Overexpressed BRH1, a RING finger gene, alters rosette leaf shape in Arabidopsis thaliana.

Leaves are the most important plant parts for photosynthesis and respiration. Many genes are involved in determining leaf shape; however, little is known about the effects of brassinosteroid (BR) signaling-pathway genes on the development of leaf shape. Here, the brassinosteroid-responsive RING-H2 (BRH1) gene, which is suppressed by 24-epi-brassinolide treatment, was isolated from Arabidopsis thaliana. The amino acid sequence contained a highly conserved RING finger domain. In a phylogenetic analysis, BRH1 clustered closely with GLYMA11G02470.1. The leaves of brh1 mutant plants were not much different to those of the wild-type, while transgenic plants with high BRH1 expression levels had rounder rosette leaves. Mutants of the BR synthesis pathway also had a similar round leaf phenotype, and greater BRH1 expression levels. Moreover, the related marker genes KNAT1, AtHB13 and ROT4, which are known to control leaf shape, altered transcriptional levels in both transgenic BRH1 and BR-synthesis mutant lines. Thus, BRH1 may be involved in the BR signaling pathway and regulate the growth and development of rosette leaves. Research on BRH1 may prove valuable for understanding the regulatory mechanism of leaf shape and improving the leaf shapes of ornamental plants.