought-tolerant cultivar [92]. The differences in the relative water content (RWC) and water potential of leaves between these cultivars indicate that there is greater prevention of water loss in the tolerant cultivar during drought, which may be associated with the rapid and adequate down-regulation of the *AQPs* [92]. However, it should be kept in mind that the adaptive mechanism for reducing the effects of water deficit stress in which the *TIP* or other *AQP* expression is changed should be further analysed by a functional characterisation of these candidate genes or proteins [52].

The regulation of water transport has been postulated as being the most important and the best recognised function of all of the AQPs including TIPs under drought stress. A second important function could be their involvement in the movement of hydrogen peroxide (H2O2), which is one of the reactive oxygen species (ROS), which include the unstable, highly reactive molecules that are produced during abiotic stress, e.g. drought [83, 93]. This activity makes the AQPs important players in both the redox signalling network and in H2O2 detoxification [94]. TIPs can facilitate the movement of H2O2 across the membranes that have already been shown by their *in vitro* expression in the yeast or oocyte (**Table 1**). In barley under drought stress, the expression of the *HvTIP3;1* gene increase 5000-fold compared to their expression under optimal water conditions [89].

Soil salination and a high salt accumulation affects the growth, development and metabolism and yield of plants [95]. A wide range of physiological and biochemical alterations in plants are induced by salinity, which causes a lower water potential in the soil solution, ionic disequilibrium and also a higher accumulation of reactive oxygen species (ROS) [96]. Salinity stress leads to changes in the expression profiles of the *TIP* genes, which was shown in many plant species. In Arabidopsis (*Arabidopsis thaliana*), the plants were treated with 100 mm NaCl, which led to osmotic stress. Macroarray experiments with gene-specific tags were performed to investigate the expression of all of the *AQPs* including the *TIP* subfamily in roots that had been under salt treatment for 24 hours [97]. The *AtTIP1;1, AtTIP1;2, AtTIP2;2* and *AtTIP2;3* genes were highly expressed in the roots and their expression was maximally reduced at 6 h of treatment and remained low until 24 h of treatment, except for *AtTIP1;1*. In turn, in *Festuca arundinacea,* the plants were exposed to salt stress by irrigating them with 250 mM NaCl solution over 21 days, which resulted in an increase in the abundance of the *FaTIP1;1* transcript in two contrasting salt tolerance genotypes compared to the control conditions. This increase was noticed earlier on day six of the NaCl treatment in the high-salt tolerant (HST) genotypes and later on day 11 in the low-salt tolerant (LST) genotype [90].

Similar to water and salt stresses, cold stress is an important abiotic stress factor that significantly limits plant growth and development [98]. In *Festuca pratensis*,

**431**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

cold acclimation was associated with a lower transcript level of the *FpTIP1;1* gene in the leaves in both the high and low frost-tolerant genotypes. The authors concluded that the down-regulation of these isoforms during the exposure to cold may be one of the cold-acclimation components that prevents frost-induced cellular dehydration [90]. A similar pattern of expression was observed in roots in rice (*Oryza sativa* L*.*) under cold treatment. A 4°C treatment caused a decrease in the transcript level of the *OsTIP1;1* and *OsTIP2;2* genes. The mRNA levels of these genes started to decrease after 48 hours and continued to decrease after 72 hours of a chilling treatment [57]. One more example of a change in the expression of the *TIP* member genes comes from the cold treatment of cotton (*Gossypium hirsutum*). The *GhTIP1;1* transcripts mainly accumulated in the roots and hypocotyls under normal conditions, but were dramatically up-regulated in the cotyledons and down-regulated in the roots within a few hours after the cotton seedlings had been

Phytohormones play vital roles in the ability of plants to acclimatise to varying environments, by mediating growth, development, and nutrient allocation [100]. Interestingly, it has been shown that the *TIPs* expression is also altered by phytohormones, including abscisic acid (ABA), cytokinin (CK), gibberellins (GA), and jasmonates (JA). Abscisic acid (ABA) is a plant growth regulator that plays an essential role in the abiotic stress response mainly during water stress [101]. It regulates the movement of the stomatal guard cells [102]. Jasmonates act as stress hormones that play an important role in the plant response to biotic and abiotic stresses [103]. In general, JA inhibits plant growth and modulate many growth and developmental processes of plants including root, shoot and leaf growth, trichome and tuber formation, fruit ripening and leaf senescence [104]. The gibberellins stimulate the growth of most organs via cell elongation and also respond to abiotic stresses [105]. Cytokinins play a role in regulating plant growth, development and

Cytokinin has been reported to influence the expression of the aquaporin genes. The expression of *PgTIP1* from ginseng (*Panax ginseng*) was positively regulated by applying cytokinin in suspension-cultured hormone-autotrophic ginseng cells [108]. Methyl jasmonate treatment caused a decrease in the nitrogen content in barley leaves, which was associated with an increased expression of the four tonoplast aquaporin genes (*HvTIP1;2, HvTIP2;2, HvTIP4;1* and *HvTIP4;2*), which are predicted to transport the nitrogen compounds from the vacuole to the cytosol. The up-regulation of the nitrogen-transporting *HvTIPs* may lead to a vacuolar unloading of ammonia and urea, which could both be remobilised when the nitrogen content in barley leaves decreases [109]. In barley, the changes in the expression of all of the investigated *HvTIPs* in response to MeJA treatment were associated with the presence of the *cis*-regulatory elements in their promotor regions, which are recognised by the jasmonate-related transcription factors [109]. Other types of elements that possibly participate in the response to phytohormones in the *HvTIP* promotor regions such as abscisic acid (ABA), gibberellins (GA) and auxin were also identified [89]. In barley, the effect of ABA and GA on the expression of the *HvTIP1;2, HvTIP2;1, HvTIP2;2, HvTIP2;3* and *HvTIP4;1* genes after 24 hours of treatment was studied in both the shoots and roots using quantitative real-time RT-PCR [110]. Interestingly, the exogenous application of ABA increased the expression of *HvTIP2;1* and *HvTIP4;1,* while the GA-treatment led to an increase of *HvTIP1;2* and *HvTIP4;1* in the roots compared to the control conditions. However, in the shoots, the ABA

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

cold treated [99].

**4.2 Phytohormone treatment**

their acclimation to environmental stresses [106, 107].

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

*Abiotic Stress in Plants*

candidate genes or proteins [52].

their expression under optimal water conditions [89].

on day 11 in the low-salt tolerant (LST) genotype [90].

drought-tolerant cultivar. This was connected with a gradual stomatal closure in this cultivar, which was further associated with conservative water use [79]. In turn, in soybean (*Glycine max*), the difference in gene expression was investigated using RNA-seq and it was found that the expression level of seven *TIP* genes (*GmTIP2;1, 2;2, 2;3, 2;4, 2;5, 3;2* and *5;1*) in the leaves was lower in the slow-wilting soybean lines, but that it increased in the fast-wilting soybean lines after drought stress [74]. Slow wilting is an important physiological parameter that is used in stress tolerance studies of plants. A cultivar-specific *TIP* expression under drought has also been observed in the common bean (*Phaseolus vulgaris* L.) [92]. In this study, the expression of *PvTIP1;1* and *PvTIP4;1* decreased under drought compared to the control conditions in two cultivars, which has different phenotypes in terms of their tolerance to drought and yield at harvest, which were determined by time that was required for the plants to wilt after withholding water. Interestingly, the gene expression of *PvTIP4;1* during drought was cultivar specific with greater downregulation of these gene in the drought-tolerant cultivar [92]. The differences in the relative water content (RWC) and water potential of leaves between these cultivars indicate that there is greater prevention of water loss in the tolerant cultivar during drought, which may be associated with the rapid and adequate down-regulation of the *AQPs* [92]. However, it should be kept in mind that the adaptive mechanism for reducing the effects of water deficit stress in which the *TIP* or other *AQP* expression is changed should be further analysed by a functional characterisation of these

The regulation of water transport has been postulated as being the most important and the best recognised function of all of the AQPs including TIPs under drought stress. A second important function could be their involvement in the movement of hydrogen peroxide (H2O2), which is one of the reactive oxygen species (ROS), which include the unstable, highly reactive molecules that are produced during abiotic stress, e.g. drought [83, 93]. This activity makes the AQPs important players in both the redox signalling network and in H2O2 detoxification [94]. TIPs can facilitate the movement of H2O2 across the membranes that have already been shown by their *in vitro* expression in the yeast or oocyte (**Table 1**). In barley under drought stress, the expression of the *HvTIP3;1* gene increase 5000-fold compared to

Soil salination and a high salt accumulation affects the growth, development and metabolism and yield of plants [95]. A wide range of physiological and biochemical alterations in plants are induced by salinity, which causes a lower water potential in the soil solution, ionic disequilibrium and also a higher accumulation of reactive oxygen species (ROS) [96]. Salinity stress leads to changes in the expression profiles of the *TIP* genes, which was shown in many plant species. In Arabidopsis (*Arabidopsis thaliana*), the plants were treated with 100 mm NaCl, which led to osmotic stress. Macroarray experiments with gene-specific tags were performed to investigate the expression of all of the *AQPs* including the *TIP* subfamily in roots that had been under salt treatment for 24 hours [97]. The *AtTIP1;1, AtTIP1;2, AtTIP2;2* and *AtTIP2;3* genes were highly expressed in the roots and their expression was maximally reduced at 6 h of treatment and remained low until 24 h of treatment, except for *AtTIP1;1*. In turn, in *Festuca arundinacea,* the plants were exposed to salt stress by irrigating them with 250 mM NaCl solution over 21 days, which resulted in an increase in the abundance of the *FaTIP1;1* transcript in two contrasting salt tolerance genotypes compared to the control conditions. This increase was noticed earlier on day six of the NaCl treatment in the high-salt tolerant (HST) genotypes and later

Similar to water and salt stresses, cold stress is an important abiotic stress factor that significantly limits plant growth and development [98]. In *Festuca pratensis*,

**430**

cold acclimation was associated with a lower transcript level of the *FpTIP1;1* gene in the leaves in both the high and low frost-tolerant genotypes. The authors concluded that the down-regulation of these isoforms during the exposure to cold may be one of the cold-acclimation components that prevents frost-induced cellular dehydration [90]. A similar pattern of expression was observed in roots in rice (*Oryza sativa* L*.*) under cold treatment. A 4°C treatment caused a decrease in the transcript level of the *OsTIP1;1* and *OsTIP2;2* genes. The mRNA levels of these genes started to decrease after 48 hours and continued to decrease after 72 hours of a chilling treatment [57]. One more example of a change in the expression of the *TIP* member genes comes from the cold treatment of cotton (*Gossypium hirsutum*). The *GhTIP1;1* transcripts mainly accumulated in the roots and hypocotyls under normal conditions, but were dramatically up-regulated in the cotyledons and down-regulated in the roots within a few hours after the cotton seedlings had been cold treated [99].

#### **4.2 Phytohormone treatment**

Phytohormones play vital roles in the ability of plants to acclimatise to varying environments, by mediating growth, development, and nutrient allocation [100]. Interestingly, it has been shown that the *TIPs* expression is also altered by phytohormones, including abscisic acid (ABA), cytokinin (CK), gibberellins (GA), and jasmonates (JA). Abscisic acid (ABA) is a plant growth regulator that plays an essential role in the abiotic stress response mainly during water stress [101]. It regulates the movement of the stomatal guard cells [102]. Jasmonates act as stress hormones that play an important role in the plant response to biotic and abiotic stresses [103]. In general, JA inhibits plant growth and modulate many growth and developmental processes of plants including root, shoot and leaf growth, trichome and tuber formation, fruit ripening and leaf senescence [104]. The gibberellins stimulate the growth of most organs via cell elongation and also respond to abiotic stresses [105]. Cytokinins play a role in regulating plant growth, development and their acclimation to environmental stresses [106, 107].

