Responsible for the deacetylation of lysine residues on the N-terminal part of the core histones (H2A, H2B, H3 and H4). Histone deacetylation gives a tag for epigenetic repression and plays an important role in transcriptional regulation, cell cycle progression and developmental events. Histone deacetylases act via the formation of large multiprotein complexes. HDA19 is involved in jasmonic acid and ethylene signaling of pathogen response. Part of a repressor complex including APETALA2 (AP2) and TOPLESS (TPL) that control the expression domains of numerous floral organ identity genes (PubMed:23034631). Involved in negative regulation of salinity stress response (PubMed:29018096). Represses the expression of stress tolerance-related genes, genes coding for late embryogenesis abundant (LEA) proteins that prevent protein aggregation, and positive regulators of abscisic acid (ABA) signaling, such as ABI5 and NAC019 (PubMed:29018096). H2O + N(6)-acetyl-L-lysyl-[histone] = acetate + L-lysyl-[histone] Binds 1 zinc ion per subunit. Interacts with SIN3, SAP18 and TPR1. Interacts with CDKE-1, MED14 and LUG. Interacts with TPL (PubMed:23034631). Interacts with AHL22 (PubMed:22442143). excluded from the nucleolus, but associated with the condensing chromatids. A number of isoforms are produced. According to EST sequences. Highly expressed in leaves, stems, flowers and young siliques. Induced by jasmonic acid, ethylene, wounding and pathogen infection. Inhibited by sodium butyrate. Loss-of-function mutant (antisense inhibition) has an increased level of tetraacetylated histone H4 and shows late flowering, developmental pleiotropy and increased symptoms when infected by a pathogen. Belongs to the histone deacetylase family. HD type 1 subfamily.