Overexpression Alters Plant Architecture, Grain Shape, and Seed Fertility.

OVATE family proteins (OFPs) play important roles in plant growth and development, hormone signaling, and stress response pathways. However, the functions of OsOFPs in rice are largely unknown. In this study, a novel gain-of-function rice mutant, , was identified. This mutant exhibited decreased plant height, erect leaves, reduced panicle size, short and wide seeds, delayed seed germination time, and reduced fertility. These phenotypic changes were attributed to the increased expression of , which was caused by a T-DNA insertion. Complementation of the phenotype by knockout of using the CRISPR/Cas9 system confirmed that the phenotype was caused by overexpression. In addition, transgenic plants overexpressing OsOFP6 with the 35S promoter mimicked the phenotype. Cytological observations of the glumes showed that overexpression altered the grain shape, mainly by altering the cell shape. Hormone response experiments showed that was involved in the gibberellin (GA) and brassinolide (BR) signaling responses. Further studies revealed that OsOFP6 interacts with E3BB, which is orthologous to the central organ size-control protein BIG BROTHER (BB). This study further elucidates the regulation mechanism of the rice OFP family on plant architecture and grain shape.