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Soren Rosendahl - One of the best experts on this subject based on the ideXlab platform.
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transcriptional profiling of medicago truncatula roots after infection with Aphanomyces Euteiches oomycota identifies novel genes upregulated during this pathogenic interaction
Physiological and Molecular Plant Pathology, 2003Co-Authors: Oyunbileg Nyamsuren, Philipp Franken, Soren Rosendahl, Frank Colditz, Mbarek Tamasloukht, Thomas Bekel, Folker Meyer, Helge Kuester, Franziska KrajinskiAbstract:Common root rot of pea caused by Aphanomyces Euteiches has been the major yield-reducing factor for pea production during the last decades. In this study, a systematic sequencing of expressed sequence tags (ESTs) was chosen to obtain a first global picture of the assembly of genes involved in pathogenesis. For this purpose, a pathosystem between the model legume Medicago truncatula and A. Euteiches was established. Typical symptoms of this disease such as root discoloration and a reduction of root mass were observed in the model legume. Significant transcriptional changes in the host plant occurred already 6 days after inoculation. To identify a large number of plant ESTs, which are induced at this time point, a cDNA-library was established by Suppression Subtractive Hybridization. Five hundred and sixty ESTs have been generated of this library. On the one hand, EST-annotations showed homologies to a number of classical pathogenesis-related (PR) and defense genes. A notable number of the ESTs, however, were derived from novel genes not matching entries of the large-scale M. truncatula sequence collection. Hybridization experiments showed that also within these new ESTs, 21% are induced after pathogen infection. Hence, the here presented transcriptomic approach demonstrates that classical pathogenesis mechanisms as well as new specific gene regulations are involved in root rot disease development caused by A. Euteiches.
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Interactions between indigenous arbuscular mycorrhizal fungi and Aphanomyces Euteiches in field-grown pea
Mycorrhiza, 2002Co-Authors: Lars Bodker, Rasmus Kjoller, Kristian Kristensen, Soren RosendahlAbstract:This is the first reported study of the interactions between indigenous arbuscular mycorrhizal fungi (AMF) and Aphanomyces Euteiches in pea under field conditions. A. Euteiches was applied to the soil by adding oospores produced in vitro. Attempts were made to create a non-mycorrhizal control by incorporating carbendazim (Derosal Fl) in the topsoil before sowing. However, all carbendazim-treated plants showed approximately 20% root colonisation with AMF. Pea plants not treated with carbendazim showed a wide variation in AMF colonisation of 35–70% at the full flowering stage. In these control plots, root length infected with oospores of A. Euteiches and colonisation by AMF were negatively correlated. Application of carbendazim increased the percent root length infected with oospores by 50–70%, depending on inoculum density of A. Euteiches . Despite the lower levels of AMF colonisation in these treated plots, a negative correlation with oospore-containing root length was still observed. No correlation was found between AMF colonisation and disease severity, disease incidence or pathogen enzymatic activity (glucose-6-phosphate dehydrogenase). Thus, AMF do not seem to influence the vegetative stage of pathogen development during which cortical root rotting takes place, but rather the reproductive stage when oospores are produced. The results of this study underline the importance of field experiments for validating the significance of mycorrhizal fungi for plant health.
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effect of phosphate and the arbuscular mycorrhizal fungus glomus intraradices on disease severity of root rot of peas pisum sativum caused by Aphanomyces Euteiches
Mycorrhiza, 1998Co-Authors: Lars Bodker, Rasmus Kjoller, Soren RosendahlAbstract:The effects of inorganic phosphate levels and the presence of arbuscular mycorrhiza on disease severity of Aphanomyces Euteiches in pea roots were studied. Disease severity on roots and epicotyl as well as the oospore number within infected root tissue were correlated with the phosphorus (P) level in the growth medium. The arbuscular mycorrhizal fungus Glomus intraradices increased P uptake and the P concentration in the plant but reduced disease development in peas. Polyacrylamide gel electrophoresis followed by densitometry of glucose-6-phosphate dehydrogenase specific to A.Euteiches was used to measure the activity of the pathogen in roots. The enzyme activity increased with disease severity and disease incidence, except in plants supplemented with P at the highest level, where a peak in activity was seen 12 days after inoculation with the pathogen, followed by a decrease in activity. The epicotyl of mycorrhizal plants showed a reduction in disease severity although this part of the plants was not mycorrhizal. Thus, an induced systemic factor may be responsible for increased resistance in mycorrhizal plants.
