Tünde Pusztahelyi | University of Debrecen (original) (raw)

Papers by Tünde Pusztahelyi

Mycological Research, 2005

Journal of basic microbiology, Jan 16, 2015

The application of yeasts has great potential in reducing the economic damage caused by toxigenic... more The application of yeasts has great potential in reducing the economic damage caused by toxigenic fungi in the agriculture. Some yeasts may act as biocontrol agents inhibiting the growth of filamentous fungi. These species may also gain importance in the preservation of agricultural products and in the reduction of their mycotoxin contamination, yet the extent of mycotoxin production in the presence of biocontrol agents is relatively less understood. The application of yeasts in various technological processes may have a direct inhibitory effect on the toxin production of certain molds, which is independent of their growth suppressing effect. Furthermore, several yeast species are capable of accumulating mycotoxins from agricultural products, thereby effectively decontaminating them. Probiotic yeasts or products containing yeast cell wall are also applied to counteract mycotoxicosis in livestock. Several yeast strains are also able to degrade toxins to less-toxic or even non-toxic s...

Acta microbiologica et immunologica Hungarica, 2014

Hydrolytic enzyme production is typical of the autolysis in filamentous fungi; however, less atte... more Hydrolytic enzyme production is typical of the autolysis in filamentous fungi; however, less attention has been given to the physiological role of the enzymes. Here, the aim was to investigate the possible relation of the chitinolytic enzymes to the changes in the biomass in some filamentous fungi of high importance for pharmaceutical or food industry. In Penicillium and Aspergillus filamentous fungi, which showed different characteristics in submerged cultures, the growth and biomass decline rates were calculated and correlated to the chitinase and N-acetyl-β-D-glucosaminidase enzyme productions. Correlation was found between the biomass decrease rate and the chitinase level at the stationary growth phase; while chitinase production covariates negatively with N-acetyl-β-D-glucosaminidase activities. The chitinase production and the intensive autolysis hindered the production of N-acetyl-β-D-glucosaminidase and, therefore, could hinder the cell death in the cultures.

Fungal Genetics and Biology, 2013

The cell wall integrity (CWI) signaling pathway is responsible for cell wall remodeling and reinf... more The cell wall integrity (CWI) signaling pathway is responsible for cell wall remodeling and reinforcement upon cell wall stress, which is proposed to be universal in fungal cultures. In Aspergillus nidulans, both the deletion of rlmA encoding the RlmA transcription factor in CWI signaling and low concentrations of the cell wall polymer intercalating agent Congo Red caused significant physiological changes. The gene deletion mutant ΔrlmA strain showed decreased CWI and oxidative stress resistances, which indicated the connection between the CWI pathway and the oxidative stress response system. The Congo Red stress resulted in alterations in the cell wall polymer composition in submerged cultures due to the induction of the biosynthesis of the alkali soluble fraction as well as the hydrolysis of cell wall biopolymers. Both RlmA and RlmA-independent factors induced by Congo Red stress regulated the expression of glucanase (ANID_00245, engA) and chitinase (chiB, chiA) genes, which promoted the autolysis of the cultures and also modulated the pellet sizes. CWI stress and rlmA deletion affected the expression of brlA encoding the early conidiophore development regulator transcription factor BrlA and, as a consequence, the formation of conidiophores was significantly changed in submerged cultures. Interestingly, the number of conidiospores increased in surface cultures of the ΔrlmA strain. The in silico analysis of genes putatively regulated by RlmA and the CWI transcription factors AnSwi4/AnSwi6 in the SBF complex revealed only a few jointly regulated genes, including ugmA and srrA coding for UgmA UDP-galactopyranose mutase and SrrA stress response regulator, respectively.

