光是自然界中影响植物生长和发育最重要的环境因素之一。外界光信号如何通过光受体传递到下游信号蛋白，下游蛋白如何根据光信号变化调控植物生长发育，这些具体的信号转导分子机理是光信号研究的核心问题。近年来，申请人在光信号调控生物节律建成、开花时间调节, 及光信号途径关键转录因子FHY3的下游转录调控网络等方面进行了系统地研究并取得较好的研究进展。但外界光信号如何传递到FHY3，其分子调节机理仍不清楚。为此，在本项目中，我们将围绕 FHY3的上游信号途径展开，通过分别研究从黑暗到光下和从光下到黑暗FHY3蛋白表达调控和信号转导分子调节机理，着重解决外界环境光信号如何由光受体phyA传递到FHY3并调控下游基因表达和植物生长发育这一关键问题，阐明FHY3蛋白被26S蛋白酶体途径降解机理及光形态建成负调控因子在FHY3蛋白降解过程中的作用，进一步明确FHY3蛋白表达调控对植物生长发育的分子调节机理。

Light is one of the most important and basic environmental factors affecting plant growth and development. How the light signals are percepted by photoreceptors and transduced to the downstream components of light signaling pathway, and how these components transduced light signals to the nuclear targets and regulated its gene expression is one of the fundamental questions of light signaling studies. Recently, we showed how light signals affecting the entrainment of the circadian clock and flowering time regulation through FHY3, FAR1 and HY5, three positive regulators of the phytochrome A signaling pathway in Arabidopsis. We also characterized the transcriptional regulation network of FHY3 and identified ARC5 as one of the downstream targets of FHY3 which directly involved in chloroplast division. Conversely, How light signals transduced to FHY3 is still less well charcterized. Here, we will investigate the upstream signal transduction of FHY3 and address how the protein expression of FHY3 is generated and controlled by light and darkness, respectly. Whithin this project, we will demonstrate how the environmental light signals transduced from phyA to FHY3 and regulated its downstream gene expression. The molecular mechanism of FHY3 protein degradation and the molecular function of photomorgenesis suppressors in this process also will be characterized. Results from our studies could establish the molecular link between phyA and FHY3, and also will provide more evidences which could help us underlying the molecular mechanism of light regulated plant growth and development.