Bract suppression regulated by the miR156/529-SPLs-NL1-PLA1 module is required for the transition from vegetative to reproductive branching in rice.

Reproductive transition of grasses is characterized by switching the pattern of lateral branches featuring the suppression of outgrowth of the subtending leaves (bracts) and rapid formation of higher-order branches in the inflorescence (panicle). However, the underlying molecular mechanisms of such changes are largely unknown. Here, we show that bract suppression is required for the reproductive branching in rice. We identified a pathway involving the intrinsic time ruler microRNA156/529, their targets SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes, NECK LEAF1 (NL1) and PLASTOCHRON1 (PLA1) that regulate the bract outgrowth, thus affecting the pattern switch between vegetative and reproductive branching. Suppression of the bract results in global reprogramming of transcriptome and chromatin accessibility following the reproductive transition, while these processes are largely dysregulated in the mutants of these genes. The elucidation of such mechanisms may enhance our understanding of the dynamic plant architecture and provide novel insights for improving crop yields.