Publications by authors named "Tamás Emri"

68 Publications

The DUG Pathway Governs Degradation of Intracellular Glutathione in Aspergillus nidulans.

Appl Environ Microbiol 2021 04 13;87(9). Epub 2021 Apr 13.

Department of Molecular Biotechnology and Microbiology, Faculty of Sciences and Technology, University of Debrecen, Debrecen, Hungary

Glutathione (GSH) is an abundant tripeptide that plays a crucial role in shielding cellular macromolecules from various reactive oxygen and nitrogen species in fungi. Understanding GSH metabolism is of vital importance for deciphering redox regulation in these microorganisms. In the present study, to better understand the GSH metabolism in filamentous fungi, we investigated functions of the and genes in the model fungus These genes are orthologues of and , which are involved in cytosolic GSH degradation in The deletion of , , or both resulted in a moderate increase in the GSH content in mycelia grown on glucose, reduced conidium production, and disturbed sexual development. In agreement with these observations, transcriptome data showed that genes encoding mitogen-activated protein (MAP) kinase pathway elements (e.g., , , , and ) or regulatory proteins of conidiogenesis and sexual differentiation (e.g., , , , , , , and ) were downregulated in the Δ Δ mutant. Deletion of and/or slowed the depletion of GSH pools during carbon starvation. It also reduced accumulation of reactive oxygen species and decreased autolytic cell wall degradation and enzyme secretion but increased sterigmatocystin formation. Transcriptome data demonstrated that enzyme secretions-in contrast to mycotoxin production-were controlled at the posttranscriptional level. We suggest that GSH connects starvation and redox regulation to each other: cells utilize GSH as a stored carbon source during starvation. The reduction of GSH content alters the redox state, activating regulatory pathways responsible for carbon starvation stress responses. Glutathione (GSH) is a widely distributed tripeptide in both eukaryotes and prokaryotes. Owing to its very low redox potential, antioxidative character, and high intracellular concentration, GSH profoundly shapes the redox status of cells. Our observations suggest that GSH metabolism and/or the redox status of cells plays a determinative role in several important aspects of fungal life, including oxidative stress defense, protein secretion, and secondary metabolite production (including mycotoxin formation), as well as sexual and asexual differentiations. We demonstrated that even a slightly elevated GSH level can substantially disturb the homeostasis of fungi. This information could be important for development of new GSH-producing strains or for any biotechnologically relevant processes where the GSH content, antioxidant capacity, or oxidative stress tolerance of a fungal strain is manipulated.
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http://dx.doi.org/10.1128/AEM.01321-20DOI Listing
April 2021

Shed Light in the DaRk LineagES of the Fungal Tree of Life-STRES.

Life (Basel) 2020 Dec 19;10(12). Epub 2020 Dec 19.

Microbiology & Plant Pathology, University of California Riverside, Riverside, CA 92521, USA.

The polyphyletic group of black fungi within the Ascomycota (Arthoniomycetes, Dothideomycetes, and Eurotiomycetes) is ubiquitous in natural and anthropogenic habitats. Partly because of their dark, melanin-based pigmentation, black fungi are resistant to stresses including UV- and ionizing-radiation, heat and desiccation, toxic metals, and organic pollutants. Consequently, they are amongst the most stunning extremophiles and poly-extreme-tolerant organisms on Earth. Even though ca. 60 black fungal genomes have been sequenced to date, [mostly in the family Herpotrichiellaceae (Eurotiomycetes)], the class Dothideomycetes that hosts the largest majority of extremophiles has only been sparsely sampled. By sequencing up to 92 species that will become reference genomes, the "Shed light in The daRk lineagES of the fungal tree of life" (STRES) project will cover a broad collection of black fungal diversity spread throughout the Fungal Tree of Life. Interestingly, the STRES project will focus on mostly unsampled genera that display different ecologies and life-styles (e.g., ant- and lichen-associated fungi, rock-inhabiting fungi, etc.). With a resequencing strategy of 10- to 15-fold depth coverage of up to ~550 strains, numerous new reference genomes will be established. To identify metabolites and functional processes, these new genomic resources will be enriched with metabolomics analyses coupled with transcriptomics experiments on selected species under various stress conditions (salinity, dryness, UV radiation, oligotrophy). The data acquired will serve as a reference and foundation for establishing an encyclopedic database for fungal metagenomics as well as the biology, evolution, and ecology of the fungi in extreme environments.
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http://dx.doi.org/10.3390/life10120362DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7767062PMC
December 2020

FvmnSOD is involved in oxidative stress defence, mitochondrial stability and apoptosis prevention in Fusarium verticillioides.

J Basic Microbiol 2020 Nov 23;60(11-12):994-1003. Epub 2020 Nov 23.

Department of Molecular Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

Superoxide dismutases are key enzymes in elimination of the superoxide anion radical (O ) generated intracellularly or by exogenous oxidative stress eliciting agents, like menadione. In this study, we investigated the physiological role of the manganese superoxide dismutase-encoding gene in Fusarium verticillioides via the construction of a gene deletion mutant, ΔFvmnSOD and comparing its phenotype with that of the wild-type parental strain and a ΔFvmnSOD' C strain, complemented with the functional manganese superoxide dismutase gene. Deletion of FvmnSOD had no effect on the relative intracellular superoxide ratio but increased the sensitivity of the fungus to menadione sodium bisulphite on Czapek-Dox stress agar plates. The lack of FvmnSOD caused changes in mitochondrial morphology and physiology: The volumetric ratio of these cell organelles in the second hyphal segment, as well as the total, the KCN-sensitive cytochrome c-dependent and the KCN+SHAM (salicylhidroxamic acid)-resistant residual respiration rates, were higher in the mutant as compared to the wild-type and the complemented strains. Nevertheless, changes in the respiration rates were attributable to the higher volumetric ratio of mitochondria found in the gene deletion mutant. Changes in the mitochondrial functions also brought about higher sensitivity to apoptotic cell death elicited by the Penicillium chrysogenum antifungal protein. The gene deletion mutant developed significantly thinner hyphae in comparison to the wild-type strain. Deletion of FvmnSOD had no effect on fumonisin B and B production of the fungus grown in Myro medium as a static culture.
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http://dx.doi.org/10.1002/jobm.202000560DOI Listing
November 2020

FvatfA regulates growth, stress tolerance as well as mycotoxin and pigment productions in Fusarium verticillioides.

