分枝或分蘖数目是影响植物株型、产量和生物量的关键因素，而环境中光照条件是影响分枝的主要因子之一。密植或遮荫下红光与远红光比率下降，激发了植物的避荫反应，导致分枝数目减少。光敏色素是植物感知红光和远红光的主要光受体。在拟南芥中光敏色素B (phyB)及互作蛋白PIF因子在调控避荫反应中起关键作用，但phyB和PIF因子如何调控植物分枝的分子机理目前仍不清楚。我们的前期研究结果暗示拟南芥phyB和PIF因子很可能直接调控miR156家族基因的表达，而miR156可以抑制其下游SPL基因家族的表达，从而控制分枝的发生。本项目拟综合生物化学、分子生物学、遗传学等研究手段验证我们的工作假说。预期取得的研究成果将有助于阐明光照质量变化影响植株分枝发生的分子机理，加深我们对光照因素影响植株生长发育和作物理想株型分子调控机理的理解，同时为耐荫、耐密植作物新品种的培育以增加单位面积产量提供重要理论依据。

The branch/ tiller number is a key component of plant architecture, and thus yield and biomass. Light is a major environmental factor that regulates shoot branching. The shade of nearby vegetation reduces the ratio of red to far-red light (R/FR) and can trigger shade avoidance responses, including reduced branching. Phytochromes are the major photoreceptors perceiving red and far-red light in plants. Phytochrome B (phyB) and its interacting partners (PIFs) play a critical role inregulating shade avoidance response and branching in Arabidopsis, however, the detailed molecular mechanism of how phyB and PIFs act to regulate branching remains largely unknown. Our preliminary studies revealed that Arabidopsis PIFs may directly regulate the expression of miR156, another conserved key regulator of branching (tillering) in diverse plant species. In turn, miR156 could regulate branching via inhibition of its downstream target genes SPL (SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE). In this project, we will conduct a series of molecular, biochemical and genetic experiments to further substantiate this hypothesis. This work will help to elucidate the molecular mechanism of light and miR156 regulation of branching in Arabidopsis, which will greatly deepen our understanding of light control of plant development and ideal plant architecture, and provide guidance for breeding of shade-tolerant varieties for high density planting to increase crop yield per unit land.