Divergent Targets of Aspergillus fumigatus AcuK and AcuM Transcription Factors during GrowthIn Vitroversus Invasive Disease

Abstract

InAspergillus nidulans, the AcuK and AcuM transcription factors form a complex that regulates gluconeogenesis. InAspergillus fumigatus, AcuM governs gluconeogenesis and iron acquisitionin vitroand virulence in immunosuppressed mice. However, the function of AcuK was previously unknown. Throughin vitrostudies, we found thatA. fumigatusΔacuKsingle and ΔacuKΔacuMdouble mutants had impaired gluconeogenesis and iron acquisition, similar to the ΔacuMmutant. Also, the ΔacuK, ΔacuM, and ΔacuKΔacuMmutants had similar virulence defects in mice. However, the ΔacuKmutant had a milder defect in extracellular siderophore activity and induction of epithelial cell damagein vitrothan did the ΔacuMmutant. Moreover, overexpression ofacuMin the ΔacuKmutant altered expression of 3 genes and partially restored growth under iron-limited conditions, suggesting that AcuM can govern some genes independently of AcuK. Although the ΔacuKand ΔacuMmutants had very similar transcriptional profilesin vitro, their transcriptional profiles during murine pulmonary infection differed both from theirin vitroprofiles and from each other. While AcuK and AcuM governed the expression of only a few iron-responsive genesin vivo, they influenced the expression of other virulence-related genes, such ashexAanddvrA. Therefore, inA. fumigatus, while AcuK and AcuM likely function as part of the same complex, they can also function independently of each other. Furthermore, AcuK and AcuM have different target genesin vivothanin vitro, suggesting thatin vivoinfection stimulates unique transcriptional regulatory pathways inA. fumigatus.