Appl Microbiol Biotechnol 2020 Sep 27;104(18):7879-7899. Epub 2020 Jul 27.

Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

FvatfA from the maize pathogen Fusarium verticillioides putatively encodes the Aspergillus nidulans AtfA and Schizasaccharomyces pombe Atf1 orthologous bZIP-type transcription factor, FvAtfA. In this study, a ΔFvatfA deletion mutant was constructed and then genetically complemented with the fully functional FvatfA gene. Comparing phenotypic features of the wild-type parental, the deletion mutant and the restored strains shed light on the versatile regulatory functions played by FvAtfA in (i) the maintenance of vegetative growth on Czapek-Dox and Potato Dextrose agars and invasive growth on unwounded tomato fruits, (ii) the preservation of conidiospore yield and size, (iii) the orchestration of oxidative (HO, menadione sodium bisulphite) and cell wall integrity (Congo Red) stress defences and (iv) the regulation of mycotoxin (fumonisins) and pigment (bikaverin, carotenoid) productions. Expression of selected biosynthetic genes both in the fumonisin (fum1, fum8) and the carotenoid (carRA, carB) pathways were down-regulated in the ΔFvatfA strain resulting in defected fumonisin production and considerably decreased carotenoid yields. The expression of bik1, encoding the polyketide synthase needed in bikaverin biosynthesis, was not up-regulated by the deletion of FvatfA meanwhile the ΔFvatfA strain produced approximately ten times more bikaverin than the wild-type or the genetically complemented strains. The abolishment of fumonisin production of the ΔFvatfA strain may lead to the development of new-type, biology-based mycotoxin control strategies. The novel information gained on the regulation of pigment production by this fungus can be interesting for experts working on new, Fusarium-based biomass and pigment production technologies. Key points • FvatfA regulates vegetative and invasive growths of F. verticillioides. • FvatfA also orchestrates oxidative and cell wall integrity stress defenses. • The ΔFvatfA mutant was deficient in fumonisin production. • FvatfA deletion resulted in decreased carotenoid and increased bikaverin yields.
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http://dx.doi.org/10.1007/s00253-020-10717-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7447684PMC
September 2020

Supplementation of Aspergillus glaucus with gfdB gene encoding a glycerol 3-phosphate dehydrogenase in Aspergillus nidulans.

J Basic Microbiol 2020 Aug 8;60(8):691-698. Epub 2020 Jun 8.

Department of Molecular Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

In Aspergillus nidulans, there are two putative glycerol 3-phosphate dehydrogenases encoded by the genes gfdA and gfdB, while the genome of the osmophilic Aspergillus glaucus harbors only the ortholog of the A. nidulans gfdA gene. Our aim was to insert the gfdB gene into the genome of A. glaucus, and we reached this goal with the adaptation of the Agrobacterium tumefaciens-mediated transformation method. We tested the growth of the gfdB-complemented A. glaucus strains on a medium containing 2 mol l sorbitol in the presence of oxidative stress generating agents such as tert-butyl hydroperoxide, H O , menadione sodium bisulfite, as well as the cell wall integrity stress-inducing agent Congo Red and the heavy metal stress eliciting CdCl . The growth of the complemented strains was significantly higher than that of the wild-type strain on media supplemented with these stress generating agents. The A. nidulans ΔgfdB mutant was also examined under the same conditions and resulted in a considerably lower growth than that of the control strain in all stress exposure experiments. Our results shed light on the fact that the gfdB gene from A. nidulans was also involved in the stress responses of the complemented A. glaucus strains supporting our hypothesis on the antioxidant function of GfdB in the Aspergilli. Nevertheless, the osmotolerant nature of A. glaucus could not be explained by the lack of the gfdB gene in A. glaucus, as we hypothesized earlier.
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http://dx.doi.org/10.1002/jobm.202000067DOI Listing
August 2020

Increased Cd biosorption capability of Aspergillus nidulans elicited by crpA deletion.

J Basic Microbiol 2020 Jul 25;60(7):574-584. Epub 2020 May 25.

Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

The P-type ATPase CrpA is an important Cu /Cd pump in the Aspergilli, significantly contributing to the heavy metal stress tolerance of these ascomycetous fungi. As expected, the deletion of crpA resulted in Cu /Cd -sensitive phenotypes in Aspergillus nidulans on stress agar plates inoculated with conidia. Nevertheless, paradoxical growth stimulations were observed with the ΔcrpA strain in both standard Cu stress agar plate experiments and cellophane colony harvest (CCH) cultures, when exposed to Cd . These observations reflect efficient compensatory mechanisms for the loss of CrpA operating under these experimental conditions. It is remarkable that the ΔcrpA strain showed a 2.7 times higher Cd biosorption capacity in CCH cultures, which may facilitate the development of new, fungal biomass-based bioremediation technologies to extract harmful Cd ions from the environment. The nullification of crpA also significantly changed the spatial distribution of Cu and Cd in CCH cultures, as demonstrated by the combined particle-induced X-ray emission and scanning transmission ion microscopy technique. Most important, the centers of gravity for Cu and Cd accumulations of the ΔcrpA colonies shifted toward the older regions as compared with wild-type surface cultures.
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http://dx.doi.org/10.1002/jobm.202000112DOI Listing
July 2020

General stress response or adaptation to rapid growth in Aspergillus nidulans?

Fungal Biol 2020 05 28;124(5):376-386. Epub 2019 Oct 28.

Department of Molecular Biotechnology and Microbiology, University of Debrecen, Egyetem tér 1, Debrecen, 4032, Hungary. Electronic address:

