Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus

The ubiquitous fungus Aspergillus flavus is notorious for contaminating many important crops and food-stuffs with the carcinogenic mycotoxin, aflatoxin. This fungus is also the second most frequent Aspergillus pathogen after A. fumigatus infecting immunosuppressed patients. In many human fungal pathogens including A. fumigatus, the ability to defend from toxic levels of copper (Cu) is essential in pathogenesis. In A. fumigatus, the Cu-fist DNA binding protein, AceA, and the Cu ATPase transporter, CrpA, play critical roles in Cu defense. Here, we show that A. flavus tolerates higher concentrations of Cu than A. fumigatus and other Aspergillus spp. associated with the presence of two homologs of A. fumigatus CrpA termed CrpA and CrpB. Both crpA and crpB are transcriptionally induced by increasing Cu concentrations via AceA activity. Deletion of crpA or crpB alone did not alter high Cu tolerance, suggesting they are redundant. Deletion of both genes resulted in extreme Cu sensitivity that was greater than that following deletion of the regulatory transcription factor aceA. The ΔcrpAΔcrpB and ΔaceA strains were also sensitive to ROI stress. Compared to wild type, these mutants were impaired in the ability to colonize maize seed treated with Cu fungicide but showed no difference in virulence on non-treated seed. A mouse model of invasive aspergillosis showed ΔcrpAΔcrpB and to a lesser degree ΔaceA to be significantly reduced in virulence, following the greater sensitivity of ΔcrpAΔcrpB to Cu than ΔaceA.