Histone Modification Complex JMJ704-HDA709 Negatively Regulates Salinity Tolerance in Rice.

Soil salinity poses a significant threat to global crop productivity. Understanding the molecular mechanisms underlying plant response to salt stress is crucial for enhancing crop resilience and yield. Here, we show that histone demethylase JMJ704 interacts with HDA709, a deacetylase that is specific for H3K9ac, to synergistically modulate salt tolerance in rice. Genetic analysis revealed that overexpressing either JMJ704 or HDA709 enhanced salt sensitivity, whereas the hda709 mutant exhibited a salt-tolerant phenotype. Interestingly, while the jmj704 mutant showed no significant change in salt sensitivity, the jmj704hda709 double mutant demonstrated markedly improved salt tolerance. Immunoblot analysis showed bidirectional crosstalk between JMJ704-catalyzed H3K4me3 demethylation and HDA709-mediated H3K9ac deacetylation, with both enzymes exhibiting synergistic functional interplay. We further demonstrated that under salt stress, JMJ704 forms a chromatin-modifying complex with HDA709, which, together with the transcription factor OsWRKY72, co-regulates peroxidase and salt-responsive genes. This recruitment facilitates transcriptional silencing through concurrent erasure of H3K4me3 and H3K9ac marks. Collectively, our work reveals that the JMJ704-HDA709 complex interacts with OsWRKY72 to negatively regulate rice salt tolerance by modulating ROS metabolism and salt-responsive genes. This finding provides evidence for the pivotal role of epigenetic regulation of plant abiotic stress responses and offers new insights for developing stress-resilient crops.