Fungiandplantsarerichsourcesofthousandsofsecondarymetabolites.Thegeneticallycodedpossibilitiesfor... more Fungiandplantsarerichsourcesofthousandsofsecondarymetabolites.Thegeneticallycodedpossibilitiesforsecondarymetaboliteproduction,thestimulioftheproduction,andthespecialphytotoxinsbasicallydeterminethemicroscopicfungi-hostplantinteractionsandthepathogeniclifestyleoffungi.Thereviewintroducesplantsecondarymetabolitesusuallywithantifungaleffectaswellastheimportanceofsignalingmoleculesininducedsystemicresistanceandsystemicacquiredresistanceprocesses.Thereviewalsoconcernsthemimickingofplanteffectormoleculeslikeauxins,gibberellinsandabscisicacidbyfungalsecondarymetabolitesthatmodulateplantgrowthorevencansubverttheplantdefenseresponsessuchasprogrammedcelldeathtogainnutrientsforfungalgrowthandcolonization.Italsolooksthroughthespecialsecondarymetaboliteproductionandhostselectivetoxinsofsomesignificantfungalpathogensandtheplantresponseinformofphytoalexinproduction.Newresultscomingfromgenomeandtranscriptionalanalysesincontextofselectedfungalpathogensandtheirhostsarealsodiscussed.

Archives of Microbiology, 2006

SLH domains (for surface layer homology) are involved in the attachment of proteins to bacterial ... more SLH domains (for surface layer homology) are involved in the attachment of proteins to bacterial cell walls. The data presented here assign the conserved TRAE motif within SLH domains a key role for the binding. The charged amino acids arginine (R) or/and glutamic acid (E) were replaced via site-directed mutagenesis by different amino acids. Effects were visualized in an in vitro binding assay using native cell wall sacculi of Thermoanaerobacterium thermosulfurigenes EM1 and different variants of an SLH protein which consisted of the triplicate SLH domain of xylanase XynA of this bacterium and which was purified after expression in Escherichia coli. The results indicated (1) that the TRAE motif is critical for the binding function of SLH domains, (2) that a functional TRAE motif is necessary in all three domains, (3) that a least one (preferentially positively) charged amino acid in the TRAE motif is required for the functionality of the SLH domain, and (4) that the position of the negatively and positively charged amino acids is important. The finding that the cell wall of T. thermosulfurigenes EM1 contains pyruvate (4 μg mg−1) is in agreement with the hypothesis that pyruvylated secondary cell wall polymers function as ligand for SLH domains.

Acta Biologica Hungarica, 2003

The complete identification of coding sequences in a number of species has led to announce the be... more The complete identification of coding sequences in a number of species has led to announce the beginning of the post-genomic era, new tools have become available to study complex phenomena in biological systems. Rapid advances in genomic sequencing and bioinformatics have established the field of genomics to investigate thousands genes' activity through mRNA display. However, recent studies have demonstrated a lack of correlation between the transcriptional profiles and the actual protein levels in cells, so investigation of the expressed part of the genome is also required to link genomic data to biological function. It is possible that evolutional development occured by increasing complexity of regulation processes at the level of RNA and protein molecules instead of simple increase in gene number, so investigation of proteins and protein complexes became important fields of our post-genomic era. High-resolution two-dimensional gels combined with sensitive mass spectrometry can reveal virtually all proteins present in cells opening new insights into functions of cells, tissues and whole organisms.

Applied Biochemistry and Biotechnology, 2004

Thirty Trichoderma strains representing 15 species within the genus were screened for extracellul... more Thirty Trichoderma strains representing 15 species within the genus were screened for extracellular production of chitinolytic enzymes in solid substrate fermentation. Trichoderma longibrachiatum IMI 92027 (ATCC 36838) gave the highest yield (5.0 IU/g of dry matter of substrate) after 3 d of fermentation on wheat bran-crude chitin (9:1 mixture) medium. The optimal moisture content (66.7%), chitin content (20%), initial pH of the medium (2.0–5.0), and time course (5 d) of solid substrate fermentation were determined for strain IMI 92027. Cellulase, xylanase, α-amylase, and β-xylosidase activities were also detected. The pH and temperature optima of the chitinase complex of T. longibrachiatum IMI 92027 were 4.5 and 55°C, respectively. The enzyme totally lost its activity at 70°C in 5 min in the absence of the substrate but retained about 15% of its initial activity even at 70°C after a 60-min incubation in the presence of solid substrate fermentation solids. Purification of protein extract from the solid substrate fermentation material revealed high chitinolytic activities between pI 5.9 and 4.8, where N-acetyl-β-d-hexosaminidase and chitinase peaks have been found in the same pI range. Two chitinases of 43.5 and 30 kDa were purified at acidic pI.