Genome-wide transcriptional changes in Aspergillus nidulans induced by nine different stress conditions were evaluated to reveal the general environmental stress response gene set showing unidirectional expressional changes under various types of stress. Clustering the genes by their transcriptional changes was a useful technique for identifying large groups of co-regulated genes. Altogether, 1642 co-upregulated and 3916 co-downregulated genes were identified. Nevertheless, the co-regulated genes describe the difference between the transcriptomes recorded under the stress conditions tested and one chosen reference culture condition which is designated as the "unstressed" condition. Obviously, the corresponding transcriptional differences may be attributed to either the general stress response or the reference condition. Accordingly, reduced growth and increased transcription of certain antioxidative enzymes observed under stress may be interpreted as elements of the general stress response or as a feature of the "optimal growth" reference condition and decreased antioxidative protection due to "rapid growth" stress. Reversing the many to one comparison underlying the identification of co-regulated gene sets allows the same procedure to highlight changes under a single condition with respect to a set of other "background" conditions. As an example, we compared menadione treatment to our other conditions and identified downregulation of endoplasmic reticulum dependent processes and upregulation of iron-sulfur cluster assembly as well as glutathione-S-transferase genes as changes characteristic of MSB-treated cultures. Deletion of the atfA gene markedly altered the co-regulated gene sets primarily by changing the reference transcriptome; not by changing the stress responsiveness of genes. The functional characterization of AtfA-dependent co-regulated genes demonstrated the involvement of AtfA in the regulation of both vegetative growth and conidiogenesis in untreated cultures. Our data also suggested that the diverse effects of atfA gene deletion on the transcriptome under different stress conditions were the consequence of the altered transcription of several phosphorelay signal transduction system genes, including fphA, nikA, phkA, srrB, srrC, sskA and tcsB. Hopefully, this study will draw further attention to the importance of the proper selection of reference cultures in fungal transcriptomics studies especially when elements of specific stress responses are mapped.
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http://dx.doi.org/10.1016/j.funbio.2019.10.009DOI Listing
May 2020

The Third International Symposium on Fungal Stress - ISFUS.

Fungal Biol 2020 05 24;124(5):235-252. Epub 2020 Feb 24.

Universidade Brasil, São Paulo, SP, Brazil. Electronic address:

Stress is a normal part of life for fungi, which can survive in environments considered inhospitable or hostile for other organisms. Due to the ability of fungi to respond to, survive in, and transform the environment, even under severe stresses, many researchers are exploring the mechanisms that enable fungi to adapt to stress. The International Symposium on Fungal Stress (ISFUS) brings together leading scientists from around the world who research fungal stress. This article discusses presentations given at the third ISFUS, held in São José dos Campos, São Paulo, Brazil in 2019, thereby summarizing the state-of-the-art knowledge on fungal stress, a field that includes microbiology, agriculture, ecology, biotechnology, medicine, and astrobiology.
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http://dx.doi.org/10.1016/j.funbio.2020.02.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7438019PMC
May 2020

Rare earth element sequestration by biomass.

Environ Technol 2020 Mar 16:1-11. Epub 2020 Mar 16.

Department of Molecular Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

The fungus could be shown to be a viable alternative for biosorption of valuable metals from solution. Fungal biomass can be obtained easily in high quantities as a waste of biofermentation processes, and used in a complex, multi-phase solution mimicking naturally occurring, mining-affected water samples. With test solution formulated after natural conditions, formation of secondary Al and Fe phases co-precipitating Ce was recorded in addition to specific biosorption of rare earth elements. Remarkably, the latter were removed from the solution despite the presence of high concentrations of interfering Fe and Al. The biomass was viable even after prolonged incubation in the metal solution, and minimal inhibitory concentrations for single metals were higher than those in the test solution. While precipitation/biosorption of Ce (maximal biosorption efficiency was 58.0 ± 22.3% after 6 h of incubation) coincided with the gross removal of Fe from the metal solution, Y (81.5 ± 11.3% efficiency, 24 h incubation) and Nd (87.4 ± 9.1% efficiency, 24 h incubation) were sequestered later, similarly to Ni and Zn. The biphasic binding pattern specific to single metals could be connected to dynamically changing pH and NH concentrations, which were attributed to the physiological changes taking place in starving biomass. The metals were found extracellularly in minerals associated with the cell wall, and intracellularly precipitated in the vacuoles. The latter process was explained with intracellular metal detoxification resulting in metal resistance.
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http://dx.doi.org/10.1080/09593330.2020.1739146DOI Listing
March 2020

Deletion of the fungus specific protein phosphatase Z1 exaggerates the oxidative stress response in Candida albicans.

BMC Genomics 2019 Nov 19;20(1):873. Epub 2019 Nov 19.

Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.

Background: Candida albicans is an opportunistic pathogen which is responsible for widespread nosocomial infections. It encompasses a fungus specific serine/threonine protein phosphatase gene, CaPPZ1 that is involved in cation transport, cell wall integrity, oxidative stress response, morphological transition, and virulence according to the phenotypes of the cappz1 deletion mutant.

Results: We demonstrated that a short-term treatment with a sublethal concentration of tert-butyl hydroperoxide suppressed the growth of the fungal cells without affecting their viability, both in the cappz1 mutant and in the genetically matching QMY23 control strains. To reveal the gene expression changes behind the above observations we carried out a global transcriptome analysis. We used a pilot DNA microarray hybridization together with extensive RNA sequencing, and confirmed our results by quantitative RT-PCR. Novel functions of the CaPpz1 enzyme and oxidative stress mechanisms have been unraveled. The numbers of genes affected as well as the amplitudes of the transcript level changes indicated that the deletion of the phosphatase sensitized the response of C. albicans to oxidative stress conditions in important physiological functions like membrane transport, cell surface interactions, oxidation-reduction processes, translation and RNA metabolism.

Conclusions: We conclude that in the wild type C. albicans CaPPZ1 has a protective role against oxidative damage. We suggest that the specific inhibition of this phosphatase combined with mild oxidative treatment could be a feasible approach to topical antifungal therapy.
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http://dx.doi.org/10.1186/s12864-019-6252-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6862791PMC
November 2019

Physiological and Transcriptional Responses of Candida parapsilosis to Exogenous Tyrosol.

Appl Environ Microbiol 2019 10 1;85(20). Epub 2019 Oct 1.

