**7. Function of ncRNA concerning prospective areas of utilization of ncRNA in plant breeding**

A major portion of eukaryotic transcriptomes comprised of ncRNAs, which were considered "junk" till the recent past, actually carry out significant roles in almost all the biological processes via regulation of gene expression at transcriptional and posttranslational stages. Thus, these diverse ncRNA plays a vital role in plant development and environmental responses, which can be well employed in applied plant breeding and crop improvement. In drosophila, 30 UTR of mRNA is required for oogenesis [74]. Many studies also report the significant role of 30 UTR mRNAs in transmitting information required for cell proliferation as well as cell differentiation during cancers [75].

#### **7.1 Abiotic and biotic stress response**

These ncRNAs have considerable responsibility for plant stress response as well as plant immunity that can be better utilized in plant breeding for crop improvements. Jha *et al.* [76] have highlighted the differential expressions of ncRNAs in plants when they are ubjected to unfavorable conditions. Zhang *et al*. [68] identified that 17 microRNA were downregulated and 16 upregulated when subjected to drought stress at the seedling stage. A similar study was carried out on maize screened for drought conditions by Liu *et al.* [77]. When drought condition was induced, eight and seven miRNAs were enhanced in leaves and roots, respectively, whereas 13 and seven miR-NAs were found to be suppressed in leaves and roots, respectively. In addition, a single miRNA can be upregulated and downregulated to express the same stress reaction. For example, in maize miR156, miR164, and miR171 undergo varying expressions when subjected to drought conditions. Similarly, differential expression was exhibited by miR156, and miR171 in rice was also reported [78, 79]. **Table 5** depicts the use of various miRNA in stress responses.

Sunar *et al*. [121] have found the role of siRNAs in response to abiotic stresses. Several studies of abiotic stress tolerance in wheat indicate that siRNA is upregulated when exposed to cold stress but are down-regulated when subjected to heat stress, NaCl and dehydration conditions [122]. Wang *et al*. [123] reported the contribution



#### **Table 5.**

*Application of RNAi in crop quality and stress breeding.*

*Non-Coding RNA and Its Prospective Utilization in Plant Breeding DOI: http://dx.doi.org/10.5772/intechopen.106429*

of lncRNA in abiotic stress response by utilizing two distinct mechanisms, either they block the miRNA interactions with their target by mimicking as competitive endogenous RNAs. This mechanism of abiotic stress tolerance was reported in rice. The alternative mechanism followed by lncRNAs is antisense lncRNAs interact with sense mRNAs, forming double-stranded RNAs thereby preventing the expression of the gene. Zhang *et al.* [124] mentioned such interactions in drought stress studies of maize.

#### **7.2 Plant immunity**

ncRNAs also regulate plant disease resistance by switching on downstream R-genes, as well as the genes responsible for pathogenesis-related proteins or phenolic compounds or phytoalexins, and several other phytohormones signals in response to pathogen attack. miRNAs are engaged in Resistance gene (R-gene) regulation, whose activation is essential at the time of invasion by the pathogen. miRNAs, such as miR482, are downregulated during pathogen infection in potato, whereas its overexpression may lead to hypersensitive reactions [125]. **Tables 6** and **7** shows the crop-wise representation of different miRNA and other ncRNAs in maintaining plant immunity.

Other than stress breeding, the aspects of immunity, ncRNA, especially miRNA, have been explored in detail for their potential use in different attributes of crop breeding like enhancing the quality of the yield and its keeping quality, deposition of the secondary metabolites. It can also be used to induce male sterility in the plant, which is an important aspect of hybrid breeding. **Table 5** encapsulates different reports of usage of miRNA in various crops in the above-mentioned aspects of crop breeding.
