Roles and Mechanisms of Histone Deacetylases in Plant Abiotic Stress Responses.

Histone deacetylases (HDACs) are key epigenetic enzymes governing lysine deacetylation. This modification is tightly coupled to cellular redox homeostasis and antioxidant signaling in plants. Plant HDACs are grouped into three subfamilies: RPD3/HDA1, SIR2, and plant-specific HD2. HDACs target both histone residues (e.g., H3K9 and H4K5) and a broad set of non-histone substrates (e.g., transcription factors and metabolic enzymes). Via coordinated chromatin remodeling and non-histone protein modification, HDACs integrate phytohormone signals, reactive oxygen species (ROS) bursts and NAD+ metabolic fluctuations to orchestrate plant abiotic stress responses, balancing antioxidant defense, redox equilibrium and normal growth. This review systematically sorts the divergent stress-response traits, substrate preferences and bidirectional regulatory logic of the three HDAC subfamilies; integrates chromatin-dependent and transcription factor-centered transcriptional branches; and summarizes crosstalk rules between HDAC-mediated deacetylation and other epigenetic marks. We further hierarchically clarify current research bottlenecks spanning basic mechanism dissection, multi-crop validation and field breeding transformation and propose targeted stratified research directions. We further construct a complete regulatory cascade linking environmental stimuli, ROS/ABA/NAD+ signals, HDAC activity and downstream antioxidant/stress gene expression, filling gaps in previous reviews that overlook redox-dependent HDAC functions. This mechanistic framework delivers integrated epigenetic and redox theoretical references for breeding stress-tolerant crops with reinforced antioxidant capacity.