Histone Deacetylase Complex 1 is a novel regulator of hypocotyl elongation in Arabidopsis thaliana

Photomorphogenesis is one of the primary plant responses occurring when seedlings are first exposed to light. Upon red-light, this process is based on the interaction between the photoreceptor Phytochrome B (phyB) and its downstream components. Histone Deacetylase Complex 1 (HDC1) is a member of the histone deacetylation complex (HDAC) that shapes the sensitivity and growth of Arabidopsis in response to environmental stimuli. Here we report that HDC1 positively regulates hypocotyl elongation specifically when plants are exposed to monochromatic low red-light conditions. Chromatin immunoprecipitation combined with next generation sequencing (ChIP-seq) and qPCR analyses revealed that HDC1 is responsible for deacetylating the promoter regions of growthrelated genes and thereby modulating their transcriptional levels. Protein interaction assays showed that HDC1 can directly interact with light components and regulating their abundance. Taken together, our findings reveal a novel connection between the light signaling pathway and chromatin remodelers by defining a new function for HDC1 in plant.