201

Towards Engineering Smart Transcription Factors for Enhanced Abiotic Stress

However, development of novel high throughput tools such as CRISPR/

Cas9 has provided vast possibilities to simultaneously manipulate several

regulatory genes in a genome to introduce the tailored genetic switches in the

plants for stress tolerance (Bagdanove & Voytas, 2011; Bortesi & Fischer,

2015).

7.2.1 TRANSCRIPTION FACTORS INVOLVED IN SIGNALING

NETWORKS UNDER ABIOTIC STRESSES

Signaling pathway in plants composed of three main steps viz Signal

perception and transduction, and expression of several stress-responsive

downstream genes, which in turn activate physiological, biochemical, and

molecular adaptive responses (Huang et al., 2012; Hrmova & Lopato, 2014).

Environmental stimuli-caused signals are recognized by different transcel­

lular membranes which are present in cell wall or membrane including Ca²⁺

channels and Ca²⁺ binding proteins, histidine kinases, and G-protein coupled

receptors (Misra et al., 2007; Schaller et al., 2008; Thapa et al., 2011; Boud­

socq & Sheen, 2013; Hrmova & Lopato, 2014). Signal transductions occur

through conversion of extracellular signals into intracellular ones through

de novo synthesis of specific second messengers such as ROS, inositol

phosphate, diacylglycerols, hexaphosphate. Stress signals are transduced

to subsequent components in the signaling pathway towards the nucleus

(Baxter et al., 2014; Zhu, 2016). Signaling molecules such as protein kinases,

phosphatases, and others play central role in signal transduction under

abiotic stresses in plants. These signaling molecules (activated kinases and

phosphatases) initiate phosphorylation/dephosphorylation of TFs proteins

(Danquah et al., 2014; Kudla et al., 2018; Noman et al., 2021). As a result of

phosphorylation/dephosphorylation cascade, TFs lead to the expression of

several stress-responsive downstream genes (Danquah et al., 2014; Noman et

al., 2021). However, differential expression of stress-responsive genes under

specific stress led to different transcription pattern compared to non-stressed

control (Kulda et al., 2018). Meanwhile, accumulation of various stress-

related proteins and molecules occur in vegetative tissues because of expres­

sion of various structural genes which lead to stress tolerance (Bhargava &

Sawant, 2013; Schulz et al., 2013; Hrmova & Lopato, 2014; Ho et al., 2015).

Complete pathway consists of complex regulatory circuits to manipulate the

several stress-responsive downstream genes resulting in plant acclimation,

survival under unfavorable environmental conditions (Ishihama & Yoshioka,