Regulatory Role of Jasmonate Signaling in Dark-, Drought-, and Salt-Induced Leaf Senescence

Drought and salinity are among the most severe abiotic stresses limiting global agricultural productivity, and their frequency and intensity are expected to increase under ongoing climate change. Concurrently, the growing human population necessitates the development of crop varieties that combine high yield with enhanced stress tolerance. Jasmonates, including jasmonic acid (JA) and its derivatives, play pivotal roles in plant responses to abiotic stresses and are widely regarded as stress hormones. The bioactive conjugate jasmonoyl-isoleucine (JA-Ile) acts as a ligand for the coronatine insensitive 1 (COI1) receptor. Jasmonates regulate essential physiological processes, including leaf senescence, secondary metabolism, and nutrient homeostasis, which collectively contribute to plant adaptation to drought and salinity stress. In this review, we summarize recent advances in understanding the role of jasmonate signaling in plant responses to drought and salinity, with particular emphasis on the initiation and progression of leaf senescence and chlorophyll degradation pathways. By integrating genetic, biochemical, and physiological evidence, we discuss how targeted modulation of jasmonate levels and signaling components may be exploited to breed or engineer crops with improved tolerance to water-deficit and saline conditions.