Genome-wide comparative analysis of pogo-like transposable elements in different Fusarium species.

The recent availability of genome sequences of four different Fusarium species offers the opportunity to perform extensive comparative analyses, in particular of repeated sequences. In a recent work, the overall content of such sequences in the genomes of three phylogenetically related Fusarium species, F. graminearum, F. verticillioides, and F. oxysporum f. sp. lycopersici has been estimated. In this study, we present an exhaustive characterization of pogo-like elements, named Fots, in four Fusarium genomes. Overall 10 Fot and two Fot-related miniature inverted-repeat transposable element families were identified, revealing a diversification of multiple lineages of pogo-like elements, some of which accompanied by a gain of introns. This analysis also showed that such elements are present in an unusual high proportion in the genomes of F. oxysporum f. sp. lycopersici and Nectria haematococca (anamorph F. solani f. sp. pisi) in contrast with most other fungal genomes in which retroelements are the most represented. Interestingly, our analysis showed that the most numerous Fot families all contain potentially active or mobilisable copies, thus conferring a mutagenic potential of these transposable elements and consequently a role in strain adaptation and genome evolution. This role is strongly reinforced when examining their genomic distribution which is clearly biased with a high proportion (more than 80%) located on strain- or species-specific regions enriched in genes involved in pathogenicity and/or adaptation. Finally, the different reproductive characteristics of the four Fusarium species allowed us to investigate the impact of the process of repeat-induced point mutations on the expansion and diversification of Fot elements.