Signal transduction mechanism of phytochrome

我们借助组织特异性启动子以组织特异性方式表达cry2-GFP。将这些构建体转化到拟南芥cry2突变体中。对这些品系的详细分析表明，在维管束中表达的cry2-GFP能有效地促进开花。相比之下，在其他组织中表达的那些无效。我们还证实，cry2-GFP促进了维管束中开花关键调控因子FT的表达。这些观察结果与phyB形成鲜明对比，后者在叶肉而不是维管束中起作用。综上所述，我们的工作已经证明，光感受器在叶子的空间分离部分起作用，并且这些不同组织之间存在通信。我们分析了phyB n端部分的氨基酸取代。在这一年里，我们专注于在不改变分子光谱性质的情况下降低分子信号活动的突变。四个这样的突变中有三个是在PAS结构域中发现的，而剩下的一个是在GAF结构域中发现的。我们将这些突变逐个导入到全长phyB中，并在拟南芥phyB突变体中表达。正如预期的那样，这些突变分子在植物中表现出降低的信号活性。为了研究phyA信号转导的位置，我们表达了带或不带核定位信号（NLS）或核输出信号（NES）的phyA- gfp。将构建的基因置于PHYA基因启动子的下游，转化为拟南芥PHYA突变体。然后，我们测试了这些线对连续远红光的响应。这种反应被称为FR-HIR反应，它完全由phyA控制。正如预期的那样，NLS的phyA-GFP对治疗的反应几乎正常，而NES的则没有。因此，与phyB的情况一样，细胞核是phyA信号转导的重要部位。

We expressed cry2-GFP in tissue-specific manners with the aids of tissue specific promoters. The constructs were transformed into the cry2 mutant of Arabidopsis. Detailed analyses of those lines indicated that cry2-GFP that was expressed in the vascular bundles effectively promoted the flowering. By contrast, those expressed in other tissues were not effective. We also confirmed that cry2-GFP promoted the expression of FT, a key regulator of flowering, in vascular bundles. These observations are in striking contrast with those for phyB, which functions in the mesophyll rather than vascular bundles. Taken together, our work has demonstrated that photoreceptors are functioning in spatially separate parts of the leaf and communications between those different tissues exsit.We analyzed amino acid substitutions in the N-terminal moiety of phyB. In this year, we focused on the mutations that reduced the signaling activity of the molecule without changing its spectral nature. Three of four such mutations were fund in the PAS domain whereas the remaining one was found within the GAF domain. We introduced those mutations one by on into the full-length phyB and expressed them in the phyB mutant of Arabidopsis. As expected, those mutated molecules exhibited reduced signaling activity in planta.To examine the site of phyA signal transduction, we expressed phyA-GFP with or without the nuclear localization signal (NLS) or nuclear export signal (NES). The constructed genes were placed downstream of the authentic PHYA gene promoter and transformed into the phyA mutant of Arabidopsis. We then tested those lines with respect to the responses to continuous far-red light. Such responses are known as FR-HIR responses, which is controlled solely by phyA. As expected, phyA-GFP with NLS responded almost normally to the treatment whereas that with NES did not. Hence, as is the case with phyB, the nucleus is an important site for the phyA signal transduction.