The histone deacetylase HDA703 interacts with OsBZR1 to regulate rice brassinosteroid signaling, growth and heading date through repression of Ghd7 expression

The plant steroid hormones brassinosteroids (BRs) play crucial roles in plant growth and development. The BR signal transduction pathway from perception to the key transcription factors has been well understood inArabidopsis thalianaand in rice (Oryza sativa); however, the mechanisms conferring BR-mediated growth and flowering remain largely unknown, especially in rice. In this study, we show that HDA703 is a histone H4K8 and H4K12 deacetylase in rice.Hda703mutants display a typical BR loss-of-function phenotype and reduced sensitivity to brassinolide, the most active BR. Rice plants overexpressingHDA703exhibit some BR gain-of-function phenotypes dependent on BR biosynthesis and signaling. We also show thatHDA703is a direct target of BRASSINAZOLE-RESISTANT1 (OsBZR1), a primary regulator of rice BR signaling, and HDA703 interacts with OsBZR1 in rice. We further show thatGRAIN NUMBER, PLANT HEIGHT, and HEADING DATE 7(Ghd7), a central regulator of growth, development, and the stress response, is a direct target of OsBZR1. HDA703 directly targetsGhd7and represses its expression through histone H4 deacetylation.HDA703-overexpressing rice plants phenocopyGhd7-silencing rice plants in both growth and heading date. Together, our study suggests that HDA703, a histone H4 deacetylase, interacts with OsBZR1 to regulate rice BR signaling, growth, and heading date through epigenetic regulation ofGhd7.