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enzymatic activity of the mycelium compared with oospore development during infection of pea roots by Aphanomyces Euteiches
Phytopathology, 1998Co-Authors: Rasmus Kjoller, Soren RosendahlAbstract:ABSTRACT To describe the disease cycle of the root pathogen Aphanomyces Euteiches, enzymatic activity in the mycelium was compared with the development of oospores in pea roots. Plants were inoculated with two zoospore concentrations to achieve different disease levels. Hyphae were stained for fungal alkaline phosphatase activity in the roots. Additionally, enzyme activity was measured after electrophoresis of an A. Euteiches-specific glucose-6-phosphate isozyme. Development of oospores in the roots was measured after staining the oospores with trypan blue. In plants inoculated with the higher zoospore concentration, the enzymatic activity of the pathogen mycelium peaked 10 to 14 days after inoculation, when oospore formation was initiated. Oospore formation was associated with a gradual increase in disease symptoms. At the last harvest, plants inoculated with the higher zoospore concentration had died. In these plants, oospores were found in 90% of the root length, while the enzymatic activity of the myc...
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polyacrylamide gel electrophoresis page and densitometric measurement of enzyme activity of the pea root pathogen Aphanomyces Euteiches in pea roots
Journal of Phytopathology, 1997Co-Authors: R Kioller, Soren RosendahlAbstract:A new method to measure enzyme activity of the fungal root pathogen Aphanomyces Euteiches in pea roots is described. The specific enzymes of the fungus and the host were separated by polyacrylamide gel electrophoresis (PAGE) and the activity of fungal Glucose-6-phosphate dehydrogenase and Phosphoglucomutase were quantified by densitometry. Fungal activity could be correlated to the percentage infected root length and to the disease symptoms of the plants. The activity of A. Euteiches was studied in a time course experiment with increasing levels of zoospore inoculum. The results indicated that an increase in inoculum level resulted in a faster disease development in the plants. The relation between fungal enzyme activity and infection level is discussed.
Rasmus Kjoller - One of the best experts on this subject based on the ideXlab platform.
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Interactions between indigenous arbuscular mycorrhizal fungi and Aphanomyces Euteiches in field-grown pea
Mycorrhiza, 2002Co-Authors: Lars Bodker, Rasmus Kjoller, Kristian Kristensen, Soren RosendahlAbstract:This is the first reported study of the interactions between indigenous arbuscular mycorrhizal fungi (AMF) and Aphanomyces Euteiches in pea under field conditions. A. Euteiches was applied to the soil by adding oospores produced in vitro. Attempts were made to create a non-mycorrhizal control by incorporating carbendazim (Derosal Fl) in the topsoil before sowing. However, all carbendazim-treated plants showed approximately 20% root colonisation with AMF. Pea plants not treated with carbendazim showed a wide variation in AMF colonisation of 35–70% at the full flowering stage. In these control plots, root length infected with oospores of A. Euteiches and colonisation by AMF were negatively correlated. Application of carbendazim increased the percent root length infected with oospores by 50–70%, depending on inoculum density of A. Euteiches . Despite the lower levels of AMF colonisation in these treated plots, a negative correlation with oospore-containing root length was still observed. No correlation was found between AMF colonisation and disease severity, disease incidence or pathogen enzymatic activity (glucose-6-phosphate dehydrogenase). Thus, AMF do not seem to influence the vegetative stage of pathogen development during which cortical root rotting takes place, but rather the reproductive stage when oospores are produced. The results of this study underline the importance of field experiments for validating the significance of mycorrhizal fungi for plant health.
