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Biology and Biotechnology of Environmental Stress Tolerance in Plants, Volume 3

cell-to-cell migration of a short-range silencing signal. According to several

supporting investigations RNAi is also mechanistically related to various

conserved RNA silencing pathways that are associated with cellular regula­

tion of gene expression, protection of genome from mobile repetitive DNA

sequences, retroelements, and transposons (Aravin et al., 2007; Baulcombe,

2002). The phenomenon of RNAi involves all types of non-coding sRNAs

resulted from the cleavage product of dsRNA (Kamthan et al., 2015). In the

case of local RNA silencing, the silencing signals can gradually spread from

a cell to the group of its adjacent cells (Dunoyer et al., 2013; Marin-Gonzalez

& Suarez-Lopez, 2012). On the contrary systematic silencing takes place

over a certain distance and the silencing signal can spread from a cell to the

distantly located cells. With the up-gradation of next-generation sequence

technology a huge number of novel and conserved miRNAs and siRNAs

have been identified in various plant species (Jover-Gil et al., 2004; Sun,

2012; Sunkar et al., 2012). Some of them were recognized through sequence

analysis of constructed sRNA libraries, contrary others were predicted

through in silico methods by utilizing recently accumulating sequence data.

The gene silencing process needs some catalytic molecule that triggers the

silencing of many homologous transcripts (Hinas et al., 2012; Hunter et al.,

2006).

9.6 MODE OF ACTIONS OF SMALL RNAS IN PLANTS GROWN

UNDER SALT STRESS CONDITION

In most parts of the world, salinity appears to be a regular and recurrent

crucial abiotic stress factor, which plays a vital role in restricting food

production and is regarded as one of the major threats to biodiversity.

Stress has simply referred to any kind of impairment in the growth and

development of living organisms. Factors that generate stressful conditions

are called stressors. In the context of plant science, the stressful situation

causes delayed seed germination, insufficient growth, and decreased yield.

Plant stress responses are fully reliant on accurate gene expression and

correct gene regulation at several levels, including transcriptional, post-

transcriptional, and post-translational (Mirlohi & He, 2016). Among the

gene regulation, post-transcriptional regulation has been discovered to have

a role in maintaining cellular homeostasis under stress conditions, as well as

assisting cells in recovering from the detrimental effects of stress (Sunkar et

al., 2012). Among the abiotic stresses, the most damaging one is salt-induced