Optimization of rice panicle architecture by specifically suppressing ligand–receptor pairs

Rice panicle architecture determines the grain number per panicle and therefore impacts grain yield. The OsER1–OsMKKK10–OsMKK4–OsMPK6 pathway shapes panicle architecture by regulating cytokinin metabolism. However, the specific upstream ligands perceived by the OsER1 receptor are unknown. Here, we report that the EPIDERMAL PATTERNING FACTOR (EPF)/EPF-LIKE (EPFL) small secreted peptide family members OsEPFL6, OsEPFL7, OsEPFL8, and OsEPFL9 synergistically contribute to rice panicle morphogenesis by recognizing the OsER1 receptor and activating the mitogen-activated protein kinase cascade. Notably, OsEPFL6, OsEPFL7, OsEPFL8, and OsEPFL9 negatively regulate spikelet number per panicle, but OsEPFL8 also controls rice spikelet fertility. A osepfl6 osepfl7 osepfl9 triple mutant had significantly enhanced grain yield without affecting spikelet fertility, suggesting that specifically suppressing the OsEPFL6–OsER1, OsEPFL7–OsER1, and OsEPFL9–OsER1 ligand–receptor pairs can optimize rice panicle architecture. These findings provide a framework for fundamental understanding of the role of ligand–receptor signaling in rice panicle development and demonstrate a potential method to overcome the trade-off between spikelet number and fertility.