Histone Deacetylases HD2A and HD2B undergo Feedback Regulation by ABA and Modulate Drought Tolerance via Mediating ABA-induced Transcriptional

Histone deacetylation catalyzed by histone deacetylase plays a critical role in gene silencing and subsequently control of many important biological processes. It was reported that the expression of plant-specific histone deacetylase subfamily HD2s is repressed by ABA in Arabidopsis. However, little is known about the molecular relationship between HD2A/HD2B and ABA during the vegetative phase. Here, we describe that the hd2ahd2b mutant shows hypersensitivity to exogenous ABA during the germination and post-germination period. Additionally, transcriptome analyses revealed that the transcription of ABA-responsive genes was reprogrammed and the global H4K5ac level is specifically up-regulated in hd2ahd2b plants. ChIP-Seq and ChIP-qPCR results further verified that both HD2A and HD2B could directly and specifically bind to certain ABA-responsive genes. As consequence, Arabidopsis hd2ahd2b plants displayed enhanced drought resistance in comparison to WT, which is consistent with increased ROS content, reduced stomatal aperture, and up-regulated drought resistance-related genes. Moreover, HD2A and HD2B repressed ABA biosynthesis via deacetylating H4K5ac at AtNCED9. Taken together, our results indicate that HD2A and HD2B partly function through ABA signaling and act as negative regulators during drought resistance response via regulating ABA biosynthesis and response genes.