Cytokinin has been reported to influence the expression of the aquaporin genes. The expression of *PgTIP1* from ginseng (*Panax ginseng*) was positively regulated by applying cytokinin in suspension-cultured hormone-autotrophic ginseng cells [108]. Methyl jasmonate treatment caused a decrease in the nitrogen content in barley leaves, which was associated with an increased expression of the four tonoplast aquaporin genes (*HvTIP1;2, HvTIP2;2, HvTIP4;1* and *HvTIP4;2*), which are predicted to transport the nitrogen compounds from the vacuole to the cytosol. The up-regulation of the nitrogen-transporting *HvTIPs* may lead to a vacuolar unloading of ammonia and urea, which could both be remobilised when the nitrogen content in barley leaves decreases [109]. In barley, the changes in the expression of all of the investigated *HvTIPs* in response to MeJA treatment were associated with the presence of the *cis*-regulatory elements in their promotor regions, which are recognised by the jasmonate-related transcription factors [109]. Other types of elements that possibly participate in the response to phytohormones in the *HvTIP* promotor regions such as abscisic acid (ABA), gibberellins (GA) and auxin were also identified [89]. In barley, the effect of ABA and GA on the expression of the *HvTIP1;2, HvTIP2;1, HvTIP2;2, HvTIP2;3* and *HvTIP4;1* genes after 24 hours of treatment was studied in both the shoots and roots using quantitative real-time RT-PCR [110]. Interestingly, the exogenous application of ABA increased the expression of *HvTIP2;1* and *HvTIP4;1,* while the GA-treatment led to an increase of *HvTIP1;2* and *HvTIP4;1* in the roots compared to the control conditions. However, in the shoots, the ABA

treatment decreased the expression of *HvTIP1;2*, while the GA treatment led to the up-regulation of *HvTIP4;1* [110].

#### **5. Genetic manipulation of the TIP-encoding genes**

The tonoplast intrinsic proteins genes have been reported to be involved in the increasing the abiotic stress tolerance in several plant species using genetic modification technology (**Table 4**). It was shown that manipulations of the expression of


#### **Table 4.**

*Genetic manipulation of the TIP genes in different plant species and its effect on the phenotype.*

**433**

**6. Conclusions**

**Acknowledgements**

**Conflict of interest**

project 2015/19/D/NZ1/03441.

The author declares no conflict of interest.

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

the *TIP*-encoding genes in plants could have the potential to improve their abiotic stress tolerance (**Table 4**). In tomato (*Solanum lycopersicum* L.), overexpression of *SlTIP2;2* has been shown to substantially improve the water homeostasis under drought stress. Conversely, this overexpression also promoted more prodigal water use [112]. Another gene, *TIP1;1*, was artificially manipulated in a few studies *via* genetic engineering (**Table 4**). It is not only believed to be play an important role during plant growth and development, but also to be beneficial for growth under stress when it is overexpressed. The overexpression of the *PgTIP1;1* gene from *Panax ginseng* in Arabidopsis led to a general acceleration of plant development, which included a faster growth, precocious flowering and a higher accumulation of

biomass compared to the wild type (wt), or the accumulation of more Na+

in its water status. Moreover, the mutant was alive and thriving [119].

depending on TIP isoforms and the type and degree of stress treatment.

This work was supported by the National Science Centre, Poland, SONATA

It is believed that aquaporins and, among them, the tonoplast intrinsic proteins may be important players in the plant water relations at the cell, tissue, organ and whole plant levels. TIP proteins could have a vast impact on the acquisition of knowledge about plant tolerance against abiotic stress and could serve as a target sequence for genetic modifications. A drawback in this approach is that in the genome of each plant species, many genes encode the same subgroup of isoforms. It is possible that some of these have a redundant function. Taken together, TIPs probably play complex and diversified roles in the response of plants to abiotic stresses

salt stress and also caused a superior performance under drought stress compared to wt [85, 108]. The authors concluded that PgTIP1;1 plays an important role in the growth and development of plant cells and suggested that regulating it in the water movement across the tonoplast has a great impact on plant vigour under favourable growth conditions and also in the responses of plants to drought, salt and cold stresses [85]. Therefore, *TIP1;1* might be a potential target in biotechnology and agriculture. It was interesting to determine whether silencing this gene would have the opposite effect on growth in control and stress condition. First, it was shown that the down-regulation of *AtTIP1;1* using RNA interference (RNAi) resulted in early senescence and plant death [118]. However, later research using transposon insertion did not confirm these results [119]. A single mutant (tip1;1–1) that had been generated using transposon insertion showed any significant effect on the metabolism or elemental composition of the plants. Additionally, a double mutant in the *AtTIP1;1* and *AtTIP1;2* genes (tip1;1–1 tip1;2–1) had a small increase in its anthocyanin content and a decrease in its catalase activity, but showed no changes

under

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

#### *TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

*Abiotic Stress in Plants*

AQUA1 (TIP) *Populus alba* L.

SlTIP2;2 *Solanum lycopersicum* L.

SlTIP2;2 *Solanum lycopersicum* L.

PgTIP1 *Panax ginseng*

PgTIP1 *Panax ginseng*

PgTIP1 *Panax ginseng*

CsTIP2;1 *Citrus spp.*

JcTIP1;3 *Jatropha curcas*

AtTIP5;1 *Arabidopsis thaliana*

AtTIP1;1 *Arabidopsis thaliana*

AtTIP2;2 *Arabidopsis thaliana*

AtTIP1;1 -mutant AtTIP1;2 and AtTIP1;2 -double mutant

*Arabidopsis thaliana*

the up-regulation of *HvTIP4;1* [110].

**TIP name/species Method/expression in species**

> OX *Populus alba*

OX

OX

OX *Glycine max*

OX

OX

OX

OX

OX

KO

KO

*Solanum lycopersicum*

*Arabidopsis thaliana*

*Arabidopsis thaliana*

*Arabidopsis thaliana*

*Nicotiana tabacum*

*Arabidopsis thaliana*

*Arabidopsis thaliana*

Transposon insertion

T-DNA insertion

*OX-overexpression, KO- knockout, RNAi-RNA interference, PEG- polyethylene glycol.*

*Genetic manipulation of the TIP genes in different plant species and its effect on the phenotype.*

technology

Down-regulation /RNAi

**5. Genetic manipulation of the TIP-encoding genes**

treatment decreased the expression of *HvTIP1;2*, while the GA treatment led to

The tonoplast intrinsic proteins genes have been reported to be involved in the increasing the abiotic stress tolerance in several plant species using genetic modification technology (**Table 4**). It was shown that manipulations of the expression of

**Phenotype References**

[111]

[112]

[85]

[108]

[115]

[116]

[119]

[120]

Increased plant growth rate and water use efficiency under excess Zn conditions

Enhances the tolerance to salt stress [113]

Higher tolerance to salinity [114]

Acceleration of plant development, with faster growth, precocious flowering and a higher accumulation of biomass, increased seed size and seed mass, greatly

Accumulated more Na + under salt stress, and exhibited superior performance

Increased plant growth and tolerance to

Increased tolerance to boron toxicity [117]

Early senescence and plant death [118]

Single mutant -no significant effect on the metabolism or elemental composition of

Double mutant -minor increase in the anthocyanin content, and a decrease in catalase activity, no changes in the water status, mutant alive and thriving

Less sensitive to abiotic stresses (mannitol, NaCl and PEG)

Increased tolerance to drought and salinity, improved germination under high salt and mannitol stress

Increased drought tolerance due to the ability of plant to regulate its transpiration under drought stress conditions, improved CO2 uptake and a balanced

nutrient supply

increased growth rate

under drought stress

drought and salinity

the plants

**432**

**Table 4.**

the *TIP*-encoding genes in plants could have the potential to improve their abiotic stress tolerance (**Table 4**). In tomato (*Solanum lycopersicum* L.), overexpression of *SlTIP2;2* has been shown to substantially improve the water homeostasis under drought stress. Conversely, this overexpression also promoted more prodigal water use [112]. Another gene, *TIP1;1*, was artificially manipulated in a few studies *via* genetic engineering (**Table 4**). It is not only believed to be play an important role during plant growth and development, but also to be beneficial for growth under stress when it is overexpressed. The overexpression of the *PgTIP1;1* gene from *Panax ginseng* in Arabidopsis led to a general acceleration of plant development, which included a faster growth, precocious flowering and a higher accumulation of biomass compared to the wild type (wt), or the accumulation of more Na+ under salt stress and also caused a superior performance under drought stress compared to wt [85, 108]. The authors concluded that PgTIP1;1 plays an important role in the growth and development of plant cells and suggested that regulating it in the water movement across the tonoplast has a great impact on plant vigour under favourable growth conditions and also in the responses of plants to drought, salt and cold stresses [85]. Therefore, *TIP1;1* might be a potential target in biotechnology and agriculture. It was interesting to determine whether silencing this gene would have the opposite effect on growth in control and stress condition. First, it was shown that the down-regulation of *AtTIP1;1* using RNA interference (RNAi) resulted in early senescence and plant death [118]. However, later research using transposon insertion did not confirm these results [119]. A single mutant (tip1;1–1) that had been generated using transposon insertion showed any significant effect on the metabolism or elemental composition of the plants. Additionally, a double mutant in the *AtTIP1;1* and *AtTIP1;2* genes (tip1;1–1 tip1;2–1) had a small increase in its anthocyanin content and a decrease in its catalase activity, but showed no changes in its water status. Moreover, the mutant was alive and thriving [119].

#### **6. Conclusions**

It is believed that aquaporins and, among them, the tonoplast intrinsic proteins may be important players in the plant water relations at the cell, tissue, organ and whole plant levels. TIP proteins could have a vast impact on the acquisition of knowledge about plant tolerance against abiotic stress and could serve as a target sequence for genetic modifications. A drawback in this approach is that in the genome of each plant species, many genes encode the same subgroup of isoforms. It is possible that some of these have a redundant function. Taken together, TIPs probably play complex and diversified roles in the response of plants to abiotic stresses depending on TIP isoforms and the type and degree of stress treatment.

#### **Acknowledgements**

This work was supported by the National Science Centre, Poland, SONATA project 2015/19/D/NZ1/03441.

#### **Conflict of interest**

The author declares no conflict of interest.

*Abiotic Stress in Plants*

#### **Author details**

Marzena Małgorzata Kurowska University of Silesia in Katowice, Katowice, Poland

\*Address all correspondence to: marzena.kurowska@us.edu.pl

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**435**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

[9] Liu LH, Ludewig U, Gassert B, Frommer WB, von Wirén N. Urea transport by nitrogen-regulated tonoplast intrinsic proteins in Arabidopsis. Plant Physiol.

