拟南芥TOC1基因调控FHY3/FAR1远红光信号的分子机理

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.

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。

光是自然界中影响植物生长发育十分重要的环境因子,不仅提供了光合作用所需要的能量，也可以作为一种信号直接调控植物的生长发育。植物感受外界光照等信号的输入，传递到生物钟中央振荡器，继而通过输出途径调节植物的生长发育。已有研究表明，生物钟的很多关键基因的突变体具有光形态建成改变的表型，暗示生物钟可以反馈调控光信号转导，但这种相关的信号机理尚不清楚。本研究通过分子生物学和生物化学以及遗传学手段，解析生物钟关键基因TOC1和CCA1与远红光信号转导因子FHY3相互作用，共同调控下游FHY1/FHL基因的转录水平，从而参与FHY3介导的远红光信号转导。我们研究发现，TOC1和CCA1可以与FHY3蛋白直接相互作用并抑制其转录活性，受其影响，FHY1/FHL基因的表达水平在TOC1和CCA1超表达株系中显著降低，从而影响了光敏色素phyA进入细胞核。同时，我们还发现FHY1及其phyA下游很多基因的表达模式呈现节律性的特点，TOC1和CCA1参与了这种节律性表达模式的调控。该研究揭示了生物钟信号反馈调控植物远红光信号的输入，将加深我们对植物如何在生长发育中整合生物钟信号和光信号机制的认识。

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