Abstract
To enhance our understanding of brassinosteroid (BR) metabolism and signaling, we have been studied BR-related rice mutants and identified 6 matabolic enzyme genes and one receptor gene. To date, 11 alleles with different severity of phenotype have been identified in d61, the loss-of-function mutants of the rice BR receptor gene, OsBRI1. In this study, we selected 4 BR-insensitive mutants having different phenotype from previously known d61 mutants. However, 3 of 4 mutants were alleles of d61 and only one mutant was novel. This novel mutant showed various BR-related phenotypes including increased endogenous bioactive BR level. Double mutant with d61 have increased severity of phenotype suggesting that the corresponding gene, which encodes ubiquitin E3 ligase, acts downstream of BR receptor. Based on recent experiments, we will discuss the biological function of this E3 ligase in BR signaling.