2003;133(3):1220-1228. DOI: 10.1104/

[10] Klebl F, Wolf M, Sauer N. A defect in the yeast plasma membrane urea transporter Dur3p is complemented by CpNIP1, a Nod26-like protein from zucchini (*Cucurbita pepo* L.), and by Arabidopsis thaliana delta-TIP or gamma-TIP. FEBS Lett. 2003;547(1-3):69-74. DOI: 10.1016/

[11] Loqué D, Ludewig U, Yuan L, von Wirén N. Tonoplast intrinsic proteins AtTIP2;1 and AtTIP2;3 facilitate NH3 transport into the vacuole. Plant Physiol. 2005;137(2):671-680. DOI: 10.1104/

pp.103.027409

s0014-5793(03)00671-9

[12] Bienert GP, Møller AL, Kristiansen KA, et al. Specific aquaporins facilitate the diffusion of hydrogen peroxide across membranes. J Biol Chem. 2007;282(2):1183-1192. DOI:

10.1074/jbc.M603761200

[13] Soto G, Alleva K, Mazzella MA, Amodeo G, Muschietti JP. AtTIP1;3 and AtTIP5;1, the only highly expressed Arabidopsis pollen-specific aquaporins,

transport water and urea. FEBS Lett. 2008;582(29):4077-4082. DOI:

[14] Besse M, Knipfer T, Miller A, Verdeil JL, Jahn TP, Fricke W. Developmental pattern of aquaporin expression in barley (Hordeum vulgare L.) leaves. J Exp Bot. 2011; 62(12):4127-

10.1016/j.febslet.2008.11.002

42. DOI: 10. 1093/jxb/err175

[15] Jahn TP, Møller AL, Zeuthen T, et al. Aquaporin homologues in plants and mammals transport ammonia.

pp.104.051268

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

[1] Maurel C, Chrispeels MJ.

[2] Li C, Wang W. Molecular Biology of Aquaporins. Adv Exp Med Biol. 2017;969:1-34. DOI: 10.1007/978-94-024-1057-0

s12551-017-0313-3

5910

nar/15.2.813

Aquaporins. A molecular entry into plant water relations. Plant Physiol. 2001;125(1):135-138. DOI: 10.1104/ pp.125.1.135 PMID: 11154316

[3] Sutka M, Amodeo G, Ozu M. Plant and animal aquaporins crosstalk: what can be revealed from distinct perspectives. Biophys Rev. 2017; 9(5):545-562. DOI: 10.1007/

[4] Bezerra-Neto JP, de Araújo FC, Ferreira-Neto JRC, da Silva MD, Pandolfi V, Aburjaile FF, et al. Plant Aquaporins: Diversity, Evolution and Biotechnological Applications. Curr Protein Pept Sci. 2019; 20 (4):368-395. DOI: 10.2174/138920372066618110209

[5] Fortin MG, Morrison NA, Verma DP. Nodulin-26, a peribacteroid membrane nodulin is expressed independently of the development of the peribacteroid compartment. Nucleic Acids Res. 1987;15(2):813-824. DOI: 10.1093/

[6] Maurel C, Reizer J, Schroeder JI, Chrispeels MJ. The vacuolar membrane protein gamma-TIP creates water specific channels in Xenopus oocytes,

[7] Kapilan R, Vaziri M, Zwiazek JJ. Regulation of aquaporins in plants under stress. Biol Res. 2018; 16; 51 (1):4. DOI: 10.1186/s40659-018-0152-0

EMBO J. 1993;12: 2241-2247

[8] Quigley F, Rosenberg JM, Shachar-Hill Y, Bohnert HJ. From genome to function: the Arabidopsis aquaporins. Genome Biol. 2002;3(1).

DOI: 10.1186/gb-2001-3-1

**References**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

#### **References**

*Abiotic Stress in Plants*

**434**

**Author details**

Marzena Małgorzata Kurowska

University of Silesia in Katowice, Katowice, Poland

provided the original work is properly cited.

\*Address all correspondence to: marzena.kurowska@us.edu.pl

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

[1] Maurel C, Chrispeels MJ. Aquaporins. A molecular entry into plant water relations. Plant Physiol. 2001;125(1):135-138. DOI: 10.1104/ pp.125.1.135 PMID: 11154316

[2] Li C, Wang W. Molecular Biology of Aquaporins. Adv Exp Med Biol. 2017;969:1-34. DOI: 10.1007/978-94-024-1057-0

[3] Sutka M, Amodeo G, Ozu M. Plant and animal aquaporins crosstalk: what can be revealed from distinct perspectives. Biophys Rev. 2017; 9(5):545-562. DOI: 10.1007/ s12551-017-0313-3

[4] Bezerra-Neto JP, de Araújo FC, Ferreira-Neto JRC, da Silva MD, Pandolfi V, Aburjaile FF, et al. Plant Aquaporins: Diversity, Evolution and Biotechnological Applications. Curr Protein Pept Sci. 2019; 20 (4):368-395. DOI: 10.2174/138920372066618110209 5910

[5] Fortin MG, Morrison NA, Verma DP. Nodulin-26, a peribacteroid membrane nodulin is expressed independently of the development of the peribacteroid compartment. Nucleic Acids Res. 1987;15(2):813-824. DOI: 10.1093/ nar/15.2.813

[6] Maurel C, Reizer J, Schroeder JI, Chrispeels MJ. The vacuolar membrane protein gamma-TIP creates water specific channels in Xenopus oocytes, EMBO J. 1993;12: 2241-2247

[7] Kapilan R, Vaziri M, Zwiazek JJ. Regulation of aquaporins in plants under stress. Biol Res. 2018; 16; 51 (1):4. DOI: 10.1186/s40659-018-0152-0

[8] Quigley F, Rosenberg JM, Shachar-Hill Y, Bohnert HJ. From genome to function: the Arabidopsis aquaporins. Genome Biol. 2002;3(1). DOI: 10.1186/gb-2001-3-1

[9] Liu LH, Ludewig U, Gassert B, Frommer WB, von Wirén N. Urea transport by nitrogen-regulated tonoplast intrinsic proteins in Arabidopsis. Plant Physiol. 2003;133(3):1220-1228. DOI: 10.1104/ pp.103.027409

[10] Klebl F, Wolf M, Sauer N. A defect in the yeast plasma membrane urea transporter Dur3p is complemented by CpNIP1, a Nod26-like protein from zucchini (*Cucurbita pepo* L.), and by Arabidopsis thaliana delta-TIP or gamma-TIP. FEBS Lett. 2003;547(1-3):69-74. DOI: 10.1016/ s0014-5793(03)00671-9

[11] Loqué D, Ludewig U, Yuan L, von Wirén N. Tonoplast intrinsic proteins AtTIP2;1 and AtTIP2;3 facilitate NH3 transport into the vacuole. Plant Physiol. 2005;137(2):671-680. DOI: 10.1104/ pp.104.051268

[12] Bienert GP, Møller AL, Kristiansen KA, et al. Specific aquaporins facilitate the diffusion of hydrogen peroxide across membranes. J Biol Chem. 2007;282(2):1183-1192. DOI: 10.1074/jbc.M603761200

[13] Soto G, Alleva K, Mazzella MA, Amodeo G, Muschietti JP. AtTIP1;3 and AtTIP5;1, the only highly expressed Arabidopsis pollen-specific aquaporins, transport water and urea. FEBS Lett. 2008;582(29):4077-4082. DOI: 10.1016/j.febslet.2008.11.002

[14] Besse M, Knipfer T, Miller A, Verdeil JL, Jahn TP, Fricke W. Developmental pattern of aquaporin expression in barley (Hordeum vulgare L.) leaves. J Exp Bot. 2011; 62(12):4127- 42. DOI: 10. 1093/jxb/err175

[15] Jahn TP, Møller AL, Zeuthen T, et al. Aquaporin homologues in plants and mammals transport ammonia.

FEBS Lett. 2004;574(1-3):31-36. DOI: 10.1016/j.febslet.2004.08.004

[16] Holm LM, Jahn TP, Møller AL, et al. NH3 and NH4+ permeability in aquaporin-expressing Xenopus oocytes. Pflugers Arch. 2005;450(6):415-428. DOI: 10.1007/s00424-005-1399-1

[17] Bertl A, Kaldenhoff R. Function of a separate NH3-pore in Aquaporin TIP2;2 from wheat. FEBS Lett. 2007;581(28):5413-5417. DOI: 10.1016/j. febslet.2007.10.034

[18] Bárzana G, Aroca R, Bienert GP, Chaumont F, Ruiz-Lozano JM. New insights into the regulation of aquaporins by the arbuscular mycorrhizal symbiosis in maize plants under drought stress and possible implications for plant performance. Mol Plant Microbe Interact. 2014;27(4):349- 363. DOI: 10.1094/MPMI-09-13-0268-R

[19] Gu R, Chen X, Zhou Y, Yuan L. Isolation and characterization of three maize aquaporin genes, ZmNIP2;1, ZmNIP2;4 and ZmTIP4;4 involved in urea transport. BMB Rep. 2012;45(2):96-101. DOI: 10.5483/ BMBRep.2012.45.2.96

[20] Lopez F, Bousser A, Sissoëff I, Hoarau J, Mahé A. Characterization in maize of ZmTIP2-3, a root-specific tonoplast intrinsic protein exhibiting aquaporin activity. J Exp Bot. 2004;55(396):539-541. DOI: 10.1093/ jxb/052

[21] Li GW, Peng YH, Yu X, et al. Transport functions and expression analysis of vacuolar membrane aquaporins in response to various stresses in rice. J Plant Physiol. 2008;165(18):1879-1888. DOI: 10.1016/j. jplph.2008.05.002

[22] Higuchi T, Suga S, Tsuchiya T, et al. Molecular cloning, water channel activity and tissue specific expression of two isoforms of radish vacuolar

aquaporin. Plant Cell Physiol. 1998;39(9):905-913. DOI: 10.1093/ oxfordjournals.pcp.a029453

[23] Sarda X, Tousch D, Ferrare K, et al. Two TIP-like genes encoding aquaporins are expressed in sunflower guard cells. Plant J. 1997;12(5):1103-1111. DOI: 10.1046/j.1365-313x.1997.12051103.x

[24] Gerbeau P, Güçlü J, Ripoche P, Maurel C. Aquaporin Nt-TIPa can account for the high permeability of tobacco cell vacuolar membrane to small neutral solutes. Plant J. 1999;18(6): 577-587. DOI: 10.1046/j.1365-313x. 1999.00481.x

[25] Marty F. Plant vacuoles. Plant Cell. 1999;11(4):587-600. DOI: 10.1105/ tpc.11.4.587

[26] Paris N, Stanley CM, Jones RL, Rogers JC. Plant cells contain two functionally distinct vacuolar compartments. Cell. 1996;85(4):563-572. DOI: 10.1016/ s0092-8674(00)81256-8

[27] Wink M. The plant vacuole: a multifunctional compartment. J. Exp. Bot. (supplement), 44, 231-246 (1993).