Department of Medical Microbiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary

Tyrosol plays a key role in fungal morphogenesis and biofilm development. Also, it has a remarkable antifungal effect at supraphysiological concentrations. However, the background of the antifungal effect remains unknown, especially in the case of non- species such as We examined the effect of tyrosol on growth, adhesion, redox homeostasis, virulence, as well as fluconazole susceptibility. To gain further insights into the physiological consequences of tyrosol treatment, we also determined genome-wide gene expression changes using transcriptome sequencing (RNA-Seq). A concentration of 15 mM tyrosol caused significant growth inhibition within 2 h of the addition of tyrosol, while the adhesion of yeast cells was not affected. Tyrosol increased the production of reactive oxygen species remarkably, as revealed by a dichlorofluorescein test, and it was associated with elevated superoxide dismutase, glutathione peroxidase, and catalase activities. The interaction between fluconazole and tyrosol was antagonistic. Tyrosol exposure resulted in 261 and 181 differentially expressed genes with at least a 1.5-fold increase or decrease in expression, respectively, which were selected for further study. Genes involved in ribosome biogenesis showed downregulation, while genes related to the oxidative stress response and ethanol fermentation were upregulated. In addition, tyrosol treatment upregulated the expression of efflux pump genes, including and , and downregulated the expression of the and virulence genes involved in desaturated fatty acid formation. Our data demonstrate that exogenous tyrosol significantly affects the physiology and gene expression of , which could contribute to the development of treatments targeting quorum sensing in the future.-secreted quorum-sensing molecules (i.e., farnesol and tyrosol) are key regulators in fungal physiology, which induce phenotypic adaptations, including morphological changes, altered biofilm formation, and synchronized expression of virulence factors. Moreover, they have a remarkable antifungal activity at supraphysiological concentrations. Limited data are available concerning the tyrosol-induced molecular and physiological effects on non- species such as In addition, the background of the previously observed antifungal effect caused by tyrosol remains unknown. This study reveals that tyrosol exposure enhanced the oxidative stress response and the expression of efflux pump genes, while it inhibited growth and ribosome biogenesis as well as several virulence-related genes. Metabolism was changed toward glycolysis and ethanol fermentation. Furthermore, the initial adherence was not influenced significantly in the presence of tyrosol. Our results provide several potential explanations for the previously observed antifungal effect.
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http://dx.doi.org/10.1128/AEM.01388-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6805090PMC
October 2019

Physiological background of the remarkably high Cd tolerance of the Aspergillus fumigatus Af293 strain.

J Basic Microbiol 2018 Nov 31;58(11):957-967. Epub 2018 Aug 31.

Department of Biotechnology and Microbiology, Faculty of Sciences and Technology, University of Debrecen, Debrecen, Hungary.

The physiological background of the unusually high cadmium tolerance (MIC  > 2 mM) of Aspergillus fumigatus Af293 was investigated. The cadmium tolerance of the tested environmental and clinical A. fumigatus strains varied over a wide range (0.25 mM < MIC  < 1 mM). Only the Af293 strain showed a MIC value of >2 mM, and this phenotype was accompanied by increased in vivo virulence in mice. A strong correlation was found between the cadmium tolerance and the transcription of the pcaA gene, which encodes a putative cadmium efflux pump. The cadmium tolerance also correlated with the iron tolerance and the extracellular siderophore production of the strains. In addition to these findings, Af293 did not show the synergism between iron toxicity and cadmium toxicity that was detected in the other strains. Based on these results, we suggest that the primary function of PcaA should be acting as a ferrous iron pump and protecting cells from iron overload. Nevertheless, the heterologous expression of pcaA may represent an attractive strain improvement strategy to construct fungal strains for use in biosorption or biomining processes or to prevent accumulation of this toxic metal in crops.
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http://dx.doi.org/10.1002/jobm.201800200DOI Listing
November 2018

Additional oxidative stress reroutes the global response of Aspergillus fumigatus to iron depletion.

BMC Genomics 2018 May 10;19(1):357. Epub 2018 May 10.

Department of Biotechnology and Microbiology, Faculty of Sciences and Technology, University of Debrecen, Egyetem tér 1, Debrecen, H-4032, Hungary.

Background: Aspergillus fumigatus has to cope with a combination of several stress types while colonizing the human body. A functional interplay between these different stress responses can increase the chances of survival for this opportunistic human pathogen during the invasion of its host. In this study, we shed light on how the HO-induced oxidative stress response depends on the iron available to this filamentous fungus, using transcriptomic analysis, proteomic profiles, and growth assays.

Results: The applied HO treatment, which induced only a negligible stress response in iron-replete cultures, deleteriously affected the fungus under iron deprivation. The majority of stress-induced changes in gene and protein expression was not predictable from data coming from individual stress exposure and was only characteristic for the combination of oxidative stress plus iron deprivation. Our experimental data suggest that the physiological effects of combined stresses and the survival of the fungus highly depend on fragile balances between economization of iron and production of essential iron-containing proteins. One observed strategy was the overproduction of iron-independent antioxidant proteins to combat oxidative stress during iron deprivation, e.g. the upregulation of superoxide dismutase Sod1, the thioredoxin reductase Trr1, and the thioredoxin orthologue Afu5g11320. On the other hand, oxidative stress induction overruled iron deprivation-mediated repression of several genes. In agreement with the gene expression data, growth studies underlined that in A. fumigatus iron deprivation aggravates oxidative stress susceptibility.

Conclusions: Our data demonstrate that studying stress responses under separate single stress conditions is not sufficient to understand how A. fumigatus adapts in a complex and hostile habitat like the human body. The combinatorial stress of iron depletion and hydrogen peroxide caused clear non-additive effects upon the stress response of A. fumigatus. Our data further supported the view that the ability of A. fumigatus to cause diseases in humans strongly depends on its fitness attributes and less on specific virulence factors. In summary, A. fumigatus is able to mount and coordinate complex and efficient responses to combined stresses like iron deprivation plus HO-induced oxidative stress, which are exploited by immune cells to kill fungal pathogens.
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http://dx.doi.org/10.1186/s12864-018-4730-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5946477PMC
May 2018

Endophytic fungi from the roots of horseradish (Armoracia rusticana) and their interactions with the defensive metabolites of the glucosinolate - myrosinase - isothiocyanate system.

BMC Plant Biol 2018 May 9;18(1):85. Epub 2018 May 9.

Department of Botany, Division of Pharmacognosy, University of Debrecen, Egyetem tér 1, Debrecen, H-4010, Hungary.

Background: The health of plants is heavily influenced by the intensively researched plant microbiome. The microbiome has to cope with the plant's defensive secondary metabolites to survive and develop, but studies that describe this interaction are rare. In the current study, we describe interactions of endophytic fungi with a widely researched chemical defense system, the glucosinolate - myrosinase - isothiocyanate system. The antifungal isothiocyanates are also of special interest because of their beneficial effects on human consumers.

