The Phytochrome-Interacting Factor OsPIL11 Coordinates Grain Weight and Grain Number Via Directly Regulating the Expression of OsMIR530 and OsCKX2 in Rice

Grain weight and panicle architecture are pivotal determinants of rice yield, yet the regulatory mechanisms coordinating these traits remain elusive. Here, we functionally characterized a phytochrome-interacting factor, OsPIL11, serving as a negative regulator of grain weight and grain number per panicle. Knocking out OsPIL11 resulted in increased grain weight and grain number per panicle. OsPIL11 regulates grain weight by affecting cell expansion and division in the spikelet hulls, and controls grain number per panicle by regulating the number of primary branches. We further identified MicroRNA530, and cytokinin oxidase/dehydrogenase 2 as the target genes of OsPIL11 to regulate grain size and grain number in rice. Analysis of genetic variations suggested that there are two main haplotypes (Hap1 and Hap2) of OsPIL11. Hap1 confers the increased grain width and grain weight compared to Hap2, implying Hap1 as a superior haplotype for yield improvement. These findings provide novel insights into the molecular mechanisms underlying the regulation of rice yield, offering valuable genetic resources for the development of high-yield rice varieties through molecular breeding approaches.