Journal of General and Applied Microbiology, 2001

Journal of Basic Microbiology, 1999

... Original Paper. Physiological and enzymological characterization of the β-N-acetylhexosaminid... more ... Original Paper. Physiological and enzymological characterization of the β-N-acetylhexosaminidase of Penicillium chrysogenum. István Pócsi Dr.,; Imre Pócsi,; Tünde Pusztahelyi. Article first published online: 24 JUN 1999. ... Get PDF (177K). More content like this. ...

Fems Microbiology Letters, 1998

Acta Microbiologica Et Immunologica Hungarica, 2008

Enzyme and Microbial Technology, 2005

Applied Biochemistry and Biotechnology, 2004

The morphologic and physiologic effects of vitamin E, a powerful antioxidant, on the autolysis an... more The morphologic and physiologic effects of vitamin E, a powerful antioxidant, on the autolysis and sporulation of Aspergillus nidulans FGSC26 were studied. In carbon-depleted submerged cultures, reactive oxygen species (ROS) accumulated in the cells and, concomitantly, progressing autolysis was observed, which was characterized by decreasing dry cell masses and pellet diameters as well as by increasing extracellular chitinase activities. Vitamin E supplemented at a concentration of 1 g/L hindered effectively the intracellular accumulation of ROS, the autolytic loss of biomass, the disintegration of pellets, and the release of chitinase activities. In surface cultures, vitamin E inhibited autolysis of both A. nidulans FGSC26 and a loss-of-function FlbA autolytic phenotype mutant. In addition, supplementation of the culture medium with this antioxidant also had a negative effect on the sporulation of strain FGSC26 and the FadA G203R hypersporulating phenotype mutant. These results suggest that accumulation of ROS was involved in the initiation of both sporulation and autolysis in this filamentous fungus, but that FadA/FlbA signaling was not involved in this vitamin E-dependent regulation. Vitamin E can be recommended as a supplement in fermentations in which the disintegration of pellets and gross autolysis should be avoided.

Acta Biologica Hungarica, 2007

The bulk formation of yeast-like (arthrospore-like) cells were typical in carbon-depleted submerg... more The bulk formation of yeast-like (arthrospore-like) cells were typical in carbon-depleted submerged cultures of the high beta-lactam producer Penicillium chrysogenum NCAIM 00237 strain independently of the nitrogen-content of the culture medium. This morphogenetic switch was still quite common in carbon-starving cultures of the low-penicillin-producer strain P. chrysogenum ATCC 28089 (Wis 54-1255) when the nitrogen-content of the medium was low but was a very rare event in wild-type P. chrysogenum cultures. The mycelium-->yeast-like cell transition correlated well with a relatively high glutathione concentration and a reductive glutathione/glutathione disulfite (GSH/GSSG) redox balance in autolysing cultures, which was a consequence of industrial strain development. Paradoxically, the development of high beta-lactam productivity resulted in a high intracellular GSH level and, concomitantly, in an increased y-glutamyltranspeptidase (i.e. GSH-decomposing) activity in the autolytic phase of growth of P. chrysogenum NCAIM 00237. The hypothesized causal connection between GSH metabolism and cell morphology, if verified, may help us in future metabolic engineering of industrially important filamentous fungi.