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endoproteolytic activities in pea roots inoculated with the arbuscular mycorrhizal fungus glomus mosseae and or Aphanomyces Euteiches in relation to bioprotection
New Phytologist, 1999Co-Authors: Sophie Slezack, Rasmus Kjoller, Eliane Dumasgaudot, Michel Paynot, S Rosendahl, Jonathan Negrel, Silvio GianinazziAbstract:summary Arbuscular mycorrhizal (AM) symbioses are known to play a role in increased resistance of plants against soilborne pathogens. Mechanisms involved in this phenomenon are not yet well understood. This work investigates possible roles of endoproteolytic activities in bioprotection of Pisum sativum roots by Glomus mosseae against Aphanomyces Euteiches. First, it is demonstrated that bioprotection occurs only in pre-mycorrhizal plants. Second, endoproteolytic activities were analysed qualitatively and quantitatively during AM symbiosis, in plants infected with either zoospores or mycelium of A. Euteiches, and in mycorrhizal plants infected with the pathogen. In mycorrhizal symbiosis a progressive increase in endoproteolytic activities was observed following root colonization by G. mosseae. By contrast, in roots inoculated with A. Euteiches, a drastic increase in endoproteolytic activities was observed which was correlated with the amount of pathogen occurring in roots. Qualitative dierences were seen among the endoproteolytic activities detected in roots inoculated with zoospores or mycelium. The constitutive as well as mycorrhizal and pathogen-induced activities were further characterized as ‘trypsin-like’ serine endoproteases. Interestingly, in a situation of bioprotection, only low levels of the activities normally associated with the infection by A. Euteiches were detected, suggesting that the synthesis of these proteins is directly linked to the growth or virulence of the pathogen.
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effect of phosphate and the arbuscular mycorrhizal fungus glomus intraradices on disease severity of root rot of peas pisum sativum caused by Aphanomyces Euteiches
Mycorrhiza, 1998Co-Authors: Lars Bodker, Rasmus Kjoller, Soren RosendahlAbstract:The effects of inorganic phosphate levels and the presence of arbuscular mycorrhiza on disease severity of Aphanomyces Euteiches in pea roots were studied. Disease severity on roots and epicotyl as well as the oospore number within infected root tissue were correlated with the phosphorus (P) level in the growth medium. The arbuscular mycorrhizal fungus Glomus intraradices increased P uptake and the P concentration in the plant but reduced disease development in peas. Polyacrylamide gel electrophoresis followed by densitometry of glucose-6-phosphate dehydrogenase specific to A.Euteiches was used to measure the activity of the pathogen in roots. The enzyme activity increased with disease severity and disease incidence, except in plants supplemented with P at the highest level, where a peak in activity was seen 12 days after inoculation with the pathogen, followed by a decrease in activity. The epicotyl of mycorrhizal plants showed a reduction in disease severity although this part of the plants was not mycorrhizal. Thus, an induced systemic factor may be responsible for increased resistance in mycorrhizal plants.
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enzymatic activity of the mycelium compared with oospore development during infection of pea roots by Aphanomyces Euteiches
Phytopathology, 1998Co-Authors: Rasmus Kjoller, Soren RosendahlAbstract:ABSTRACT To describe the disease cycle of the root pathogen Aphanomyces Euteiches, enzymatic activity in the mycelium was compared with the development of oospores in pea roots. Plants were inoculated with two zoospore concentrations to achieve different disease levels. Hyphae were stained for fungal alkaline phosphatase activity in the roots. Additionally, enzyme activity was measured after electrophoresis of an A. Euteiches-specific glucose-6-phosphate isozyme. Development of oospores in the roots was measured after staining the oospores with trypan blue. In plants inoculated with the higher zoospore concentration, the enzymatic activity of the pathogen mycelium peaked 10 to 14 days after inoculation, when oospore formation was initiated. Oospore formation was associated with a gradual increase in disease symptoms. At the last harvest, plants inoculated with the higher zoospore concentration had died. In these plants, oospores were found in 90% of the root length, while the enzymatic activity of the myc...
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the presence of the arbuscular mycorrhizal fungus glomus intraradices influences enzymatic activities of the root pathogen Aphanomyces Euteiches in pea roots
Mycorrhiza, 1997Co-Authors: Rasmus Kjoller, Soren RosendahlAbstract:Fungal enzyme activities were quantified in an interaction study between the fungus Glomus intraradices and the pea pathogen Aphanomyces Euteiches. Fungal and host enzymes were separated by polyacrylamide gel electrophoresis and the activity of A. Euteiches–specific glucose-6-phosphate dehydrogenase (Gd), phosphoglucomutase and peptidase (PEP) enzymes were quantified by densitometry. The activity of A. Euteiches–specific enzymes increased until 14 days after inoculation with A. Euteiches, and then decreased. The plants preinoculated with G. intraradices showed no symptoms of severe root rot even though the pathogen was present and active in these plants. Thus, plants preinoculated with G. intraradices were more tolerant of infection with A. Euteiches than non-mycorrhizal plants. This effect was evident even though the A. Euteiches infection levels of mycorrhizal and non-mycorrhizal plants were the same. A. Euteiches enzyme activities in the mycorrhizal plants were different to those in non-mycorrhizal plants. The peaks of PEP and Gd enzyme activity of A. Euteiches were lower and the development of A. Euteiches PEP activity was later in the mycorrhizal plants than in the non-mycorrhizal plants.
