Molecular Perspective on the Mechanisms Regulating Leaf Senescence in Plants Under Water Stress

Abstract Leaf senescence is an irreversible growth process that determines plant productivity and survival, especially under environmental stress. Among water stresses, drought and submergence significantly influence senescence pathways through distinct molecular mechanisms. Drought stress accelerates leaf senescence by impairing photosynthesis, reducing leaf expansion, and disrupting water balance, with transcription factors such as NAC, WRKY, and AP2/ERF playing critical roles in its regulation. In particular, the NAC transcription factor family modulates key senescence-associated genes, while WRKY and AP2/ERF members coordinate stress responses through ABA-dependent and independent pathways. Submergence, on the other hand, induces ethylene-mediated senescence, primarily through hypoxia-induced metabolic shifts and light deprivation. ERF transcription factors, particularly ERFVII, regulate hypoxia-responsive genes, whereas bHLH and WRKY transcription factors contribute to ethylene-induced senescence. Furthermore, NAC family regulators, along with EIN3, modulate dark-induced senescence under submergence, revealing mechanistic overlap with natural senescence processes. Recent advances further reveal that epi-genetic modifications dynamically alter chromatin accessibility, activating or suppressing senescence. Moreover, posttranslational regulation through ubiquitin-proteasome degradation and autophagy modulates senescence, with the proteasome accelerating it and autophagy delaying it through selective protein turnover. This review comprehensively explores the transcriptional regulation of leaf senescence under drought and submergence stresses, along with epigenetic and posttranslational regulation, and emphasizes the role of key transcription factor families. Understanding the molecular and physiological mechanisms regulating leaf senescence under these contrasting water stresses is critical for developing stress-resilient crops and enhancing agricultural sustainability in the face of climate change.