**6. Quality**

Over two billion people worldwide are malnourished as a result of nutritional stress. Genetically modified (GM) crops have the potential to fulfil the worldwide


#### *Genetically Modified Crops and Their Impact on New Era of Agriculture DOI: http://dx.doi.org/10.5772/intechopen.105937*


#### **Table 5.**

*Genes responsible for abiotic stress tolerance in various crops.*

need for high-quality food through genetic engineering by doing more than merely boosting nutritional quality.

#### **6.1 Golden rice**

The carotenoid biosynthesis pathway in plants is a multistep process and is accomplished via four desaturation reactions to produce all-trans-lycopene from 15-cis-phytoene by phytoene desaturase (*PDS)*, ζ-carotene isomerase (*Z-ISO*), ζ-carotene desaturase (*ZDS*), and carotenoid isomerase (*CRTISO*) whereas, a single enzyme encoded by the crtI gene accomplishes all the four reaction steps to produce lycopene in bacteria [128, 129]. In the carotenoid pathway, lycopene is an important branch point because it functions as the substrate for two competing enzymes, lycopene β-cyclase (*LYCB*), and lycopene ε-cyclase (*LYCE)*. Lycopene is converted into γ-carotene, which is rapidly converted into β-carotene (has pro-vitamin A activity) by *LYCB* in a single pathway. The bacterial gene *crtY* encodes *LYCB* to produce β-carotene. Alternatively, with *LYCE* lycopene generates δ-carotene (which has no pro-vitamin A activity) [130–132].

About 60–80% by weight of total seed protein in rice is glutelin, and about 20–30% are prolamins which are the prime choice of promoter sequences responsible for expression of carotenoids in rice endosperm [133]. Six promoters of rice glutelin genes *(GluA-1, GluA-2, GluA-3, GluB-3, GluB-5, and GluC*) were isolated and examined in rice and listed in tables with their site of expression (**Table 6**) [134]. Newly reported promoters like *PROLAM26 RAL2 (LOC\_Os07g11330), RAL4 (LOC\_ Os07g11380), and CAPIP (LOC\_Os06g33640*) could be useful in the future [135].

A combination of Daffodils *phytoene synthase* (psy) gene, *lycopene-cyclase* (lcy) gene and *crtI* gene from bacteria *(Erwinia uredovora*) PDS (phytoene desaturase) are used to generate japonica rice with ß-carotene expression (mentioned here as GR1) [136, 137]. Gtu-1 promoter was used for psy, lcy and a constitutive CaMV35S promoter with a plastidspecific transit peptide (TP) used for the expression of *CrtI* gene [138, 139] in GR1, Under Gtu-1 promoter, an alliance of maize phytoene synthase (*Zmpsy*) gene with bacterial *crtI* has been expressed in rice to develop an improved golden rice variety (mentioned here as GR2) [140]. The synthetic gene constructions of two carotenoid biosynthetic genes, *psy* from Capsicum (*Capsicum annuum*) and *crtI* from Pantoea, were also reported for golden rice development. To create the PIC (Psy-IRES-CrtI) and PAC (Psy-2A-CrtI) constructions, coupling of two genes using either the synthetic codon-optimised 2A sequence (from foot-and-mouth disease virus) or the IRES sequence (the internal ribosome entry site) were utilised (**Figure 1**) [141, 142].

ZFN and TALENs mediated gene mutation of *IPK1* gene of the rice *OsBADH2* gene respectively encoded inositol1,3,4,5,6-penta-kisphosphate 2-kinase, resulted in both herbicide tolerance and reduction of phytate in developing seeds and production

*Genetically Modified Crops and Their Impact on New Era of Agriculture DOI: http://dx.doi.org/10.5772/intechopen.105937*


#### **Table 6.**

*List of promoters and expressing region involved in Golden rice.*

#### **Figure 1.** *A simplified version of ß-carotene expression in golden rice.*

of fragrant rice by increased synthesis of fragrance compound 2-acetyl-1-pyrroline (2AP) [143]. In monocot plants, the *k1C* gene in sorghum plant was targeted using CRISPR for gene disruption at the N-terminal ER signal peptide region, resulting in greater Lysine content and improved protein digestibility [144]. Naim et al. deployed CRISPR-Cas to target the PDS, Phytoene desaturase expressing gene in Cavendish banana (*Musa acuminata*) for gene knockout to target the Albinism phenotype. CRISPR-Cas9 was used to disrupt rice genes critical for defining amylose concentration, fine structure of amylopectin, and physiochemical characteristics of starch, resulting in a larger proportion of long chains in amylopectin. The GBSS gene, which encodes Granule-bound starch synthase and is responsible for amylose production in the Potato plant, was targeted using CRISPR-Cas for Gene knockouts, resulting in a product with elevated amylopectin content [145].

In *Camelina sativa* the *FAD2* gene, which is important for fatty acid production, was targeted using CRISPR-Cas9 for gene deletion to enhance seed Oleic acid content. In tomato, CRISPR-Cas9 was used to target *SlAGL6*, a transcription factor that plays important roles in flower meristem and floral organ development, for gene deletion, resulting in a parthenocarpic phenotype [146]. The *CAO1* and *LAZY1* genes, which are responsible for synthesis of chlorophyll b from chlorophyll a and regulating shoot gravitropism, were disrupted using CRISPR-Cas to target the faulty synthesis of chlorophyll b and tiller spreading phenotypes, respectively (**Table 7**) [147].


#### **Table 7.**

*List of different genes transformed for quality character in different crops.*
