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Towards Engineering Smart Transcription Factors for Enhanced Abiotic Stress

al., 2016; Khan et al., 2018). The importance of TFs is also evident from

the fact that around 10% of completely sequenced plant genomes encode

TFs (Baillo et al., 2019). Sequencing data have also reported the presence

of 3,337, 1,611, 2,450, 1,922 TFs in maize, rice, sorghum, and Arabidopsis,

respectively (Wang et al., 2011; Hoang et al., 2017; Baillo et al., 2019;

Hrmova & Hussain, 2021). Therefore, specific TFs in functional states

may be needed in different biological systems including abiotic stresses.

Similarly, Inukai et al. (2017) provided a detailed description of systematic

engagement of TFs and their interactions during gene regulation and expres­

sion. Besides multigenic in nature, stress tolerance is one of complex plant

trait and TFs have the potential to regulate simultaneously several stress

responsive downstream in plants (Mittler & Blumwald, 2010; Hussain et al.,

2011a; Atkinson & Urwin, 2012).

Transcription factors are central regulatory proteins that underpins the

regulation of plant gene by binding to the cis-element of a specific gene and

control critical aspects of gene function such as stress tolerance, ensuring

normal growth and development of plants under extreme stresses (Bartels &

Sunkar, 2005; Hrmova & Lopato, 2014). Several TFs have been identified

in plants and common TFs involved in stress mitigation in plants include the

APETALA2/ethylene response factor proteins (Hinz et al., 2010; Quan et

al., 2010; Liu et al., 2012; Schmidt et al., 2013; Vogel et al., 2014; Zhu et al.,

2014), NAC (De Clercq et al., 2013; Singh et al., 2013; Van Ha et al., 2014;

Fang et al., 2015), basic region leucine zipper motifs (Kang et al., 2002;

Fujita et al., 2005; Furihata et al., 2006; Hartmann et al., 2015), WRKY (Seo

et al., 2012; Jiang et al., 2014; Huang et al., 2015; Diao et al., 2016; He et

al., 2016), MYB (Meng et al., 2014, 2015; Sun et al., 2014; Cai et al., 2015),

NAC (NAM, CUC2, ATAF1/2), and homeodomain-leucine zipper protein

families (Xiang et al., 2008; Fujita et al., 2011; Huang et al., 2012; Puranik

et al., 2012; Todaka et al., 2012; Ehong et al., 2016; Liu et al., 2018; Mao

et al., 2019; Yu et al., 2021; Ma et al., 2021). Several crop and model plants

overexpressing different TFs demonstrated enhanced tolerance to different

abiotic stresses due to expression of many stress-responsive genes (Xiong

et al., 2014; Alvarez-Gerding et al., 2015; Jisha et al., 2015; Zhang et al.,

2015; Zhu et al., 2015; Liu et al., 2016; Rahman et al., 2016; Yu et al., 2021).

Taken together, these findings suggest that genetic engineering of plants

using different TFs genes has the potential to stimulate general or specific

pathways related to abiotic responses, leading to improved plant tolerance to

various abiotic stresses (Table 7.1).