[28] Jauh GY, Fischer AM, Grimes HD, Ryan CA Jr, Rogers JC. delta-Tonoplast intrinsic protein defines unique plant vacuole functions. Proc Natl Acad Sci U S A. 1998;95(22):12995-12999. DOI: 10.1073/pnas.95.22.12995

[29] Jauh GY, Phillips TE, Rogers JC. Tonoplast intrinsic protein isoforms as markers for vacuolar functions. Plant Cell. 1999;11(10):1867-1882. DOI: 10.1105/tpc.11.10.1867

[30] Ludevid D, Höfte H, Himelblau E, Chrispeels MJ. The Expression Pattern of the Tonoplast Intrinsic Protein gamma-TIP in Arabidopsis thaliana Is Correlated with Cell Enlargement. Plant Physiol. 1992;100(4):1633-1639. DOI: 10.1104/pp.100.4.1633

**437**

2017.07.021

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

[38] Sui H, Han BG, Lee JK, Walian P, Jap BK. Structural basis of water-specific transport through the AQP1 water channel. Nature. 2001;414(6866):872-878. DOI:

[39] Wu B, Steinbronn C, Alsterfjord M, Zeuthen T, Beitz E. Concerted action of two cation filters in the aquaporin water channel. EMBO J. 2009;28(15):2188- 2194. DOI: 10.1038/emboj.2009.182

[40] Guan XG, Su WH, Yi F, et al. NPA motifs play a key role in plasma membrane targeting of aquaporin-4. IUBMB Life. 2010;62(3):222-226. DOI:

[41] Froger A, Tallur B, Thomas D, Delamarche C. Prediction of functional residues in water channels and related proteins. Protein Sci. 1998;7(6):1458- 1468. DOI: 10.1002/pro.5560070623

Sankararamakrishnan *R. major* intrinsic protein superfamily: channels with unique structural features and diverse selectivity filters. Methods Enzymol. 2015a;557:485-520. DOI: 10.1016/

Sankararamakrishnan R. Intra-helical salt-bridge and helix destabilizing residues within the same helical turn: Role of functionally important loop E half-helix in channel regulation of major intrinsic proteins. Biochim Biophys Acta. 2015b;1848(6):1436-1449. DOI: 10.1016/j.bbamem.2015.03.013

[44] Gomes D, Agasse A, Thiébaud P, Delrot S, Gerós H, Chaumont F. Aquaporins are multifunctional water and solute transporters highly divergent in living organisms. Biochim Biophys Acta. 2009;1788(6):1213-1228. DOI: 10.1016/j.

[45] Törnroth-Horsefield S, Wang Y, Hedfalk K, et al. Structural mechanism

bbamem.2009.03.009

[42] Verma RK, Gupta AB,

[43] Verma RK, Prabh ND,

bs.mie.2014.12.006

10.1038/414872a

10.1002/iub.311

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

[31] Johnson KD, Herman EM, Chrispeels MJ. An abundant, highly conserved tonoplast protein in seeds. Plant Physiol. 1989;91(3):1006-1013.

DOI: 10.1104/pp.91.3.1006

1):299-310.

[32] Hoh B, Hinz G, Jeong BK,

[33] Zybailov, B.L.; Rutschow, H.; Friso, G.; Rudella, A.; Emanuelsson, O.; Sun, Q.; Van Wijk, K.J. Sorting Signals, N-Terminal Modifications and Abundance of the Chloroplast Proteome. PLoS ONE 2008; 3, e1994. DOI: 10.1371/journal.pone.0001994.

[34] Ferro, M.; Brugière, S.; Salvi, D.; Seigneurin-Berny, D.; Court, M.; Moyet, L.; Ramus, C.; Miras, S.; Mellal, M.; Le Gall, S.; et al. AT\_CHLORO, a comprehensive chloroplast proteome database with subplastidial localization and curated information on envelope proteins. Mol. Cell. Proteom. 2010; 9, 1063-84. DOI: 10.1074/mcp.

[35] Simm, S.; Papasotiriou, D.G.; Ibrahim, M.; Leisegang, M.S.; Müller, B.; Schorge, T.; Karas, M.; Mirus, O.; Sommer, M.S.; Schleiff, E. Defining the core proteome of the chloroplast envelope membranes Front. Plant Sci. 2013; 4, 11. DOI: 10.3389/

[36] Jung JS, Preston GM, Smith BL, Guggino WB, Agre P. Molecular structure of the water channel through aquaporin CHIP. The hourglass model. J Biol Chem. 1994;269(20):14648-14654.

Chaumont F. Toward understanding of the high number of plant aquaporin isoforms and multiple regulation mechanisms. Plant Sci. 2017;264: 179-187. DOI: 10.1016/j.plantsci.

[37] Fox AR, Maistriaux LC,

M900325-MCP200.

fpls.2013.00011

Robinson DG. Protein storage vacuoles form de novo during pea cotyledon development. J Cell Sci. 1995;108 ( Pt

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

[31] Johnson KD, Herman EM, Chrispeels MJ. An abundant, highly conserved tonoplast protein in seeds. Plant Physiol. 1989;91(3):1006-1013. DOI: 10.1104/pp.91.3.1006

*Abiotic Stress in Plants*

febslet.2007.10.034

FEBS Lett. 2004;574(1-3):31-36. DOI:

aquaporin. Plant Cell Physiol. 1998;39(9):905-913. DOI: 10.1093/ oxfordjournals.pcp.a029453

[23] Sarda X, Tousch D, Ferrare K, et al. Two TIP-like genes encoding aquaporins are expressed in sunflower guard cells. Plant J. 1997;12(5):1103-1111. DOI: 10.1046/j.1365-313x.1997.12051103.x

[24] Gerbeau P, Güçlü J, Ripoche P, Maurel C. Aquaporin Nt-TIPa can account for the high permeability of tobacco cell vacuolar membrane to small neutral solutes. Plant J. 1999;18(6): 577-587. DOI: 10.1046/j.1365-313x.

[25] Marty F. Plant vacuoles. Plant Cell. 1999;11(4):587-600. DOI: 10.1105/

[26] Paris N, Stanley CM, Jones RL, Rogers JC. Plant cells contain two functionally distinct vacuolar

1996;85(4):563-572. DOI: 10.1016/

[27] Wink M. The plant vacuole: a multifunctional compartment. J. Exp. Bot. (supplement), 44, 231-246 (1993).

[28] Jauh GY, Fischer AM, Grimes HD, Ryan CA Jr, Rogers JC. delta-Tonoplast intrinsic protein defines unique plant vacuole functions. Proc Natl Acad Sci U S A. 1998;95(22):12995-12999. DOI:

[29] Jauh GY, Phillips TE, Rogers JC. Tonoplast intrinsic protein isoforms as markers for vacuolar functions. Plant Cell. 1999;11(10):1867-1882. DOI:

[30] Ludevid D, Höfte H, Himelblau E, Chrispeels MJ. The Expression Pattern of the Tonoplast Intrinsic Protein gamma-TIP in Arabidopsis thaliana Is Correlated with Cell Enlargement. Plant Physiol. 1992;100(4):1633-1639. DOI:

1999.00481.x

tpc.11.4.587

compartments. Cell.

s0092-8674(00)81256-8

10.1073/pnas.95.22.12995

10.1105/tpc.11.10.1867

10.1104/pp.100.4.1633

[16] Holm LM, Jahn TP, Møller AL, et al. NH3 and NH4+ permeability in aquaporin-expressing Xenopus oocytes. Pflugers Arch. 2005;450(6):415-428. DOI: 10.1007/s00424-005-1399-1

[17] Bertl A, Kaldenhoff R. Function of a separate NH3-pore in Aquaporin TIP2;2 from wheat. FEBS Lett.

2007;581(28):5413-5417. DOI: 10.1016/j.

[18] Bárzana G, Aroca R, Bienert GP, Chaumont F, Ruiz-Lozano JM. New insights into the regulation of aquaporins by the arbuscular

mycorrhizal symbiosis in maize plants under drought stress and possible implications for plant performance. Mol Plant Microbe Interact. 2014;27(4):349- 363. DOI: 10.1094/MPMI-09-13-0268-R

[19] Gu R, Chen X, Zhou Y, Yuan L. Isolation and characterization of three maize aquaporin genes, ZmNIP2;1, ZmNIP2;4 and ZmTIP4;4 involved in urea transport. BMB Rep. 2012;45(2):96-101. DOI: 10.5483/

[20] Lopez F, Bousser A, Sissoëff I, Hoarau J, Mahé A. Characterization in maize of ZmTIP2-3, a root-specific tonoplast intrinsic protein exhibiting

aquaporin activity. J Exp Bot. 2004;55(396):539-541. DOI: 10.1093/

[21] Li GW, Peng YH, Yu X, et al. Transport functions and expression analysis of vacuolar membrane aquaporins in response to various stresses in rice. J Plant Physiol.

2008;165(18):1879-1888. DOI: 10.1016/j.

[22] Higuchi T, Suga S, Tsuchiya T, et al. Molecular cloning, water channel activity and tissue specific expression of two isoforms of radish vacuolar

BMBRep.2012.45.2.96

10.1016/j.febslet.2004.08.004

**436**

jxb/052

jplph.2008.05.002

[32] Hoh B, Hinz G, Jeong BK, Robinson DG. Protein storage vacuoles form de novo during pea cotyledon development. J Cell Sci. 1995;108 ( Pt 1):299-310.

[33] Zybailov, B.L.; Rutschow, H.; Friso, G.; Rudella, A.; Emanuelsson, O.; Sun, Q.; Van Wijk, K.J. Sorting Signals, N-Terminal Modifications and Abundance of the Chloroplast Proteome. PLoS ONE 2008; 3, e1994. DOI: 10.1371/journal.pone.0001994.

[34] Ferro, M.; Brugière, S.; Salvi, D.; Seigneurin-Berny, D.; Court, M.; Moyet, L.; Ramus, C.; Miras, S.; Mellal, M.; Le Gall, S.; et al. AT\_CHLORO, a comprehensive chloroplast proteome database with subplastidial localization and curated information on envelope proteins. Mol. Cell. Proteom. 2010; 9, 1063-84. DOI: 10.1074/mcp. M900325-MCP200.

[35] Simm, S.; Papasotiriou, D.G.; Ibrahim, M.; Leisegang, M.S.; Müller, B.; Schorge, T.; Karas, M.; Mirus, O.; Sommer, M.S.; Schleiff, E. Defining the core proteome of the chloroplast envelope membranes Front. Plant Sci. 2013; 4, 11. DOI: 10.3389/ fpls.2013.00011

[36] Jung JS, Preston GM, Smith BL, Guggino WB, Agre P. Molecular structure of the water channel through aquaporin CHIP. The hourglass model. J Biol Chem. 1994;269(20):14648-14654.

[37] Fox AR, Maistriaux LC, Chaumont F. Toward understanding of the high number of plant aquaporin isoforms and multiple regulation mechanisms. Plant Sci. 2017;264: 179-187. DOI: 10.1016/j.plantsci. 2017.07.021

[38] Sui H, Han BG, Lee JK, Walian P, Jap BK. Structural basis of water-specific transport through the AQP1 water channel. Nature. 2001;414(6866):872-878. DOI: 10.1038/414872a

[39] Wu B, Steinbronn C, Alsterfjord M, Zeuthen T, Beitz E. Concerted action of two cation filters in the aquaporin water channel. EMBO J. 2009;28(15):2188- 2194. DOI: 10.1038/emboj.2009.182

[40] Guan XG, Su WH, Yi F, et al. NPA motifs play a key role in plasma membrane targeting of aquaporin-4. IUBMB Life. 2010;62(3):222-226. DOI: 10.1002/iub.311

[41] Froger A, Tallur B, Thomas D, Delamarche C. Prediction of functional residues in water channels and related proteins. Protein Sci. 1998;7(6):1458- 1468. DOI: 10.1002/pro.5560070623

[42] Verma RK, Gupta AB, Sankararamakrishnan *R. major* intrinsic protein superfamily: channels with unique structural features and diverse selectivity filters. Methods Enzymol. 2015a;557:485-520. DOI: 10.1016/ bs.mie.2014.12.006

[43] Verma RK, Prabh ND, Sankararamakrishnan R. Intra-helical salt-bridge and helix destabilizing residues within the same helical turn: Role of functionally important loop E half-helix in channel regulation of major intrinsic proteins. Biochim Biophys Acta. 2015b;1848(6):1436-1449. DOI: 10.1016/j.bbamem.2015.03.013

