András Szekeres - Academia.edu (original) (raw)

Papers by András Szekeres

Cereal Research Communications

The FHB resistance QTL region of wheat chromosome 2DS (QFhs.kibr-2D) flanks the reduced height ge... more The FHB resistance QTL region of wheat chromosome 2DS (QFhs.kibr-2D) flanks the reduced height gene Rht8, which might be a resistance gene complex consisting of morphological traits controlled by Rht8 for type I resistance and a specific gene(s) to control type II resistance by detoxification of DON. In this paper, we discussed relationship between plant height and FHB resistance for the QTL on the wheat chromosome 2DS, QFhs.kibr-2DS.

Rapid Communications in Mass Spectrometry, 2016

Surfactins are mixtures of cyclic lipopeptides consisting of variants of a heptapeptide and a lin... more Surfactins are mixtures of cyclic lipopeptides consisting of variants of a heptapeptide and a linked β-hydroxy fatty acid with various chain lengths of 13-15 carbon atoms. A lactone bridge between the β-hydroxy functional group of the fatty acid and the carboxy terminal functional component of the peptide chain form their cyclic structures. Such lipopeptides, produced mainly by Bacillus species, possess several remarkable biological effects such as antitumor and antimicrobial activities, some of which are highly promising for utilization in plant disease biocontrol. The strain Bacillus subtilis SZMC 6179J was previously shown to exert significant antifungal properties against various phytopathogenic filamentous fungi; therefore, we characterized the structural features of the surfactins produced by this strain in order to explore the origin of the observed antagonistic effects of this potential biocontrol organism. Bacillus subtilis SZMC 6179J was used to produce surfactins, which were characterized by high-performance liquid chromatography/electrospray ionisation ion trap mass spectrometry (HPLC/ESI-ITMS) techniques after precipitation and extraction steps. The 26 isoforms separated and identified represent three types of known surfactin variants and a fourth, previously unknown group characterised by the replacement of the leucine residue by valine in position 2. The relative amounts of this newly identified surfactin group were below 1%, and their cyclic structures were closed by C13-C15 hydroxy fatty acids. The structural assessment of the isoforms by MS(2) measurements led to the characterisation and description of a new fragmentation mechanism of surfactins. The detected new natural lipoheptapeptide compounds with modified structures have significant potential for biotechnological and biocontrol applications. The complementary ITMS(2) data as well as the described internal fragmentation mechanism obtained from the sodiated surfactin molecules may further facilitate the structural elucidation of cyclic lipopeptides in the future. Copyright © 2016 John Wiley & Sons, Ltd.

Antonie van Leeuwenhoek, 2006

The sensitivity of two cold-tolerant Trichoderma strains belonging to the species T. harzianum an... more The sensitivity of two cold-tolerant Trichoderma strains belonging to the species T. harzianum and T. atroviride was determined to a series of pesticides widely used in agriculture. From the 16 pesticides tested, seven fungicides: copper sulfate, carbendazim, mancozeb, tebuconazole, imazalil, captan and thiram inhibited colony growth of the test strains significantly with minimal inhibitory concentrations of 300, 0.4, 50, 100, 100, 100 and 50 microg/ml, respectively. Mutants resistant to carbendazim and tebuconazole were produced from both wild type strains by means of UV-mutagenesis. The cross-resistance capabilities and in vitro antagonistic properties of the mutants were determined. Carbendazim-resistant mutants showed total cross-resistance to benomyl and thiabendazole at a concentration of 20 microg/ml. Intraspecific protoplast fusion was carried out between carbendazim- and tebuconazole-resistant mutants of both parental strains, and putative haploid recombinants with stable resistance to both pesticides were produced in the case of T. atroviride. These pesticide-polyresistant progenies are potential candidates for application in an integrated pest management system.

