Wang Fuxiang, Lin Jiexin, Yang Fan, Chen Xiaofeng, Liu Yiyi, Yan Lingnan, Chen Jing, Wang Zonghua, Xie Huaan, Zhang Jianfu, Xu Huibin, Chen Songbiao
Marine and Agricultural Biotechnology Laboratory, College of Geography and Oceanography, Minjiang University, Fuzhou, 350108, China.
National Rice Engineering Laboratory of China, Rice Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, 350003, China.
J Integr Plant Biol. 2024 Dec;66(12):2648-2663. doi: 10.1111/jipb.13786. Epub 2024 Oct 30.
Grain size and grain weight are important determinants for grain yield. In this study, we identify a novel OsMAPK5-OsWRKY72 module that negatively regulates grain length and grain weight in rice. We found that loss-of-function of OsMAPK5 leads to larger cell size of the rice spikelet hulls and a significant increase in both grain length and grain weight in an indica variety Minghui 86 (MH86). OsMAPK5 interacts with OsMAPKK3/4/5 and OsWRKY72 and phosphorylates OsWRKY72 at T86 and S88. Similar to the osmapk5 MH86 mutants, the oswrky72 knockout MH86 mutants exhibited larger size of spikelet hull cells and increased grain length and grain weight, whereas the OsWRKY72-overexpression MH86 plants showed opposite phenotypes. OsWRKY72 targets the W-box motifs in the promoter of OsARF6, an auxin response factor involved in auxin signaling. Dual-luciferase reporter assays demonstrated that OsWRKY72 activates OsARF6 expression. The activation effect of the phosphorylation-mimicking OsWRKY72 on OsARF6 expression was significantly enhanced, whereas the effects of the OsWRKY72 phosphorylation-null mutants were significantly reduced. In addition, auxin levels in young panicles of the osmapk5 and oswrky72 mutants were significantly higher than that in the wild-type MH86. Collectively, our study uncovered novel connections of the OsMAPKK3/4/5-OsMAPK5-mediated MAPK signaling, OsWRKY72-mediated transcription regulation, and OsARF6-mediated auxin signaling pathways in regulating grain length and grain weight in an indica-type rice, providing promising targets for molecular breeding of rice varieties with high yield and quality.
籽粒大小和粒重是决定粮食产量的重要因素。在本研究中，我们鉴定出一个新的OsMAPK5 - OsWRKY72模块，该模块对水稻粒长和粒重起负调控作用。我们发现，在籼稻品种明恢86（MH86）中，OsMAPK5功能缺失导致水稻颖壳细胞变大，粒长和粒重均显著增加。OsMAPK5与OsMAPKK3/4/5和OsWRKY72相互作用，并在T86和S88位点磷酸化OsWRKY72。与osmapk5 MH86突变体类似，oswrky72敲除的MH86突变体表现出颖壳细胞更大，粒长和粒重增加，而OsWRKY72过表达的MH86植株则表现出相反的表型。OsWRKY72靶向OsARF6启动子中的W - box基序，OsARF6是一种参与生长素信号传导的生长素响应因子。双荧光素酶报告基因检测表明，OsWRKY72激活OsARF6表达。模拟磷酸化的OsWRKY72对OsARF6表达的激活作用显著增强，而OsWRKY72磷酸化缺失突变体的作用则显著降低。此外，osmapk5和oswrky72突变体幼穗中的生长素水平显著高于野生型MH86。总的来说，我们的研究揭示了OsMAPKK3/4/5 - OsMAPK5介导的MAPK信号传导、OsWRKY72介导的转录调控以及OsARF6介导的生长素信号通路在调控籼稻粒长和粒重方面的新联系，为高产优质水稻品种的分子育种提供了有前景的靶点。
