Towards understanding the diversity, evolutionary origins, and host spectrum of the overlooked oomycete genus Lagena

长久以来被认为只包含单一物种的拉丁那属，最近通过环境测序发现包含了更多的多样性。深入了解该类群的多样性、寄生宿主和致病性背后的基因组特征，对于了解褐藻类卵菌的进化和在该类群中获得专性生物营养至关重要。在我们以前的工作中，我们已经证明了全果属的拉丁那不仅含有植物的寄生虫，而且还有硅藻的寄生虫。这个项目的目的是进一步探索仍属于其他属的拉格纳和类似拉丁那物种的多样性和进化，检验如下假设：1)拉丁那物种在硅藻宿主上多样化，而归属于拉丁藻属的硅藻的寄生虫属于拉丁那；2)拉丁那是一种广泛但被忽视的根部寄生虫，并且有专门针对某些寄主群体的谱系；3)除了硅藻和被子植物外，还有其他宿主被拉丁那属感染，例如丝状蓝藻和卵菌。4)拉丁那全结实孢子的产生是一种衍生状态，是一个较大的营养菌丝还原成全结实的菌体的结果。5)基因组特征与寄主和生理有关(专性与兼性生物营养)。对这些假说的检验将产生对一组明显广泛和多样化、但大多被忽视的与腐霉密切相关的小型全结实卵菌的基本见解。总体而言，关于这些鲜为人知的寄生虫的系统发育、致病多样性、基因组特征和进化过程的知识将是理解褐孢子虫卵菌进化的关键一步。这也将构成未来研究的基础，例如，菌丝体向全结实菌体的减少以及不同卵菌群中专性生物营养的平行进化。

The genus Lagena, long thought to contain just a single species, has recently been revealed by environmental sequencing to encompass much more diversity. Gaining insights into the diversity of the group, the hosts they parasitise and the genomic features underlying pathogenicity is crucial for understanding the evolution of pythiaceeous oomycetes and the acquisition of obligate biotrophy in this group. In our previous work we could already show that the holocarpic genus Lagena not only contains parasites of plants, but also parasitoids of diatoms. It is the aim of this project to explore the diversity and evolution of Lagena and Lagena-like species still placed in other genera further, testing the hypotheses that 1) Lagena species have diversified in diatom hosts and the parasites of diatoms assigned to Lagenidium belong to Lagena instead, 2) Lagena is a widespread but overlooked root parasite, and there are lineages specialised to certain host groups, 3) There are hosts other than diatoms and angiosperms infected by the genus Lagena, e.g. filamentous cyanobacteria and oomycetes. 4) Holocarpic spore production in Lagena is a derived state, resulting from the reduction of a larger vegetative mycelium into a holocarpic thallus. 5) There are genomic features that correlate with the hosts infected and physiology (obligate vs. facultative biotrophy). The testing of these hypotheses will yield fundamental insights into an apparently widespread and diverse, yet mostly overlooked group of small holocarpic oomycetes closely related to Pythium. Overall, the knowledge gained with respect to the phylogeny, pathogenic versatility, genomic features, and evolutionary processes of these little-studied parasites will be a vital step towards understanding the evolution of pythiacaeous oomycetes. It will also constitute the basis for future studies, e.g. into the reduction of mycelia to holocarpic thalli and the parallel evolution of obligate biotrophy in different oomycete groups.