Aspergillus fumigatus ffmA Encodes a C2H2-Containing Transcriptional Regulator That Modulates Azole Resistance and Is Required for Normal Growth

The production of a collection of deletion mutant strains corresponding to a large number of transcription factors from the filamentous fungal pathogen Aspergillus fumigatus has permitted rapid identification of transcriptional regulators involved in a range of different processes. Here, we characterize a gene designated ffmA (favors fermentative metabolism) as a C2H2-containing transcription factor that is required for azole drug resistance and normal growth. Loss of ffmA caused cells to exhibit significant defects in growth, either under untreated or azole-challenged conditions. Loss of FfmA caused a reduction in expression of the AbcG1 ATP-binding cassette transporter, previously shown to contribute to azole resistance. Strikingly, overproduction of the AtrR transcription factor gene restored a wild-type growth phenotype to an ffmA Delta strain. Overexpression of AtrR also suppressed the defect in AbcG1 expression caused by loss of FfmA. Replacement of the ffmA promoter with a doxycycline-repressible promoter restored nearly normal growth in the absence of doxycycline. Finally, chromatin immunoprecipitation experiments indicated that FfmA bound to its own promoter as well as to the abcG1 promoter. These data imply that FfmA and AtrR interact both with respect to abcG1 expression and also more broadly to regulate hyphal growth. IMPORTANCE Infections associated with azole-resistant forms of the primary human pathogen Aspergillus fumigatus are associated with poor outcomes in patient populations. This makes analysis of the mechanisms underlying azole resistance of A. fumigatus a high priority. In this work, we describe characterization of a gene designated ffmA that encodes a sequence-specific transcriptional regulator. We identified ffmA in a screen of a collection of gene deletion mutant strains made in A. fumigatus. Loss of ffmA caused sensitivity to azole drugs and also a large reduction in normal growth. We found that overproduction of the AtrR transcription factor could restore growth to ffmA null cells. We provide evidence that FfmA can recognize promoters of genes involved in azole resistance as well as the ffmA promoter itself. Our data indicate that FfmA and AtrR interact to support azole resistance and normal growth. Infections associated with azole-resistant forms of the primary human pathogen Aspergillus fumigatus are associated with poor outcomes in patient populations. This makes analysis of the mechanisms underlying azole resistance of A. fumigatus a high priority.

Automated summary

In this study, we characterized a gene designated ffmA as a sequence-specific transcriptional regulator involved in azole drug resistance and normal growth in Aspergillus fumigatus. Loss of ffmA caused sensitivity to azole drugs and a large reduction in normal growth. Overproduction of the AtrR transcription factor restored growth to ffmA null cells. Our data indicated that FfmA can recognize promoters of genes involved in azole resistance as well as its own promoter. This study sheds light on the mechanisms underlying azole resistance and normal growth in A. fumigatus.