[44] Gomes D, Agasse A, Thiébaud P, Delrot S, Gerós H, Chaumont F. Aquaporins are multifunctional water and solute transporters highly divergent in living organisms. Biochim Biophys Acta. 2009;1788(6):1213-1228. DOI: 10.1016/j. bbamem.2009.03.009

[45] Törnroth-Horsefield S, Wang Y, Hedfalk K, et al. Structural mechanism of plant aquaporin gating. Nature. 2006;439(7077):688-694. DOI: 10.1038/ nature04316

[46] Wang H, Schoebel S, Schmitz F, Dong H, Hedfalk K. Characterization of aquaporin-driven hydrogen peroxide transport. Biochim Biophys Acta Biomembr. 2020;1862(2):183065. DOI: 10.1016/j.bbamem.2019.183065

[47] Data base for Major Intrinsic Proteins, http://mipdb.genouest.org/ e107\_plugins/mipdb\_project/project. php, Accessed: 2020-07-23

[48] El Karkouri K, Gueuné H, Delamarche C. MIPDB: a relational database dedicated to MIP family proteins. Biol Cell. 2005;97(7):535-543. doi:10.1042/BC20040123

[49] Sun H, Li L, Lou Y, Zhao H, Gao Z. Genome-wide identification and characterization of aquaporin gene family in moso bamboo (*Phyllostachys edulis*). Mol Biol Rep. 2016;43(5):437- 450. DOI: 10.1007/s11033-016-3973-3

[50] Yuan D, Li W, Hua Y, King GJ, Xu F, Shi L. Genome-Wide Identification and Characterization of the Aquaporin Gene Family and Transcriptional Responses to Boron Deficiency in *Brassica napus*. Front Plant Sci. 2017;8:1336. DOI: 10.3389/fpls.2017.01336

[51] Hove RM, Ziemann M, Bhave M. Identification and Expression Analysis of the Barley (Hordeum vulgare L.) Aquaporin Gene Family. PLoS One. 2015;10(6):e0128025. DOI: 10.1371/ journal.pone.0128025

[52] Madrid-Espinoza J, Brunel-Saldias N, Guerra FP, Gutiérrez A, Del Pozo A. Genome-Wide Identification and Transcriptional Regulation of Aquaporin Genes in Bread Wheat (Triticum aestivum L.) under Water Stress. Genes (Basel). 2018;9(10):497. DOI: 0.3390/ genes9100497

[53] Zhu YX, Yang L, Liu N, et al. Genome-wide identification, structure characterization, and expression pattern profiling of aquaporin gene family in cucumber. BMC Plant Biol. 2019;19(1):345. DOI: 10.1186/ s12870-019-1953-1

[54] Singh RK, Shweta S, Muthamilarasan M, Rani R, Prasad M. Study on aquaporins of Setaria italica suggests the involvement of SiPIP3;1 and SiSIP1;1 in abiotic stress response. Funct Integr Genomics. 2019;19(4):587- 596. DOI: 10.1007/s10142-018-00653-0

[55] Bari A, Farooq M, Hussain A, Tahir ul Qama Mr, Waseem Abbas M, Mustafa G, Karim A, Ahmed I, Hussain T. Genome-Wide Bioinformatics Analysis of Aquaporin Gene Family in Maize (Zea mays L.). Journal of Phylogenetics & Evolutionary Biology 2018;6:2. DOI: 0.4172/2329-9002.1000197

[56] Venkatesh J, Yu JW, Park SW. Genome-wide analysis and expression profiling of the Solanum tuberosum aquaporins. Plant Physiol Biochem. 2013;73:392-404. DOI: 10.1016/j. plaphy.2013.10.025

[57] Sakurai J, Ishikawa F, Yamaguchi T, Uemura M, Maeshima M. Identification of 33 rice aquaporin genes and analysis of their expression and function. Plant Cell Physiol. 2005;46(9):1568-1577. DOI: 10.1093/pcp/pci172

[58] Azad AK, Ahmed J, Alum MA, et al. Genome-Wide Characterization of Major Intrinsic Proteins in Four Grass Plants and Their Non-Aqua Transport Selectivity Profiles with Comparative Perspective. PLoS One. 2016;11(6):e0157735. DOI: 10.1371/ journal.pone.0157735

[59] Reuscher S, Akiyama M, Mori C, Aoki K, Shibata D, Shiratake K. Genome-wide identification and expression analysis of aquaporins in

**439**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

Vacuolar Membrane of Arabidopsis thaliana. Plant Physiol. 1992;99(2):561-

Characterization of a new vacuolar membrane aquaporin sensitive to mercury at a unique site. Plant Cell. 1996;8(4):587-599. DOI: 10.1105/

[68] Rodrigues MI, Takeda AA, Bravo JP, Maia IG. The Eucalyptus Tonoplast Intrinsic Protein (TIP) Gene Subfamily: Genomic Organization, Structural Features, and Expression Profiles. Front Plant Sci. 2016;7:1810. DOI: 10.3389/ fpls.2016.01810570. doi:10.1104/

[69] Liu Q, Umeda M, Uchimiya H. Isolation and expression analysis of two rice genes encoding the major intrinsic protein. Plant Mol Biol. 1994;26(6):2003-2007. DOI: 10.1007/

[70] Yamamoto YT, Taylor CG, Acedo GN, Cheng CL, Conkling MA. Characterization of cis-acting sequences regulating root-specific gene expression in tobacco. Plant Cell. 1991;3(4):371-382. DOI: 10.1105/

[71] Singh RK, Deshmukh R, Muthamilarasan M, Rani R,

Phosphorylation-Dependent

[73] Yang, I.; Kim, S. Analysis of whole transcriptome sequencing data: Workflow and software. Genom.

Prasad M. Versatile roles of aquaporin in physiological processes and stress tolerance in plants. Plant Physiol Biochem. 2020;149:178-189. DOI: 10.1016/j.plaphy.2020.02.009

[72] Nesverova V, Törnroth-Horsefield S.

Regulation of Mammalian Aquaporins. Cells. 2019;8(2):82. DOI: 10.3390/

DOI: 10.1104/pp.99.2.561

tpc.8.4.587

pp.99.2.561

BF00019511

tpc.3.4.371

cells8020082

[67] Daniels MJ, Chaumont F, Mirkov TE, Chrispeels MJ.

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

tomato. PLoS One. 2013;8(11):e79052. DOI: 10.1371/journal.pone.0079052

[60] Vander Willigen C, Postaire O, Tournaire-Roux C, Boursiac Y, Maurel C. Expression and inhibition of aquaporins in germinating Arabidopsis seeds. Plant Cell Physiol. 2006;47(9):1241-1250.

[61] Soto G, Fox R, Ayub N, Alleva K, Guaimas F, Erijman EJ, Mazzella A, Amodeo G, Muschietti J. TIP5;1 is an aquaporin specifically targeted to

remobilization in Arabidopsis thaliana. Plant J. 2010; 64, 1038-1047 DOI: 10.1111/j.1365-313X.2010.04395

[62] Pérez Di Giorgio JA, Barberini ML, Amodeo G, Muschietti JP. Pollen aquaporins: What are they there for? Plant Signal Behav. 2016;11(9):e1217375. DOI: 10.1080/15592324.2016.1217375

DOI: 10.1093/pcp/pcj094

pollen mitochondria and is probably involved in nitrogen

[63] Sato R, Maeshima M. The ER-localized aquaporin SIP2;1 is involved in pollen germination and pollen tube elongation in

s11103-019-00865-3

Arabidopsis thaliana. Plant Mol Biol. 2019;100(3):335-349. DOI: 10.1007/

[64] Rodrigues O, Reshetnyak G, Grondin A, et al. Aquaporins facilitate hydrogen peroxide entry into guard cells to mediate ABA- and pathogentriggered stomatal closure. Proc Natl Acad Sci U S A. 2017;114(34):9200- 9205. DOI: 10.1073/pnas.1704754114

[65] Ding L, Chaumont F. Are Aquaporins Expressed in Stomatal Complexes Promising Targets to Enhance Stomatal Dynamics?. Front Plant Sci. 2020;11:458. DOI: 10.3389/

[66] Höfte H, Hubbard L, Reizer J, Ludevid D, Herman EM, Chrispeels MJ. Vegetative and Seed-Specific Forms of Tonoplast Intrinsic Protein in the

fpls.2020.00458

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

tomato. PLoS One. 2013;8(11):e79052. DOI: 10.1371/journal.pone.0079052

*Abiotic Stress in Plants*

nature04316

of plant aquaporin gating. Nature. 2006;439(7077):688-694. DOI: 10.1038/ [53] Zhu YX, Yang L, Liu N, et al. Genome-wide identification, structure characterization, and expression pattern profiling of aquaporin gene family in cucumber. BMC Plant Biol. 2019;19(1):345. DOI: 10.1186/

s12870-019-1953-1

[54] Singh RK, Shweta S,

[55] Bari A, Farooq M,

Muthamilarasan M, Rani R, Prasad M. Study on aquaporins of Setaria italica suggests the involvement of SiPIP3;1 and SiSIP1;1 in abiotic stress response. Funct Integr Genomics. 2019;19(4):587- 596. DOI: 10.1007/s10142-018-00653-0

Hussain A, Tahir ul Qama Mr, Waseem

Abbas M, Mustafa G, Karim A, Ahmed I, Hussain T. Genome-Wide Bioinformatics Analysis of Aquaporin Gene Family in Maize (Zea mays L.). Journal of Phylogenetics & Evolutionary Biology 2018;6:2. DOI:

0.4172/2329-9002.1000197

plaphy.2013.10.025

DOI: 10.1093/pcp/pci172

journal.pone.0157735

[56] Venkatesh J, Yu JW, Park SW. Genome-wide analysis and expression profiling of the Solanum tuberosum aquaporins. Plant Physiol Biochem. 2013;73:392-404. DOI: 10.1016/j.

[57] Sakurai J, Ishikawa F, Yamaguchi T, Uemura M, Maeshima M. Identification of 33 rice aquaporin genes and analysis of their expression and function. Plant Cell Physiol. 2005;46(9):1568-1577.

[58] Azad AK, Ahmed J, Alum MA, et al. Genome-Wide Characterization of Major Intrinsic Proteins in Four Grass Plants and Their Non-Aqua Transport Selectivity Profiles with Comparative Perspective. PLoS One. 2016;11(6):e0157735. DOI: 10.1371/

[59] Reuscher S, Akiyama M, Mori C, Aoki K, Shibata D, Shiratake K. Genome-wide identification and expression analysis of aquaporins in

[46] Wang H, Schoebel S, Schmitz F, Dong H, Hedfalk K. Characterization of aquaporin-driven hydrogen peroxide transport. Biochim Biophys Acta Biomembr. 2020;1862(2):183065. DOI:

10.1016/j.bbamem.2019.183065

[47] Data base for Major Intrinsic Proteins, http://mipdb.genouest.org/ e107\_plugins/mipdb\_project/project.

php, Accessed: 2020-07-23

doi:10.1042/BC20040123

10.3389/fpls.2017.01336

journal.pone.0128025

[52] Madrid-Espinoza J, Brunel-Saldias N, Guerra FP,

[48] El Karkouri K, Gueuné H, Delamarche C. MIPDB: a relational database dedicated to MIP family proteins. Biol Cell. 2005;97(7):535-543.

