Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement & Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
South China National Botanical Garden, Guangzhou 510650, China.
J Exp Bot. 2024 Feb 2;75(3):789-801. doi: 10.1093/jxb/erad397.
F-box proteins participate in the regulation of many processes, including cell division, development, and plant hormone responses. Brassinosteroids (BRs) regulate plant growth and development by activating core transcriptional and other multiple factors. In rice, OVATE family proteins (OFPs) participate in BR signalling and regulate grain size. Here we identified an F-box E3 ubiquitin ligase, FBX206, that acts as a negative factor in BR signalling and regulates grain size and yield in rice. Suppressed expression of FBX206 by RNAi leads to promoted plant growth and increased grain yield. Molecular analyses showed that the expression levels of BR biosynthetic genes were up-regulated, whereas those of BR catabolic genes were down-regulated in FBX206-RNAi plants, resulting in the accumulation of 28-homoBL, one of the bioactive BRs. FBX206 interacted with OsOFP8, a positive regulator in BR signalling, and OsOFP19, a negative regulator in BR signalling. SCFFBX206 mediated the degradation of OsOFP8 but suppressed OsOFP19 degradation. OsOFP8 interacted with OsOFP19, and the reciprocal regulation between OsOFP8 and OsOFP19 required the presence of FBX206. FBX206 itself was ubiquitinated and degraded, but interactions of OsOFP8 and OsOFP19 synergistically suppressed the degradation of FBX206. Genetic interactions indicated an additive effect between FBX206 and OsOFP8 and epistatic effects of OsOFP19 on FBX206 and OsOFP8. Our study reveals the regulatory networks of FBX206, OsOFP8, and OsOFP19 in BR signalling that regulate grain size and yield in rice.
F-box 蛋白参与许多过程的调节，包括细胞分裂、发育和植物激素反应。油菜素内酯（BRs）通过激活核心转录因子和其他多种因子来调节植物的生长和发育。在水稻中，卵形家族蛋白（OFPs）参与 BR 信号转导并调节粒大小。在这里，我们鉴定了一个 F-box E3 泛素连接酶 FBX206，它作为 BR 信号转导的负因子，调节水稻的粒大小和产量。通过 RNAi 抑制 FBX206 的表达会导致植物生长促进和产量增加。分子分析表明，BR 生物合成基因的表达水平上调，而 BR 分解代谢基因的表达水平下调，导致 28-羟基油菜素内酯（一种生物活性 BR）的积累。FBX206 与 OsOFP8（BR 信号转导的正调节剂）和 OsOFP19（BR 信号转导的负调节剂）相互作用。SCFFBX206 介导 OsOFP8 的降解，但抑制 OsOFP19 的降解。OsOFP8 与 OsOFP19 相互作用，OsOFP8 和 OsOFP19 之间的相互调节需要 FBX206 的存在。FBX206 自身被泛素化和降解，但 OsOFP8 和 OsOFP19 的相互作用协同抑制 FBX206 的降解。遗传相互作用表明 FBX206 和 OsOFP8 之间存在累加效应，而 OsOFP19 对 FBX206 和 OsOFP8 具有上位性效应。我们的研究揭示了 FBX206、OsOFP8 和 OsOFP19 在 BR 信号转导中调节粒大小和产量的调控网络。
