Transposition of autonomous and engineered impala transposons in Fusarium oxysporum and a related species

The impala transposon of Fusarium oxysporum is an active element. We demons trated that the imp160 copy, transposed into the gene encoding nitrate redu ctase, is an autonomous element, since it excises from this: gene and reins erts at a new genomic position in backgrounds free of active elements. An e lement in which the transposase gene was replaced by a hygromycin B resista nce gene was used (1) to demonstrate the absence of endogenous transposase in several F. oxysporum strains and (2) to check the ability of different g enomic copies of impala to transactivate this defective element. This two-c omponent system allowed the identification of autonomous elements in two im pala subfamilies and revealed that transactivation can occur between highly divergent elements We also demonstrate that the autonomous copy transposes in a closely related species complex, F. moniliforme, in a fashion similar to that observed in F. oxysporum. The ability of impala to function as a t wo-component system and to transpose in a heterologous host promises furthe r advances in our understanding of the factors that modulate transposition efficiency and demonstrates the potential of impala as a means of establish ing a transposon tugging system for a wide range of fungal species.