Antimicrobial Agents and Chemotherapy, 2005

Fungal Genetics and Biology, 2011

BMC Genomics, 2005

Background In addition to their cytotoxic nature, reactive oxygen species (ROS) are also signal m... more Background In addition to their cytotoxic nature, reactive oxygen species (ROS) are also signal molecules in diverse cellular processes in eukaryotic organisms. Linking genome-wide transcriptional changes to cellular physiology in oxidative stress-exposed Aspergillus nidulans cultures provides the opportunity to estimate the sizes of peroxide (O22-), superoxide (O2•-) and glutathione/glutathione disulphide (GSH/GSSG) redox imbalance responses. Results Genome-wide transcriptional changes triggered by diamide, H2O2 and menadione in A. nidulans vegetative tissues were recorded using DNA microarrays containing 3533 unique PCR-amplified probes. Evaluation of LOESS-normalized data indicated that 2499 gene probes were affected by at least one stress-inducing agent. The stress induced by diamide and H2O2 were pulse-like, with recovery after 1 h exposure time while no recovery was observed with menadione. The distribution of stress-responsive gene probes among major physiological functional categories was approximately the same for each agent. The gene group sizes solely responsive to changes in intracellular O22-, O2•- concentrations or to GSH/GSSG redox imbalance were estimated at 7.7, 32.6 and 13.0 %, respectively. Gene groups responsive to diamide, H2O2 and menadione treatments and gene groups influenced by GSH/GSSG, O22- and O2•- were only partly overlapping with distinct enrichment profiles within functional categories. Changes in the GSH/GSSG redox state influenced expression of genes coding for PBS2 like MAPK kinase homologue, PSK2 kinase homologue, AtfA transcription factor, and many elements of ubiquitin tagging, cell division cycle regulators, translation machinery proteins, defense and stress proteins, transport proteins as well as many enzymes of the primary and secondary metabolisms. Meanwhile, a seParate set of genes encoding transport proteins, CpcA and JlbA amino acid starvation-responsive transcription factors, and some elements of sexual development and sporulation was ROS responsive. Conclusion The existence of seParate O22-, O2•- and GSH/GSSG responsive gene groups in a eukaryotic genome has been demonstrated. Oxidant-triggered, genome-wide transcriptional changes should be analyzed considering changes in oxidative stress-responsive physiological conditions and not correlating them directly to the chemistry and concentrations of the oxidative stress-inducing agent.

Acta Biologica Hungarica, 2006

NADPH is involved in many basically important anabolic processes. For a long time, pentose phosph... more NADPH is involved in many basically important anabolic processes. For a long time, pentose phosphate pathway (PPS) was regarded as the most important source of NADPH in fungi. Here we present evidence of a metabolic switch to an alternative NADPH-producing pathway in ageing Penicillium chrysogenum cultures, which involves NADP+ -specific isocitrate dehydrogenase (NADP+ -ID) rather than PPS enzymes. Considering the main biochemical functions of NADPH, we propose that NADP+ -ID could have deep impact on many physiological processes switched on glucose deprivation including proteinase production or penicillin biosynthesis. We also demonstrate that although the alternative pathway was inferior to PPS when the fungus was grown on well-utilisable carbon sources yet it could have an important role in fatty acid biosynthesis as well as in the maintenance of high intracellular NADPH/NADP+ ratios.

Mycological Research, 2005

Journal of basic microbiology, Jan 16, 2015

The application of yeasts has great potential in reducing the economic damage caused by toxigenic... more The application of yeasts has great potential in reducing the economic damage caused by toxigenic fungi in the agriculture. Some yeasts may act as biocontrol agents inhibiting the growth of filamentous fungi. These species may also gain importance in the preservation of agricultural products and in the reduction of their mycotoxin contamination, yet the extent of mycotoxin production in the presence of biocontrol agents is relatively less understood. The application of yeasts in various technological processes may have a direct inhibitory effect on the toxin production of certain molds, which is independent of their growth suppressing effect. Furthermore, several yeast species are capable of accumulating mycotoxins from agricultural products, thereby effectively decontaminating them. Probiotic yeasts or products containing yeast cell wall are also applied to counteract mycotoxicosis in livestock. Several yeast strains are also able to degrade toxins to less-toxic or even non-toxic s...

Acta microbiologica et immunologica Hungarica, 2014

Hydrolytic enzyme production is typical of the autolysis in filamentous fungi; however, less atte... more Hydrolytic enzyme production is typical of the autolysis in filamentous fungi; however, less attention has been given to the physiological role of the enzymes. Here, the aim was to investigate the possible relation of the chitinolytic enzymes to the changes in the biomass in some filamentous fungi of high importance for pharmaceutical or food industry. In Penicillium and Aspergillus filamentous fungi, which showed different characteristics in submerged cultures, the growth and biomass decline rates were calculated and correlated to the chitinase and N-acetyl-β-D-glucosaminidase enzyme productions. Correlation was found between the biomass decrease rate and the chitinase level at the stationary growth phase; while chitinase production covariates negatively with N-acetyl-β-D-glucosaminidase activities. The chitinase production and the intensive autolysis hindered the production of N-acetyl-β-D-glucosaminidase and, therefore, could hinder the cell death in the cultures.