Silvio Gianinazzi - One of the best experts on this subject based on the ideXlab platform.
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is a fully established arbuscular mycorrhizal symbiosis required for bioprotection of pisum sativum roots against Aphanomyces Euteiches
Molecular Plant-microbe Interactions, 2000Co-Authors: Sophie Slezack, Eliane Dumasgaudot, Michel Paynot, Silvio GianinazziAbstract:Bioprotection of pea roots against Aphanomyces Euteiches by the arbuscular mycorrhizal fungus G. mosseae was demonstrated to depend on a fully established symbiosis. This was related with induction of mycorrrhiza-related chitinolytic enzymes. Possible mechanisms implicated in bioprotection are discussed.
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endoproteolytic activities in pea roots inoculated with the arbuscular mycorrhizal fungus glomus mosseae and or Aphanomyces Euteiches in relation to bioprotection
New Phytologist, 1999Co-Authors: Sophie Slezack, Rasmus Kjoller, Eliane Dumasgaudot, Michel Paynot, S Rosendahl, Jonathan Negrel, Silvio GianinazziAbstract:summary Arbuscular mycorrhizal (AM) symbioses are known to play a role in increased resistance of plants against soilborne pathogens. Mechanisms involved in this phenomenon are not yet well understood. This work investigates possible roles of endoproteolytic activities in bioprotection of Pisum sativum roots by Glomus mosseae against Aphanomyces Euteiches. First, it is demonstrated that bioprotection occurs only in pre-mycorrhizal plants. Second, endoproteolytic activities were analysed qualitatively and quantitatively during AM symbiosis, in plants infected with either zoospores or mycelium of A. Euteiches, and in mycorrhizal plants infected with the pathogen. In mycorrhizal symbiosis a progressive increase in endoproteolytic activities was observed following root colonization by G. mosseae. By contrast, in roots inoculated with A. Euteiches, a drastic increase in endoproteolytic activities was observed which was correlated with the amount of pathogen occurring in roots. Qualitative dierences were seen among the endoproteolytic activities detected in roots inoculated with zoospores or mycelium. The constitutive as well as mycorrhizal and pathogen-induced activities were further characterized as ‘trypsin-like’ serine endoproteases. Interestingly, in a situation of bioprotection, only low levels of the activities normally associated with the infection by A. Euteiches were detected, suggesting that the synthesis of these proteins is directly linked to the growth or virulence of the pathogen.
Lars Bodker - One of the best experts on this subject based on the ideXlab platform.
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arbuscular mycorrhizal fungi reduce development of pea root rot caused by Aphanomyces Euteiches using oospores as pathogen inoculum
European Journal of Plant Pathology, 2004Co-Authors: Karin Thygesen, John Larsen, Lars BodkerAbstract:The effects of the arbuscular mycorrhizal (AM)-fungi Glomus intraradices and Glomus claroideum on pea root-rot development caused by the pathogen Aphanomyces Euteiches were investigated in a greenhouse pot-experiment, over the course of three harvests, using oospores as pathogen inoculum. Signature whole cell fatty acids 16:1ω5c and 14:1ω9 were used to quantify AM-fungi and A. Euteiches, respectively in both roots and soil. Disease incidence was reduced in AM plants, though this effect was more pronounced in plants with G. intraradices than plants with G. claroideum, and corresponded with a greater mycorrhiza development, both intra- and extra radical in plants with G. intraradices than with G. claroideum. At the final harvest, percentage of root length with oospores was similar in roots of mycorrhizal and non-mycorrhizal plants. Despite the fact that pea root-rot development was only slightly lower in mycorrhizal plants compared to that of non-mycorrhizal plants, in terms of shoot growth and disease severity, mycorrhizal plants suffered less. This suggests a possible mycorrhiza-induced tolerance against pea root-rot. Furthermore, the degree of tolerance induction differed between the two AM-fungi included in the present study.