Rapid Communications in Mass Spectrometry, 2010

Fumonisin mycotoxins which are hazardous to humans and animals were produced in a Fusarium vertic... more Fumonisin mycotoxins which are hazardous to humans and animals were produced in a Fusarium verticillioides-infected solid rice culture. To decrease the possibility of the formation of artifacts, the fumonisins were analysed by reversed-phase high-performance liquid chromatography/electrospray ionization time-of-flight (RP-HPLC/ESI-TOFMS) and ion trap mass spectrometry (RP-HPLC/ESI-ITMS) immediately after the extraction of the culture material, without any further sample clean-up. The fumonisin isomers were separated by using a flat gradient on a special, high-coverage C(18), narrow-bore HPLC column (YMC-Pack J'sphere ODS H80) suggested for the separation of structural isomers by the manufacturer. Exact mass measurements (TOFMS) of the protonated molecules and extraction of the ion chromatogram corresponding to the empirical formula (C(34)H(59)NO(15)) of FB(1) toxins led to the identification of 29 peaks and shoulders, including those of FB(1). The FB(1) toxin and 28 of its isomers were also detected by ITMS after separation with RP-HPLC. The characteristic m/z values of the product ions, including the backbones obtained by ITMS(2), undoubtedly indicated the structures of the FB(1) isomers for 28 peaks and shoulders. In the MS(2) spectra of the protonated molecules of the FB(1) isomers, with some exceptions, 15 characteristic product ions including the hydrocarbon backbone at m/z 299 were observed. The abundance ratio of the cation at m/z 299 ranged up to 5.8%. The relative quantities of the isomers found in the sample extract were expressed as percentages of the FB(1) content (0.001-0.579%). The total amount of the 28 FB(1) isomers was 2.803% of the quantity of FB(1) that is important from the aspect of food and feed safety.

-1 yeast extract, 5 g l -1 glucose, 5 g l -1 KH2PO4, 20 g l -1 agar in distilled water). In vitro... more -1 yeast extract, 5 g l -1 glucose, 5 g l -1 KH2PO4, 20 g l -1 agar in distilled water). In vitro antagonism experiments were carried out on media containing 1 g l-1 yeast extract, 2 g l -1 glucose, 1 g l -1 KH2PO4, 1 g l -1 MgSO4 and 20 g l -1 agar in distilled water.

During the last two decades, several case reports have been published worldwide about green mould... more During the last two decades, several case reports have been published worldwide about green mould infections of cultivated Agaricus bisporus, and the causative agents were identified as Trichoderma aggressivum. More recently, the green mould disease of Pleurotus spp. caused by Trichoderma has also been reported in several countries. Pleurotus ostreatus is the third-most important commercially grown basidiomycete worldwide, and its production is being increasingly affected by green mould infections causing great crop losses. The fungi responsible for the green mould disease of Pleurotus proved to be different from T. aggressivum, based on their cultural, morphological, physiological and molecular properties. e causative agents of the disease have been described as the new species Trichoderma pleurotum S.H. Yu & M.S. Park and Trichoderma pleuroticola S.H. Yu & M.S. Park, and the isolates from other countries were shown to be identical to them. The aim of this article is to give an ove...

Since the early 80s, several reports have been published in Europe and North America about green ... more Since the early 80s, several reports have been published in Europe and North America about green mould infections of cultivated Agaricus bisporus, and the causative agents were described as Trichoderma aggressivum f. europaeum and T. aggressivum f. aggressivum, respectively. In the latest years the green mould disease of Pleurotus spp. caused by Trichoderma also occurred in several countries, and the most serious cases were reported in South Korea, Italy, Hungary and Romania. The fungi responsible for the green mould disease of oyster mushroom were found to be different from T. aggressivum based on their cultural, morphological, physiological and molecular properties, therefore they have been described as the new species T. pleurotum and T. pleuroticola. Since the green mould disease of P. ostreatus is spreading fast worldwide, the aim of this work was to develop a PCR-based technique for the rapid detection of the causative agents.

The action of fungal hydrolytic enzymes is playing a crucial role in the biocontrol process of Tr... more The action of fungal hydrolytic enzymes is playing a crucial role in the biocontrol process of Trichoderma strains. In the present study, information was collected about the distribution of mono- and disaccharide-releasing extracellular enzyme production abilities within a Hungarian Trichoderma population from winter wheat rhizosphere.

In this study, a prenyl pyrophosphate synthase gene was cloned and characterized in the zygomycet... more In this study, a prenyl pyrophosphate synthase gene was cloned and characterized in the zygomycete fungus Gilbertella persicaria. The coding region of the isolatedgene comprises a total of 1328 bp determining a 350 amino acids length putative protein and five introns (60, 65, 43, 59, and 48 bp in length) dispersed in the whole coding region. Based on the analysis of the nucleotide and the corresponding amino acid sequence, the gene encodes a farnezyl pyrophosphate synthase, and it was named as isoA. In a phylogeny inferred from amino acid sequences of fungal prenyl pyrophosphate synthases, the Gilbertella isoA proved to be the most closely related to that of Mucor circinelloides. Carotenoid composition of G. persicaria was also investigated: it produces -carotene as the main carotenoid, but it also contains small amounts of -cryptoxanthin, zeaxanthin and astaxanthin.

