一个新的OsBRI1弱等位突变体的鉴定及其调控种子大小的功能研究

水稻(Oryza sativa)籽粒大小是影响其产量的关键农艺性状, 克隆并研究水稻籽粒大小相关基因对于提高水稻产量具有重要意义。为深入探究水稻籽粒大小的调控机制, 通过EMS诱变品种宽叶粳(KYJ), 分离了一系列水稻籽粒大小改变的突变体, 其中smg12表现为籽粒变小, 株高变矮, 一级枝梗数和二级枝梗数减少。遗传分析表明, 该小粒突变体受隐性单基因控制。细胞学分析显示, 该突变体颖壳纵向细胞长度显著变短, 表明SMG12主要影响细胞扩展。利用Mutmap方法对候选基因进行克隆, 筛选出SMG12的候选基因OsBRI1, 该基因编码油菜素内酯受体激酶。OsBRI1外显子上的第2 074个碱基发生了由C到T的置换, 产生非同义突变, 使得该位置编码的脯氨酸变为丝氨酸, 从而影响OsBRI1的功能。综上, 该研究鉴定了OsBRI1基因的1个新等位变异, 揭示了油菜素内酯途径调控水稻籽粒大小的细胞和分子基础。

Identification of a New OsBRI1 Weak Allele and Analysis of its Function in Grain Size Control

Rice (Oryza sativa) grain size and grain weight are key agronomic traits that affect rice yield. Cloning and study of grain size genes are helpful to increase rice production. In order to further understand the mechanism of rice grain size control, a set of mutants with altered grain size from an EMS-treated elite japonica cultivar KYJ (Kuanyejing) were isolated. smg12 exhibits small grains, short plants, and reduced number of primary branches and secondary branches. Genetic analyses show that the smg12 mutant phenotypes are controlled by a single recessive gene. Our celluar analyses show that the small grain size phenotype of smg12 is caused by the decrease in cell size of glumes, indicating that SMG12 affects cell expansion. By using the Mutmap method, we reveal that the candidate gene for SMG12 is OsBRI1, which encodes a brassinolide receptor kinase. The smg12 mutant causes a substitution of the 2 074^th base (C to T) in OsBRI1, which results in an amino acid change (proline to serine). Therefore, this study identified a new mutant allele of OsBRI1 and provides a cellular and molecular basis for BR-mediated grain size control in rice.