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

tolerance. As opposed to structural genes, TFs are complex proteins and

control multiple steps in biochemical pathways leading to stress tolerance.

Therefore, TFs have emerged as promising tools for the manipulation of

complex stress-responsive regulatory pathways in plants. Recently, the func­

tions of a number of plant TFs have been investigated in drought and associ­

ated stresses, which may lead to devising powerful and workable strategies

for engineering transgenic plants with enhanced tolerance. As a result of

collection of huge data on the involvement of plant bZIP, HD-Zip, DREB/

CBF, WRKY, and MYB TFs in the regulation of stress responses including

drought, discussion in this chapter move around these TFs. Prospects of

commercial manipulation of rationally designed TFs and CRISPR-Cas9

based TFs manipulations in agricultural biotechnology along with interac­

tions among TFs within stress responsive networks is discussed. The main

objective of this chapter is to discuss approaches for engineering improved

stress tolerance of crop plants using naturally existing as well as synthetic/

tailored variants of TFs for enhanced abiotic stress tolerance.

7.1 INTRODUCTION

Abiotic stresses are known causes of significant yield loss of crop plants

around the globe, leading to an average yield loss of over 50% for most

major crops (Hussain et al., 2011a; Hu & Xiong, 2014; Khoshmanzar et al.,

2019). Drought stress alone have the potential to reduce crop yield by more

than 50% when it occurs at reproductive stage of crop plants (Valliyodan &

Nguyen, 2006; Langridge et al., 2006; Hussain et al., 2012; Guttikonda et al.,

2014). Abiotic stresses such as drought and associated stresses have nega­

tive impact on several vital crop traits (Aroca et al., 2012; Calvo-Polanco

et al., 2012; Theocharis et al., 2012; Shrivastava et al., 2015; Hoang et al.,

2017) including normal growth and development, photosynthetic capacity,

biomass accumulation, and plant yield (Fleury et al., 2010; Kreuzweiser

& Rennenberg, 2014; Asgari Lajayer et al., 2017), hence leading to global

food insecurity. Plant breeders have made immense progress in generating

and improving abiotic stress-tolerant crop plant, but still serious efforts are

required because plant productivity and crop yield fail to meet global food

demands in the face of harsh weather conditions, climate change scenarios

and ever-increasing world population (Hu & Xiong, 2014; Baillo et al.,

2019). Considering that the yield of important cereal crops such as maize,

rice, wheat, barley, and sorghum could not be increased in near future (Ray