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

effects of abiotic and biotic stressors and increase the beneficial

effects of plant-microbe interactions.

5. In many studies sRNAs have been exhibited to regulate the level of

secondary metabolites, proteins, and therapeutic substances in plants

(de Fougerolles et al., 2007; Mello & Conte, 2004).

9.5.2 SMALL RNA-MEDIATED RNA SILENCING

The discovery of RNA silencing (RNAi) was a surprising and accidental

observation. Jorgensen and his team in 1990 introduced an exogenous

transgene in Petunia and attempted to increase the expression of a gene that

codes for the enzyme Chalcone Synthase (catalyze the biogenesis of specific

pigment compound) under the control of 35S promoter (Ali et al., 2010;

Napoli et al., 1990). The experiment showed that the plants were unable

to produce the usual deep purple flower and in spite of this often-produced

variegated flowers with complete loss of color. Some workers considered it

as co-suppression and explained that in Petunia both introduced transgene

and added DNA interfere with the expression of endogenous loci (Pradhan

et al., 2015). In the late 1990 Fire and colleagues conducted an experi­

ment in Caenorhabditis elegans and showed that dsRNA can effectively

execute silencing of endogenous genes through a sequence-specific mode of

silencing (Fire et al., 1998). Later the process was coined as RNA interfer­

ence or RNA silencing. Technically RNAi refers to the phenomenon that

involves dsRNA mediated sequence-specific gene regulation and resulting

in inhibition of either translation or transcription (Kamthan et al., 2015). The

discovery of RNA interference has accelerated an enormous research effort

in most of the fields of plant science and other relevant fields of science. In

1998, Andrew Fire and Craig Mello discovered that injecting dsRNA with

both sense and antisense strands is more effective for silencing than injecting

dsRNA with only one strand. Subsequent studies also confirmed the finding,

which proved to be a defining moment in RNAi technology (Ali et al., 2010;

Tabara et al., 1998). However, in the earlier mentioned discoveries are actu­

ally deals with the reporting of basic molecular mechanism related to gene

silencing. In broad-spectrum RNA silencing is a non-cellular autonomous

event as the silencing is initiated in one or few cells and progressively

transmits RNA mediated sequence-specific suppression of homologous

sequences in neighboring cell (Jorgensen et al., 1998; Voinnet & Baulcombe,

1997). Kalantidis et al. (2008) concluded that RNA silencing is transmitted

from one plant cell to another via plasmodesmata, which is caused due to