[49] Sun H, Li L, Lou Y, Zhao H, Gao Z. Genome-wide identification and characterization of aquaporin gene family in moso bamboo (*Phyllostachys edulis*). Mol Biol Rep. 2016;43(5):437- 450. DOI: 10.1007/s11033-016-3973-3

[50] Yuan D, Li W, Hua Y, King GJ, Xu F, Shi L. Genome-Wide Identification and Characterization of the Aquaporin Gene Family and Transcriptional Responses to Boron Deficiency in *Brassica napus*. Front Plant Sci. 2017;8:1336. DOI:

[51] Hove RM, Ziemann M, Bhave M. Identification and Expression Analysis of the Barley (Hordeum vulgare L.) Aquaporin Gene Family. PLoS One. 2015;10(6):e0128025. DOI: 10.1371/

Gutiérrez A, Del Pozo A. Genome-Wide Identification and Transcriptional Regulation of Aquaporin Genes in Bread Wheat (Triticum aestivum L.) under Water Stress. Genes (Basel). 2018;9(10):497. DOI: 0.3390/

**438**

genes9100497

[60] Vander Willigen C, Postaire O, Tournaire-Roux C, Boursiac Y, Maurel C. Expression and inhibition of aquaporins in germinating Arabidopsis seeds. Plant Cell Physiol. 2006;47(9):1241-1250. DOI: 10.1093/pcp/pcj094

[61] Soto G, Fox R, Ayub N, Alleva K, Guaimas F, Erijman EJ, Mazzella A, Amodeo G, Muschietti J. TIP5;1 is an aquaporin specifically targeted to pollen mitochondria and is probably involved in nitrogen remobilization in Arabidopsis thaliana. Plant J. 2010; 64, 1038-1047 DOI: 10.1111/j.1365-313X.2010.04395

[62] Pérez Di Giorgio JA, Barberini ML, Amodeo G, Muschietti JP. Pollen aquaporins: What are they there for? Plant Signal Behav. 2016;11(9):e1217375. DOI: 10.1080/15592324.2016.1217375

[63] Sato R, Maeshima M. The ER-localized aquaporin SIP2;1 is involved in pollen germination and pollen tube elongation in Arabidopsis thaliana. Plant Mol Biol. 2019;100(3):335-349. DOI: 10.1007/ s11103-019-00865-3

[64] Rodrigues O, Reshetnyak G, Grondin A, et al. Aquaporins facilitate hydrogen peroxide entry into guard cells to mediate ABA- and pathogentriggered stomatal closure. Proc Natl Acad Sci U S A. 2017;114(34):9200- 9205. DOI: 10.1073/pnas.1704754114

[65] Ding L, Chaumont F. Are Aquaporins Expressed in Stomatal Complexes Promising Targets to Enhance Stomatal Dynamics?. Front Plant Sci. 2020;11:458. DOI: 10.3389/ fpls.2020.00458

[66] Höfte H, Hubbard L, Reizer J, Ludevid D, Herman EM, Chrispeels MJ. Vegetative and Seed-Specific Forms of Tonoplast Intrinsic Protein in the

Vacuolar Membrane of Arabidopsis thaliana. Plant Physiol. 1992;99(2):561- DOI: 10.1104/pp.99.2.561

[67] Daniels MJ, Chaumont F, Mirkov TE, Chrispeels MJ. Characterization of a new vacuolar membrane aquaporin sensitive to mercury at a unique site. Plant Cell. 1996;8(4):587-599. DOI: 10.1105/ tpc.8.4.587

[68] Rodrigues MI, Takeda AA, Bravo JP, Maia IG. The Eucalyptus Tonoplast Intrinsic Protein (TIP) Gene Subfamily: Genomic Organization, Structural Features, and Expression Profiles. Front Plant Sci. 2016;7:1810. DOI: 10.3389/ fpls.2016.01810570. doi:10.1104/ pp.99.2.561

[69] Liu Q, Umeda M, Uchimiya H. Isolation and expression analysis of two rice genes encoding the major intrinsic protein. Plant Mol Biol. 1994;26(6):2003-2007. DOI: 10.1007/ BF00019511

[70] Yamamoto YT, Taylor CG, Acedo GN, Cheng CL, Conkling MA. Characterization of cis-acting sequences regulating root-specific gene expression in tobacco. Plant Cell. 1991;3(4):371-382. DOI: 10.1105/ tpc.3.4.371

[71] Singh RK, Deshmukh R, Muthamilarasan M, Rani R, Prasad M. Versatile roles of aquaporin in physiological processes and stress tolerance in plants. Plant Physiol Biochem. 2020;149:178-189. DOI: 10.1016/j.plaphy.2020.02.009

[72] Nesverova V, Törnroth-Horsefield S. Phosphorylation-Dependent Regulation of Mammalian Aquaporins. Cells. 2019;8(2):82. DOI: 10.3390/ cells8020082

[73] Yang, I.; Kim, S. Analysis of whole transcriptome sequencing data: Workflow and software. Genom.

Inform.2015, 13, 119-125. DOI: 10.5808/ GI.2015.13.4.119

[74] Song L, Nguyen N, Deshmukh RK, et al. Soybean TIP Gene Family Analysis and Characterization of GmTIP1;5 and GmTIP2;5 Water Transport Activity. Front Plant Sci. 2016;7:1564. DOI: 10.3389/fpls.2016.01564

[75] Zhang DY, Kumar M, Xu L, et al. Genome-wide identification of Major Intrinsic Proteins in *Glycine soja* and characterization of GmTIP2;1 function under salt and water stress Sci Rep. 2017;7(1):4106. DOI: 10.1038/ s41598-017-04253-z

[76] Atkinson NJ, Urwin PE. The interaction of plant biotic and abiotic stresses: from genes to the field. J. Exp. Bot. 2014;63, 3523-43. DOI: 10.1093/jxb/ ers100

[77] Osakabe Y, Osakabe K, Shinozaki K, Tran LS. Response of plants to water stress. Front. Plant Sci. 2014; DOI: 10.3389/fpls.2014.00086

[78] Golldack D, Li C, Mohan H, Probst N. Tolerance to drought and salt stress in plants, unraveling the signaling networks. Front. Plant Sci. 2014; DOI: 10.3389/fpls.2014.00151.

[79] Merlaen B, De Keyser E, Ding L, Leroux O, Chaumont F, Van Labeke MC. Physiological responses and aquaporin expression upon drought and osmotic stress in a conservative vs prodigal Fragaria x ananassa cultivar. Plant Physiol Biochem. 2019;145:95-106. DOI: 10.1016/j.plaphy.2019.10.030

[80] Qiao Y, Ren J, Yin L, Liu Y, Deng X, Liu P, Wang S. Exogenous melatonin alleviates PEG-induced short-term water deficiency in maize by increasing hydraulic conductance. BMC Plant Biol. 2020;14,20(1):218. DOI: 10.1186/ s12870-020-02432-1

[81] Cominelli E, Conti L, Tonelli C, Galbiati M. Challenges and perspectives to improve crop drought and salinity tolerance. N Biotechnol. 2013;30(4):355- 361. DOI: 10.1016/j.nbt.2012.11.001

[82] Singh B, Kukreja S, Goutam U. Milestones achieved in response to drought stress through reverse genetic approaches. F1000Res. 2018;7:1311. DOI: 10.12688/ f1000research.15606.1

[83] Fahad S, Bajwa AA, Nazir U, Anjum SA, Farooq A, Zohaib A, Sadia S, NasimW, Adkins S, Saud S, Ihsan MZ, Alharby H,Wu C,Wang D, Huang J. Crop production under drought and heat stress: Plant responses and Management Options. Front Plant Sci. 2017; 8:1147. DOI: 10.3389/ fpls.2017.01147

[84] Dolferus R. To grow or not to grow: a stressful decision for plants. Plant Sci. 2014;229:247-261. DOI: 10.1016/j. plantsci.2014.10.002

[85] Peng Y, Lin W, Cai W, Arora R. Overexpression of a Panax ginseng tonoplast aquaporin alters salt tolerance, drought tolerance and cold acclimation ability in transgenic Arabidopsis plants. Planta. 2007;226(3):729-740. DOI: 10.1007/s00425-007-0520-4

[86] Smart LB, Moskal WA, Cameron KD, Bennett AB. MIP genes are down-regulated under drought stress in *Nicotiana glauca*. Plant Cell Physiol. 2001; 42(7):686-93. DOI: 10.1093/pcp/pce085

[87] Alexandersson E, Fraysse L, Sjo¨ vall-Larsen S, Gustavsson S, Fellert M, Karlsson M, et al. Whole gene family expression and drought stress regulation of aquaporins. Plant Mol Biol. 2005; 59(3):469-84. DOI: 10.1007/ s11103-005-0352-1

[88] Feng ZJ, Xu SC, Liu N, Zhang GW, Hu QZ, Xu ZS, et al. Identification of the AQP members involved in abiotic stress responses from Arabidopsis. Gene.

**441**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

[96] Kamran M, Parveen A, Ahmar S, et al. An Overview of Hazardous Impacts of Soil Salinity in Crops, Tolerance Mechanisms, and Amelioration through Selenium Supplementation. Int J Mol Sci. 2019;21(1):148. DOI: 10.3390/

Luu DT, Sorieul M, van den Dries N, Maurel C. Early effects of salinity on water transport in Arabidopsis roots. Molecular and cellular features of aquaporin expression. Plant Physiol. 2005;139(2):790-805. DOI: 10.1104/

[98] Afzal Z, Howton TC, Sun Y, Mukhtar MS. The Roles of

Aquaporins in Plant Stress Responses. J Dev Biol. 2016;4(1):9. DOI: 10.3390/

[99] Li DD, Tai FJ, Zhang ZT, et al. A cotton gene encodes a tonoplast aquaporin that is involved in cell tolerance to cold stress. Gene. 2009;438(1-2):26-32. DOI: 10.1016/j.

ijms21010148

pp.105.065029

jdb4010009

gene.2009.02.023

[100] Fahad S, Hussain S, Matloob A, Khan FA, Khaliq A, Saud S, Hassan S, Shan D, Khan F, Ullah N, Faiq M, Khan MR, Tareen AK, Khan A, Ullah A, Ullah N, Huang J. Phytohormones and plant responses to salinity stress: A review. Plant Growth Regul. 2014; 75(2):391-404. DOI: 10.1007/s10725-014-0013-y

[101] Yoshida T, Christmann A, Yamaguchi-Shinozaki K, Grill E, Fernie AR. Revisiting the Basal Role of ABA - Roles Outside of Stress. Trends Plant Sci. 2019;24(7):625-635. DOI: 10.1016/j.tplants.2019.04.008

[102] Cai S, Chen G, Wang Y, et al. Evolutionary Conservation of ABA Signaling for Stomatal Closure. Plant Physiol. 2017;174(2):732-747. DOI:

10.1104/pp.16.01848

[97] Boursiac Y, Chen S,

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

Gajek K, Szarejko I. Drought stress and re-watering affect the abundance of TIP aquaporin transcripts in barley. PLoS One. 2019;14(12):e0226423. DOI:

Perlikowski D, Gondek K, Kosmala A. Abiotic stresses influence the transcript abundance of PIP and TIP aquaporins in Festuca species. J Appl Genet. 2017; 58(4):421-435. DOI: 10.1007/

[91] Miniussi M, Del Terra L, Savi T, Pallavicini A, Nardini A. Aquaporins in *Coffea arabica* L.: Identification, expression, and impacts on plant water relations and hydraulics. Plant Physiol Biochem. 2015;95:92-102. DOI:

10.1016/j.plaphy.2015.07.024

[92] Zupin M, Sedlar A, Kidrič M, Meglič V. Drought-induced expression of aquaporin genes in leaves of two common bean cultivars differing in tolerance to drought stress. J Plant Res. 2017;130(4):735-745. DOI: 10.1007/

[93] Choudhury, F.K.; Rivero, R.M.; Blumwald, E.; Mittler, R. Reactive oxygen species, abiotic stress and stress combination. Plant J. 2017, 90, 856-867.

