Evolution des types sexuels et des chromosomes sexuels chez les champignons – FungiSex

This program unites researchers from different institutions with fundamental expertise in diverse areas of biology (evolution, fungal biology, genetics, genomics, bio-informatics, and phylogenetics) to address questions of major importance. Why do mating types evolve, are maintained, and in which numbers' Why and how do sex chromosomes evolve' The originality of this project relies on the use of a commonly neglected group, the Fungi, to study these major questions of Evolutionary Biology. Fungi appear to have had multiple transitions in their numbers of alternate mating types. Some fungi also have nascent or true sex chromosomes. These characteristics, along with the ability to grow and manipulate the haploid stage, make them highly suitable models to address the above questions. We will advance our understanding of evolutionary forces acting on the number of alternate mating types. We will produce a comprehensive review on review the number of mating types in fungi (all ascomycetes and basidiomycetes for which data are available) and record the parameters considered to play a role in their evolution (anisogamy, mating system, population size, mitochondria inheritance, recombination suppression around mating types, etc.). We will also investigate the selective forces that have play a role in the evolution of the mating type genes in basidiomycetes. We will look in particular for footprints of balancing selection, purifying selection and trans-specific polymorphism at mating type genes. Finally, we will study the origins of sex chromosomes by genomic approaches on the model fungus Microbotryum. We will sequence the whole sex chromosomes of different Microbotryum species to investigate the evolution of recombination suppression associated with regions adjacent to the mating type locus, and its consequences, such as degeneresence and transposable elements accumulation. We will attempt to understand what were the selective forces responsible for the evolution of recombination suppression, and how does this fit with the conventional wisdom on sex chromosome evolution, This program represents the first comprehensive study performed on a large taxonomic group to address questions of the evolution of sexes, mating types and sex chromosomes, fully integrating multiple approaches and competences, which should bring novel answers on these fundamental issues. Beyond the expected results for the understanding of sex chromosomes and mating type evolution, this program will help to establish important fungi, Microbotryum, as a model for evolutionary biology. These organisms have much to bring to the field, but remain poorly studied on the genomics of sexual reproduction. Further, this project will help conceptually advancing our understanding of the selective forces responsible for the evolution of mating types and sex chromosomes in general. Also, pathogenicity genes have been shown to be linked to mating types in a fungal human pathogen, Cryptococcus neoformans (Basidiomycetes) (Lin et al., 2006 ), that has a large region of recombination suppression around its mating type locus (Lengeler et al., 2002). Advancing our understanding of the reasons why sex chromosomes evolve may therefore have applied consequences for human diseases.