Uncovering novel cross-talks between epigenetic modifiers and environmental signals during plant development

Photomorphogenesis is a key transitional event occurring when young 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 changes1,2. Here we report that HDC1 positively regulates hypocotyl elongation specifically when plants are exposed to red-light conditions. Chromatin immunoprecipitation combined with next generation sequencing (ChIP-seq) and qPCR analyses revealed that HDC1 is responsible for deacetylating regulatory regions of growth-related genes and thereby moderating their expression. Protein interaction assays showed that HDC1 can directly interact with light components and regulating their abundance. Additionally, chromatin accessibility profiles of Arabidopsis seedlings unveil novel mechanisms modulating environmental responses. Taken together, our findings further explore the connection between light signalling pathway and the chromatin state and assign another function to HDC1 in plants.