2018; 10;646:64-73. DOI: 10.1016/j.

[89] Kurowska MM, Wiecha K,

10.1371/journal.pone.0226423

[90] Pawłowicz I, Rapacz M,

s13353-017-0403-8

s10265-017-0920-x

DOI: 10.1111/tpj.13299

PMID:24060746

2011;43:539-548.

[94] Bienert GP, Chaumont F.

Aquaporin-facilitated transmembrane diffusion of hydrogen peroxide. Biochim Biophys Acta. 2014; 1840(5):1596-604. DOI: 10.1016/j.bbagen.2013.09.017

[95] Nabati J., Kafi M., Nezami A.,

Mehrjerdi M.Z. Effect of salinity on biomass production and activities of some key enzymatic antioxidants in Kochia (*Kochia scoparia*) Pak. J. Bot.

Moghaddam P.R., Ali M.,

gene.2017.12.048

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

2018; 10;646:64-73. DOI: 10.1016/j. gene.2017.12.048

*Abiotic Stress in Plants*

GI.2015.13.4.119

10.3389/fpls.2016.01564

s41598-017-04253-z

10.3389/fpls.2014.00086

10.3389/fpls.2014.00151.

10.1016/j.plaphy.2019.10.030

s12870-020-02432-1

[78] Golldack D, Li C, Mohan H, Probst N. Tolerance to drought and salt stress in plants, unraveling the signaling networks. Front. Plant Sci. 2014; DOI:

[79] Merlaen B, De Keyser E, Ding L, Leroux O, Chaumont F, Van Labeke MC. Physiological responses and aquaporin expression upon drought and osmotic stress in a conservative vs prodigal Fragaria x ananassa cultivar. Plant Physiol Biochem. 2019;145:95-106. DOI:

[80] Qiao Y, Ren J, Yin L, Liu Y, Deng X, Liu P, Wang S. Exogenous melatonin alleviates PEG-induced short-term water deficiency in maize by increasing hydraulic conductance. BMC Plant Biol. 2020;14,20(1):218. DOI: 10.1186/

[81] Cominelli E, Conti L, Tonelli C, Galbiati M. Challenges and perspectives

ers100

Inform.2015, 13, 119-125. DOI: 10.5808/

to improve crop drought and salinity tolerance. N Biotechnol. 2013;30(4):355- 361. DOI: 10.1016/j.nbt.2012.11.001

[82] Singh B, Kukreja S, Goutam U. Milestones achieved in response to drought stress through reverse genetic approaches. F1000Res. 2018;7:1311. DOI: 10.12688/ f1000research.15606.1

[83] Fahad S, Bajwa AA, Nazir U, Anjum SA, Farooq A, Zohaib A, Sadia S, NasimW, Adkins S, Saud S, Ihsan MZ, Alharby H,Wu C,Wang D, Huang J. Crop production under drought and heat stress: Plant responses and Management Options. Front Plant Sci. 2017; 8:1147. DOI: 10.3389/

[84] Dolferus R. To grow or not to grow: a stressful decision for plants. Plant Sci. 2014;229:247-261. DOI: 10.1016/j.

[85] Peng Y, Lin W, Cai W, Arora R. Overexpression of a Panax ginseng tonoplast aquaporin alters salt tolerance, drought tolerance and cold acclimation ability in transgenic Arabidopsis plants. Planta. 2007;226(3):729-740. DOI: 10.1007/s00425-007-0520-4

[86] Smart LB, Moskal WA,

10.1093/pcp/pce085

s11103-005-0352-1

Cameron KD, Bennett AB. MIP genes are down-regulated under drought stress in *Nicotiana glauca*. Plant Cell Physiol. 2001; 42(7):686-93. DOI:

[87] Alexandersson E, Fraysse L, Sjo¨ vall-Larsen S, Gustavsson S, Fellert M, Karlsson M, et al. Whole gene family expression and drought stress regulation of aquaporins. Plant Mol Biol. 2005; 59(3):469-84. DOI: 10.1007/

[88] Feng ZJ, Xu SC, Liu N, Zhang GW, Hu QZ, Xu ZS, et al. Identification of the AQP members involved in abiotic stress responses from Arabidopsis. Gene.

fpls.2017.01147

plantsci.2014.10.002

[74] Song L, Nguyen N, Deshmukh RK, et al. Soybean TIP Gene Family Analysis and Characterization of GmTIP1;5 and GmTIP2;5 Water Transport Activity. Front Plant Sci. 2016;7:1564. DOI:

[75] Zhang DY, Kumar M, Xu L, et al. Genome-wide identification of Major Intrinsic Proteins in *Glycine soja* and characterization of GmTIP2;1 function under salt and water stress Sci Rep. 2017;7(1):4106. DOI: 10.1038/

[76] Atkinson NJ, Urwin PE. The interaction of plant biotic and abiotic stresses: from genes to the field. J. Exp. Bot. 2014;63, 3523-43. DOI: 10.1093/jxb/

[77] Osakabe Y, Osakabe K, Shinozaki K, Tran LS. Response of plants to water stress. Front. Plant Sci. 2014; DOI:

**440**

[89] Kurowska MM, Wiecha K, Gajek K, Szarejko I. Drought stress and re-watering affect the abundance of TIP aquaporin transcripts in barley. PLoS One. 2019;14(12):e0226423. DOI: 10.1371/journal.pone.0226423

[90] Pawłowicz I, Rapacz M, Perlikowski D, Gondek K, Kosmala A. Abiotic stresses influence the transcript abundance of PIP and TIP aquaporins in Festuca species. J Appl Genet. 2017; 58(4):421-435. DOI: 10.1007/ s13353-017-0403-8

[91] Miniussi M, Del Terra L, Savi T, Pallavicini A, Nardini A. Aquaporins in *Coffea arabica* L.: Identification, expression, and impacts on plant water relations and hydraulics. Plant Physiol Biochem. 2015;95:92-102. DOI: 10.1016/j.plaphy.2015.07.024

[92] Zupin M, Sedlar A, Kidrič M, Meglič V. Drought-induced expression of aquaporin genes in leaves of two common bean cultivars differing in tolerance to drought stress. J Plant Res. 2017;130(4):735-745. DOI: 10.1007/ s10265-017-0920-x

[93] Choudhury, F.K.; Rivero, R.M.; Blumwald, E.; Mittler, R. Reactive oxygen species, abiotic stress and stress combination. Plant J. 2017, 90, 856-867. DOI: 10.1111/tpj.13299

[94] Bienert GP, Chaumont F. Aquaporin-facilitated transmembrane diffusion of hydrogen peroxide. Biochim Biophys Acta. 2014; 1840(5):1596-604. DOI: 10.1016/j.bbagen.2013.09.017 PMID:24060746

[95] Nabati J., Kafi M., Nezami A., Moghaddam P.R., Ali M., Mehrjerdi M.Z. Effect of salinity on biomass production and activities of some key enzymatic antioxidants in Kochia (*Kochia scoparia*) Pak. J. Bot. 2011;43:539-548.

[96] Kamran M, Parveen A, Ahmar S, et al. An Overview of Hazardous Impacts of Soil Salinity in Crops, Tolerance Mechanisms, and Amelioration through Selenium Supplementation. Int J Mol Sci. 2019;21(1):148. DOI: 10.3390/ ijms21010148

[97] Boursiac Y, Chen S,

Luu DT, Sorieul M, van den Dries N, Maurel C. Early effects of salinity on water transport in Arabidopsis roots. Molecular and cellular features of aquaporin expression. Plant Physiol. 2005;139(2):790-805. DOI: 10.1104/ pp.105.065029

[98] Afzal Z, Howton TC, Sun Y, Mukhtar MS. The Roles of Aquaporins in Plant Stress Responses. J Dev Biol. 2016;4(1):9. DOI: 10.3390/ jdb4010009

[99] Li DD, Tai FJ, Zhang ZT, et al. A cotton gene encodes a tonoplast aquaporin that is involved in cell tolerance to cold stress. Gene. 2009;438(1-2):26-32. DOI: 10.1016/j. gene.2009.02.023

[100] Fahad S, Hussain S, Matloob A, Khan FA, Khaliq A, Saud S, Hassan S, Shan D, Khan F, Ullah N, Faiq M, Khan MR, Tareen AK, Khan A, Ullah A, Ullah N, Huang J. Phytohormones and plant responses to salinity stress: A review. Plant Growth Regul. 2014; 75(2):391-404. DOI: 10.1007/s10725-014-0013-y

[101] Yoshida T, Christmann A, Yamaguchi-Shinozaki K, Grill E, Fernie AR. Revisiting the Basal Role of ABA - Roles Outside of Stress. Trends Plant Sci. 2019;24(7):625-635. DOI: 10.1016/j.tplants.2019.04.008

[102] Cai S, Chen G, Wang Y, et al. Evolutionary Conservation of ABA Signaling for Stomatal Closure. Plant Physiol. 2017;174(2):732-747. DOI: 10.1104/pp.16.01848

[103] Jang G, Yoon Y, Choi YD. Crosstalk with Jasmonic Acid Integrates Multiple Responses in Plant Development. Int J Mol Sci. 2020;21(1):305. DOI: 10.3390/ ijms21010305

[104] Yang J, Duan G, Li C, et al. The Crosstalks Between Jasmonic Acid and Other Plant Hormone Signaling Highlight the Involvement of Jasmonic Acid as a Core Component in Plant Response to Biotic and Abiotic Stresses. Front Plant Sci. 2019;10:1349. DOI: 10.3389/fpls.2019.01349

[105] Colebrook EH, Thomas SG, Phillips AL, Hedden P. The role of gibberellin signalling in plant responses to abiotic stress. J Exp Biol. 2014;217: 67-75. DOI: 10.1242/jeb.089938.

