Low grain weight, a new allele of BRITTLE CULM12, affects grain size through regulating GW7 expression in rice

Yafeng Ye; Shuoxun Wang; Yan Ren; Huijie Yang; Junyao Guo; Hongrui Jiang; Xiaotong Zhu; Wenhao Li; Liangzhi Tao; Yue Zhan; Yuejin Wu; Xiangdong Fu; Kun Wu; Binmei Liu

doi:10.3389/fpls.2022.997624

Low grain weight, a new allele of BRITTLE CULM12, affects grain size through regulating GW7 expression in rice

Front Plant Sci. 2022 Sep 13:13:997624. doi: 10.3389/fpls.2022.997624. eCollection 2022.

Authors

Yafeng Ye^{1

2}, Shuoxun Wang³, Yan Ren^{1

2}, Huijie Yang^{1

2}, Junyao Guo^{1

2}, Hongrui Jiang^{1

2}, Xiaotong Zhu^{1

2}, Wenhao Li^{1

2}, Liangzhi Tao^{1

2}, Yue Zhan^{1

2}, Yuejin Wu^{1

2}, Xiangdong Fu³, Kun Wu³, Binmei Liu^{1

2}

Affiliations

¹ Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.
² Anhui Province Key Laboratory of Environmental Toxicology and Pollution Control Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China.
³ State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.

Abstract

Grain weight is a major determinant in rice yield, which is tightly associated with grain size. However, the underlying molecular mechanisms that control this trait remain unclear. Here, we report a rice (Oryza sativa) mutant, low grain weight (lgw), which shows that reduced grain length is caused by decreased cell elongation and proliferation. Map-based cloning revealed that all mutant phenotypes resulted from a nine-base pair (bp) deletion in LGW, which encodes the kinesin-like protein BRITTLE CULM12 (BC12). Protein sequence alignment analysis revealed that the mutation site was located at the nuclear localization signal (NLS) of LGW/BC12, resulting in the lgw protein not being located in the nucleus. LGW is preferentially expressed in both culms and roots, as well as in the early developing panicles. Overexpression of LGW increased the grain length, indicating that LGW is a positive regulator for regulating grain length. In addition, LGW/BC12 is directly bound to the promoter of GW7 and activates its expression. Elevating the GW7 expression levels in lgw plants rescued the small grain size phenotype. We conclude that LGW regulates grain development by directly binding to the GW7 promoter and activating its expression. Our findings revealed that LGW plays an important role in regulating grain size, and manipulation of this gene provides a new strategy for regulating grain weight in rice.

Keywords: GW7; LGW; gene expression; grain size; grain yield; rice.