Function of a subunit of heterotrimeric G protein in brassinosteroid response of rice plants

摘要

The alpha subunit of heterotrimeric G-proteins (G alpha) is involved in a broad range of aspects of the brassinosteroid (BR) response, such as the enhancement of lamina bending. However, it has been suggested from epistatic analysis of d1 and d61, which are mutants deficient for Goc and the BR receptor BRI1, that GOC and BRI1 may function via distinct pathways in many cases. In this study, we investigated further the genetic interaction between Goc and BRI1. We report the analysis of transformants ofT65dl and T65d1/ d61-7 into which were introduced a constitutively active form of Goc, Q223L. The application of 24-epi-brassinolide (24-epiBL) to T65dl expressing Q223L still resulted in elongation of the coleoptile and, in fact, it was enhanced over the wild-type plant (WT) level in a concentration dependent manner. In T65dl/d61-7 expressing Q223L, the seed size was enlarged over that of d6l-7 due to activation of Goc. These results suggest that Q223L is able to augment the BR response in response to24-epiBL and also that Q223L functions independently of BRI1 in the process of determining seed morphology, given that Q223L was functional in the BRI1-deficient mutant, d61-7.