Evolution of phytochrome signalling and nuclear transport

在种子植物中，光敏色素A （phytochrome A, phyA）光感受器在远红光丰富的环境中发挥着关键作用，它对极低强度光的响应至关重要。phyA被光激活后，与FHY1结合，介导phyA核的转运和积累。相比之下，隐胞体被认为是细胞质和/或膜相关蛋白。虽然phy基因谱系分裂为phyA和其他phys只发生在种子植物中，但在蕨类植物、苔藓和绿藻中可以鉴定到FHY1样蛋白，而这些植物中不含有phyA样蛋白。所有这些隐球菌FHY1蛋白都与phyA和隐球菌物理相互作用。有趣的是，phyA信号传导的其他关键成分也在小立壶菌基因组中有体现，这表明phyA可能采用了隐孢子虫已有的信号系统，并且隐孢子虫在细胞核中也有功能。将利用表达YFP标记物理的转基因小水泡菌系来验证这一假设。此外，将使用随机诱变/Y2H方法绘制phyA/cryptogam phys的FHY1结合位点，这将进一步深入了解phyA信号传导和phy/FHY1系统的进化过程。

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.