OsmiR530 acts downstream of OsPIL15 to regulate grain yield in rice.

MicroRNAs (miRNAs) are a class of small noncoding RNAs that play important roles in plant growth and development as well as in stress responses. However, little is known about their regulatory functions affecting rice grain yield. We functionally characterized a novel miRNA in rice, OsmiR530, its target OsPL3, and its upstream regulator phytochrome-interacting factor-like 15 (OsPIL15). Their effects on rice yield were dissected comprehensively. We determined that OsmiR530 negatively regulates grain yield. Blocking OsmiR530 increases grain yield, whereas OsmiR530 overexpression significantly decreases grain size and panicle branching, leading to yield loss. Additionally, OsPL3, which encodes a PLUS3 domain-containing protein, is targeted directly by OsmiR530. Knocking out OsPL3 decreases the grain yield. In-depth analyses indicated that OsPIL15 activates OsMIR530 expression by directly binding to the G-box elements in the promoter. Analyses of genetic variations suggested that the OsMIR530 locus has likely been subjected to artificial selection during rice breeding. The results presented herein reveal a novel OsPIL15-OsmiR530 module controlling rice grain yield, thus providing researchers with a new target for the breeding of high-yielding rice.