Drought Tolerance in Plants: Physiological and Molecular Responses

Abstract

Drought, a significant environmental challenge, presents a substantial risk to worldwide agriculture and the security of food supplies. In response, plants can perceive stimuli from their environment and activate defense pathways via various modulating networks to cope with stress. Drought tolerance, a multifaceted attribute, can be dissected into distinct contributing mechanisms and factors. Osmotic stress, dehydration stress, dysfunction of plasma and endosome membranes, loss of cellular turgidity, inhibition of metabolite synthesis, cellular energy depletion, impaired chloroplast function, and oxidative stress are among the most critical consequences of drought on plant cells. Understanding the intricate interplay of these physiological and molecular responses provides insights into the adaptive strategies plants employ to navigate through drought stress. Plant cells express various mechanisms to withstand and reverse the cellular effects of drought stress. These mechanisms include osmotic adjustment to preserve cellular turgor, synthesis of protective proteins like dehydrins, and triggering antioxidant systems to counterbalance oxidative stress. A better understanding of drought tolerance is crucial for devising specific methods to improve crop resilience and promote sustainable agricultural practices in environments with limited water resources. This review explores the physiological and molecular responses employed by plants to address the challenges of drought stress.

Keywords: dehydration; drought stress; dry weather; osmotic stress; water deficit.

Figure 1

Physiological effects of drought stress on plants and the outcomes that cause growth and yield reduction.

Figure 2

Plants employ various strategies, such as tolerance, recovery, avoidance, and escape, to cope with drought.

Figure 3

Molecular mechanisms of drought stress tolerance in plants. Abbreviations: ABA, abscisic acid; PYR1/PYL, pyrabactin resistance/PYR1-like; RCAR, Regulatory Component of ABA Receptor; PP2C, type 2C protein-phosphatase; SnRK2, sucrose non-fermenting 1-related protein kinase subfamily 2; ABF, ABA-responsive element binding factors; RAV1, Related to ABI3/VP1; DREB2, dehydration responsive element-binding protein 2; NAC, named based on its three domains: NAM, ATAF1,2 and CUC2; AREB, abscisic acid–responsive element binding protein; DRE/CRT, Dehydration Responsive Element/C-repeat Binding Factor; NACR, NAC recognition sequence; ABRE, ABA-responsive element; LEAs, Late embryogenesis-abundant; DHNs, Dehydrins, SMPs, seed maturation protein; TIPs, tonoplast intrinsic proteins; NIPs, nodulin 26-like intrinsic proteins, DSPs, desiccation-stress proteins, RAPs, resistance-associated proteins, Ca²⁺, calcium ion; ROS, reactive oxygen species; cGMP, 3’,5’-cyclic guanosine monophosphate; cAMP, cyclic adenosine monophosphate; MAPK, mitogen-activated protein kinase; CDPK, Calcium-dependent protein kinase; WRKY, WRKY transcription factors; MYB, MYB transcription factors; AP/EREAP, Activator protein/element of the apoptosis promoting; CAT, catalase; SOD, superoxide dismutase; APX, ascorbate peroxidase; POD, peroxidase; GR, glutathione reductase; GPX, Glutathione Peroxidase.