ZipV Is Required for Oxidative Stress Resistance and Pathogenicity in Aspergillus fumigatus

The functions of the putative bZIP (basic leucine zipper) transcription factors ZipV (Afu3g032301) and ZipZ (Afu2g14350) were investigated using wild-type, gene-deficient, and complemented strains of Aspergillus fumigatus. Deletion of zipV increased oxidative stress sensitivity and reduced in vivo virulence in a Galleria mellonella model, whereas complementation restored the wild-type phenotype. In contrast, deletion of zipZ resulted in no detectable phenotypic changes, even though transcription of both genes was modulated by oxidative stress. Phenotypic characterization of conidia, transcriptomic analyses of growing cultures and reverse-transcription quantitative real-time PCR of conidia-producing cultures suggested that ZipV regulates the development of certain conidial traits. The conidia of the ∆zipV mutant showed reduced heat stress tolerance, decreased catalase activity and delayed germination in comparison to the wild-type or the complemented strain. In the ∆zipV mutant, the transcription of catA encoding conidial catalase was impaired. This defect explains the reduced catalase activity and the oxidative stress sensitivity of the mutant and may contribute to its reduced virulence. The increased transcriptional activity of the alternative oxidase gene aoxA observed in the absence of ZipV suggests a compensatory response aimed at mitigating oxidative stress.