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

6. For all categories of sRNA, biogenesis takes place through four basic

steps.: (i) Transcription of sRNA is brought about by dsRNA and an

RNA polymerase (RNAP) act as a driving agent of the transcription

of the corresponding gene; (ii) then the dsRNA has become 18–25

nucleotide long sRNA; (iii) next to this 3’ end of sRNA become meth-

ylated; and (iv) ultimately the sRNA binds with effector complex,

i.e., RISC, which allow it to detect and interact with its target site

(Voinnet, 2009; Budak & Akpinar, 2015).

7. Generally, RNase III type ribonuclease Dicer-like (DCL) protein

control the processing of sRNA and after incorporation into Argo-

naute (AGO) proteins, it silences genes at the transcriptional level

by modifying DNA or histones, and at the post-transcriptional level

either by cleavage and destruction of mRNA or protein repression

(Baulcombe, 2004; Chapman & Carrington, 2007).

8. sRNAs play important roles in a wide range of biological processes,

along with morphological development, genomic stability,

physiological balance, and various biotic and abiotic responses

(Vaucheret, 2006). During stress conditions, miRNAs and siRNAs

can be upregulated or downregulated, and due to such modifications,

the post-transcriptional activity of respective target genes is altered,

which in turn results in adaptive responses in plants (Leung & Sharp,

2010).

9. sRNA is a mobile element and can move from a gene locus to another

or even from one cell to others and play a significant role in non-

cell-autonomous gene silencing, which may be local or systematic in

nature (Baldrich et al., 2019).

10. Several researchers confirmed that sRNA can move from plant cells

to pathogens and such transferred sRNA permits plants to control the

expression of genes in the invading pathogens or parasites through a

process called host-induced gene silencing (HIGS) (Baldrich et al.,

2019).

11. Although a large number of studies have proven mobile RNAs in the

plant, it is still not possible to determine the mechanism by which

these RNAs move (Baldrich et al., 2019).

12. Both in the cytoplasmic level and nuclear level sRNA regulate gene

expression through versatile and complex mechanisms and it is fact

that slight alteration of sRNA mediated regulatory mechanisms may

influence normal cellular functions (Catalanotto et al., 2016).