Résumé
In most mammals, the genomic localization of recombination hotspots is directed by the PRDM9 protein. The complete or partial loss of PRDM9 in other taxa such as birds, some teleost fishes or invertebrates, results in a different localization of hotspots and an apparently more stable dynamics of recombination landscapes than in mammals. The existence of mammalian-like recombination landscapes in taxa that have retained a functional PRDM9 remains unclear, raising questions about the ancestral role of PRDM9 in animals. Salmonid fishes have a full-copy of the PRDM9 gene - Is it involved in the regulation of recombination as in humans and mice? To address this question, we used linkage disequilibrium information from whole-genome polymorphism data to build fine-scale population-based recombination maps in three Salmonid species: Oncorhynchus kisutch, O. mykiss and Salmo salar. The three species showed recombination rate variation at both broad and fine scales, with a tendency for hotspots to be localized away from transcription start sites, similarly to mammals. Moreover, the comparison of recombination landscapes among species of salmonids revealed a rapid evolution of the recombination rate distribution. These findings strongly suggest that PRDM9 has a function of directing DNA double strand breaks in salmonids, arguing in favor of an ancestrally PRDM9-mediated recombination process in vertebrates. Confirmation of these results via ChipSeq and binding motif analysis is on its way.