Acta Biologica Szegediensis

The peptaibols, such as alamethicin are secondary metabolites belonging to the family of fungal p... more The peptaibols, such as alamethicin are secondary metabolites belonging to the family of fungal peptide antibiotics. These compounds are linear, amphipathic oligopeptides classified into 4 subfamilies and composed of 5-20 amino acids. Their backbones usually contain several nonproteinogenic amino acid residues representing characteristic building blocks of the structure. In our present work, the mass spectrometric analysis of alamethicin has been investigated by on-line reversed-phase high performance liquid chromatography (HPLC) coupled to electrospray ionization tandem mass spectrometry (ES-MS). Initially, the parameters of the MS were optimized by the continuous infusion of an alamethicin standard solution directly into the ESI source. Then, the proper HPLC method was developed for the analysis of the alamethicin components, which was capable to separate the peaks of F50-5, F50-6a, F50-7 and F50-8b from each other, which could be identified based on their mass spectra.

Acta Biologica Szegediensis

Peptaibiotics are bioactive secondary metabolites belonging to a constantly growing family of fun... more Peptaibiotics are bioactive secondary metabolites belonging to a constantly growing family of fungal peptide antibiotics. They are linear, amphipathic oligopeptides consisting of 5-20 amino acids, usually containing nonproteinogenic amino acid residues as characteristic building blocks of the structure. The majority of the peptaibiotics described so far are produced by members of the filamentous fungal genus Trichoderma. Species of this genus are known as important sources of antibiotics and enzymes, and they are also known as promoters of plant growth, decomposers of xenobiotics and as commercial biofungicides. In this work, a rapid, bacterium-based screening method was developed and optimized for the detection of peptaibiotic production in liquid cultures of Trichoderma strains. The method was validated with the commercially available alamethicin as a peptaibiotic reference compound.

Cereal Research Communications

The FHB resistance QTL region of wheat chromosome 2DS (QFhs.kibr-2D) flanks the reduced height ge... more The FHB resistance QTL region of wheat chromosome 2DS (QFhs.kibr-2D) flanks the reduced height gene Rht8, which might be a resistance gene complex consisting of morphological traits controlled by Rht8 for type I resistance and a specific gene(s) to control type II resistance by detoxification of DON. In this paper, we discussed relationship between plant height and FHB resistance for the QTL on the wheat chromosome 2DS, QFhs.kibr-2DS.

Rapid Communications in Mass Spectrometry, 2016

Surfactins are mixtures of cyclic lipopeptides consisting of variants of a heptapeptide and a lin... more Surfactins are mixtures of cyclic lipopeptides consisting of variants of a heptapeptide and a linked β-hydroxy fatty acid with various chain lengths of 13-15 carbon atoms. A lactone bridge between the β-hydroxy functional group of the fatty acid and the carboxy terminal functional component of the peptide chain form their cyclic structures. Such lipopeptides, produced mainly by Bacillus species, possess several remarkable biological effects such as antitumor and antimicrobial activities, some of which are highly promising for utilization in plant disease biocontrol. The strain Bacillus subtilis SZMC 6179J was previously shown to exert significant antifungal properties against various phytopathogenic filamentous fungi; therefore, we characterized the structural features of the surfactins produced by this strain in order to explore the origin of the observed antagonistic effects of this potential biocontrol organism. Bacillus subtilis SZMC 6179J was used to produce surfactins, which were characterized by high-performance liquid chromatography/electrospray ionisation ion trap mass spectrometry (HPLC/ESI-ITMS) techniques after precipitation and extraction steps. The 26 isoforms separated and identified represent three types of known surfactin variants and a fourth, previously unknown group characterised by the replacement of the leucine residue by valine in position 2. The relative amounts of this newly identified surfactin group were below 1%, and their cyclic structures were closed by C13-C15 hydroxy fatty acids. The structural assessment of the isoforms by MS(2) measurements led to the characterisation and description of a new fragmentation mechanism of surfactins. The detected new natural lipoheptapeptide compounds with modified structures have significant potential for biotechnological and biocontrol applications. The complementary ITMS(2) data as well as the described internal fragmentation mechanism obtained from the sodiated surfactin molecules may further facilitate the structural elucidation of cyclic lipopeptides in the future. Copyright © 2016 John Wiley & Sons, Ltd.

