Morphological, physiological, and molecular mechanisms underlying heat stress memory in plants

Increasing climatic unpredictability makes plants suffer different environmental stresses, with escalating global temperatures positioning heat stress as a principal abiotic constraint. Exposure to excessive heat destabilizes cellular homeostasis, impairing growth trajectories and photosynthetic capacity while potentially triggering irreversible physiological impairments. Nevertheless, plants exhibit stress-priming capabilities through heat-induced molecular memory mechanisms that bolster tolerance to recurrent thermal challenges. In the context of global warming, elucidating the mechanisms underlying plants' heat stress memory and response is crucial for improving crops' resilience and adaptation. This review systematically elaborated the morphological, physiological, and molecular mechanisms underlying heat stress memory, in which phytohormones are key signaling molecules regulating the stress memory. The role of Hsfs (heat shock transcription factor), HSPs (heat shock proteins), and genetic and epigenetic regulation in plant heat stress memory were clarified. Furthermore, the factors (e.g., priming and recovery duration, species, and genotype differences) affecting heat stress memory were clarified. This study will contribute to mitigating the adverse effects of global warming on crop productivity and propose novel strategies for incorporating these findings into molecular breeding programs to enhance crop thermotolerance.