Results: Seven endophytic fungi were isolated from horseradish roots (Armoracia rusticana), from the genera Fusarium, Macrophomina, Setophoma, Paraphoma and Oidiodendron. LC-ESI-MS analysis of the horseradish extract incubated with these fungi showed that six of seven strains could decompose different classes of glucosinolates. Aliphatic, aromatic, thiomethylalkyl and indolic glucosinolates were decomposed by different strains at different rates. SPME-GC-MS measurements showed that two strains released significant amounts of allyl isothiocyanate into the surrounding air, but allyl nitrile was not detected. The LC-ESI-MS analysis of many strains' media showed the presence of allyl isothiocyanate - glutathione conjugate during the decomposition of sinigrin. Four endophytic strains also accepted sinigrin as the sole carbon source. Isothiocyanates inhibited the growth of fungi at various concentrations, phenylethyl isothiocyanate was more potent than allyl isothiocyanate (mean IC was 2.30-fold lower). As a control group, ten soil fungi from the same soil were used. They decomposed glucosinolates with lower overall efficiency: six of ten strains had insignificant or weak activities and only three could use sinigrin as a carbon source. The soil fungi also showed lower AITC tolerance in the growth inhibition assay: the median IC values were 0.1925 mM for endophytes and 0.0899 mM for soil fungi.

Conclusions: The host's glucosinolates can be used by the tested endophytic fungi as nutrients or to gain competitive advantage over less tolerant species. These activities were much less apparent among the soil fungi. This suggests that the endophytes show adaptation to the host plant's secondary metabolites and that host metabolite specific activities are enriched in the root microbiome. The results present background mechanisms enabling an understanding of how plants shape their microbiome.
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http://dx.doi.org/10.1186/s12870-018-1295-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5944135PMC
May 2018

Fungal Stress Database (FSD)--a repository of fungal stress physiological data.

Database (Oxford) 2018 01;2018

Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary.

Abstract: The construction of the Fungal Stress Database (FSD) was initiated and fueled by two major goals. At first, some outstandingly important groups of filamentous fungi including the aspergilli possess remarkable capabilities to adapt to a wide spectrum of environmental stress conditions but the underlying mechanisms of this stress tolerance have remained yet to be elucidated. Furthermore, the lack of any satisfactory interlaboratory standardization of stress assays, e.g. the widely used stress agar plate experiments, often hinders the direct comparison and discussion of stress physiological data gained for various fungal species by different research groups. In order to overcome these difficulties and to promote multilevel, e.g. combined comparative physiology-based and comparative genomics-based, stress research in filamentous fungi, we constructed FSD, which currently stores 1412 photos taken on Aspergillus colonies grown under precisely defined stress conditions. This study involved altogether 18 Aspergillus strains representing 17 species with two different strains for Aspergillus niger and covered six different stress conditions. Stress treatments were selected considering the frequency of various stress tolerance studies published in the last decade in the aspergilli and included oxidative (H2O2, menadione sodium bisulphite), high-osmolarity (NaCl, sorbitol), cell wall integrity (Congo Red) and heavy metal (CdCl2) stress exposures. In the future, we would like to expand this database to accommodate further fungal species and stress treatments. URL: http://www.fung-stress.org/
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http://dx.doi.org/10.1093/database/bay009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5810435PMC
January 2018

Autolytic hydrolases affect sexual and asexual development of Aspergillus nidulans.

Folia Microbiol (Praha) 2018 Sep 30;63(5):619-626. Epub 2018 Mar 30.

Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, Debrecen, 4032, Hungary.

Radial growth, asexual sporulation, and cleistothecia formation as well as extracellular chitinase and proteinase formation of Aspergillus nidulans were monitored in surface cultures in order to study the physiological role of extracellular hydrolase production in carbon-stressed cultures. We set up carbon-stressed and carbon-overfed experimental conditions by varying the starting glucose concentration within the range of 2.5 and 40 g/L. Glucose starvation induced radial growth and hydrolase production and enhanced the maturation of cleistothecia; meanwhile, glucose-rich conditions enhanced mycelial biomass, conidia, and cleistothecia production. Double deletion of chiB and engA (encoding an extracellular endochitinase and a β-1,3-endoglucanase, respectively) decreased conidia production under carbon-stressed conditions, suggesting that these autolytic hydrolases can support conidia formation by releasing nutrients from the cell wall polysaccharides of dead hyphae. Double deletion of prtA and pepJ (both genes encode extracellular proteases) reduced the number of cleistothecia even under carbon-rich conditions except in the presence of casamino acids, which supports the view that sexual development and amino acid metabolism are tightly connected to each other in this fungus.
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http://dx.doi.org/10.1007/s12223-018-0601-8DOI Listing
September 2018

Autolytic enzymes are responsible for increased melanization of carbon stressed Aspergillus nidulans cultures.

J Basic Microbiol 2018 May 20;58(5):440-447. Epub 2017 Dec 20.

Faculty of Science and Technology, Department of Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary.

Melanization of carbon stressed Aspergillus nidulans cultures were studied. Melanin production showed strong positive correlation with the activity of the secreted chitinase and ß-1,3-glucanase. Deletion of either chiB encoding an autolytic endochitinase or engA encoding an autolytic ß-1,3-endoglucanase, or both, almost completely prevented melanization of carbon stressed cultures. In contrast, addition of Trichoderma lyticase to cultures induced melanin production. Synthetic melanin could efficiently inhibit the purified ChiB chitinase activity. It could also efficiently decrease the intensity of hyphal fragmentation and pellet disorganization in Trichoderma lyticase treated cultures. Glyphosate, an inhibitor of L-3,4-dihydroxyphenylalanine-type melanin synthesis, could prevent melanization of carbon-starved cultures and enhanced pellet disorganization, while pyroquilon, a 1,8-dihydroxynaphthalene-type melanin synthesis inhibitor, enhanced melanization, and prevented pellet disorganization. We concluded that cell wall stress induced by autolytic cell wall hydrolases was responsible for melanization of carbon-starved cultures. The produced melanin can shield the living cells but may not inhibit the degradation and reutilization of cell wall materials of dead hyphae. Controlling the activity of autolytic hydrolase production can be an efficient approach to prevent unwanted melanization in the fermentation industry, while applying melanin synthesis inhibitors can decrease the resistance of pathogenic fungi against the chitinases produced by the host organism.
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http://dx.doi.org/10.1002/jobm.201700545DOI Listing
May 2018

Transcriptome-Based Modeling Reveals that Oxidative Stress Induces Modulation of the AtfA-Dependent Signaling Networks in .

Int J Genomics 2017 9;2017:6923849. Epub 2017 Jul 9.

Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, P.O. Box 63 H-4010, Hungary.

