The roles of plant proteases and protease inhibitors in drought response: a review

Abstract

Upon exposure to drought, plants undergo complex signal transduction events with concomitant changes in the expression of genes, proteins and metabolites. For example, proteomics studies continue to identify multitudes of drought-responsive proteins with diverse roles in drought adaptation. Among these are protein degradation processes that activate enzymes and signalling peptides, recycle nitrogen sources, and maintain protein turnover and homeostasis under stressful environments. Here, we review the differential expression and functional activities of plant protease and protease inhibitor proteins under drought stress, mainly focusing on comparative studies involving genotypes of contrasting drought phenotypes. We further explore studies of transgenic plants either overexpressing or repressing proteases or their inhibitors under drought conditions and discuss the potential roles of these transgenes in drought response. Overall, the review highlights the integral role of protein degradation during plant survival under water deficits, irrespective of the genotypes’ level of drought resilience. However, drought-sensitive genotypes exhibit higher proteolytic activities, while drought-tolerant genotypes tend to protect proteins from degradation by expressing more protease inhibitors. In addition, transgenic plant biology studies implicate proteases and protease inhibitors in various other physiological functions under drought stress. These include the regulation of stomatal closure, maintenance of relative water content, phytohormonal signalling systems including abscisic acid (ABA) signalling, and the induction of ABA-related stress genes, all of which are essential for maintaining cellular homeostasis under water deficits. Therefore, more validation studies are required to explore the various functions of proteases and their inhibitors under water limitation and their contributions towards drought adaptation.

Exogenous abscisic acid treatment regulates protein secretion in sorghum cell suspension cultures

“…In addition, nine of these 12 proteins were up-regulated (Table S6). Our recent review 96 and references therein project proteases and their inhibitors as critical role players in numerous physiological processes under normal growth and during stress response. Furthermore, transgenic studies using gain or loss-of-function mutants implicate proteases and/or protease inhibitors in ABA signaling processes.…”

“…Furthermore, transgenic studies using gain or loss-of-function mutants implicate proteases and/or protease inhibitors in ABA signaling processes. 96 Apoplastic proteases are also regarded as defense systems against plant pathogen infection. 97 , 98 …”

ZmHDT103 Negatively Regulates Drought Stress Tolerance in Maize Seedlings

“…Additionally, changes in physiological indicators such as relative water content (RWC), malondialdehyde (MDA), and proline (Pro) are important parameters for evaluating drought tolerance in plants. Plants with stronger drought resistance often maintain higher RWC levels [25]. Under drought stress, lipid peroxidation occurs in plant membranes, resulting in the production of malondialdehyde (MDA).…”

Editorial: Plant proteolytic enzymes: contributions and challenges to improve food availability against climate change effects

“…This process not only aids in cell damage repair but also modulates biological responses to environmental stress. Proteases also play a key role in the biogenesis of phytohormones, which govern plant growth, development, and responses to environmental challenges (Moloi and Ngara, 2023).Modern agriculture struggles to meet the increasing food, fodder, and raw material demands due to climate change and rapid population growth. Climate change is a major factor that negatively impacts crop yield potentials.…”

“…This process not only aids in cell damage repair but also modulates biological responses to environmental stress. Proteases also play a key role in the biogenesis of phytohormones, which govern plant growth, development, and responses to environmental challenges ( Moloi and Ngara, 2023 ).…”