淀粉是植物碳水化合物的最广泛的一种存在形式,提供了生长发育所需的物质和能量。在叶片中，淀粉在白天合成作为糖的主要储存形式进行积累，夜晚降解提供各种生命活动所需的能量。近年来人们发现淀粉的代谢受到昼夜变化的光信号、糖信号和生物钟的共同调控，但具体的调节机制并不明确。在前期研究中，我们发现拟南芥光信号转导途径中三个重要的转录因子FHY3、FAR1和HY5与淀粉的代谢直接相关。在本研究中，我们将利用分子生物学、生物化学和遗传学等多种研究方法，深入解析光信号蛋白FHY3、FAR1和HY5协同调控淀粉合成过程中淀粉去分支酶ISA2的转录调控机理，以及HY5调控淀粉降解过程中关键酶SEX1、SEX4和BAMs的转录调控机理。我们的研究将建立环境光信号与体内淀粉代谢的直接分子联系，有助于阐明植物体内淀粉代谢相关基因节律性表达的调控网络，为进一步理解作物的“源强”和产量提高奠定科研基础和理论依据。

In the living organisms, all the life processes are strongly affected by the daily light/dark cycles. During the day, photosynthesis in plants uses light energy derived from the sun for the synthesis of carbohydrates which primary accumulate as starch in chloroplast for a transient storage or being converted to sucrose for export to the sites of growth or non-photosynthetic organs for long-term storage. In the dark, transitory starch is degrade and remobilize to sustain the carbon and energy metabolism. Numerous studies have shown that plants defective in starch synthesis or degrade have reduced growth rates, thereby affecting the yield and quality of crop plants. It has been reported that starch metabolism is regulated by daily light dark cycle, such as environmental light signals, circadian clock and endogenous sugar contents. However, the underlying molecular mechanism for coordinating the daily starch metabolism is still poorly understood. Our preliminary study indicated that light signal protein FHY3 and FAR1 positively regulate starch synthesis, whereas HY5 positively regulate starch degradation in Arabidopsis. In this study, we will use multiple molecular, genetic and biochemistry methods to identify how FHY3, FAR1 and HY5 working together to regulate the transcription of starch debranching enzyme ISA2, and how HY5 regulate the transcription of SEX1, SEX4 and BAMs, thus influence starch metabolism. Our study will establish the molecular link between environmental light signals and starch metabolism and will provide the molecular evidences to understand the dynamic transcriptional regulation of starch metabolism related genes, thus will help us to further investigate the starch metabolism mechanism in crop plants.