An-1 Encodes a Basic Helix-Loop-Helix Protein That Regulates Awn Development, Grain Size, and Grain Number in Rice

作者：Jianghong Luo, Hui Liu, Taoying Zhou, Benguo Gu, Xuehui Huang, Yingying Shangguan, Jingjie Zhu, Yán Li, Yan Zhao, Yongchun Wang, Qiang Zhao, Ahong Wang, Ziqun Wang, Tao Sang, Zixuan Wang, Bin Han · 发表于：The Plant Cell · 年份：2013 · DOI：10.1105/tpc.113.113589 · 被引用次数：274 · 研究领域：Genetic Mapping and Diversity in Plants and Animals、Plant Molecular Biology Research、Plant Reproductive Biology

Long awns are important for seed dispersal in wild rice (Oryza rufipogon), but are absent in cultivated rice (Oryza sativa). The genetic mechanism involved in loss-of-awn in cultivated rice remains unknown. We report here the molecular cloning of a major quantitative trait locus, An-1, which regulates long awn formation in O. rufipogon. An-1 encodes a basic helix-loop-helix protein, which regulates cell division. The nearly-isogenic line (NIL-An-1) carrying a wild allele An-1 in the genetic background of the awnless indica Guangluai4 produces long awns and longer grains, but significantly fewer grains per panicle compared with Guangluai4. Transgenic studies confirmed that An-1 positively regulates awn elongation, but negatively regulates grain number per panicle. Genetic variations in the An-1 locus were found to be associated with awn loss in cultivated rice. Population genetic analysis of wild and cultivated rice showed a significant reduction in nucleotide diversity of the An-1 locus in rice cultivars, suggesting that the An-1 locus was a major target for artificial selection. Thus, we propose that awn loss was favored and strongly selected by humans, as genetic variations at the An-1 locus that cause awn loss would increase grain numbers and subsequently improve grain yield in cultivated rice.