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

点击翻译按钮获取中文摘要

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.