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Biology and Biotechnology of Environmental Stress Tolerance in Plants, Volume 3

in protection of the cellular machinery during different cellular processes

(Vierling, 1991; Hendrick & Hartl, 1993; Boston et al., 1996; Hartl, 1996;

Waters et al., 1996; Török et al., 2001). Similar to HSPs, LEA-type proteins

have been identified and characterized in diverse plant species where these

are responsible for conferring tolerance to various abiotic stresses in plants

(Kasuga et al., 1999; Shih et al., 2004; Grelet et al., 2005; Jyothsnakumari et

al., 2009). In 2010, a group of researchers floated the idea of multifunctional

gene (Hu et al., 2010). A multifunctional gene is a specific gene that can

simultaneously control several kinds of traits and effectively manifest several

different types of functions. Based on the above concept, LEA, sHSPs, and

other proteins perform multiple functions in plants under stress. Therefore,

plant tolerance to stresses can be developed by transforming plants with

multifunctional genes (Hussain et al., 2011b).

Transcription factors (TFs) are one of the major genetic circuits in the gene

regulatory pathways underlying plant responses to abiotic stresses (Baldoni

et al., 2015; Hrmova & Hussain, 2021). TFs are responsible for regulation

of transcriptional expressions of stress-related genes by binding specifically

to cis-elements in the promoter regions of target genes, thereby regulating

stress tolerance/resistance of plants under abiotic stresses (Baldoni et al.,

2015; Hoang et al., 2017; Hrmova & Hussain, 2021). Based of differences

in DNA-binding domains, TFs have been divided into 64 families such as

NAC, WRKY, MYB, HD-ZIP, bZIP, EREBP/AP2 (Hoang et al., 2017). A

plethora of research has shown that these TFs families have a central role in

defining plant tolerance to abiotic stresses via abscisic acid (ABA) depen­

dent and independent pathways (Yamaguchi-Shinozaki & Shinozaki, 2005,

2006; Pandey & Somssich, 2009; Dubos et al., 2010; Chen et al., 2012;

Nuruzzaman et al., 2013). Overexpression of TFs have resulted in abiotic

stress tolerance in plants, thereby promising candidates for enhancing stress

tolerance in crop plants via genetic engineering.

7.2 TRANSCRIPTION FACTORS IN ABIOTIC STRESS

Plants being sessile, have developed clever defense mechanisms to abiotic

stresses such as interconnected genetic networks and circuits which are

mainly managed by highly sensitive signal transduction cascades (Hrmova

& Hussain, 2021). Several studied have highlighted the central role of TFs

in gene regulation and expression which is known as transcriptional control

(Kang et al., 2002; Bartels & Sunkar, 2005; Hussain et al., 2011a; Wang et