To better understand the molecular functions of the master stress-response regulator AtfA in , transcriptomic analyses of the null mutant and the appropriate control strains exposed to menadione sodium bisulfite- (MSB-), -butylhydroperoxide- and diamide-induced oxidative stresses were performed. Several elements of oxidative stress response were differentially expressed. Many of them, including the downregulation of the mitotic cell cycle, as the MSB stress-specific upregulation of FeS cluster assembly and the MSB stress-specific downregulation of nitrate reduction, tricarboxylic acid cycle, and ER to Golgi vesicle-mediated transport, showed AtfA dependence. To elucidate the potential global regulatory role of AtfA governing expression of a high number of genes with very versatile biological functions, we devised a model based on the comprehensive transcriptomic data. Our model suggests that an important function of AtfA is to modulate the transduction of stress signals. Although it may regulate directly only a limited number of genes, these include elements of the signaling network, for example, members of the two-component signal transduction systems. AtfA acts in a stress-specific manner, which may increase further the number and diversity of AtfA-dependent genes. Our model sheds light on the versatility of the physiological functions of AtfA and its orthologs in fungi.
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http://dx.doi.org/10.1155/2017/6923849DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5523550PMC
July 2017

Study on the glutathione metabolism of the filamentous fungus Aspergillus nidulans.

Acta Microbiol Immunol Hung 2017 Sep 6;64(3):255-272. Epub 2017 Mar 6.

1 Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen , Debrecen, Hungary.

Yeast protein sequence-based homology search for glutathione (GSH) metabolic enzymes and GSH transporters demonstrated that Aspergillus nidulans has a robust GSH uptake and metabolic system with several paralogous genes. In wet laboratory experiments, two key genes of GSH metabolism, gcsA, and glrA, encoding γ-l-glutamyl-l-cysteine synthetase and glutathione reductase, respectively, were deleted. The gene gcsA was essential, and the ΔgcsA mutant required GSH supplementation at considerably higher concentration than the Saccharomyces cerevisiae gsh1 mutant (8-10 mmol l vs. 0.5 μmol l). In addition to some functions known previously, both genes were important in the germination of conidiospores, and both gene deletion strains required the addition of extra GSH to reach wild-type germination rates in liquid cultures. Nevertheless, the supplementation of cultures with 10 mmol l GSH was toxic for the control and ΔglrA strains especially during vegetative growth, which should be considered in future development of high GSH-producer fungal strains. Importantly, the ΔglrA strain was characterized by increased sensitivity toward a wide spectrum of osmotic, cell wall integrity and antimycotic stress conditions in addition to previously reported temperature and oxidative stress sensitivities. These novel phenotypes underline the distinguished functions of GSH and GSH metabolic enzymes in the stress responses of fungi.
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http://dx.doi.org/10.1556/030.64.2017.003DOI Listing
September 2017

Comparative genomics reveals high biological diversity and specific adaptations in the industrially and medically important fungal genus Aspergillus.

Authors:
Ronald P de Vries Robert Riley Ad Wiebenga Guillermo Aguilar-Osorio Sotiris Amillis Cristiane Akemi Uchima Gregor Anderluh Mojtaba Asadollahi Marion Askin Kerrie Barry Evy Battaglia Özgür Bayram Tiziano Benocci Susanna A Braus-Stromeyer Camila Caldana David Cánovas Gustavo C Cerqueira Fusheng Chen Wanping Chen Cindy Choi Alicia Clum Renato Augusto Corrêa Dos Santos André Ricardo de Lima Damásio George Diallinas Tamás Emri Erzsébet Fekete Michel Flipphi Susanne Freyberg Antonia Gallo Christos Gournas Rob Habgood Matthieu Hainaut María Laura Harispe Bernard Henrissat Kristiina S Hildén Ryan Hope Abeer Hossain Eugenia Karabika Levente Karaffa Zsolt Karányi Nada Kraševec Alan Kuo Harald Kusch Kurt LaButti Ellen L Lagendijk Alla Lapidus Anthony Levasseur Erika Lindquist Anna Lipzen Antonio F Logrieco Andrew MacCabe Miia R Mäkelä Iran Malavazi Petter Melin Vera Meyer Natalia Mielnichuk Márton Miskei Ákos P Molnár Giuseppina Mulé Chew Yee Ngan Margarita Orejas Erzsébet Orosz Jean Paul Ouedraogo Karin M Overkamp Hee-Soo Park Giancarlo Perrone Francois Piumi Peter J Punt Arthur F J Ram Ana Ramón Stefan Rauscher Eric Record Diego Mauricio Riaño-Pachón Vincent Robert Julian Röhrig Roberto Ruller Asaf Salamov Nadhira S Salih Rob A Samson Erzsébet Sándor Manuel Sanguinetti Tabea Schütze Kristina Sepčić Ekaterina Shelest Gavin Sherlock Vicky Sophianopoulou Fabio M Squina Hui Sun Antonia Susca Richard B Todd Adrian Tsang Shiela E Unkles Nathalie van de Wiele Diana van Rossen-Uffink Juliana Velasco de Castro Oliveira Tammi C Vesth Jaap Visser Jae-Hyuk Yu Miaomiao Zhou Mikael R Andersen David B Archer Scott E Baker Isabelle Benoit Axel A Brakhage Gerhard H Braus Reinhard Fischer Jens C Frisvad Gustavo H Goldman Jos Houbraken Berl Oakley István Pócsi Claudio Scazzocchio Bernhard Seiboth Patricia A vanKuyk Jennifer Wortman Paul S Dyer Igor V Grigoriev

Genome Biol 2017 02 14;18(1):28. Epub 2017 Feb 14.

US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA, 94598, USA.

Background: The fungal genus Aspergillus is of critical importance to humankind. Species include those with industrial applications, important pathogens of humans, animals and crops, a source of potent carcinogenic contaminants of food, and an important genetic model. The genome sequences of eight aspergilli have already been explored to investigate aspects of fungal biology, raising questions about evolution and specialization within this genus.

Results: We have generated genome sequences for ten novel, highly diverse Aspergillus species and compared these in detail to sister and more distant genera. Comparative studies of key aspects of fungal biology, including primary and secondary metabolism, stress response, biomass degradation, and signal transduction, revealed both conservation and diversity among the species. Observed genomic differences were validated with experimental studies. This revealed several highlights, such as the potential for sex in asexual species, organic acid production genes being a key feature of black aspergilli, alternative approaches for degrading plant biomass, and indications for the genetic basis of stress response. A genome-wide phylogenetic analysis demonstrated in detail the relationship of the newly genome sequenced species with other aspergilli.