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Interactions between indigenous arbuscular mycorrhizal fungi and Aphanomyces Euteiches in field-grown pea
Mycorrhiza, 2002Co-Authors: Lars Bodker, Rasmus Kjoller, Kristian Kristensen, Soren RosendahlAbstract:This is the first reported study of the interactions between indigenous arbuscular mycorrhizal fungi (AMF) and Aphanomyces Euteiches in pea under field conditions. A. Euteiches was applied to the soil by adding oospores produced in vitro. Attempts were made to create a non-mycorrhizal control by incorporating carbendazim (Derosal Fl) in the topsoil before sowing. However, all carbendazim-treated plants showed approximately 20% root colonisation with AMF. Pea plants not treated with carbendazim showed a wide variation in AMF colonisation of 35–70% at the full flowering stage. In these control plots, root length infected with oospores of A. Euteiches and colonisation by AMF were negatively correlated. Application of carbendazim increased the percent root length infected with oospores by 50–70%, depending on inoculum density of A. Euteiches . Despite the lower levels of AMF colonisation in these treated plots, a negative correlation with oospore-containing root length was still observed. No correlation was found between AMF colonisation and disease severity, disease incidence or pathogen enzymatic activity (glucose-6-phosphate dehydrogenase). Thus, AMF do not seem to influence the vegetative stage of pathogen development during which cortical root rotting takes place, but rather the reproductive stage when oospores are produced. The results of this study underline the importance of field experiments for validating the significance of mycorrhizal fungi for plant health.
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quantification of Aphanomyces Euteiches in pea roots using specific fatty acids
Fungal Biology, 2000Co-Authors: John Larsen, Keld Mansfeldgiese, Lars BodkerAbstract:The fatty acid composition of pea roots with and without the root pathogen Aphanomyces Euteiches was studied using whole cell fatty acids (WCFA), phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA). Initial screening for A. Euteiches markers using WCFA analysis showed that the fatty acids 14:1·9, 14:0, 20:4 and 20:5 were specific to roots infected with A. Euteiches. The amounts of these fatty acids correlated positively with the percentage of the root system containing A. Euteiches oospores, suggesting that they could be useful indicators of A. Euteiches root-infection levels. Analysis of the composition of phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA) of pea roots with and without A. Euteiches showed similar specificity as found with WCFA analysis. PLFAs and NLFAs specific to roots inoculated with A. Euteiches were also present in mycelium from pure culture of A. Euteiches. The PLFAs 14:0, 20:4 and 20:5 were used to estimate biomass of A. Euteiches and the NLFAs 14:1·9, 14:0, 20:4 and 20:5 were used as indicators of energy reserves of the pathogen. The possible use of specific fatty acids to study growth and development of A. Euteiches in pea roots is discussed.
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effect of phosphate and the arbuscular mycorrhizal fungus glomus intraradices on disease severity of root rot of peas pisum sativum caused by Aphanomyces Euteiches
Mycorrhiza, 1998Co-Authors: Lars Bodker, Rasmus Kjoller, Soren RosendahlAbstract:The effects of inorganic phosphate levels and the presence of arbuscular mycorrhiza on disease severity of Aphanomyces Euteiches in pea roots were studied. Disease severity on roots and epicotyl as well as the oospore number within infected root tissue were correlated with the phosphorus (P) level in the growth medium. The arbuscular mycorrhizal fungus Glomus intraradices increased P uptake and the P concentration in the plant but reduced disease development in peas. Polyacrylamide gel electrophoresis followed by densitometry of glucose-6-phosphate dehydrogenase specific to A.Euteiches was used to measure the activity of the pathogen in roots. The enzyme activity increased with disease severity and disease incidence, except in plants supplemented with P at the highest level, where a peak in activity was seen 12 days after inoculation with the pathogen, followed by a decrease in activity. The epicotyl of mycorrhizal plants showed a reduction in disease severity although this part of the plants was not mycorrhizal. Thus, an induced systemic factor may be responsible for increased resistance in mycorrhizal plants.
Bernard Dumas - One of the best experts on this subject based on the ideXlab platform.
