Strain-specific retrotransposon-mediated recombination in commercially used Aspergillus niger strain.

Transposons are usually present in multiple copies in their hosts' genomes. Recombination between two transposon copies can result in chromosomal rearrangements. Here, we describe a recombination event between two copies of the retrotransposon ANiTa1 within the genome of the fungus Aspergillus niger (strain CBS513.88). The observed chromosomal rearrangement appears to be strain-specific, as the corresponding genomic region in another strain, ATCC1015, shows a different organization. Strain ATCC1015 actually seems to lack full-length ANiTa1 copies and possesses only solo LTR sequences. Presumably strain ATCC1015 was once colonized by ANiTa1, but then the genome subsequently lost the ANiTa1 copies. The striking genomic differences in ANiTa1 copy distribution leading to differences in the chromosomal structure between the two strains, ATTC1015 and CBS513.88, suggest that the activity of transposons may profoundly affect the evolution of different fungal strains.