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

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12.2.2.1 COLD STRESS

Plant growth and development is adversely impacted with cold climatic

condition (Chew & Halliday, 2011). Plants have developed an advanced

mechanism to sense the alteration in temperature and adjust their physiology

accordingly for survival (Chinnusamy et al., 2006; Kaplan et al., 2004).

Plants in the temperate regions use the process of cold acclimation to survive

under freezing stress. The expression of cold-responsive (COR) genes is

turned on. The expression of CORs is controlled by C-repeat-binding factors

(CBFs) (Liu et al., 2019). Like Arabidopsis sp. homologous CBF is also

found in different plant species, e.g., Brassica campestries (Wang et al.,

2014), Hordeum vulgare (Marozsán-Tóth et al., 2015), Rapeseed (Jaglo et

al., 2001), tomato (Zhang et al., 2004), rice (Dubouzet et al., 2003). Cold

stress induces the transcription factor CBF binds with the promoter region of

COR genes containing C-repeat (CRT)/DREs. When Arabidopsis is exposed

to cold temperatures, the repressive histone mark, i.e., H3K27me3 on the

COR genes (COR15A and ATGOLS3) diminish slowly (Kwon et al., 2009).

In Arabidopsis PICKLE (PKL) is a well-reported, ATP dependent, CHD3­

type chromatin remodeling factor that regulates growth and development

also RNA-directed DNA methylation (RdDM). PKL has a significant part in

cold stress response. It regulates numerous COR genes, as well as RD29A,

COR15A, and COR15B, by regulating the expression of the CBF3 gene

(Yang et al., 2019). Under cold stress there is a decrease in the deposition

of histone repressive mark H3K27me3 on the COR genes COR15A and

galactinol synthase 3 (GOLS3), this mark is irreversible even under normal

temperature, indicate H3K27me3 can function as a memory indicator

(Kwon et al., 2009). Moreover, histone methylation, histone acetylation

even plays a crucial role in low-temperature stress response on a significant

percentage of cold-induced genes (Park et al., 2018). On the promoter region

of different COR genes like COR15A and COR47 histone acetylation takes

place under low-temperature treatment (Pavangadkar et al., 2010). Histone

acetyltransferase (HATs) and histone deacetylases (HDACs) regulate the

histone acetylation dynamically. Cell membranes are frequently damaged

under cold stress. Malondialdehyde (MDA) is a key indicator of membrane

system damage and degradation in cellular metabolism. MDA levels remain

substantially greater under low-temperature stress when compared to the

control level. Cold stress treatment led to a gradual increase in malondi­

aldehyde (MDA) concentration when Arabidopsis histone deacetylase 2D

(HD2D) was overexpressed (Chang et al., 2020).