The OsmiR396c‐OsGRF4‐OsGIF1 regulatory module determines grain size and yield in rice

Summary Grain weight is the most important component of rice yield and is mainly determined by grain size, which is generally controlled by quantitative trait loci ( QTL s). Although numerous QTL s that regulate grain weight have been identified, the genetic network that controls grain size remains unclear. Herein, we report the cloning and functional analysis of a dominant QTL , grain length and width 2 ( GLW 2 ), which positively regulates grain weight by simultaneously increasing grain length and width. The GLW 2 locus encodes OsGRF4 (growth‐regulating factor 4) and is regulated by the micro RNA miR396c in vivo . The mutation in OsGRF4 perturbs the OsmiR396 target regulation of OsGRF4 , generating a larger grain size and enhanced grain yield. We also demonstrate that Os GIF 1 (GRF‐interacting factors 1) directly interacts with OsGRF4, and increasing its expression improves grain size. Our results suggest that the miR396c‐OsGRF4‐Os GIF 1 regulatory module plays an important role in grain size determination and holds implications for rice yield improvement.