Hua Yuan , Zhengyan Xu , Weilan Chen , Chaoyang Deng , Yi Liu , Min Yuan , Peng Gao , Hui Shi , Bin Tu , Ting Li , Liangzhu Kang , Bingtian Ma , Yuping Wang , Jing Wang , Xuewei Chen , Shigui Li* , Peng Qin*
Journal of Experimental Botany（TOP，IF=6.992），2022
Grain size is an important trait that directly affects grain yield in rice; however, the genetic and molecular mechanisms regulating grain size remain unclear. In this study, we identified a mutant, grain length and grain weight 10 (glw10), which exhibited significantly reduced grain length and grain weight. Histological analysis demonstrated that GLW10 affects cell expansion, which regulates grain size. MutMap-based gene mapping and transgenic experiments demonstrated that GLW10 encodes a putative brassinosteroid (BR)-signaling kinase, OsBSK2. OsBSK2 is a plasma membrane protein, and an N-myristoylation site is needed for both its membrane localization and functions. OsBSK2 directly interacts with the BR receptor kinase OsBRI1, however, genetic experiments have demonstrated that OsBSK2 likely regulates grain size independently of the BR signaling pathway. OsBSK2 can form a homodimer or heterodimers with OsBSK3 and OsBSK4, and silencing OsBSK2, OsBSK3, and OsBSK4 reduced grain size. This indicates that OsBSKs seem to function as homodimers or heterodimers to positively regulate grain size in rice. They are both highly expressed in young panicles and spikelet hulls, which indicates that they regulate grain size. In summary, our results provide novel insights into the function of BSKs in rice and novel targets for improving grain size during crop breeding.
Keywords：rice, grain size, 1000-grain weight, OsBSK2, cell expansion, brassinosteroid signaling