, a Novel Allele of , Regulates Grain Size and Flag Leaf Angle in Rice.

Grain size and flag leaf angle are two important traits that determining grain yield in rice. However, the mechanisms regulating these two traits remain largely unknown. In this study, a rice () mutant with a large flag leaf angle was identified, and map-based cloning revealed that a single base substitution followed by a 2 bp insertion in the gene resulted in larger grains, a larger flag leaf angle, and higher plant height than the wild type. Sequence analysis revealed that is a novel allele of (), which encodes a cytochrome P450 protein. Functional complementation and overexpression tests showed that can rescue the bigger grain size and larger flag leaf angle in the Xiushui11 (XS) background. Knockdown of the transcription level by RNA interference resulted in elevated grain size and flag leaf angle in the Nipponbare (NIP) background. Morphological and cellular analyses suggested that regulated grain size and flag leaf angle by promoting cell expansion and cell proliferation. Our results provided new insight into the functions of in rice, especially in regulating grain size and flag leaf angle, indicating a potential target for the improvement of rice breeding.