Antonie van Leeuwenhoek, 2006

The sensitivity of two cold-tolerant Trichoderma strains belonging to the species T. harzianum an... more The sensitivity of two cold-tolerant Trichoderma strains belonging to the species T. harzianum and T. atroviride was determined to a series of pesticides widely used in agriculture. From the 16 pesticides tested, seven fungicides: copper sulfate, carbendazim, mancozeb, tebuconazole, imazalil, captan and thiram inhibited colony growth of the test strains significantly with minimal inhibitory concentrations of 300, 0.4, 50, 100, 100, 100 and 50 microg/ml, respectively. Mutants resistant to carbendazim and tebuconazole were produced from both wild type strains by means of UV-mutagenesis. The cross-resistance capabilities and in vitro antagonistic properties of the mutants were determined. Carbendazim-resistant mutants showed total cross-resistance to benomyl and thiabendazole at a concentration of 20 microg/ml. Intraspecific protoplast fusion was carried out between carbendazim- and tebuconazole-resistant mutants of both parental strains, and putative haploid recombinants with stable resistance to both pesticides were produced in the case of T. atroviride. These pesticide-polyresistant progenies are potential candidates for application in an integrated pest management system.

Rapid Communications in Mass Spectrometry, 2010

Fumonisin mycotoxins which are hazardous to humans and animals were produced in a Fusarium vertic... more Fumonisin mycotoxins which are hazardous to humans and animals were produced in a Fusarium verticillioides-infected solid rice culture. To decrease the possibility of the formation of artifacts, the fumonisins were analysed by reversed-phase high-performance liquid chromatography/electrospray ionization time-of-flight (RP-HPLC/ESI-TOFMS) and ion trap mass spectrometry (RP-HPLC/ESI-ITMS) immediately after the extraction of the culture material, without any further sample clean-up. The fumonisin isomers were separated by using a flat gradient on a special, high-coverage C(18), narrow-bore HPLC column (YMC-Pack J'sphere ODS H80) suggested for the separation of structural isomers by the manufacturer. Exact mass measurements (TOFMS) of the protonated molecules and extraction of the ion chromatogram corresponding to the empirical formula (C(34)H(59)NO(15)) of FB(1) toxins led to the identification of 29 peaks and shoulders, including those of FB(1). The FB(1) toxin and 28 of its isomers were also detected by ITMS after separation with RP-HPLC. The characteristic m/z values of the product ions, including the backbones obtained by ITMS(2), undoubtedly indicated the structures of the FB(1) isomers for 28 peaks and shoulders. In the MS(2) spectra of the protonated molecules of the FB(1) isomers, with some exceptions, 15 characteristic product ions including the hydrocarbon backbone at m/z 299 were observed. The abundance ratio of the cation at m/z 299 ranged up to 5.8%. The relative quantities of the isomers found in the sample extract were expressed as percentages of the FB(1) content (0.001-0.579%). The total amount of the 28 FB(1) isomers was 2.803% of the quantity of FB(1) that is important from the aspect of food and feed safety.

-1 yeast extract, 5 g l -1 glucose, 5 g l -1 KH2PO4, 20 g l -1 agar in distilled water). In vitro... more -1 yeast extract, 5 g l -1 glucose, 5 g l -1 KH2PO4, 20 g l -1 agar in distilled water). In vitro antagonism experiments were carried out on media containing 1 g l-1 yeast extract, 2 g l -1 glucose, 1 g l -1 KH2PO4, 1 g l -1 MgSO4 and 20 g l -1 agar in distilled water.

During the last two decades, several case reports have been published worldwide about green mould... more During the last two decades, several case reports have been published worldwide about green mould infections of cultivated Agaricus bisporus, and the causative agents were identified as Trichoderma aggressivum. More recently, the green mould disease of Pleurotus spp. caused by Trichoderma has also been reported in several countries. Pleurotus ostreatus is the third-most important commercially grown basidiomycete worldwide, and its production is being increasingly affected by green mould infections causing great crop losses. The fungi responsible for the green mould disease of Pleurotus proved to be different from T. aggressivum, based on their cultural, morphological, physiological and molecular properties. e causative agents of the disease have been described as the new species Trichoderma pleurotum S.H. Yu & M.S. Park and Trichoderma pleuroticola S.H. Yu & M.S. Park, and the isolates from other countries were shown to be identical to them. The aim of this article is to give an ove...

