BEAR1, a bHLH transcription factor, controls seedling growth by regulating gibberellins biosynthesis in rice
Yantong Teng,
Maohong Cai,
Qinyu Xie,
Qinglong Liu,
Haiwen Zhang,
Tao Chen
Affiliations
Yantong Teng
Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou 311121, Zhejiang, China; College of Life Sciences, Inner Mongolia University, Hohhot 010021, Inner Mongolia, China
Maohong Cai
Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou 311121, Zhejiang, China
Qinyu Xie
Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou 311121, Zhejiang, China
Qinglong Liu
Institute of Crop and Nuclear Technology Utilization, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, Zhejiang, China
Haiwen Zhang
Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Tao Chen
Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, College of Life and Environmental Science, Hangzhou Normal University, Hangzhou 311121, Zhejiang, China; Corresponding author.
The genetic pathways of rice seedling growth have a major impact on seedling emergence from soil and development. In this study, we identified a new bHLH transcription factor, BEAR1, from rice RNAi mutant library. Both the BEAR1-RNAi and bear1 CRISPR mutants had accelerated seedling growth. Histological section of leaves showed accelerated development of lacuna and vascular bundles in bear1 mutant. GUS staining revealed that BEAR1 was highly expressed in coleoptiles and leaves at seedling stage. Expression analysis of gibberellin (GA) biosynthesis and metabolic genes and content determination of active GAs indicated that the expression of GA biosynthesis genes, especially OsKS4 and OsCPS2, were upregulated and the GAs content were significantly increased in bear1, which correlated with the seedling phenotype of bear1 mutant. Molecular and biochemical assays revealed that BEAR1 directly binds to the promoter of OsKS4, thereby repressing its expression. Haplotypes analysis showed clear differentiation in indica and japonica rice varieties, and a strong correlation with seedling height. These findings provide novel insights into the regulation of seedling growth in rice.
