BLA1 Affects Leaf Angles by Altering Brassinosteroid Biosynthesis in Rice ( L.).

Brassinosteroids (BRs) are crucial plant hormones influencing diverse developmental processes in rice. While several enzymes in BR biosynthesis have been identified, their regulatory mechanisms remain largely unknown. This study highlights a novel regulatory pathway wherein the CHD3 chromatin remodeler, epigenetically modulates the expression of key BR biosynthesis genes, and Phenotypic analysis of mutants revealed significant alterations, such as increased leaf angles and longer mesocotyls, which were alleviated by BR synthesis inhibitors. Moreover, the mutants showed elevated BR levels that correlated with the significant upregulation of the expression levels of and , particularly at the lamina joint sites. Mechanistically, the yeast one-hybrid and chromatin immunoprecipitation assays revealed specific binding of BLA1 to the promoter regions of and accompanied by a marked enrichment of the transcriptionally active histone modification, H3K4me3, on these loci in the mutant. Functional assessments of the and mutants confirmed their reduced sensitivity to BR, further underscoring their critical regulatory roles in BR-mediated developmental processes. Our findings uncovered an epigenetic mechanism that governs BR biosynthesis and orchestrates the expression of and to modulate BR levels and influence rice growth and development.