Since the early 80s, several reports have been published in Europe and North America about green ... more Since the early 80s, several reports have been published in Europe and North America about green mould infections of cultivated Agaricus bisporus, and the causative agents were described as Trichoderma aggressivum f. europaeum and T. aggressivum f. aggressivum, respectively. In the latest years the green mould disease of Pleurotus spp. caused by Trichoderma also occurred in several countries, and the most serious cases were reported in South Korea, Italy, Hungary and Romania. The fungi responsible for the green mould disease of oyster mushroom were found to be different from T. aggressivum based on their cultural, morphological, physiological and molecular properties, therefore they have been described as the new species T. pleurotum and T. pleuroticola. Since the green mould disease of P. ostreatus is spreading fast worldwide, the aim of this work was to develop a PCR-based technique for the rapid detection of the causative agents.

The action of fungal hydrolytic enzymes is playing a crucial role in the biocontrol process of Tr... more The action of fungal hydrolytic enzymes is playing a crucial role in the biocontrol process of Trichoderma strains. In the present study, information was collected about the distribution of mono- and disaccharide-releasing extracellular enzyme production abilities within a Hungarian Trichoderma population from winter wheat rhizosphere.

In this study, a prenyl pyrophosphate synthase gene was cloned and characterized in the zygomycet... more In this study, a prenyl pyrophosphate synthase gene was cloned and characterized in the zygomycete fungus Gilbertella persicaria. The coding region of the isolatedgene comprises a total of 1328 bp determining a 350 amino acids length putative protein and five introns (60, 65, 43, 59, and 48 bp in length) dispersed in the whole coding region. Based on the analysis of the nucleotide and the corresponding amino acid sequence, the gene encodes a farnezyl pyrophosphate synthase, and it was named as isoA. In a phylogeny inferred from amino acid sequences of fungal prenyl pyrophosphate synthases, the Gilbertella isoA proved to be the most closely related to that of Mucor circinelloides. Carotenoid composition of G. persicaria was also investigated: it produces -carotene as the main carotenoid, but it also contains small amounts of -cryptoxanthin, zeaxanthin and astaxanthin.

Acta Biologica Szegediensis

The peptaibols, such as alamethicin are secondary metabolites belonging to the family of fungal p... more The peptaibols, such as alamethicin are secondary metabolites belonging to the family of fungal peptide antibiotics. These compounds are linear, amphipathic oligopeptides classified into 4 subfamilies and composed of 5-20 amino acids. Their backbones usually contain several nonproteinogenic amino acid residues representing characteristic building blocks of the structure. In our present work, the mass spectrometric analysis of alamethicin has been investigated by on-line reversed-phase high performance liquid chromatography (HPLC) coupled to electrospray ionization tandem mass spectrometry (ES-MS). Initially, the parameters of the MS were optimized by the continuous infusion of an alamethicin standard solution directly into the ESI source. Then, the proper HPLC method was developed for the analysis of the alamethicin components, which was capable to separate the peaks of F50-5, F50-6a, F50-7 and F50-8b from each other, which could be identified based on their mass spectra.

Acta Biologica Szegediensis

Peptaibiotics are bioactive secondary metabolites belonging to a constantly growing family of fun... more Peptaibiotics are bioactive secondary metabolites belonging to a constantly growing family of fungal peptide antibiotics. They are linear, amphipathic oligopeptides consisting of 5-20 amino acids, usually containing nonproteinogenic amino acid residues as characteristic building blocks of the structure. The majority of the peptaibiotics described so far are produced by members of the filamentous fungal genus Trichoderma. Species of this genus are known as important sources of antibiotics and enzymes, and they are also known as promoters of plant growth, decomposers of xenobiotics and as commercial biofungicides. In this work, a rapid, bacterium-based screening method was developed and optimized for the detection of peptaibiotic production in liquid cultures of Trichoderma strains. The method was validated with the commercially available alamethicin as a peptaibiotic reference compound.