植物在生长发育过程中受到很多环境因素的影响，重力是植物面临的一个非常重要的环境因素。植物重力反应是指植物在感受重力刺激后重新调整生长方向的一种重要生长发育过程。水稻分蘖角度是决定水稻株型、与水稻产量有直接关系的重要农艺性状之一。植株地上部分的重力反应是决定分蘖角度的关键因素。已知生长素在重力反应过程中起着关键的作用，但目前对于植物重力反应特别是地上部分重力反应的机制还非常有限。我们通过研究水稻重力反应缺陷突变体la1的抑制子发现，新近发现的植物分枝形成的抑制激素独角金内酯可以通过调控生长素合成途径来控制水稻地上部分的重力反应，进而影响分蘖角度。我们前期的研究结果为阐明植物重力反应及分蘖角度的分子机制提供了新的突破口。本项目将在此基础上，继续通过遗传学、分子生物学、细胞生物学、生物信息学等技术手段，揭示独角金内酯与生长素互作调控植物重力反应及水稻分蘖角度的分子网络。

Plant shoot gravitropism is a process of plant perception of gravity stimuli and reorienting growth direction during the plant growth and development. Although auxin redistribution upon gravistimulation plays an important role in shoot gravitropism, the mechanism underlying the auxin regulation of shoot gravitropism is not yet understood. Tiller angle, a key agronomic trait for achieving ideal plant architecture and increasing grain yield, is mainly regulated by shoot gravitropism. Strigolactones (SLs) are a group of newly identified plant hormones that are essential for shoot branching/rice tillering and still have increasing biological functions to be uncovered. Through screening suppressors of la1 (sols), a classic rice mutant exhibiting large tiller angle and defective shoot gravitropism, we identified multiple SOLs that are components involved in the SL pathway. Our study suggests that SL pathway mutants can rescue the spreading phenotype of la1. We further reveal that SLs can inhibit auxin biosynthesis and attenuate rice shoot gravitropism mainly through reducing the local IAA content. Based on our previous results, we will further elucidate the interaction of strigolactones and auxin in the regulation of plant shoot gravitropism and rice tiller angle in this project.

本项目在前期发现独脚金内酯与生长素相互作用调控重力反应及分蘖角度机理的基础上,通过重力反应动态转录组揭示独脚金内酯与生长素调控分蘖角度的重要组分,同时解析调控水稻分蘖角度的分子网络。研究结果发现，在重力反应早期和后期分别有958和3246个基因发生显著变化。深入的分析发现，生长素相关基因在转录水平呈现显著变化，而独脚金内酯相关基因的变化并不显著，暗示独脚金内酯可能不参与转录水平的调控。进一步的转基因验证表明，动态转录组数据对于揭示生长素调控重力反应及分蘖角度的分子网络及挖掘有应用价值的新基因提供了重要的资源。