Guo Jia, Zhang Hongshan, Fan Mengyu, Xiao Yongkang, Zhu Yongshuang, Chen Congping, Shu Hao, Wei Miaomiao, Luo Yating, Yang Xiaorong, Liu Yue, Xu Jinze, Zhao Ke, Wang San, Yang Bin, Sun Changhui, Deng Xiaojian, Wang Pingrong
State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu, China.
Rice Research Institute, Sichuan Agricultural University, Chengdu, China.
Plant Biotechnol J. 2025 Aug;23(8):3024-3040. doi: 10.1111/pbi.70128. Epub 2025 May 9.
Brassinosteroids (BRs) are a crucial class of plant hormones and regulate many important agronomic traits in crops. In Arabidopsis (Arabidopsis thaliana), BIR3 interacts with the BR receptor BRI1 and coreceptor BAK1 to negatively regulate BR signalling. In contrast, OsBIR3 interacts with OsBRI1 and OsBAK1 to positively regulate BR signalling in rice (Oryza sativa). However, our understanding of OsBIR3 remains incomplete. In this study, we isolated a reduced upper branch (rub1) mutant of rice, exhibiting a significant reduction in grain number. The causal gene for the mutant phenotype was LOC_Os04g41030 (OsBIR3). OsBIR3 interacts with both OsBRI1 and the remorin protein OsREM4.1, but interactions of the mutated Osbir3 with both OsBRI1 and OsREM4.1 were decreased. Furthermore, BL interferes with the interaction of OsBIR3 with OsBRI1, but promotes the interaction of OsBIR3 with OsREM4.1. Overexpression of OsREM4.1 and OsBRI1 individually in the rub1 mutant caused an exacerbation of the mutant phenotype. Additionally, OsBIR3 interacts with Brd2, involving BR biosynthesis in the early stage, and the interaction of the mutated brd2 with wild-type OsBIR3 was increased. Besides, BL promotes the interaction between OsBIR3 and Brd2. Collectively, the data indicate that OsBIR3 plays a key role in maintaining the homeostasis of OsBRI1, OsREM4.1, and Brd2 at their respective protein levels. This work provides insight into the roles of OsBIR3 in BR signalling and biosynthesis pathways of rice.
油菜素甾醇（BRs）是一类关键的植物激素，调控作物许多重要的农艺性状。在拟南芥（Arabidopsis thaliana）中，BIR3与BR受体BRI1和共受体BAK1相互作用，负向调控BR信号传导。相反，OsBIR3与水稻（Oryza sativa）中的OsBRI1和OsBAK1相互作用，正向调控BR信号传导。然而，我们对OsBIR3的了解仍不完整。在本研究中，我们分离出一个水稻上部分枝减少（rub1）突变体，其粒数显著减少。该突变体表型的因果基因是LOC_Os04g41030（OsBIR3）。OsBIR3与OsBRI1和类remorin蛋白OsREM4.1均相互作用，但突变的Osbir3与OsBRI1和OsREM4.1的相互作用均减弱。此外，油菜素内酯（BL）干扰OsBIR3与OsBRI1的相互作用，但促进OsBIR3与OsREM4.1的相互作用。在rub1突变体中分别过表达OsREM4.1和OsBRI1会使突变体表型加剧。此外，OsBIR3与Brd2相互作用，参与早期BR生物合成，且突变的brd2与野生型OsBIR3的相互作用增强。此外，BL促进OsBIR3与Brd2之间的相互作用。总体而言，数据表明OsBIR3在维持OsBRI1、OsREM4.1和Brd2各自蛋白质水平的稳态中起关键作用。这项工作为深入了解OsBIR3在水稻BR信号传导和生物合成途径中的作用提供了思路。
