Evolution of fungal mating-type chromosomes

Informations projet

MatTypeEvol

N° de convention de subvention: 701646

DOI

10.3030/701646

Projet clôturé le 31 Août 2017

Date de signature de la CE 15 Février 2016

Date de début 1 Mars 2016

Date de fin 28 Février 2018

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 173 076,00

Contribution de l’UE

€ 173 076,00

Coordonné par

UNIVERSITE PARIS-SACLAY
France

Periodic Reporting for period 1 - MatTypeEvol (Evolution of fungal mating-type chromosomes)

Période du rapport: 2016-03-01 au 2018-02-28

Résumé du contexte et des objectifs généraux du projet

Sex chromosomes often show extensive areas of suppressed recombination and cytological differentiation, a well-documented phenomenon in animals and plants. Lack of recombination is expected to limit the efficacy of natural selection, leading to degeneration in gene content. Similarly, fungal mating-type chromosomes can display patterns of suppressed recombination, however the mechanisms responsible and the extent of genic degeneration are still unclear. The proposed research investigates the evolution of fungal mating-type chromosomes, more specifically the patterns and mechanisms underlying genomic regions with suppressed recombination linked to mating compatibility genes and how this phenomenon impacts fitness and the genome. I use comparative genomics and a model fungal system with dimorphic mating-type chromosomes of different degrees and ages for understanding the steps involved in the evolution of suppressed recombination and genomic degeneration. This project compiles results that yield unprecedented insights into the evolution of mating-type chromosomes, the dynamics of genome degradation in sexual eukaryotic species, and more generally contribute for a unified view of evolution in dimorphic chromosomes with suppressed recombination.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

During the completion of this project a total of 31 fungal genomes were sequenced with Pacific Biosciences technology, assembled and annotated. These high quality genomes were used to compile a phylogeny for the Microbotryum violaceum complex and detect and compare regions of suppressed recombination across species.
One of the main findings of the study were that fungal mating type chromosomes evolve in a very similar way to sex chromosomes in plants and animals. It was previously thought that the typical sex chromosome structure (with strong asymmetry and one highly degenerated chromosome, such as the Y in humans) was caused by the existence of separate sexes and alleles specifically beneficial in one sex or the other. Given that fungi display mating types (with very few loci defining mating compatibility) and do not have separate sexes, finding the exact same chromosome structure in fungi and plants/animals with traditional sex chromosomes implies that separate sexes alone cannot be responsible for sex chromosome architecture.
The project also investigated the evolution of suppressed recombination in Microbotryum and documented for the first time repeated independent events of recombination suppression in closely related species. Recombination suppression leads to higher gamete compatibility in these selfing species and is under strong selection. Comprehensive genomic analyses indicated at least five independent events of recombination suppression, with distinct chromosomal arrangements and different ages.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

This project made crucial contributions for the understanding of sexual reproduction in eukaryotes. Finding such striking parallel across plants, animals and fungi will foster discussion and revision of current theories for the evolution of sexual reproduction in eukaryotes beyond sexual antagonism. Furthermore, two graduate students were trained in genomics throughout the course of the project, one of which from an underrepresented background.

Microbotryum violaceum infecting a Silene latifolia flower. Photo by Michale Hood.