The relevance of Aspergillus for human daily life is immeasurable: not only because of its industrial
applications but also because of its clinical implications. Most Aspergillus laboratories world-wide use
mutants in the non-homologous end joining (NHEJ) pathway (KU70 or KU80) to do genetic modifications
in the strains under study due to a higher frequency of homologous integrations after transformation of
DNA constructs. KU70 is involved in a DNA repair mechanism highly conserved in eukaryotes, and
genetic manipulations are much faster in NHEJ mutant (ΔKU70) strains in many fungal species.
Three Aspergillus species were selected for this study to allow for comparative genetics and genomics: A.
flavus, A. fumigatus and A. nidulans. Wild-type and NHEJ mutants were grown on solid media for 60
growth passages using asexual spores (ca. 3,000 mitosis). In the case of A. nidulans ten passages with
sexual cleistothecia were also independently performed. Genome sequences were obtained and
analyzed. In both A. flavus and A. fumigatus, the KU70 mutants accumulated on average more mutations
than the wild type strains (8.37 +/- 1.80 vs 6.12 +/- 1.76 in A. flavus, and 5.75 +/- 2.33 vs 4.12 +/- 1.76
in A. fumigatus). The higher number of non-synonymous mutations in A. fumigatus and of mutations in
the intergenic regions in A. flavus in the KU70 mutants was statistically significant. None of the sexual
passages of the A. nidulans KU70 strain could be completed due to the lack of cleistothecia formation,
while the majority of the wild type passages reached ten passages. Collectively here we provide an
assessment of the effects of the NHEJ pathway in the genomic stability in Aspergilli.
Full conference title:
- Asperfest 14 (2017)