AtINO80 represses photomorphogenesis by modulating nucleosome density and H2A.Z incorporation in light-related genes.

Abstract

Photomorphogenesis is a critical developmental process bridging light-regulated transcriptional reprogramming with morphological changes in organisms. Strikingly, the chromatin-based transcriptional control of photomorphogenesis remains poorly understood. Here, we show that the <i>Arabidopsis</i> (<i>Arabidopsis thaliana</i>) ortholog of ATP-dependent chromatin-remodeling factor AtINO80 represses plant photomorphogenesis. Loss of AtINO80 inhibited hypocotyl cell elongation and caused anthocyanin accumulation. Both light-induced genes and dark-induced genes were affected in the <i>atino80</i> mutant. Genome-wide occupancy of the H2A.Z histone variant and levels of histone H3 were reduced in <i>atino80</i> In particular, AtINO80 bound the gene body of <i>ELONGATED HYPOCOTYL 5</i> (<i>HY5</i>), resulting in lower chromatin incorporations of H2A.Z and H3 at <i>HY5</i> in <i>atino80</i> Genetic analysis revealed that AtINO80 acts in a phytochrome B- and HY5-dependent manner in the regulation of photomorphogenesis. Together, our study elucidates a mechanism wherein AtINO80 modulates nucleosome density and H2A.Z incorporation and represses the transcription of light-related genes, such as <i>HY5</i>, to fine tune plant photomorphogenesis.