Fungal Genetics and Biology, 2013

The cell wall integrity (CWI) signaling pathway is responsible for cell wall remodeling and reinf... more The cell wall integrity (CWI) signaling pathway is responsible for cell wall remodeling and reinforcement upon cell wall stress, which is proposed to be universal in fungal cultures. In Aspergillus nidulans, both the deletion of rlmA encoding the RlmA transcription factor in CWI signaling and low concentrations of the cell wall polymer intercalating agent Congo Red caused significant physiological changes. The gene deletion mutant ΔrlmA strain showed decreased CWI and oxidative stress resistances, which indicated the connection between the CWI pathway and the oxidative stress response system. The Congo Red stress resulted in alterations in the cell wall polymer composition in submerged cultures due to the induction of the biosynthesis of the alkali soluble fraction as well as the hydrolysis of cell wall biopolymers. Both RlmA and RlmA-independent factors induced by Congo Red stress regulated the expression of glucanase (ANID_00245, engA) and chitinase (chiB, chiA) genes, which promoted the autolysis of the cultures and also modulated the pellet sizes. CWI stress and rlmA deletion affected the expression of brlA encoding the early conidiophore development regulator transcription factor BrlA and, as a consequence, the formation of conidiophores was significantly changed in submerged cultures. Interestingly, the number of conidiospores increased in surface cultures of the ΔrlmA strain. The in silico analysis of genes putatively regulated by RlmA and the CWI transcription factors AnSwi4/AnSwi6 in the SBF complex revealed only a few jointly regulated genes, including ugmA and srrA coding for UgmA UDP-galactopyranose mutase and SrrA stress response regulator, respectively.

Fungiandplantsarerichsourcesofthousandsofsecondarymetabolites.Thegeneticallycodedpossibilitiesfor... more Fungiandplantsarerichsourcesofthousandsofsecondarymetabolites.Thegeneticallycodedpossibilitiesforsecondarymetaboliteproduction,thestimulioftheproduction,andthespecialphytotoxinsbasicallydeterminethemicroscopicfungi-hostplantinteractionsandthepathogeniclifestyleoffungi.Thereviewintroducesplantsecondarymetabolitesusuallywithantifungaleffectaswellastheimportanceofsignalingmoleculesininducedsystemicresistanceandsystemicacquiredresistanceprocesses.Thereviewalsoconcernsthemimickingofplanteffectormoleculeslikeauxins,gibberellinsandabscisicacidbyfungalsecondarymetabolitesthatmodulateplantgrowthorevencansubverttheplantdefenseresponsessuchasprogrammedcelldeathtogainnutrientsforfungalgrowthandcolonization.Italsolooksthroughthespecialsecondarymetaboliteproductionandhostselectivetoxinsofsomesignificantfungalpathogensandtheplantresponseinformofphytoalexinproduction.Newresultscomingfromgenomeandtranscriptionalanalysesincontextofselectedfungalpathogensandtheirhostsarealsodiscussed.

Archives of Microbiology, 2006

SLH domains (for surface layer homology) are involved in the attachment of proteins to bacterial ... more SLH domains (for surface layer homology) are involved in the attachment of proteins to bacterial cell walls. The data presented here assign the conserved TRAE motif within SLH domains a key role for the binding. The charged amino acids arginine (R) or/and glutamic acid (E) were replaced via site-directed mutagenesis by different amino acids. Effects were visualized in an in vitro binding assay using native cell wall sacculi of Thermoanaerobacterium thermosulfurigenes EM1 and different variants of an SLH protein which consisted of the triplicate SLH domain of xylanase XynA of this bacterium and which was purified after expression in Escherichia coli. The results indicated (1) that the TRAE motif is critical for the binding function of SLH domains, (2) that a functional TRAE motif is necessary in all three domains, (3) that a least one (preferentially positively) charged amino acid in the TRAE motif is required for the functionality of the SLH domain, and (4) that the position of the negatively and positively charged amino acids is important. The finding that the cell wall of T. thermosulfurigenes EM1 contains pyruvate (4 μg mg−1) is in agreement with the hypothesis that pyruvylated secondary cell wall polymers function as ligand for SLH domains.