Conclusions: Many aspects of biological differences between fungal species cannot be explained by current knowledge obtained from genome sequences. The comparative genomics and experimental study, presented here, allows for the first time a genus-wide view of the biological diversity of the aspergilli and in many, but not all, cases linked genome differences to phenotype. Insights gained could be exploited for biotechnological and medical applications of fungi.
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http://dx.doi.org/10.1186/s13059-017-1151-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5307856PMC
February 2017

Optimization of desferrioxamine E production by Streptomyces parvulus.

Acta Microbiol Immunol Hung 2016 Dec;63(4):475-489

3 Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen , Debrecen, Hungary.

Siderophores are produced by a number of microbes to capture iron with outstandingly high affinity, which property also generates biomedical and industrial interests. Desferrioxamine E (DFO-E) secreted by streptomycetes bacteria can be an ideal candidate for iron chelation therapy, which necessitates its cost-effective production for in vitro and animal studies. This study focused on the optimization of DFO-E production by Streptomyces parvulus CBS548.68. Different combinations of various carbon and nitrogen sources as well as the addition of 3-morpholinopropane-1-sulfonic acid (MOPS) markedly affected DFO-E yields, which were attributed, at least in part, to the higher biomass productions found in MOPS-supplemented cultures. In MOPS-supplemented glucose and sodium glutamate medium, DFO-E productions as high as 2,009 ± 90 mg/l of culture medium were reached. High-performance liquid chromatography analysis demonstrated that a simple two-step purification process yielded DFO-E preparations with purities of ∼97%. Matrix assisted laser desorption ionization-time of flight mass spectrometry analysis showed that purified DFO-E always contained traces of desferrioxamine D2.
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http://dx.doi.org/10.1556/030.63.2016.029DOI Listing
December 2016

Effects of hemin, CO, and pH on the branching of Candida albicans filamentous forms.

Acta Microbiol Immunol Hung 2016 Dec 12;63(4):387-403. Epub 2016 Dec 12.

1 Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen , Debrecen, Hungary.

Morphological transitions of wild-type and oxidative stress-tolerant Candida albicans strains were followed in the RPMI-FBS culture medium at pH values and CO levels characteristic for the anatomical niches inhabited by this opportunistic human pathogen fungus, including the oral cavity as well as the intestinal and vaginal lumens. Selected cultures were also supplemented with hemin modeling bleedings. Germination as well as elongation and branching of hyphae were monitored in the cultures using time-lapse video microscopy. Unexpectedly, branching time, which is defined as the time taken until the first branch of hypha emerges for the first time after germination, correlated well with alterations in the environmental conditions meanwhile no such correlations were found for germination time (time lasted until the appearance of the germination tube). Based on these observations, hypotheses were set up to estimate the significance of branching time in the pathogenesis of both superficial and systemic candidiases.
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http://dx.doi.org/10.1556/030.63.2016.023DOI Listing
December 2016

Detection of Transcriptionally Active Mycotoxin Gene Clusters: DNA Microarray.

Methods Mol Biol 2017 ;1542:345-365

Faculty of Science and Technology, Department of Biotechnology and Microbiology,, University of Debrecen, Egyetem tér 1., H-4032, Debrecen, Hungary.

Various bioanalytical tools including DNA microarrays are frequently used to map global transcriptional changes in mycotoxin producer filamentous fungi. This effective hybridization-based transcriptomics technology helps researchers to identify genes of secondary metabolite gene clusters and record concomitant gene expression changes in these clusters initiated by versatile environmental conditions and/or gene deletions. Such transcriptional data are of great value when future mycotoxin control technologies are considered and elaborated. Giving the readers insights into RNA extraction and DNA microarray hybridization steps routinely used in our laboratories and also into the normalization and evaluation of primary gene expression data, we would like to contribute to the interlaboratory standardization of DNA microarray based transcriptomics studies being carried out in many laboratories worldwide in this important field of fungal biology.
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http://dx.doi.org/10.1007/978-1-4939-6707-0_23DOI Listing
January 2018

Glutathione protects Candida albicans against horseradish volatile oil.

J Basic Microbiol 2016 Oct 7;56(10):1071-1079. Epub 2016 Jun 7.

Department of Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary.

Horseradish essential oil (HREO; a natural mixture of different isothiocyanates) had strong fungicide effect against Candida albicans both in volatile and liquid phase. In liquid phase this antifungal effect was more significant than those of its main components allyl, and 2-phenylethyl isothiocyanate. HREO, at sublethal concentration, induced oxidative stress which was characterized with elevated superoxide content and up-regulated specific glutathione reductase, glutathione peroxidase, catalase and superoxide dismutase activities. Induction of specific glutathione S-transferase activities as marker of glutathione (GSH) dependent detoxification was also observed. At higher concentration, HREO depleted the GSH pool, increased heavily the superoxide production and killed the cells rapidly. HREO and the GSH pool depleting agent, 1-chlore-2,4-dinitrobenzene showed strong synergism when they were applied together to kill C. albicans cells. Based on all these, we assume that GSH metabolism protects fungi against isothiocyanates.
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http://dx.doi.org/10.1002/jobm.201600082DOI Listing
October 2016

Characterization of the aodA, dnmA, mnSOD and pimA genes in Aspergillus nidulans.

Sci Rep 2016 Feb 5;6:20523. Epub 2016 Feb 5.

Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

Mitochondria play key roles in cellular energy generation and lifespan of most eukaryotes. To understand the functions of four nuclear-encoded genes predicted to be related to the maintenance of mitochondrial morphology and function in Aspergillus nidulans, systematic characterization was carried out. The deletion and overexpression mutants of aodA, dnmA, mnSOD and pimA encoding alternative oxidase, dynamin related protein, manganese superoxide dismutase and Lon protease, respectively, were generated and examined for their growth, stress tolerances, respiration, autolysis, cell death, sterigmatocystin production, hyphal morphology and size, and mitochondrial superoxide production as well as development. Overall, genetic manipulation of these genes had less effect on cellular physiology and ageing in A. nidulans than that of their homologs in another fungus Podospora anserina with a well-characterized senescence. The observed interspecial phenotypic differences can be explained by the dissimilar intrinsic stabilities of the mitochondrial genomes in A. nidulans and P. anserina. Furthermore, the marginally altered phenotypes observed in A. nidulans mutants indicate the presence of effective compensatory mechanisms for the complex networks of mitochondrial defense and quality control. Importantly, these findings can be useful for developing novel platforms for heterologous protein production, or on new biocontrol and bioremediation technologies based on Aspergillus species.
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http://dx.doi.org/10.1038/srep20523DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4742808PMC
February 2016

Core oxidative stress response in Aspergillus nidulans.

