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Small RNAs – The Big Players in Developing Salt-Resistant Plants

stress. In a salt-sensitive plant slight increase of salt concentration from the

critical value may lead to harmful effects on the structural integration and

functioning of the plant. Disorganization of the cell membrane, formation

of poisonous metabolites, development of reactive oxygen species, and

suppression of photosynthetic processes are some of the most obvious and

prevalent effects of salt on plant cells (Hasegawa et al., 2000). Alteration of

cell membrane fluidity results in disruption of protein homeostasis, which in

turn results in improper functioning of cellular processes in plants. Salinity

can disturb the plant from seed germination to its maturation. In salt medi­

ated stress conditions plants reprogramed their genetic organization at the

transcription level in such a way that protective genes are up-regulated while

the genes influence negatively are down-regulated. Modification of such a

transcriptional system is one of the essential steps to trigger the adaptation

processes under salinity (Gehan et al., 2015; Nakashima et al., 2014; Priest et

al., 2014). The expression of numerous genes is modified in plants growing

under salt-induced stressful conditions, and gene regulatory sRNAs should

play a key role in the regulation of genes or gene-coded metabolites. Gradual

research on sRNA mediated gene regulation has confirmed that under

salinity the expressions of various miRNAs and siRNAs are altered while

such modified sRNAs then alters the timing, location, and level of proteins

expression of their target genes under salinity. The genetic model plant, i.e.,

Arabidopsis thaliana is readily amenable to molecular modification, thereby

providing plant biology researchers with an excellent experimental system

to validate the expression of abiotic stress tolerance phenotypes introduced

through small RNA regulation and molecular modifications (Pegler et al.,

2019). Many experimental evidence points to the fact that many miRNAs

are closely linked to the salt response. According to the study of Liu et al.

(2018), 12 miRNAs in Arabidopsis, miR156, miR158, miR159, miR165,

miR167, miR168, miR169, miR171, miR319, miR393, miR394, and miR396

are elevated in reply to high salinity. In another plant Populus euphratica

Olivier, 211 miRNAs have been identified and 162 of them were screened

for salt response (Li et al., 2013). Different species of Saccharum also exhib­

ited upregulation of different miRNAs (miR156, miR159, miR166, miR167,

miR168, miR169, miR396, miR397, miR398, and miR528) under salinity

(Bottino et al., 2013; Gentile et al., 2015; Kumar et al., 2018). In a study on

Vigna unguiculata, 18 conserved miRNAs were reported from 16 miRNA

families by using a comparative genomic approach, which is expressed in

various ways under salinity (Paul et al., 2011). By analyzing sequencing

data through various sophisticated bioinformatics tools, a huge number of