Using aCGH to study intraspecific genetic variability in two pathogenic molds, Aspergillus fumigatus and Aspergillus flavus.

We have examined the feasibility of using array comparative genomic hybridization (aCGH) to explore intraspecific genetic variability at the genomic level in two pathogenic molds, Aspergillus fumigatus and Aspergillus flavus. Our analysis showed that strain-specific genes may comprise up to 2% of their genomes in comparison to isolates from different vegetative (heterokaryon) compatibility groups (VCGs). In contrast, isolates with the same VCG affiliations have almost identical gene content. Most isolate-specific genes are annotated as 'hypothetical' and located in a few large subtelomeric indels. The list includes highly polymorphic loci that contain putative het (heterokaryon compatibility) loci, which determine the individual's VCG during parasexual crossing. Incidentally, VCGs in both species seem to be significantly associated with either alpha or HMG mating type (Chi-square test, P=0.05). In conclusion CGH can be used to effectively to identify isolate-specific genes in Aspergillus species. Preliminary evidence suggests that gene flow in both species is largely constrained by VCG boundaries, although further VCG sampling is required to confirm this observation.