Mechanisms of Abscisic acid (ABA)-mediated plant defense responses: An updated review

• Abscisic acid (ABA) is a classical phytohormone involved in plant defense against stressors. • ABA enhances plant resilience by regulating root growth and rhizosphere microorganisms. • ABA modulates stomatal movement and crosstalk with other signaling molecules. • Transcriptional and epigenetic regulation involved in ABA biosynthesis and signaling cascades. • ABA acts as a master regulator in balancing plant growth and stress responses. The intensification and frequency of extreme weather events are emerging as a result of global climate change, which has a serious impact on the sustainable development of agriculture. Plants trigger a wide range of defense responses against adverse environmental conditions, including the signal generation, recognition, and transduction together with the crosstalk of defense signals and networks. Subsequently, activation of a variety of defense gene expressions and metabolic adjustments confers plant tolerance to stressors. Abscisic acid (ABA) is a vital phytohormone for balancing plant growth and adaptation to a series of environmental stresses. This review summarizes the current research progress on ABA components involved in defense responses through various mechanisms including stomatal closure, interactions with other signaling molecules such as reactive oxygen species (ROS), calcium (Ca 2+ ) and other phytohormones, transcriptional regulation, and epigenetic modifications. Additionally, the role of ABA in balancing plant growth and stress responses is also discussed. This review provides new insights for sustainable development of agriculture under current climate change scenarios.