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 molecular mechanisms underlying such changes remain 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), which regulates the bract outgrowth and thus affects 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. These discoveries contribute to our understanding of the dynamic plant architecture and provide novel insights for improving crop yields.

草的生殖过渡的特点是侧枝模式的转换，其特征是抑制对向叶（苞片）的生长，并在花序（圆锥花序）中快速形成高级分支。然而，这种变化背后的分子机制仍然很大程度上未知。在这里，我们表明水稻生殖分枝需要抑制苞片。我们确定了一条涉及内在时间标尺microRNA156 / 529的通路，它们的目标SQUAMOSA PROMOTER BINDING PROTEIN LIKE ( SPL ) 基因、NECK LEAF1 ( NL1 ) 和PLASTOCHRON1 ( PLA1 ))，它调节苞片的生长，从而影响营养分枝和生殖分枝之间的模式转换。抑制苞片会导致生殖转变后转录组和染色质可及性的全局重编程，而这些过程在这些基因的突变体中很大程度上失调。这些发现有助于我们了解动态植物结构，并为提高作物产量提供新的见解。