Abstract
Drought is the most prevalent unfavorable condition that impairs plant growth and development by altering morphological, physiological, and biochemical functions, thereby impeding plant biomass production. To survive the adverse effects, water limiting condition triggers a sophisticated adjustment mechanism orchestrated mainly by hormones that directly protect plants via the stimulation of several signaling cascades. Predominantly, water deficit signals cause the increase in the level of endogenous ABA, which elicits signaling pathways involving transcription factors that enhance resistance mechanisms to combat drought-stimulated damage in plants. These responses mainly include stomatal closure, seed dormancy, cuticular wax deposition, leaf senescence, and alteration of the shoot and root growth. Unraveling how plants adjust to drought could provide valuable information, and a comprehensive understanding of the resistance mechanisms will help researchers design ways to improve crop performance under water limiting conditions. This review deals with the past and recent updates of ABA-mediated molecular mechanisms that plants can implement to cope with the challenges of drought stress.
Highlights
As sessile organisms, plants are exposed to an ever-changing environment during their entire lifespan
They adversely affect the productivity of the crop, which is a major obstacle to attaining global food security essential for the continuously growing world population
In the least developed countries (LDCs) and low to middle-income countries (LMICs), over 34% of crop and livestock production was reduced by drought from 2008-2018 (FAO 2021) [4]
Summary
Plants are exposed to an ever-changing environment during their entire lifespan. The active SnRK2s by their well-conserved kinase catalytic domain positively regulate downstream ABA-responsive genes via the phosphorylation of TFs, which include bZIP transcription factors like ABRE (ABA-responsive element)-binding (AREB) proteins or ABRE-binding factors (ABFs) [45,46,47]. Several other TFs, including MYC (myelocytomatosis), MYB (myeloblastosis), DREB2 (drought-responsive element binding), NAC (NAM, ATAF1,2, and CUC), AP2/ERF (apetala 2/ethylene responsive factor), basic leucine zipper, and HD-ZIP (homeodomain leucine zipper), greatly influence plant abiotic stress resistance via ABA-dependent and ABA-independent signal transduction pathways by binding with specific cis-acting elements present in promoter regions of several stress-induced genes [48,49,50]. The two subunits of G-protein in rice, qPE9-1 (Gγ subunit) and RGB1 (Gβ subunit), show contrast regulation of ABA dependent stress responses acting as negative and positive regulators, respectively [61]
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