The Yarrowia lipolytica transposon content.
Serge Casaregola (1), Cécile Neuvéglise (1), Christophe Ozanne (1), Patrick Wincker (2), Claude Gaillardin (1)
(1) Microbiol. et Genet. Molec., INRA/CNRS, INA-PG, Thiverval-Grignon, 78850, France; (2) Genoscope, Centre National de Séquençage, Evry, France
Y. lipolytica, a dimorphic yeast with unusual properties, diverged well before most of the other hemiascomycetous yeasts. The complete genome sequence of the Y. lipolytica strain E150 allowed the analysis of its transposon content which proved rather unusual. Y. lipolytica carries two DNA transposons, one that we called Mutyl shares several features with MULEs (Mutator-like elements). It possesses two genes, mutA and mutB, the former sharing sequence similarities with bacterial transposases. Mutyl is present in five copies of almost identical sequence in the strain E150, but is absent in some other lineages: the analysis of a cross between two strains, whose Mutyl content differs, showed that it transposed recently. Y. lipolytica carries another type of transposable element that is rare in hemiascomycetous yeasts. Also found in C. albicans where it is being lost, a family of non-LTR retrotransoposon belonging to the L1 clade is found, over 150 copies with extremely conserved sequence in the E150 strain, indicating that it is very likely active. As expected, it is found in all the Y. lipolytica strains tested. A majority of the copies are short 5' truncates probably due to a particular mode of regulation of its propagation. The evidence that Y. lipolytica, which also carries two types of unusual LTR retrotransposons (Ylt1 and Tyl6), represents the yeast ancestral transposon content will be discussed.