Acta Biologica Hungarica, 2003

The complete identification of coding sequences in a number of species has led to announce the be... more The complete identification of coding sequences in a number of species has led to announce the beginning of the post-genomic era, new tools have become available to study complex phenomena in biological systems. Rapid advances in genomic sequencing and bioinformatics have established the field of genomics to investigate thousands genes' activity through mRNA display. However, recent studies have demonstrated a lack of correlation between the transcriptional profiles and the actual protein levels in cells, so investigation of the expressed part of the genome is also required to link genomic data to biological function. It is possible that evolutional development occured by increasing complexity of regulation processes at the level of RNA and protein molecules instead of simple increase in gene number, so investigation of proteins and protein complexes became important fields of our post-genomic era. High-resolution two-dimensional gels combined with sensitive mass spectrometry can reveal virtually all proteins present in cells opening new insights into functions of cells, tissues and whole organisms.

Applied Biochemistry and Biotechnology, 2004

Thirty Trichoderma strains representing 15 species within the genus were screened for extracellul... more Thirty Trichoderma strains representing 15 species within the genus were screened for extracellular production of chitinolytic enzymes in solid substrate fermentation. Trichoderma longibrachiatum IMI 92027 (ATCC 36838) gave the highest yield (5.0 IU/g of dry matter of substrate) after 3 d of fermentation on wheat bran-crude chitin (9:1 mixture) medium. The optimal moisture content (66.7%), chitin content (20%), initial pH of the medium (2.0–5.0), and time course (5 d) of solid substrate fermentation were determined for strain IMI 92027. Cellulase, xylanase, α-amylase, and β-xylosidase activities were also detected. The pH and temperature optima of the chitinase complex of T. longibrachiatum IMI 92027 were 4.5 and 55°C, respectively. The enzyme totally lost its activity at 70°C in 5 min in the absence of the substrate but retained about 15% of its initial activity even at 70°C after a 60-min incubation in the presence of solid substrate fermentation solids. Purification of protein extract from the solid substrate fermentation material revealed high chitinolytic activities between pI 5.9 and 4.8, where N-acetyl-β-d-hexosaminidase and chitinase peaks have been found in the same pI range. Two chitinases of 43.5 and 30 kDa were purified at acidic pI.

Journal of General and Applied Microbiology, 2001

Journal of Basic Microbiology, 1999

... Original Paper. Physiological and enzymological characterization of the β-N-acetylhexosaminid... more ... Original Paper. Physiological and enzymological characterization of the β-N-acetylhexosaminidase of Penicillium chrysogenum. István Pócsi Dr.,; Imre Pócsi,; Tünde Pusztahelyi. Article first published online: 24 JUN 1999. ... Get PDF (177K). More content like this. ...

Fems Microbiology Letters, 1998

Acta Microbiologica Et Immunologica Hungarica, 2008

Enzyme and Microbial Technology, 2005

Applied Biochemistry and Biotechnology, 2004

The morphologic and physiologic effects of vitamin E, a powerful antioxidant, on the autolysis an... more The morphologic and physiologic effects of vitamin E, a powerful antioxidant, on the autolysis and sporulation of Aspergillus nidulans FGSC26 were studied. In carbon-depleted submerged cultures, reactive oxygen species (ROS) accumulated in the cells and, concomitantly, progressing autolysis was observed, which was characterized by decreasing dry cell masses and pellet diameters as well as by increasing extracellular chitinase activities. Vitamin E supplemented at a concentration of 1 g/L hindered effectively the intracellular accumulation of ROS, the autolytic loss of biomass, the disintegration of pellets, and the release of chitinase activities. In surface cultures, vitamin E inhibited autolysis of both A. nidulans FGSC26 and a loss-of-function FlbA autolytic phenotype mutant. In addition, supplementation of the culture medium with this antioxidant also had a negative effect on the sporulation of strain FGSC26 and the FadA G203R hypersporulating phenotype mutant. These results suggest that accumulation of ROS was involved in the initiation of both sporulation and autolysis in this filamentous fungus, but that FadA/FlbA signaling was not involved in this vitamin E-dependent regulation. Vitamin E can be recommended as a supplement in fermentations in which the disintegration of pellets and gross autolysis should be avoided.

