54.HLH型転写因子をコードするイネのBU1遺伝子はBRシグナル伝達を介してラミナジョイントの屈曲を制御する(口頭発表)

概要

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Brassinosteroids (BRs) are involved in many developmental processes. However, little is known about the BR signal transduction and response network in monocots. To identify novel BR-related genes in rice, we monitored the transcriptomic response of the brassinosteroid deficient1 (brd1) mutant, with a defective BR biosynthetic gene, to brassinolide treatment. Here, we describe a novel BR-induced rice gene BRASSINOSTEROID UPREGULATED1 (BU1, previously called OsBU3), encoding a helix-loop-helix protein. Rice plants overexpressing BU1 (BU1: OX) showed enhanced bending of the lamina joint, increased grain size, and resistance to brassinazole, an inhibitor of BR biosynthesis. In contrast to BU1:OX, RNAi plants designed to repress both BU1 and its homologs displayed erect leaves. This year, we showed that the induction of BU1 by exogenous brassinolide did not require de novo protein synthesis and it was weaker in a BR receptor mutant OsbriI (d61) and a rice G protein alpha subunit (RGA1) mutant d1, compared to the wild type. These results indicate that BU1 protein is a positive regulator of BR response: it controls bending of the lamina joint in rice and it is a novel primary response gene that participates in two BR signaling pathways through OsBRI1 and RGA1. Furthermore, expression analyses showed that BU1 is expressed in several organs including lamina joint, phloem, and epithelial cells in embryos.
植物化学調節学会の論文
2009-10-06