Dynamique des génomes et évolution du métabolisme lipidique chez les levures du clade Yarrowia

Abstract : Yarrowia lipolytica belongs to a group of yeasts that have diverged very early from most other hemiascomycetous yeasts. This yeast is able to use various hydrophobic substrates as unique carbon source and to synthesize new free fatty acid from non hydrophobic compounds. These characteristics make Y. lipolytica a known oleaginous model for the lipid metabolism survey of yeasts. Its oleaginous capacity is facilitated by protein family expansions that occurred across evolution after the divergence of the Yarrowia clade. Indeed, among 190 genes involved in the lipid metabolism in Y. lipolytica, more than 67% are grouped into 30 multigenic families with up to 16 members in the lipase family. The recent sequencing of 5 genomes within the Yarrowia clade enabled to compare their gene content. The study of gene families of the lipid metabolism allowed to highlight the evolutionary mechanisms involved in this clade. All the functions necessary to lipid metabolism are present in all species studied with at least one gene per family even for species that have 500 to 1,000 fewer genes than Y. lipolytica. These species are also found to be all oleaginous through physiological studies. The observed gene families derive from multiple gene duplications of which each copy evolves independently by different processes of sub- or neofunctionalisation, fixation, pseudogenization or loss. Contractions and expansions of protein families, gene expression, synteny and relative localisation of genes in the genome were investigated. More particularly, the selection pressure acting on these gene families was compared with those acting on the rest of the genome. The combination of these approaches, physiology, genomics and transcriptomics, has improved the comprehension of the lipid metabolism, its evolution and gene regulation within a clade of oleaginous yeasts.
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Stéphanie Michely. Dynamique des génomes et évolution du métabolisme lipidique chez les levures du clade Yarrowia. Génomique, Transcriptomique et Protéomique [q-bio.GN]. AgroParisTech, 2014. Français. ⟨NNT : 2014AGPT0021⟩. ⟨tel-01178514⟩

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