植物向地性是植物对重力场作用的基本响应。而植物荷尔蒙乙烯能够调控植物茎的反向地性，促进植株保持垂直生长位置。但乙烯对植物反向地性的调节是个复杂而有趣的过程。乙烯能促进一些植物茎的反向地性弯曲，而又能抑制另一些植物的反向地性运动。即使在同一种植物中，乙烯即抑制拟南芥下胚轴的反向地性，也促进其花序茎的反向地性。而且光也参与乙烯对植物反向地性的调节过程并起着重要作用。我们认为乙烯在调节植物的反向地性弯曲和重力感应中具有复杂的信号通路网络。本研究拟利用功能定量磷酸化蛋白组学的方法，研究乙烯在这一复杂过程中的调控模式，磷酸化信号的传递过程，找到蛋白磷酸化位点及进一步诠释乙烯信号通路中磷酸化和去磷酸化的调控机理。寻找内源激素乙烯和重力感应信号在调节植物生长和重力响应方面的基本原理和分子机理，并阐明重力信号和乙烯信号传导间的相互作用，建立一个分子系统生物学的模型，为改良农作物提高农作物产量提供理论依据。

Gravitropism is a fundamental plant response to gravity. Ethylene, a plant hormone, is known to have a regulatory effect on negative gravitropic response of plant and promotes plants to maintain original vertical growth positions. However, the effects of ethylene on shoot negative gravitropic shows very complex but interesting phenomenon.Both the inhibitory and the stimulatory effects of ethylene have been found in regulation of shoot negative gravitropism. Even in the same Arabidopsis plant, ethylene inhibits negative gravitropism of hypocotyls yet stimulates its inflorescence stem gravitropic response. Thus, ethylene should further complicate the already complex signaling pathways of gravity-sensing and shoot negative gravitropism. In this proposed study, functional and quantitative phosphoproteomics methods will be employed to study transduction of phosphorylation signal in ethylene-modulated regulation, to discover phosphorylation sites, and to reveal phosphorylation and de-phosphorylation interactions in ethylene signaling pathways. This proposed research is to provide information on the molecular mechanisms underlying dynamic interplays between the internal hormone ethylene and external gravity signal transduction in regulation of shoot negative gravitropic response and to delineate the multiple ethylene signaling pathways as well as the cross-talks between ethylene and gravity signaling. The outcome of this research will contribute to the development of a model system for molecular systems biology study and could be applied to the improvement of crop productivity to feed billions of people worldwide.