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Mod5 mediates a molecular trade-off between optimal gene expression and antifungal resistance

ABSTRACT: Increasing antifungal drug resistance is a major concern associated with human fungal infections. Genetic mutation and epimutation mechanisms are clearly linked to resistance in some fungi, but few studies have investigated RNA modifications (the epitranscriptome) as a mediator of resistance. Here, deletion of the Aspergillus fumigatus tRNA-modifying isopentenyl transferase ortholog, Mod5, led to altered growth and stress response, but also unexpected resistance against the antifungal drug 5-fluorocytosine (5-FC). Simultaneous profiling of the transcriptome and proteome of 5-FC-stressed wild-type and ∆mod5 strains revealed a similar general adaptation to stress; however, the knockout displayed elevated expression of cross-pathway control (CPC) genes. Quantification of CPC transcription factor cpcA and client gene argB showed premature CPC activation in ∆mod5, which was further increased upon treatment with 5-FC. By associating codon usage patterns with proteomics abundances, we observed the number of tRNATyrGΨA-decoded codons to negatively correlate with protein abundance in the knockout, indicative of modification-tuneable transcripts. Subsequent overexpression of tRNATyrGΨA in the ∆mod5 strain rescued select phenotypes but, surprisingly, failed to reverse 5-FC resistance. Investigation of the purported tRNA gene-mediated silencing function of Mod5 uncovered a negative correlation between tRNA proximity and gene induction under normal growth, suggesting that tRNA gene-mediated silencing is active in A. fumigatus. In conclusion, 5-FC resistance in the absence of the bifunctional Mod5 protein likely originates from multifaceted transcriptional and translational changes that skew the fungus towards starvation responses over optimal growth, potentially offering a mechanism reliant on RNA modification and tRNA gene-mediated silencing capable of facilitating transient antifungal resistance.

INSTRUMENT(S): Orbitrap Exploris 480

ORGANISM(S): Aspergillus Fumigatus Cea17

SUBMITTER: Thomas Krüger

LAB HEAD: Axel A. Brakhage

PROVIDER: PXD048351 | Pride | 2024-10-23

REPOSITORIES: Pride

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Project description:Aspergillus fumigatus can cause Invasive Pulmonary Aspergillosis (IPA), the most severe form of Aspergillus-related infections. Fungicidal azoles and fungistatic caspofungin (CAS) are the first- and second-line therapies, respectively, used to treat IPA. However, azole-resistance is on the rise and new therapeutic alternatives need to be implemented. Recently, we showed that treatment of A. fumigatus with CAS or micafungin, but not voriconazole, induces production of the oxylipin 5,8-diHODE by the fungal oxygenase PpoA. Here we investigated the influence of ppo genes, that encode fatty acid oxygenases responsible for oxylipin biosynthesis, on CAS tolerance. The ppo mutants showed a very complex pattern of CAS susceptibility. PpoA and PpoC influence on CAS tolerance is mediated by MpkA phosphorylation and protein kinase A (PKA) activity. RNAseq transcriptional profiling and label-free quantitative proteomics (spectral counts) of the ppoA, and ppoC mutants showed that differentially expressed genes and proteins are related to secondary metabolites and carbohydrate metabolism. We tested several mutants of these differentially expressed genes encoding transcription factors and signal transduction proteins and some of them are more susceptible to CAS. We also characterized two clinical isolates, CNM7555 and IFM41607, that have decreased and increased susceptibility to CAS. CNM7555 does not have increased oxylipin production in the presence of CAS while the oxylipin induction upon CAS exposure is increased in the IFM41607, suggesting oxylipins are not the single mechanism involved in CAS tolerance in these isolates. Upon CAS exposure, CNM7555 has increased MpkA phosphorylation and PKA activity than IFM41607. Modulation of secondary metabolite production and carbohydrate metabolism is also essential in these clinical isolates for acquiring CAS tolerance. Our results reveal different aspects and genetic determinants involved in A. fumigatus CAS tolerance.

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	A_WT_1-a.raw	Raw
	A_WT_1-b.raw	Raw
	A_WT_1-c.raw	Raw
	A_WT_2-a.raw	Raw
	A_WT_2-b.raw	Raw

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Mod5 mediates a molecular trade-off between optimal gene expression and antifungal resistance

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