An-1 encodes a basic helix-loop-helix protein that regulates awn development, grain size, and grain number in rice.
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.
National Center for Gene Research, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200233, China.
Jianghong
J
Luo
Hui
H
Liu
Taoying
T
Zhou
Benguo
B
Gu
Xuehui
X
Huang
Yingying
Y
Shangguan
Jingjie
J
Zhu
Yan
Y
Li
Yan
Y
Zhao
Yongchun
Y
Wang
Qiang
Q
Zhao
Ahong
A
Wang
Ziqun
Z
Wang
Tao
T
Sang
Zixuan
Z
Wang
Bin
B
Han
D000483:Alleles; D001483:Base Sequence; D002455:Cell Division; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D002523:Edible Grain; D014644:Genetic Variation / Q000235:genetics*; D008969:Molecular Sequence Data; D012275:Oryza / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D040641:Quantitative Trait Loci / Q000235:genetics*; D017422:Sequence Analysis, DNA
D010940:Plant Proteins