Transposition of a fungal MITE through the action of a Tc1-like transposase.
Résumé
The mimp1 element previously identified in the ascomycete fungus Fusarium oxysporum has hallmarks of miniature inverted-repeat transposable elements (MITEs): short size, terminal inverted repeats (TIRs), structural homogeneity and a stable secondary structure. Since mimp1 has no coding capacity, its mobilization requires a transposase-encoding element. Based on the similarity of TIRs and target site preference with the autonomous Tc1-like element impala, together with a correlated distribution of both elements among the Fusarium genus, we investigated the ability of mimp1 to jump upon expression of the impala transposase provided in trans. Under these conditions, we present evidence that mimp1 transposes by a cut-an-paste mechanism into TA dinucleotides which are duplicated upon insertion. Our results also show that mimp1 reinserts very frequently, in genic regions for at least one third of the cases. We also show that the mimp1/impala double component system is fully functional in the heterologous species F. graminearum allowing the development of a highly efficient tool for gene-tagging in filamentous fungi.