Molecular mechanisms of plant thermal response: from signal transduction and epigenetic regulation to signaling integration.
Global warming intensification elevates heat stress to one of the major threats to crop productivity. This review synthesizes recent advances in understanding the mechanisms governing plant responses to both moderate and acute heat stress, with a focus on the integration of epigenetic regulation and signaling networks that underpin thermal adaptation. This review highlights how transcription factors PHYTOCHROME-INTERACTING FACTOR 4 (PIF4, during thermomorphogenesis) and HEAT SHOCK FACTOR A1s (HSFA1s, in heat shock responses) orchestrate plant adaptive growth through crosstalk among light, circadian, and hormone signaling pathways. Importantly, epigenetic mechanisms, including histone variant H2A.Z dynamics and histone modification reprogramming, function as central regulators of thermal plasticity. Key among these processes are HSFA2-mediated chromatin remodeling and small interfering RNA (siRNA)-dependent control of transgenerational thermomemory. Despite this progress, fundamental questions persist regarding temperature sensing, HSFA1s activation dynamics, and stress signal integration. Multi-omics and synthetic biology approaches are proposed to be pivotal in deciphering conserved principles of plant thermal resilience, ultimately providing a theoretical foundation and molecular breeding strategies for climate-smart crops.