Differentially Regulated Transcription Factors and ABC Transporters in a Mitochondrial Dynamics Mutant Can Alter Azole Susceptibility of Aspergillus fumigatus

Abstract

Azole resistance of the fungal pathogen Aspergillus fumigatus is an emerging problem. To identify novel mechanisms that could mediate azole resistance in A. fumigatus, we analyzed the transcriptome of a mitochondrial fission/fusion mutant that exhibits increased azole tolerance. Approximately 12% of the annotated genes are differentially regulated in this strain. This comprises upregulation of Cyp51A, the azole target structure, upregulation of ATP-binding cassette (ABC) superfamily and major facilitator superfamily (MFS) transporters and differential regulation of transcription factors. To study their impact on azole tolerance, conditional mutants were constructed of seven ABC transporters and 17 transcription factors. Under repressed conditions, growth rates and azole susceptibility of the mutants were similar to wild type. Under induced conditions, several transcription factor mutants showed growth phenotypes. In addition, four ABC transporter mutants and seven transcription factor mutants exhibited altered azole susceptibility. However, deletion of individual identified ABC transporters and transcription factors did not affect the increased azole tolerance of the fission/fusion mutant. Our results revealed the ability of multiple ABC transporters and transcription factors to modulate the azole susceptibility of A. fumigatus and support a model where mitochondrial dysfunctions trigger a drug resistance network that mediates azole tolerance of this mold.

Global Transcriptome Profile of the Oleaginous Yeast Saitozyma podzolica DSM 27192 Cultivated in Glucose and Xylose

“…Overrepresentation of transmembrane transporter GOs, which indicates active transmembrane transport of a variety of substrates has been reported in many fungi [42,43]. Unlike the observed significant and specific enrichment of these GOs in glucose and xylose grown yeast observed in this study, genes associated with both GOs (GO:0022857 and GO:0055085) were reported to be up and downregulated on glucose grown Aspergillus fumigatus mutants [44]. To evaluate the potential implication of variation in the above differentially expressed sugar (and other) transporter genes during growth of the oleaginous yeast on xylose and glucose, we performed additional annotation of the predicted proteins using conserved domain database [36], the curated UniProtKB/Swiss-Prot [37] and transporter classification [38] databases as well as prediction of transmembrane helices using TMHMM Server v2.0 [39].…”

“…Overrepresentation of transmembrane transporter GOs, which indicates active transmembrane transport of a variety of substrates has been reported in many fungi [ 42 , 43 ]. Unlike the observed significant and specific enrichment of these GOs in glucose and xylose grown yeast observed in this study, genes associated with both GOs (GO:0022857 and GO:0055085) were reported to be up and downregulated on glucose grown Aspergillus fumigatus mutants [ 44 ].…”

Mitochondria-Mediated Azole Drug Resistance and Fungal Pathogenicity: Opportunities for Therapeutic Development

“…Although mitochondrial fission is related to increased azole resistance, the molecular mechanism underlying the increased azole resistance is still unclear. One possible mechanism in A. fumigatus is that mitochondrial fission defects lead to a decrease in intracellular azole drug concentration through upregulating multiple efflux pumps ( Figure 2 ) [ 41 ], dampening the inhibition of lanosterol 14α demethylase (Cyp51A) by azole drugs. Recently, an important contribution of mitochondrial fission to azole susceptibility of C. albicans has been reported.…”

Requirement of a putative mitochondrial GTPase, GemA, for azole susceptibility, virulence, and cell wall integrity in Aspergillus fumigatus

“…Moreover, the subsequent signal pathway enrichment analysis performed using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database showed that the aforementioned differentially expressed genes were mainly mapped to metabolic processes. Of them, ATP-binding cassette (ABC) transporters ( Figure 4C ), a type of fungal drug efflux pumps (Sturm et al, 2020 ), were enriched, suggesting that gemA deletion may be affected by intracellular drug residues in the fungus. In addition, as shown in Figure 4D , the selected genes, including those encoding the ABC transporters and major facilitators superfamily (MFS, another type of drug efflux pump), were broadly upregulated in the Δ gemA mutant compared with the WT strain.…”