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a dead box rna helicase from medicago truncatula is hijacked by an rna binding effector from the root pathogen Aphanomyces Euteiches to facilitate host infection
bioRxiv, 2020Co-Authors: Laurent Camborde, Bernard Dumas, A Kiselev, Michiel J C Pel, A Leru, Alain Jauneau, Cecile Pouzet, Elodie GaulinAbstract:Abstract Microbial effectors from plant pathogens are molecules that target host components to facilitate colonization. While eukaryotic pathogens are virtually able to produce hundreds of effectors, the molecular mechanisms allowing effectors to promote infection are still largely unexplored. Here we show that the effector AeSSP1256 from the soilborne oomycete pathogen Aphanomyces Euteiches is able to interact with plant RNA. Heterologous expression of AeSSP1256 delays Medicago truncatula host roots development and facilitate pathogen colonization. Transcriptomic analyses of AeSSP1256-expressing roots show a downregulation of genes implicated in ribosome biogenesis pathway. A yeast-two hybrid approach reveals that AeSSP1256 associates with a nucleolar L7 ribosomal protein and a M. truncatula RNA helicase (MtRH10) orthologous to the Arabidopsis RNA helicase RH10. Association of AeSSP1256 with MtRH10 impaired the capacity of MtRH10 to bind nucleic acids. Promoter:GUS composite plants revealed that MtRH10 is expressed preferentially in the meristematic root cells. Missense MtRH10 plants displayed shorter roots with developmental delay and are more susceptible to A. Euteiches infection. These results show that the effector AeSSP1256 facilitates pathogen infection by causing stress on plant ribosome biogenesis and by hijacking a host RNA helicase involved in root development and resistance to root pathogens.
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a local score approach improves gwas resolution and detects minor qtl application to medicago truncatula quantitative disease resistance to multiple Aphanomyces Euteiches isolates
Heredity, 2019Co-Authors: Maxime Bonhomme, Bernard Dumas, Alain Baranger, Yacine Badis, Henri Miteul, Maria Ines Fariello, Helene Navier, Ahmed Hajri, Deborah A Samac, Christophe JacquetAbstract:Quantitative trait loci (QTL) with small effects, which are pervasive in quantitative phenotypic variation, are difficult to detect in genome-wide association studies (GWAS). To improve their detection, we propose to use a local score approach that accounts for the surrounding signal due to linkage disequilibrium, by accumulating association signals from contiguous single markers. Simulations revealed that, in a GWAS context with high marker density, the local score approach outperforms single SNP p-value-based tests for detecting minor QTL (heritability of 5-10%) and is competitive with regard to alternative methods, which also aggregate p-values. Using more than five million SNPs, this approach was applied to identify loci involved in Quantitative Disease Resistance (QDR) to different isolates of the plant root rot pathogen Aphanomyces Euteiches, from a GWAS performed on a collection of 174 accessions of the model legume Medicago truncatula. We refined the position of a previously reported major locus, underlying MYB/NB-ARC/tyrosine kinase candidate genes conferring resistance to two closely related A. Euteiches isolates belonging to pea pathotype I. We also discovered a diversity of minor resistance QTL, not detected using p-value-based tests, some of which being putatively shared in response to pea (pathotype I and III) and/or alfalfa (race 1 and 2) isolates. Candidate genes underlying these QTL suggest pathogen effector recognition and plant proteasome as key functions associated with M. truncatula resistance to A. Euteiches. GWAS on any organism can benefit from the local score approach to uncover many weak-effect QTL.
