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Towards Engineering Smart Transcription Factors for Enhanced Abiotic Stress

et al., 2012), this will force plant researchers to think about integrated and

sustainable functional approaches. Furthermore, narrow genetic base due

to absence of natural variation in plant breeding stock has led to greater

sensitivity to different abiotic stresses (Hussain et al., 2012; Lobell et al.,

2014; Khan et al., 2019). Moreover, multiple genes control the tolerance

to various abiotic stresses, thereby further increasing the complexity for

enhancing the stress tolerance of major commercial crop cultivars and seems

more challenging (Li et al., 2018). As part of the evolutionary process, plants

have developed various strategies to combat unfavorable abiotic stresses do

not seem effective in crop plants (Langridge et al., 2006; Hrmova & Lopato,

2014).

Classical approaches for improvement in plant performance under various

abiotic stresses were not very successful because genes/alleles contributing

to stress tolerance are mostly disappeared during the lengthy conventional

breeding process. This is simple to understand that these alleles are lost

because possibly these do not have a direct contribution to the yield of crop

plants (Bartels & Hussain, 2008; Zheng et al., 2008). On the other hand,

researchers have struggled hard to develop crop plants with enhanced stress

tolerance using both conventional and transgenic approaches, literally no or

little success has been achieved in the field mainly due to following reasons:

(i) fundamental molecular mechanisms of stress tolerance are not yet fully

understood; (ii) complex multigene nature of stress tolerance; and (iii) lack

of data on different stressors interaction (Hussain et al., 2011a, 2012). There­

fore, scientists around the globe are reluctant to employ classical approaches

which are less efficient, and labor intensive and time consuming (Ashraf &

Foolad, 2007; Hussain et al., 2012).

Progress in understanding of gene expression, signal transduction and

transcriptional regulation in plants responses to environmental constraints

is exceptional. Similarly, gene discovery has been greatly facilitated by

recent advances in molecular, genomic, and other high throughput tools

(Yamaguchi et al., 2007; Kitsios & Doonan, 2011; Zwack & Rashotte, 2015).

Understanding of plant responses at cellular, molecular, metabolic, physi­

ological, and genetic levels to abiotic stress conditions and development of

approaches towards improving plant stress tolerance has facilitated gene

revolution following green revolution (Hussain et al., 2011b; Cabello et al.,

2014). These discoveries made available different functional or regulatory

genes for genetic engineering for improving stress tolerance of crop plants

(Valliyodan & Nguyen, 2006; Bhatnagar-Mathur et al., 2007; Kathuria et

al., 2007; Hussain et al., 2011a, b, 2012; Hrmova & Lopato, 2014; Baillo et