环境光信号和植物内在的生物钟共同调节植物体几乎所有的生长发育过程，但它们之间相互作用的分子机制仍知之甚少。光敏色素A是感知远红光的主要光受体，被光激活后，迅速从细胞质转移到细胞核内，进而调控一系列远红光应答基因表达和下游的生理反应。我们以前的研究已经表明，FHY3和FAR1是一类转座酶衍变而来的新型转录因子，它们直接上调FHY1和FHL基因的表达，而FHY1和FHL可以介导phyA进入细胞核，从而调控FR光反应。TOC1是生物钟中央振荡器的一个关键夜晚基因。我们发现，TOC1表达水平/活性的变化引起拟南芥中FHY1和FHL基因表达水平的改变，这表明TOC1参与phyA信号转导过程的调控。本项目拟从TOC1与FHY3/FAR1之间相互调控关系入手，探索TOC1参与phyA信号转导调控的分子机制。该项目的预期成果将大大提高我们对环境光信号和内源性生物钟协同调控植物生长和发育机制的理解。

Environmental light signal and the endogenous circadian clock overlappingly regulate nearly every aspect of plant growth and development, but the molecular mechanisms underlying their cross talk remain poorly understood. Arabidopsis seedlings develop photomorphogenically in the light, but undergo skotomorphogenesis in darkness. Phytochrome A is the major phootoreceptor for perceiving far-red light. Upon activation by light, phyA is rapidly translocated from the cytoplasm into the nucleus to regulate a suite of far-red light responsive gene expression and downstream physiological responses. Our previous studies have shown that two homologous mutator-like transposase-derived transcription factors FHY3 and FAR1 directly up-regulate the expression of FHY1 and FHL, two homologous proteins essential for phyA nuclear input, and thus indirectly regulate phyA nuclear translocation and FR light responses. TOC1 is a key evening component of the central oscillator of the circadian clock. We found that reducing or increasing the levels/activities of TOC1 cause FHY1 and FHL expression level change under far-red light, indicating a role of TOC1 in regulating phyA signaling. The objective of this project is to invetstigate the molecular mechanisms by which TOC1 regulates phyA signaling and its functional relationship with FHY3/FAR1. The expected results from this project will greatly improve our understanding of how the environmental light signals and the endogenous circadian clock coordinately regulate plant growth and development.