Chinese Bulletin of Botany ›› 2020, Vol. 55 ›› Issue (3): 279-286.DOI: 10.11983/CBB19239

• EXPERIMENTAL COMMUNICATIONS • Previous Articles     Next Articles

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

Liurong Guan1,2,Zupei Liu2,3,Ran Xu2,Penggen Duan2,Guozheng Zhang2,3,Haiyue Yu2,3,Jing Li2,3,Yuehua Luo1,*(),Yunhai Li2,*()   

  1. 1Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Tropical Crops, Hainan University, Haikou 570228, China
    2State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
    3University of Chinese Academy of Sciences, Beijing 100039, China
  • Received:2019-12-25 Accepted:2020-03-23 Online:2020-05-01 Published:2020-07-06
  • Contact: Yuehua Luo,Yunhai Li


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 074th 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.

Key words: rice, grain size, cell expansion, Mutmap, OsBRI1