Acta Biologica Hungarica, 2007

The bulk formation of yeast-like (arthrospore-like) cells were typical in carbon-depleted submerg... more The bulk formation of yeast-like (arthrospore-like) cells were typical in carbon-depleted submerged cultures of the high beta-lactam producer Penicillium chrysogenum NCAIM 00237 strain independently of the nitrogen-content of the culture medium. This morphogenetic switch was still quite common in carbon-starving cultures of the low-penicillin-producer strain P. chrysogenum ATCC 28089 (Wis 54-1255) when the nitrogen-content of the medium was low but was a very rare event in wild-type P. chrysogenum cultures. The mycelium-->yeast-like cell transition correlated well with a relatively high glutathione concentration and a reductive glutathione/glutathione disulfite (GSH/GSSG) redox balance in autolysing cultures, which was a consequence of industrial strain development. Paradoxically, the development of high beta-lactam productivity resulted in a high intracellular GSH level and, concomitantly, in an increased y-glutamyltranspeptidase (i.e. GSH-decomposing) activity in the autolytic phase of growth of P. chrysogenum NCAIM 00237. The hypothesized causal connection between GSH metabolism and cell morphology, if verified, may help us in future metabolic engineering of industrially important filamentous fungi.

Antimicrobial Agents and Chemotherapy, 2005

Fungal Genetics and Biology, 2011

BMC Genomics, 2005

Background In addition to their cytotoxic nature, reactive oxygen species (ROS) are also signal m... more Background In addition to their cytotoxic nature, reactive oxygen species (ROS) are also signal molecules in diverse cellular processes in eukaryotic organisms. Linking genome-wide transcriptional changes to cellular physiology in oxidative stress-exposed Aspergillus nidulans cultures provides the opportunity to estimate the sizes of peroxide (O22-), superoxide (O2•-) and glutathione/glutathione disulphide (GSH/GSSG) redox imbalance responses. Results Genome-wide transcriptional changes triggered by diamide, H2O2 and menadione in A. nidulans vegetative tissues were recorded using DNA microarrays containing 3533 unique PCR-amplified probes. Evaluation of LOESS-normalized data indicated that 2499 gene probes were affected by at least one stress-inducing agent. The stress induced by diamide and H2O2 were pulse-like, with recovery after 1 h exposure time while no recovery was observed with menadione. The distribution of stress-responsive gene probes among major physiological functional categories was approximately the same for each agent. The gene group sizes solely responsive to changes in intracellular O22-, O2•- concentrations or to GSH/GSSG redox imbalance were estimated at 7.7, 32.6 and 13.0 %, respectively. Gene groups responsive to diamide, H2O2 and menadione treatments and gene groups influenced by GSH/GSSG, O22- and O2•- were only partly overlapping with distinct enrichment profiles within functional categories. Changes in the GSH/GSSG redox state influenced expression of genes coding for PBS2 like MAPK kinase homologue, PSK2 kinase homologue, AtfA transcription factor, and many elements of ubiquitin tagging, cell division cycle regulators, translation machinery proteins, defense and stress proteins, transport proteins as well as many enzymes of the primary and secondary metabolisms. Meanwhile, a seParate set of genes encoding transport proteins, CpcA and JlbA amino acid starvation-responsive transcription factors, and some elements of sexual development and sporulation was ROS responsive. Conclusion The existence of seParate O22-, O2•- and GSH/GSSG responsive gene groups in a eukaryotic genome has been demonstrated. Oxidant-triggered, genome-wide transcriptional changes should be analyzed considering changes in oxidative stress-responsive physiological conditions and not correlating them directly to the chemistry and concentrations of the oxidative stress-inducing agent.

Acta Biologica Hungarica, 2006

NADPH is involved in many basically important anabolic processes. For a long time, pentose phosph... more NADPH is involved in many basically important anabolic processes. For a long time, pentose phosphate pathway (PPS) was regarded as the most important source of NADPH in fungi. Here we present evidence of a metabolic switch to an alternative NADPH-producing pathway in ageing Penicillium chrysogenum cultures, which involves NADP+ -specific isocitrate dehydrogenase (NADP+ -ID) rather than PPS enzymes. Considering the main biochemical functions of NADPH, we propose that NADP+ -ID could have deep impact on many physiological processes switched on glucose deprivation including proteinase production or penicillin biosynthesis. We also demonstrate that although the alternative pathway was inferior to PPS when the fungus was grown on well-utilisable carbon sources yet it could have an important role in fatty acid biosynthesis as well as in the maintenance of high intracellular NADPH/NADP+ ratios.