Essential angiosperm-specific subunits of HDA19 histone deacetylase complexes in Arabidopsis [ChIP-Seq]

Although the Arabidopsis thaliana histone deacetylase HDA19 and its close homolog HDA6 form SIN3-type histone deacetylase complexes, they display distinct biological roles, with the reason for these differences being poorly understood. We has identified three angiosperm-specific HDA19-interacting homologous proteins, termed HDIP1, HDIP2, and HDIP3 (HDIP1/2/3). These proteins interact with HDA19 and other conserved histone deacetylase complex components, leading to the formation of HDA19-containing SIN3-type complexes, while they are not involved in the formation of HDA6-containing ones. While mutants of conserved SIN3-type complex components show phenotypes divergent from the hda19 mutant, the hdip1/2/3 mutant closely mirrors the hda19 mutant in development, abscisic acid signaling, and drought stress tolerance. Omics analyses indicate that HDIP1/2/3 and HDA19 co-occupy chromatin and jointly repress gene transcription, especially for stress-related genes. An a-helix motif within HDIP1 has the capacity to bind to nucleosomes and architectural DNA, and is required for its function in Arabidopsis plants. These findings suggest that the angiosperm SIN3-type complexes have evolved to include additional subunits for the precise regulation of histone deacetylation and gene transcription. Overall design: Examination of protein binding levels in transgenic plants;