The COMPASS-Like Complex Promotes Flowering and Panicle Branching in Rice.

Flowering time (heading date) and panicle branch number are important agronomic traits that determine yield in rice ( Oryza sativa ). The activation of flowering requires histone methylation, but the roles of trimethylation of Lys 4 of histone 3 (H3K4me3) in modulating heading date and panicle development are unclear. Here, we showed that the COMPASS-like complex promotes flowering and panicle branching. The rice ( Oryza sativa ) WD40 protein OsWDR5a interacts with the TRITHORAX-like protein OsTrx1/SET domain group protein 723 (SDG723) to form the core components of the COMPASS-like complex. Plants in which OsWDR5a or OsTrx1 expression was decreased by RNA interference produced fewer secondary branches and less grain and exhibited a delayed heading date under long-day and short-day conditions, whereas loss of OsWDR5a function resulted in embryo lethality. OsWDR5a binds to Early heading date 1 to regulate its H3K4me3 and expression levels. Together, our results show that the COMPASS-like complex promotes flowering and panicle development and suggest that modulation of H3K4me3 levels by the COMPASS-like complex is critical for rice development.