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Hydrogen peroxide scavenging mechanisms are components of Medicago truncatula partial resistance to Aphanomyces Euteiches
European Journal of Plant Pathology, 2011Co-Authors: Naceur Djebali, Bernard Dumas, Claude Lafitte, Mohamed Elarbi Aouani, Haythem Mhadhbi, Marie-thérèse Esquerré-tugayé, Christophe JacquetAbstract:The biochemical processes underlying the expression of resistance in the roots of Medicago truncatula against Aphanomyces Euteiches infection was investigated, with emphasis on oxidative stress. The levels of H_2O_2, superoxide dismutase, peroxidase, ascorbate peroxidase, catalase, soluble phenolics and lignin were measured in the roots of two lines, A17 partially resistant and F83005.5 susceptible to A. Euteiches at three infection stages; penetration of the epidermis (1 dpi), colonization of the cortex (3 dpi) and invasion of the root stele (6 dpi). A rapid and large decrease of the H_2O_2 levels in A17 roots occurred. However, in F83005.5 roots, the decrease in H_2O_2 levels was delayed until 3 dpi. In A17 roots, the activities of ascorbate peroxidase, peroxidase and catalase were induced as early as 1 dpi, whereas a general decrease in the activity of the four antioxidant enzymes was observed in F83005.5 roots. The levels of soluble phenolics and lignin were increased in A17 roots at 3 and 6 dpi, respectively. The H_2O_2 levels were negatively correlated to ascorbate peroxidase, catalase and lignin production at 1, 3 and 6 dpi, respectively in A17 roots. Physiological concentrations of H_2O_2 found in M. truncatula infected roots had no detrimental effect on the in vitro growth of this oomycete. Our data suggest that H_2O_2 does not have a direct antimicrobial effect on M. truncatula resistance to A. Euteiches , but is involved in cell wall strengthening around the root stele, preventing pathogen invasion of the vascular tissues.
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sterol metabolism in the oomycete Aphanomyces Euteiches a legume root pathogen
New Phytologist, 2009Co-Authors: Mohammedamine Madoui, Elodie Gaulin, Bernard Dumas, Justine BertrandmichelAbstract:Summary • Sterols are isoprenoid-derived molecules that have essential functions in eukaryotes but whose metabolism remains largely unknown in a large number of organisms. Oomycetes are fungus-like microorganisms that are evolutionarily related to stramenopile algae, a large group of organisms for which no sterol metabolic pathway has been reported. Here, we present data that support a model of sterol biosynthesis in Aphanomyces Euteiches, an oomycete species causing devastating diseases in legume crops. • In silico analyses were performed to identify genes encoding enzymes involved in the conversion of the isoprenoid precursor 3-hydroxy-3-methylglutaryl coenzyme A to isoprenoids. Several metabolic intermediates and two major sterol end-products were identified by gas chromatography–mass spectroscopy. • We show that A. Euteiches is able to produce fucosterol (a sterol initially identified in brown algae) and cholesterol (the major animal sterol). Mycelium development is inhibited by two sterol demethylase inhibitors used as fungicides, namely tebuconazole and epoxiconazole. • We propose the first sterol biosynthetic pathway identified in a stramenopile species. Phylogenetic analyses revealed close relationships between A. Euteiches enzyme sequences and those found in stramenopile algae, suggesting that part of this pathway could be conserved in the Stramenopila kingdom.
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cell wall chitosaccharides are essential components and exposed patterns of the phytopathogenic oomycete Aphanomyces Euteiches
Eukaryotic Cell, 2008Co-Authors: Ilham Badreddine, Vincent Bulone, Bernard Dumas, Claude Lafitte, Laurent Heux, Nicholas Skandalis, Zacharoula Spanou, Yves Martinez, Marietherese Esquerretugaye, Arnaud BottinAbstract:Chitin is an essential component of fungal cell walls, where it forms a crystalline scaffold, and chitooligosaccharides derived from it are signaling molecules recognized by the hosts of pathogenic fungi. Oomycetes are cellulosic fungus-like microorganisms which most often lack chitin in their cell walls. Here we present the first study of the cell wall of the oomycete Aphanomyces Euteiches, a major parasite of legume plants. Biochemical analyses demonstrated the presence of ca. 10% N-acetyl-D-glucosamine (GlcNAc) in the cell wall. Further characterization of the GlcNAc-containing material revealed that it corresponds to noncrystalline chitosaccharides associated with glucans, rather than to chitin per se. Two putative chitin synthase (CHS) genes were identified by data mining of an A. Euteiches expressed sequence tag collection and Southern blot analysis, and full-length cDNA sequences of both genes were obtained. Phylogeny analysis indicated that oomycete CHS diversification occurred before the divergence of the major oomycete lineages. Remarkably, lectin labeling showed that the Aphanomyces Euteiches chitosaccharides are exposed at the cell wall surface, and study of the effect of the CHS inhibitor nikkomycin Z demonstrated that they are involved in cell wall function. These data open new perspectives for the development of antioomycete drugs and further studies of the molecular mechanisms involved in the recognition of pathogenic oomycetes by the host plants.