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

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root-specific repression of TaHKt1 (Kumar et al., 2017). In saline conditions,

plants undergo histone modification in addition to DNA methylation (Kim

et al., 2015). To acclimate in the constantly changing environment, acetyla­

tion and deacetylation takes place by HATs and HDACs correspondingly.

Interestingly, high salinity is responsible for the decline of repressive marks

H3K9me2 and H3K27me3 deposition on stress-responsive genes while it

influences the accumulation of dynamic histone inscription H3K9K14Ac

and H3K4me3 on that salt stress-responsive gene (Chen & Wu, 2010; Sokol

et al., 2007; Yolcu et al., 2016). At the elevated amount of NaCl and ABA

represses HD2 family deacetylase, i.e., HD2C it is reported that the hd2c

mutant is also sensitive to NaCl (Ming Luo et al., 2012). The expression of

the Arabidopsis HKT1 gene is activated by the addition of salt when histone

H3 lysine tri-methylation (H3K27me3) is removed from the HKT1 gene

body (Sani et al., 2013). Plants under salinity stress result in another type of

histone modification, i.e., H3Ser-10 phosphorylation that is associated with

chromatin compactness. It was analyzed that H3Ser-10 phosphorylation, H3

and H4 acetylation show an over-expression under different abiotic stress

(Sokol et al., 2007). The epigenetic alterations that are mentioned do not

act in the same manner as its regulatory mechanism varies depending upon

diverse abiotic stress (Kim et al., 2015; Sokol et al., 2007).

12.2.1.1 DROUGHT

Drought is a condition when a region faces inadequate precipitation. It has

an adverse effect on the ecosystem and agriculture and the economy of the

region. Drought or water deficit is among the major abiotic stresses for

the plant’s growth, development. The warm-dry areas of the world greatly

face drought stress (Pourdad & Beg, 2003). The productivity of crops is

adversely hampered because such stresses disrupt the normal synchronized

physiological equilibrium (Gaspar et al., 2002). Drought stress takes place

due to the unavailability of water in the soil on the other hand increasing

the temperature of the environment causes continuous water loss through

transpiration and/or evaporation. Drought stress is experienced by most

plant species; however, the amount of it varies between species to species

and even in the same species (Jaleel et al., 2007). Drought stress causes the

decrease in water level in the plant cell, drop off water potential and loss in

turgor, decrease in cell elongation and growth, stomatal closure. Dreadful

water stress disturbs photosynthesis, metabolism as a result necrosis takes