BMC Genomics 2015 Jun 27;16:478. Epub 2015 Jun 27.

Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, P.O. Box 63, H-4032, Debrecen, Hungary.

Background: The b-Zip transcription factor AtfA plays a key role in regulating stress responses in the filamentous fungus Aspergillus nidulans. To identify the core regulons of AtfA, we examined genome-wide expression changes caused by various stresses in the presence/absence of AtfA using A. nidulans microarrays. We also intended to address the intriguing question regarding the existence of core environmental stress response in this important model eukaryote.

Results: Examination of the genome wide expression changes caused by five different oxidative stress conditions in wild type and the atfA null mutant has identified a significant number of stereotypically regulated genes (Core Oxidative Stress Response genes). The deletion of atfA increased the oxidative stress sensitivity of A. nidulans and affected mRNA accumulation of several genes under both unstressed and stressed conditions. The numbers of genes under the AtfA control appear to be specific to a stress-type. We also found that both oxidative and salt stresses induced expression of some secondary metabolite gene clusters and the deletion of atfA enhanced the stress responsiveness of additional clusters. Moreover, certain clusters were down-regulated by the stresses tested.

Conclusion: Our data suggest that the observed co-regulations were most likely consequences of the overlapping physiological effects of the stressors and not of the existence of a general environmental stress response. The function of AtfA in governing various stress responses is much smaller than anticipated and/or other regulators may play a redundant or overlapping role with AtfA. Both stress inducible and stress repressive regulations of secondary metabolism seem to be frequent features in A. nidulans.
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http://dx.doi.org/10.1186/s12864-015-1705-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4482186PMC
June 2015

Degradation of glutathione in Aspergillus nidulans - Short communication.

Acta Biol Hung 2015 Jun;66(2):242-5

Department of Biotechnology and Microbiology, University of Debrecen , Debrecen , Hungary.

Relative transcriptions of Aspergillus nidulans dug1-3 (orthologes of Saccharomyces cerevisiae DUG - deficient in utilization of glutathione - pathway genes) and ggtA encoding γ-glutamyl transpeptidase were studied under conditions inducing glutathione degradation. GgtA was induced in all cases when glutathione levels decreased, but addition of yeast extract, which moderated glutathione degradation, enhanced its induction. Although dug2 showed constitutive transcription, dug1 and dug3 were induced by carbon and nitrogen starvation and yeast extract did not caused significant changes in their relative transcription. The in silico reconstructed DUG pathway of A. nidulans is a promising candidate for cytosolic GSH degradation induced by carbon/nitrogen stress.
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http://dx.doi.org/10.1556/018.66.2015.2.10DOI Listing
June 2015

Betamethasone augments the antifungal effect of menadione--towards a novel anti-Candida albicans combination therapy.

J Basic Microbiol 2015 Aug 24;55(8):973-81. Epub 2015 Feb 24.

Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary.

The fluorinated glucocorticoid betamethasone stimulated both the extracellular phospholipase production and hypha formation of the opportunistic human pathogen Candida albicans and also decreased the efficiency of the polyene antimycotics amphotericin B and nystatin against C. albicans in a dose-dependent manner. Importantly, betamethasone increased synergistically the anti-Candida activity of the oxidative stress generating agent menadione, which may be exploited in future combination therapies to prevent or cure C. albicans infections, in the field of dermatology.
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http://dx.doi.org/10.1002/jobm.201400903DOI Listing
August 2015

γ-Glutamyl transpeptidase (GgtA) of Aspergillus nidulans is not necessary for bulk degradation of glutathione.

Arch Microbiol 2015 Mar 18;197(2):285-97. Epub 2014 Dec 18.

Department of Biotechnology and Microbiology, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, Debrecen, H4032, Hungary.

Aspergillus nidulans exhibited high γ-glutamyl transpeptidase (γGT) activity in both carbon-starved and carbon-limited cultures. Glucose repressed, but casein peptone increased γGT production. Null mutation of creA did not influence γGT formation, but the functional meaB was necessary for the γGT induction. Deletion of the AN10444 gene (ggtA) completely eliminated the γGT activity, and the mRNA levels of ggtA showed strong correlation with the observed γGT activities. While ggtA does not contain a canonical signal sequence, the γGT activity was detectable both in the fermentation broth and in the hyphae. Deletion of the ggtA gene did not prevent the depletion of glutathione observed in carbon-starved and carbon-limited cultures. Addition of casein peptone to carbon-starved cultures lowered the formation of reactive species (RS). Deletion of ggtA could hinder this decrease and resulted in elevated RS formation. This effect of γGT on redox homeostasis may explain the reduced cleistothecia formation of ΔggtA strains in surface cultures.
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http://dx.doi.org/10.1007/s00203-014-1057-0DOI Listing
March 2015

Penicillium antifungal protein (PAF) is involved in the apoptotic and autophagic processes of the producer Penicillium chrysogenum.

Acta Microbiol Immunol Hung 2014 Sep;61(3):379-88

University of Debrecen Department of Microbial Biotechnology and Cell Biology, Faculty of Science and Technology Debrecen Hungary.

PAF, which is produced by the filamentous fungus Pencicillium chrysogenum, is a small antifungal protein, triggering ROS-mediated apoptotic cell death in Aspergillus nidulans. In this work, we provide information on the function of PAF in the host P. chrysogenum considering that carbon-starving cultures of the Δpaf mutant strain showed significantly reduced apoptosis rates in comparison to the wild-type (wt) strain. Moreover, the addition of PAF to the Δpaf strain resulted in a twofold increase in the apoptosis rate. PAF was also involved in the regulation of the autophagy machinery of this fungus, since several Saccharomyces cerevisiae autophagy-related ortholog genes, e.g. those of atg7, atg22 and tipA, were repressed in the deletion strain. This phenomenon was accompanied by the absence of autophagosomes in the Δpaf strain, even in old hyphae.
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http://dx.doi.org/10.1556/AMicr.61.2014.3.10DOI Listing
September 2014