The early sequestered germline of fungi - spatial distribution, mechanism and generality across the kingdom

The FunGerm-project aims to investigate the phenomenon of an early sequestered germline in the fungi. As of today, it is well known that in unitary animals the germline is defined early during development, while in fungi, plants, and other metazoans, the current dogma is that the germline is defined much later in development, meaning that mutations that have accumulated over growth can enter the germline. Recent, and yet unpublished, whole-genome-sequencing data in my group show the unexpected pattern of an early sequestration of the germline in the basidiomycete fungus Marasmius oreades, suggesting convergence in evolution of this key trait among major eukaryote lineages. M. oreades grows in fairy rings: circular, underground mycelia common in lawns and grasslands across the northern hemisphere. At the edge of the ring, the annual, sexual, fruiting bodies (mushrooms) develop from the mycelium. In recent years, we have developed the system as a natural, long-term evolution experiment to study the rise and fate of new mutations over sexual generations. With an ERC Advanced grant we will be able to use this system to fully explore the finding of an early sequestered germline, and also expand it to identify the breadth of occurrence across the fungal kingdom. Specifically, I propose to use a wide range of approaches and M. oreades as model organism to investigate: I) The spatial distribution of the somatic and germline cell-lines in mycelia, II) The mechanism determining and controlling germline segregation, and III) The mutation rate and spectra of the different cell lines. Furthermore, we aim to investigate IV) the prevalence of an early germline sequestration across basidiomycetes and other fungi. With the FunGerm-project we will thoroughly test if, and how, an early germline sequestration has evolved multiple times independently, in different eukaryote kingdoms, and thereby empirically contribute to the conceptual link between development and evolution.