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，这表明植物陆地化需要感光受体和下游信号通路的适应。光敏色素（Phytochrome，PHYs）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，独立的基因重复事件导致小PHY基因家族。种子植物中的PHY功能多样化为红光和远红光传感PHY是众所周知的。然而，由于种子植物、蕨类植物和苔藓植物中PHY多样性的独立进化，蕨类植物和藓类植物中的PHY功能多样性不能根据对种子植物PHY的研究来预测。调查PHY的功能多样性是拟议项目的一个重要目标。在MAdLand第一个资助期的框架内开展的工作表明，藓类立碗藓中的PHY的三个分支在功能上多样化为分别具有红光和远红光传感PHY的进化枝，以及具有双重特异性并在红光和远红光中起作用的进化枝。在这个项目中，我们希望利用PHY基因敲除或敲低突变体来研究蕨类植物Ceratopteris richardii中PHY的功能多样化。此外，我们还想比较立碗藓属和水蕨属中不同PHY介导的红光和远红光诱导反应的特征，以确定可能指向光信号传导的共同或谱系特异性机制的相似性和差异。与蕨类植物和苔藓相反，地钱含有一个在红光和远红光下活跃的PHY。通过对地钱和立碗藓的跨物种互补研究，我们希望确定对PHY功能多样化重要的氨基酸残基或基序。我们发现陆生植物中光信号的两个关键成分可能已经在陆生植物的最后共同祖先中获得，因此可能是光信号的创新，陆地化在这个项目的最后一部分，我们想探索这个想法。

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.