Analyses of cross-talk between different photoreceptors in plant light signal transduction

植物的形态在很大程度上取决于光环境。在这些通常被称为光形态发生的反应中，红色/远红色光感受器，光敏色素和蓝色光感受器，隐花色素起着关键作用。在这一年里，我们研究了来自这些光感受器的信号如何被整合以协调调节植物的形态发生。以下是对这一成就的简要总结。1)由约200个氨基酸残基组成的PHY结构域被认为是光敏色素光感结构域（约650个氨基酸残基）内的一个子结构域。我们研究了缺乏PHY子结构域的n端结构域的信号传导活性。结果表明，PHY结构域对于信号传导是必不可少的，但对于保持光敏色素活性形式的稳定是必需的。此外，我们在phyB的n端光感区域内发现了许多错义突变体。对这些突变的分析表明光敏色素的不同亚结构域具有不同的作用。2)我们研究了光敏色素和隐色素在光诱导根系绿化中的作用。因此，我们发现两个光感受器都需要被激活才能使根完全变绿。我们目前正在测试phyB的片段是否具有类似的活性。3)我们筛选了基于t dna激活标记的拟南芥突变体，并确定了其中一个突变体的致病基因。结果表明，CYP72C1基因的过度表达降低了油菜素内酯活性水平，导致黑暗中部分光形态发生。

Morphology of plants depends very much on the light environment. In those responses, which are often referred to as photomorphogenesis, a red/far-red light photoreceptor, phytochrome, and a blue light photoreceptor, cryptochrome play a key roles. In this year, we investigated how the signal from these photoreceptors are integrated to coordinately regulate the plant's morphogenesis. A brief summary of the achievement is as follows.1)The PHY domain consisting of about 200 amino acid residues is recognized as a sub-domain of phytochrome within the photosensory domain of phytochrome (about 650 amino acid residues). We examined the signaling activity of the N-terminal domain lacking this PHY sub-domain. The results demonstrated that the PHY domain was dispensable for the signaling but was required to keep the active form of phytochrome stable. In addition, we identified many missense mutants within the N-terminal photosensory domain of phyB. Analysis of these mutations suggested different roles for different sub-domains of phytochrome. 2)We examine the involvement of phytochromes and cryptochrimes in the light-induced root greening. Consequently, we found that both the photoreceptors needed to be activated to case the full root greening. We are currently testing whether or not fragments of phyB have similar activity. 3)We screened for mutants in a T-DNA-based activation-tagged pool of Arabidopsis and identified a causal gene for one of such mutants. The results revealed that over-expression of the CYP72C1 gene reduced the level of active brassinosteroids, which led to partial photomorphogenesis in darkness.