Responsible for the deacetylation of lysine residues on the N-terminal part of the core histones (H2A, H2B, H3 and H4) (PubMed:23548744). Histone deacetylation gives a tag for epigenetic repression and plays an important role in transcriptional regulation, cell cycle progression and developmental events (PubMed:23548744). Histone deacetylases act via the formation of large multiprotein complexes (Probable). Represses chlorophyll biosynthesis and photosynthesis in the dark (PubMed:23548744). Is recruited by PIF3 to the promoters of chlorophyll biosynthetic and photosynthetic genes, and represses their transcription by histone deacetylation (PubMed:23548744). Involved in the repression of hypocotyl cell elongation to promote photomorphogenesis (PubMed:31061103). Is recruited by HY5 to the promoters of a subset of cell wall organization and auxin signaling-related genes, and represses gene expression by decreasing the levels of histone H4 acetylation in a light-dependent manner (PubMed:31061103). Promotes abscisic acid (ABA) signaling (PubMed:30979883). Is recruited by MYB96 to the promoters of a subset of Rho GTPase (ROP) genes, which repress ABA signaling at the early stages of signal transduction (PubMed:30979883). Represses ROP expression by removing acetyl groups of histone H3 and H4 from the cognate regions, particularly in the presence of ABA (PubMed:30979883). Represses the plant response to elevated ambient temperature by directly repressing warm temperature-responsive genes (PubMed:31400169). H2O + N(6)-acetyl-L-lysyl-[histone] = acetate + L-lysyl-[histone] Binds 1 zinc ion per subunit. Inhibited by trichostatin A (TSA), a well-known histone deacetylase inhibitor. Interacts with PIF3 in the dark (PubMed:23548744). Interacts with HY5 (PubMed:31061103). Interacts with MYB96 (PubMed:30979883). Forms homotetramers (PubMed:32878973). Shuttles in and out of the nucleus upon light exposure. In the absence of light, is exported out of the nucleus, and upon further exposition to light is imported to the nucleus. A number of isoforms are produced. According to EST sequences. Expressed in stems, leaves, flowers, siliques and mature seeds. Belongs to the histone deacetylase family. HD type 2 subfamily.