Evolution of phytochrome signalling and nuclear transport

在种子植物中，光敏色素A(PhyA)光感受器在远红光强光环境下的生存中起着关键作用，对于响应极低强度的光是必不可少的。在被光激活后，PhyA与FHY1结合，FHY1介导PhyA的核运输和积累。相反，隐花果皮被认为是胞质和/或膜相关蛋白。虽然PHY基因谱系的分裂只在种子植物中发生，但在蕨类植物、苔藓和绿藻中可以鉴定出FHY1类蛋白，这些植物中不包含PHYA类PHY。所有这些隐加姆FHY1蛋白都可以与PhyA相互作用，也可以与隐加姆Phy相互作用。有趣的是，PhyA信号的其他关键成分也出现在Physcomitrella基因组中，这表明PhyA可能采用了来自隐子植物的预先存在的信号系统，并且隐孢子体在细胞核中也具有功能。表达YFP标签PHY的转基因Physcomitrella品系将被用来检验这一假设。此外，将使用随机突变/Y2H方法绘制PhyA/Crypgam phys的FHY1结合位点图，这将为PhyA信号和PHY/FHY1系统的进化提供进一步的洞察。

In seed plants the phytochrome A (phyA) photoreceptor plays a key role in survival in far-red light enriched environments and it is essential for responses to very low intensities of light. After activation by light phyA binds to FHY1, which mediates phyA nuclear transport and accumulation. In contrast, cryptogam phys are believed to be cytosolic and/or membrane associated proteins. Although the split of the phy gene lineage into phyA and other phys occurred only in seed plants FHY1 like proteins can be identified in ferns, mosses and green algae, which do not contain phyA like phys. All these cryptogam FHY1 proteins interact with phyA as well as with cryptogam phys. Interestingly, also other key components of phyA signalling are represented in the Physcomitrella genome suggesting that phyA may have adopted a pre-existing signalling system from cryptogams and that also cryptogam phys have a function in the nucleus. Transgenic Physcomitrella lines expressing YFP tagged phys will be employed to test this hypothesis. Moreover, the FHY1 binding site of phyA/cryptogam phys will be mapped using a random mutagenesis/Y2H approach, which will provide further insight into how phyA signalling and the phy/FHY1 system evolved.