[106] Lubovská Z, Dobrá J, Storchová H, Wilhelmová N, Vanková R. Cytokinin oxidase/dehydrogenase overexpression modifies antioxidant defense against heat, drought and their combination in Nicotiana tabacum plants. J Plant Physiol. 2014;171(17):1625-1633. DOI: 10.1016/j.jplph.2014.06.021

[107] Ullah A, Manghwar H, Shaban M, et al. Phytohormones enhanced drought tolerance in plants: a coping strategy. Environ Sci Pollut Res Int. 2018;25(33):33103-33118. DOI: 10.1007/ s11356-018-3364-5

[108] Lin W, Peng Y, Li G, et al. Isolation and functional characterization of PgTIP1, a hormone-autotrophic cellsspecific tonoplast aquaporin in ginseng. J Exp Bot. 2007;58(5):947-956. DOI: 10.1093/jxb/erl255

[109] Kurowska MM,

Daszkowska-Golec A, Gajecka M, Kościelniak P, Bierza W, Szarejko I. Methyl Jasmonate Affects Photosynthesis Efficiency, Expression of HvTIP Genes and Nitrogen Homeostasis in Barley. Int J Mol Sci. 2020;21(12):4335. DOI: 10.3390/ijms21124335

[110] Ligaba A, Katsuhara M, Shibasaka M, Djira G. Abiotic stresses modulate expression of major intrinsic proteins in barley (Hordeum vulgare). C R Biol. 2011; 334(2):127-139. DOI: 10.1016/j.crvi.2010.11.005 PMID: 21333943

[111] Ariani A, Francini A, Andreucci A, Sebastiani L. Overexpression of AQUA1 in Populus alba Villafranca clone increases relative growth rate and water use efficiency, under Zn excess condition. Plant Cell Rep. 2016;35(2):289-301. DOI: 10.1007/ s00299-015-1883-9

[112] Sade N, Vinocur BJ, Diber A, et al. Improving plant stress tolerance and yield production: is the tonoplast aquaporin SlTIP2;2 a key to isohydric to anisohydric conversion?. New Phytol. 2009;181(3):651-661. DOI: 10.1111/j.1469-8137.2008.02689.x

[113] Xin S, Yu G, Sun L, Qiang X, Xu N, Cheng X. Expression of tomato SlTIP2;2 enhances the tolerance to salt stress in the transgenic Arabidopsis and interacts with target proteins. J Plant Res. 2014;127(6):695-708. DOI: 10.1007/ s10265-014-0658-7

[114] An, J.; Hu, Z.; Che, B.; Chen, H.; Yu, B.; Cai, W. Heterologous expression of Panax ginseng PgTIP1 confers enhanced salt tolerance of soybean cotyledon hairy roots, composite, and whole plants. Front. Plant Sci., 2017, 8, 1232. DOI: 10.3389/ fpls.2017.01232

[115] Martins, C.P.S.; Neves, D.M.; Cidade, L.C.; Mendes, A.F.S.; Silva,D.C.; Almeida, A.A. F.; Coelho-Filho, M.A.; Gesteira, A.S.; Soares-Filho, W.S.; Costa, M.G.C. Expression of the citrus CsTIP2;1 gene improves tobacco plant growth, antioxidant capacity and physiological adaptation under stress conditions. Planta, 2017, 245(5), 951-963. DOI: 10.1007/ s00425-017-2653-4

**443**

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance*

*DOI: http://dx.doi.org/10.5772/intechopen.94165*

[116] Khan, K.; Agarwal, P.; Shanware, A.; Sane, V.A. Heterologous expression of two jatropha aquaporins imparts drought and salt tolerance and improves seed viability in transgenic Arabidopsis thaliana. PLoS One, 2015, 10(6), e0128866. DOI: 10.1371/journal.

[117] Pang, Y.; Li, L.; Ren, F.; Lu, P.; Wei, P.; Cai, J.; Xin, L.; Zhang, J.; Chen, J.; Wang, X. Overexpression of the tonoplast aquaporin At-TIP5;1 conferred tolerance to boron toxicity in Arabidopsis. J. Genet. Genomics., 2010, 37(6), 389-397. DOI: 10.1016/

[118] Ma S, Quist TM, Ulanov A, Joly R, Bohnert HJ. Loss of TIP1;1 aquaporin in Arabidopsis leads to cell and plant death. Plant J. 2004;40(6):845-859. DOI: 10.1111/j.1365-313X.2004.02265.x

[119] Schüssler MD, Alexandersson E, Bienert GP, et al. The effects of the loss of TIP1;1 and TIP1;2 aquaporins

[120] Feng, Z.J.; Xu, S.C.; Liu, N.; Zhang, G.W.; Hu, Q.Z.; Xu, Z.S.; Gong, Y.M. Identification of the AQP members involved in abiotic stress responses from Arabidopsis. Gene, 2018, 646, 64-73 DOI: 10.1016/j.gene.2017.12.048

Plant J. 2008;56(5):756-767. DOI: 10.1111/j.1365-313X.2008.03632.x

S1673-8527(09)60057-6

in Arabidopsis thaliana.

pone.0128866

*TIP Aquaporins in Plants: Role in Abiotic Stress Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94165*

[116] Khan, K.; Agarwal, P.; Shanware, A.; Sane, V.A. Heterologous expression of two jatropha aquaporins imparts drought and salt tolerance and improves seed viability in transgenic Arabidopsis thaliana. PLoS One, 2015, 10(6), e0128866. DOI: 10.1371/journal. pone.0128866

*Abiotic Stress in Plants*

ijms21010305

[103] Jang G, Yoon Y, Choi YD. Crosstalk with Jasmonic Acid Integrates Multiple Responses in Plant Development. Int J Mol Sci. 2020;21(1):305. DOI: 10.3390/

[110] Ligaba A, Katsuhara M,

[111] Ariani A, Francini A, Andreucci A, Sebastiani L. Overexpression of AQUA1 in Populus alba Villafranca clone increases relative growth rate and water use efficiency, under Zn excess condition. Plant Cell Rep. 2016;35(2):289-301. DOI: 10.1007/

s00299-015-1883-9

s10265-014-0658-7

fpls.2017.01232

s00425-017-2653-4

[112] Sade N, Vinocur BJ, Diber A, et al. Improving plant stress tolerance and yield production: is the tonoplast aquaporin SlTIP2;2 a key to isohydric to anisohydric conversion?. New Phytol. 2009;181(3):651-661. DOI: 10.1111/j.1469-8137.2008.02689.x

[113] Xin S, Yu G, Sun L, Qiang X, Xu N, Cheng X. Expression of tomato SlTIP2;2 enhances the tolerance to salt stress in the transgenic Arabidopsis and interacts with target proteins. J Plant Res. 2014;127(6):695-708. DOI: 10.1007/

[114] An, J.; Hu, Z.; Che, B.; Chen, H.; Yu, B.; Cai, W. Heterologous expression of Panax ginseng PgTIP1 confers enhanced salt tolerance of soybean cotyledon hairy roots, composite, and whole plants. Front. Plant Sci., 2017, 8, 1232. DOI: 10.3389/

[115] Martins, C.P.S.; Neves, D.M.; Cidade, L.C.; Mendes, A.F.S.; Silva,D.C.;

Almeida, A.A. F.; Coelho-Filho, M.A.; Gesteira, A.S.; Soares-Filho, W.S.; Costa, M.G.C. Expression of the citrus CsTIP2;1 gene improves tobacco plant growth, antioxidant capacity and physiological adaptation under stress conditions. Planta, 2017, 245(5), 951-963. DOI: 10.1007/

21333943

Shibasaka M, Djira G. Abiotic stresses modulate expression of major intrinsic proteins in barley (Hordeum vulgare). C R Biol. 2011; 334(2):127-139. DOI: 10.1016/j.crvi.2010.11.005 PMID:

[104] Yang J, Duan G, Li C, et al. The Crosstalks Between Jasmonic Acid and Other Plant Hormone Signaling Highlight the Involvement of Jasmonic Acid as a Core Component in Plant Response to Biotic and Abiotic Stresses. Front Plant Sci. 2019;10:1349. DOI:

10.3389/fpls.2019.01349

10.1016/j.jplph.2014.06.021

tolerance in plants: a coping strategy. Environ Sci Pollut Res Int. 2018;25(33):33103-33118. DOI: 10.1007/

s11356-018-3364-5

10.1093/jxb/erl255

[109] Kurowska MM,

10.3390/ijms21124335

Daszkowska-Golec A, Gajecka M, Kościelniak P, Bierza W, Szarejko I. Methyl Jasmonate Affects Photosynthesis Efficiency, Expression of HvTIP Genes and Nitrogen Homeostasis in Barley. Int J Mol Sci. 2020;21(12):4335. DOI:

[105] Colebrook EH, Thomas SG, Phillips AL, Hedden P. The role of gibberellin signalling in plant responses to abiotic stress. J Exp Biol. 2014;217: 67-75. DOI: 10.1242/jeb.089938.

[106] Lubovská Z, Dobrá J, Storchová H, Wilhelmová N, Vanková R. Cytokinin oxidase/dehydrogenase overexpression modifies antioxidant defense against heat, drought and their combination in Nicotiana tabacum plants. J Plant Physiol. 2014;171(17):1625-1633. DOI:

[107] Ullah A, Manghwar H, Shaban M, et al. Phytohormones enhanced drought

[108] Lin W, Peng Y, Li G, et al. Isolation and functional characterization of PgTIP1, a hormone-autotrophic cellsspecific tonoplast aquaporin in ginseng. J Exp Bot. 2007;58(5):947-956. DOI:

**442**

[117] Pang, Y.; Li, L.; Ren, F.; Lu, P.; Wei, P.; Cai, J.; Xin, L.; Zhang, J.; Chen, J.; Wang, X. Overexpression of the tonoplast aquaporin At-TIP5;1 conferred tolerance to boron toxicity in Arabidopsis. J. Genet. Genomics., 2010, 37(6), 389-397. DOI: 10.1016/ S1673-8527(09)60057-6

[118] Ma S, Quist TM, Ulanov A, Joly R, Bohnert HJ. Loss of TIP1;1 aquaporin in Arabidopsis leads to cell and plant death. Plant J. 2004;40(6):845-859. DOI: 10.1111/j.1365-313X.2004.02265.x

[119] Schüssler MD, Alexandersson E, Bienert GP, et al. The effects of the loss of TIP1;1 and TIP1;2 aquaporins in Arabidopsis thaliana. Plant J. 2008;56(5):756-767. DOI: 10.1111/j.1365-313X.2008.03632.x

[120] Feng, Z.J.; Xu, S.C.; Liu, N.; Zhang, G.W.; Hu, Q.Z.; Xu, Z.S.; Gong, Y.M. Identification of the AQP members involved in abiotic stress responses from Arabidopsis. Gene, 2018, 646, 64-73 DOI: 10.1016/j.gene.2017.12.048

**445**

**Chapter 21**

*Suphia Rafique*

consequently affects crop productivity.

**Keywords:** maize, drought, nitrogen, source-sink relationship

**Abstract**

**1. Introduction**

Drought Responses on

Source-Sink Relationships

Physiological Attributes of *Zea* 

*mays* in Relation to Nitrogen and

Maize is the staple food crop and essential for world food security. Maize plants' water requirement is high for proper growth and development at vegetative stage and grain formation at reproductive stage. Drought is the major abiotic stress that affects almost all the growth stages of maize crop and it has a strong impact on all the physiological process of maize plants. Similarly, N metabolism is of central importance during drought stress. Nitrogen (N) is one of the macronutrients; it is a major requirement for crop growth and grain yield of maize. Therefore, nitrogen and water separately or in combination are the two most critical factors in maize production. Drought modifies source-sink relations and weakens the source and sink strength, which disturbs plant's growth, plant's adaptation to stress, and

Plants are nonmotile, and they protect themselves from various biotic and abiotic stresses through structural and metabolic changes like altering leaf orientation, transpirational cooling, or adjustment of membrane lipid compositions [1]. Maize is a staple food crop that grows under optimal environmental conditions and throughout their life span is often exposed to various abiotic stresses [2] like either combined stresses like drought and heat, drought and salinity, drought and low-N stresses, or singly drought. In combined stress, plants show a wide range of responses that brings changes in growth and morphology, and the plants' ability to withstand these stresses greatly varies from species to species [3]. However, drought along with high frequencies, longer durations, and large ranges occur almost yearly across the globe, even in wet and humid regions [4, 5]. Water deficit is the most detrimental environmental stress that adversely affects the maize productivity. The effect of drought is manifested at cellular, physiological biochemical, metabolic, proteins, and gene levels. Water is an essential component for plants; it maintains cell turgidity and keeps the structure intact (by keeping the pressure inside cells high) so that they are fully expanded (i.e., turgid). In wilted plants, when turgor pressure approaches to zero, the cell membranes collapses, damage and becomes

#### **Chapter 21**
