HDA9-PWR-HOS15 Is a Core Histone Deacetylase Complex Regulating Transcription and Development

Abstract

Histone deacetylases remove acetyl groups from histone proteins and play important roles in many genomic processes. How histone deacetylases perform specialized molecular and biological functions in plants is poorly understood. Here, we identify HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 15 (HOS15) as a core member of the Arabidopsis (<i>Arabidopsis thaliana</i>) HISTONE DEACETYLASE9-POWERDRESS (HDA9-PWR) complex. HOS15 immunoprecipitates with both HDA9 and PWR. Mutation of <i>HOS15</i> induces histone hyperacetylation and methylation changes similar to <i>hda9</i> and <i>pwr</i> mutants. <i>HOS15</i>, <i>HDA9</i>, and <i>PWR</i> are coexpressed in all organs, and mutant combinations display remarkable phenotypic resemblance and nonadditivity for organogenesis and developmental phase transitions. Ninety percent of <i>HOS15</i>-regulated genes are also controlled by <i>HDA9</i> and <i>PWR</i> HDA9 binds to and directly represses 92 genes, many of which are responsive to biotic and abiotic stimuli, including a family of ethylene response factor genes. Additionally, <i>HOS15</i> regulates HDA9 nuclear accumulation and chromatin association. Collectively, this study establishes that HOS15 forms a core complex with HDA9 and PWR to control gene expression and plant development.