Dataset Information

Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus.

ABSTRACT: The ubiquitous fungus Aspergillus flavus is notorious for contaminating many important crops and food-stuffs with the carcinogenic mycotoxin, aflatoxin. This fungus is also the second most frequent Aspergillus pathogen after A. fumigatus infecting immunosuppressed patients. In many human fungal pathogens including A. fumigatus, the ability to defend from toxic levels of copper (Cu) is essential in pathogenesis. In A. fumigatus, the Cu-fist DNA binding protein, AceA, and the Cu ATPase transporter, CrpA, play critical roles in Cu defense. Here, we show that A. flavus tolerates higher concentrations of Cu than A. fumigatus and other Aspergillus spp. associated with the presence of two homologs of A. fumigatus CrpA termed CrpA and CrpB. Both crpA and crpB are transcriptionally induced by increasing Cu concentrations via AceA activity. Deletion of crpA or crpB alone did not alter high Cu tolerance, suggesting they are redundant. Deletion of both genes resulted in extreme Cu sensitivity that was greater than that following deletion of the regulatory transcription factor aceA. The ?crpA?crpB and ?aceA strains were also sensitive to ROI stress. Compared to wild type, these mutants were impaired in the ability to colonize maize seed treated with Cu fungicide but showed no difference in virulence on non-treated seed. A mouse model of invasive aspergillosis showed ?crpA?crpB and to a lesser degree ?aceA to be significantly reduced in virulence, following the greater sensitivity of ?crpA?crpB to Cu than ?aceA.

SUBMITTER: Yang K

PROVIDER: S-EPMC6177249 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus.

Yang Kunlong K Shadkchan Yana Y Tannous Joanna J Landero Figueroa Julio A JA Wiemann Philipp P Osherov Nir N Wang Shihua S Keller Nancy P NP

Virulence 20180101 1

The ubiquitous fungus Aspergillus flavus is notorious for contaminating many important crops and food-stuffs with the carcinogenic mycotoxin, aflatoxin. This fungus is also the second most frequent Aspergillus pathogen after A. fumigatus infecting immunosuppressed patients. In many human fungal pathogens including A. fumigatus, the ability to defend from toxic levels of copper (Cu) is essential in pathogenesis. In A. fumigatus, the Cu-fist DNA binding protein, AceA, and the Cu ATPase transporter ...[more]

PMID: 30027796

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Project description:Melanin is an Aspergillus flavus cell wall component that provides chemical and physical protection to the organism. However, the molecular and biological mechanisms modulating melanin-mediated host-pathogen interaction in A. flavus keratitis are not well understood. This work aimed to compare the morphology, surface proteome profile, and virulence of melanized conidia (MC) and non-melanized conidia (NMC) of A. flavus. Kojic acid treatment inhibited melanin synthesis in A. flavus, and the conidial surface protein profile was significantly different in kojic acid-treated non-melanized conidia. Several cell wall-associated proteins and proteins responsible for oxidative stress, carbohydrate, and chitin metabolic pathways were found only in the formic acid extracts of NMC. Scanning electron microscopy (SEM) analysis showed the conidial surface morphology difference between the NMC and MC, indicating the role of melanin in the structural integrity of the conidial cell wall. The levels of calcofluor white staining efficiency were different, but there was no microscopic morphology difference in lactophenol cotton blue staining between MC and NMC. Evaluation of the virulence of MC and NMC in the Galleria mellonella model showed NMC was less virulent compared to MC. Our findings showed that the integrity of the conidial surface is controlled by the melanin layer. The alteration in the surface protein profile indicated that many surface proteins are masked by the melanin layer, and hence, melanin can modulate the host response by preventing the exposure of fungal proteins to the host immune defense system. The G. mellonella virulence assay also confirmed that the NMC were susceptible to host defense as in other Aspergillus pathogens. KEY POINTS: • l-DOPA melanin production was inhibited in A. flavus isolates by kojic acid, and for the first time, scanning electron microscopy (SEM) analysis revealed morphological differences between MC and NMC of A. flavus strains • Proteome profile of non-melanized conidia showed more conidial surface proteins and these proteins were mainly involved in the virulence, oxidative stress, and metabolism pathways • Non-melanized conidia of A. flavus strains were shown to be less virulent than melanised conidia in an in vivo virulence experiment with the G. melonella model.

Project description:Aspergillus flavus is an opportunistic fungal plant and human pathogen and a producer of mycotoxins, including aflatoxin B1 (AFB1). As part of our ongoing studies to elucidate the biological functions of the A. flavusrtfA gene, we examined its role in the pathogenicity of both plant and animal model systems. rtfA encodes a putative RNA polymerase II (Pol II) transcription elongation factor previously characterized in Saccharomyces cerevisiae, Aspergillus nidulans, and Aspergillus fumigatus, where it was shown to regulate several important cellular processes, including morphogenesis and secondary metabolism. In addition, an initial study in A. flavus indicated that rtfA also influences development and production of AFB1; however, its effect on virulence is unknown. The current study reveals that the rtfA gene is indispensable for normal pathogenicity in plants when using peanut seed as an infection model, as well as in animals, as shown in the Galleria mellonella infection model. Interestingly, rtfA positively regulates several processes known to be necessary for successful fungal invasion and colonization of host tissue, such as adhesion to surfaces, protease and lipase activity, cell wall composition and integrity, and tolerance to oxidative stress. In addition, metabolomic analysis revealed that A. flavusrtfA affects the production of several secondary metabolites, including AFB1, aflatrem, leporins, aspirochlorine, ditryptophenaline, and aflavinines, supporting a role of rtfA as a global regulator of secondary metabolism. Heterologous complementation of an A. flavusrtfA deletion strain with rtfA homologs from A. nidulans or S. cerevisiae fully rescued the wild-type phenotype, indicating that these rtfA homologs are functionally conserved among these three species.IMPORTANCE In this study, the epigenetic global regulator rtfA, which encodes a putative RNA-Pol II transcription elongation factor-like protein, was characterized in the mycotoxigenic and opportunistic pathogen A. flavus Specifically, its involvement in A. flavus pathogenesis in plant and animal models was studied. Here, we show that rtfA positively regulates A. flavus virulence in both models. Furthermore, rtfA-dependent effects on factors necessary for successful invasion and colonization of host tissue by A. flavus were also assessed. Our study indicates that rtfA plays a role in A. flavus adherence to surfaces, hydrolytic activity, normal cell wall formation, and response to oxidative stress. This study also revealed a profound effect of rtfA on the metabolome of A. flavus, including the production of potent mycotoxins.

Dataset Information

Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus.

Publications

Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus.

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