“神舟八号”飞船的实验结果和植物向重性研究均显示重力变化影响植物细胞内信号转导途径和代谢通路，其中最重要的是植物激素之间的相互作用途径和细胞壁的代谢途径变化。在植物向重性反应过程中，PIN蛋白对生长素的极性运输极为关键，不同信号途径可从不同层面对PIN蛋白进行调控。本课题首先拟研究ABA在向重性过程中的不对称分布状况，ABA影响PIN蛋白的胞吞作用和从胞内向质膜再周转的平衡，调控生长素的动态平衡响应重力反应；其次深入研究ABA调控生长素受体ABP1和SCFTIR1/AFB泛素化降解途径影响PIN蛋白动态平衡中的作用，揭示它们的变化对细胞壁的影响以及和细胞壁变化的关系，并影响植物向重性。同时，本研究还拟通过“实践十号”返回式科学实验卫星搭载实验材料，探讨微重力条件下ABA对PIN蛋白在质膜分布的影响。结合飞行实验和地基植物向重性研究认识ABA和生长素相互作用响应重力变化的分子机理。

The result of Shenzhou-8 spacecraft experiment and other plant gravitropism studies show that gravity changes affect plant cell signal transduction pathways and metabolism. The interactions among plant hormones signaling and the modification of cell wall metabolism are the most important changes. Auxin transport protein PIN is critical in the process of gravitropism. Different signaling pathways regulat PIN at different levels. In this study, we first intend to study the asymmetric distribution of ABA in root gravitropism and the influence of ABA balance, which regulates the dynamic balance of auxin in plant gravitropism through endocytosis of PIN and PIN protein to plasma membrame. Secondly, we intend to study the infuence of ABA on the dynamic balance of PIN proteins through regulating auxin receptor proein (ABP1) and SCFTIR/AFB ubiquitination degradation pathway, with the aim to study the effect on cell wall and relationship between the changes of PIN protein and the change of cell wall in Arabidopsis responding altered gravity. In SJ-10 experinment, we will study the influence of ABA on distribution of PIN proteins in Arabidopsis under microgravity. The molecular mechanism of the interaction between ABA and auxin on plant response to gravitropism will be better understand by microgravity experiments and ground gravitropic experiments.