DiversiPHY and conquer — Diversification of phytochromes during plant terrestrialisation

与水生栖息地相比，陆地上的光照条件可能非常不同，这表明植物的陆地化需要光感觉受体和下游信号通路的适应。光敏色素（phyys）是植物中一类重要的光感受器。在种子植物、蕨类植物和苔藓中，独立的基因复制事件导致了较小的PHY基因家族。在种子植物中，物理因子的功能分化为红光和远红光感应物理因子。然而，由于种子植物、蕨类植物和苔藓中PHY多样性的独立演化，基于种子植物PHY的研究无法预测蕨类植物和苔藓中PHY的功能多样性。MAdLand第一期资助框架内的工作表明，藓类Physcomitrium patens中的三个PHYs分支在功能上分别分化为具有红光和远红光传感的分支，以及具有双特异性并在红光和远红光下起作用的分支。在拟议的项目中，我们希望通过PHY敲除或敲低突变体来研究蕨类植物中PHY的功能多样化。此外，我们还想比较在绒球菌和角翅菌中由不同的物理信号介导的红光和远红光诱导反应的特征，以确定光信号的共同或谱系特异性机制的异同点。与蕨类植物和苔藓相比，苔类植物含有一个在红光和远红光下活跃的PHY。通过对多形地茅和藓类Physcomitrium patens的跨物种互补研究，我们希望确定对PHYs功能多样化重要的氨基酸残基或基序。最后，我们发现陆地植物光信号的两个关键组成部分可能已经从陆地植物的最后一个共同祖先那里获得，因此可能是光信号的创新，促进了植物的陆地化。在项目的最后一部分，我们想要探索这个想法。

Compared to aquatic habitats, the light conditions on land can be very different, suggesting that plant terrestrialisation required adaptations in photosensory receptors and downstream signalling pathways. Phytochromes (PHYs) are an important class of photoreceptors in plants. In seed plants, ferns, and mosses, independent gene duplications events resulted in small PHY gene families. Functional diversification of PHYs in seed plants into red and far-red light sensing PHYs is well known. However, due to the independent evolution of the PHY diversity in seed plants, ferns, and mosses, functional diversification of PHYs in ferns and mosses cannot be predicted based on studies on seed plant PHYs. Investigating the functional diversification of PHYs is an important goal of the proposed project Work in the frame of the first funding period of MAdLand has shown that the three clades of PHYs in the moss Physcomitrium patens functionally diversified into clades with red and far-red light sensing PHYs, respectively, and into a clade that has dual-specificity and acts in red and far-red light. In the proposed project, we want to investigate functional diversification of PHYs in the fern Ceratopteris richardii using PHY knock-out or knock-down mutants. In addition, we also want to compare the characteristics of red and far-red light induced responses mediated by the different PHYs in Physcomitrium and Ceratopteris to identify similarities and differences that could point to common or lineage-specific mechanisms of light signalling. In contrast to ferns and mosses, liverworts contain a single PHY that is active in red and far-red light. By cross-species complementation studies with the liverwort Marchantia polymorpha and the moss Physcomitrium patens, we then want to identify amino acid residues or motifs that are important for functional diversification of PHYs. Finally, we found that two key components of light signalling in land plants possibly have been acquired in the last common ancestor of land plants and therefore could be innovations in light signalling that facilitated plant terrestrialisation. In the last part of the project, we want to explore this idea.