Epigenetics – The Molecular Tool in Understanding Abiotic Stress Response in Plants

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(HSPs) have a critical function in heat sufferance. Generally, the main role

of HSPs is controlling protein winding and unwinding (Singh et al., 2016).

Heat stress generates a continued aggregation of H3K9ac and H3K4me3 on

HSP18, HsP22.0, APX2, and HSP70 genes within these genes (Lämke et al.,

2016). The Arabidopsis imprinted SUPPRESSOR OF DRM1 DRM2 CMT3

(SDC) gene has been stimulated by prolonged heat stress, which encodes

a suspect F-Box protein and is inhibited through DNA methylation during

vegetative growth (Sanchez & Paszkowski, 2014). The function of these

genes is to function a significant part to overcome heat stress (Olga et al.,

2013).

To overcome heat stress, ncRNAs especially miRNAs, play an important

part. A large number of heat-induced miRNAs is identified in plants (Cao

et al., 2014). Some of them target a diverse range of transcription factors

homeobox leucine-zipper proteins, F box proteins and protein kinases such

heat stress-responsive miRNAs are miRNA156, miR166, and miR393 fami­

lies. Arabidopsis expressing a miR398-resistant version of CSD (copper/zinc

superoxide dismutase) are further susceptible to heat stress. But to regulate

MYB-like family transcription factors miR159 is repressed in response to

heat stress (Ravichandran et al., 2019).

12.2.3 UV RADIATION STRESS

The depletion of the stratospheric ozone layer causes a major hazard to plants

as well as animals due to UV radiation from the sunlight with a wavelength

(10–400 nm). The UV component of sunlight causes a variety of damage that

can disrupt cellular and structural integrity, as well as growth and develop­

ment. Though many plants are unaffected by a slight increase in exposure to

UV radiation as it may depend on the area, species, and cultivator. But the

composition of the ecosystem is constantly changing which may affect the

important crops (Bornman, 1991). UV-B stress causes a change in chromatin

structure and histone H3 acetylation not DNA methylation, which results in

rapid and heritable changes of epigenetic control in a silent reporter gene

(Lang-Mladek et al., 2010). The epigenetic changes due to UV radiation stress

are linked to transcriptional activation, repression, or both and chromatin

remodeling. Numerous genes are deregulated by UV-B (280–310 nm) and

UV-C (<280 nm) exposure. DNA methylation, or 5-methylcytosine (5mC), is

revealed to be an important epigenetic marker under UV stress. DNAmethyla­

tion profiles are due to change in methylation and demethylation processes,