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

Abstract 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 numbers 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 functionally characterize OsMIR530, a regulator of grain size, and OsCKX2, a regulator of grain number, as the target genes of OsPIL11. Analysis of genetic variations suggested that OsPIL11 has likely been subjected to artificial selection during rice breeding, with Hap2 representing 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.