Fungal transposable elements and genome evolution

The transposable elements (TEs) identified in fungal genomes reflect the whole spectrum of eukaryotic transposable elements. Most of our knowledge comes from species representing different ecological situations: plant pathogens, industrial, and field strains, most of them lacking the sexual stage. A number of changes in gene structure and function has been shown to be TE-mediated: inactivation of gene expression upon insertion within or adjacent to a gene, DNA sequence variation through excision and probably extensive chromosomal rearrangements due to recombination between members of a particular family. Moreover, TEs may have other roles in evolution related to their ability to be horizontally transferred and to capture and transpose chromosomal host sequences, thus providing a mechanism for dispersing sequences to new sites. However, the activity of transposable elements and consequently their proliferation within a host genome can be affected, in some fungal species which undergo meiosis, by silencing processes. Our understanding of the biological effects of TEs on the fungal genome has increased dramatically in the past few years but elucidation of the extent to which transposons contribute to genetic variation in nature, providing the flexibility for populations to adapt successfully to environmental changes is an important area for future research.