Induction of
Aspergillus fumigatus
zinc cluster transcription factor OdrA/Mdu2 provides combined cellular responses for oxidative stress protection and multiple antifungal drug resistance
Authors: Sasse Christoph , Bastakis Emmanouil , Bakti Fruzsina , Höfer Annalena M. , Zangl Isabella , Schüller Christoph , Köhler Anna M. , Gerke Jennifer , Krappmann Sven , Finkernagel Florian , Harting Rebekka , Strauss Joseph , Heimel Kai , Braus Gerhard H. 
Published: November 2023

ABSTRACT

Z
inc
c
luster transcription
f
actors (Zcfs) encoding
zcf
genes are exclusive for fungi and required for multiple cellular processes including metabolism and development. Genome-wide screening of 228 zinc cluster transcription factor encoding genes by overexpression in
Aspergillus fumigatus
revealed 11 genes which provided increased tolerance to the broadly applied azole voriconazole or to the polyene amphotericin B or to both. These include four
o
xidative stress and
d
rug
r
esistance genes (
odrA-D
) genes encoding factors, which provide broad cellular stress protection. Thereby, the corresponding fungal OdrA/Mdu2- and AtrR/OdrD-dependent genetic networks are interconnected. OdrA/Mdu2 activates
atrR
/
odrD
transcription by direct binding to the promoter, whereas AtrR/OdrD functions as repressor of
odrA
/
mdu2
expression.
odrA
/
mdu2
overexpression provides combined resistance to amphotericin B, voriconazole, itraconazole, and reactive oxygen species generated by menadione. OdrA/Mdu2-mediated itraconazole resistance is evoked by direct regulation of the transporter encoding gene
mdr1
. Oxidative stress-inducing substances like amphotericin B and menadione promote OdrA/Mdu2 accumulation in the nucleus to regulate stress response genes like
mdr1
and the putative glutathione-S-transferase encoding gene
gstD
. The expression levels and external stress conditions fostering nuclear accumulation of OdrA/Mdu2 determine the regulation of the target genes. Hence, OdrA/Mdu2 provides a combined adaptation strategy for survival in nature or within a potential host, where this fungus represents the most common agent for human mold pneumonia worldwide. The OdrA/Mdu2 controlled genetic network highlights the tight connection between oxidative stress response and antifungal drug adaption to secure
A. fumigatus
survival in various hostile environments.

IMPORTANCE

An overexpression screen of 228 zinc cluster transcription factor encoding genes of
A. fumigatus
revealed 11 genes conferring increased tolerance to antifungal drugs. Out of these, four oxidative stress and drug tolerance transcription factor encoding
odr
genes increased tolerance to oxidative stress and antifungal drugs when overexpressed. This supports a correlation between oxidative stress response and antifungal drug tolerance in
A. fumigatus
. OdrA/Mdu2 is required for the cross-tolerance between azoles, polyenes, and oxidative stress and activates genes for detoxification. Under oxidative stress conditions or when overexpressed, OdrA/Mdu2 accumulates in the nucleus and activates detoxifying genes by direct binding at their promoters, as we describe with the
mdr1
gene encoding an itraconazole specific efflux pump. Finally, this work gives new insights about drug and stress resistance in the opportunistic pathogenic fungus
A. fumigatus
.