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Andrea Polle - One of the best experts on this subject based on the ideXlab platform.
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amelioration of nitrate uptake under salt stress by ectomycorrhiza with and without a hartig net
New Phytologist, 2019Co-Authors: Jun Yao, Andrea Polle, Chen Deng, Jian Liu, Yinan Zhang, Zhimei Zhu, Yuhong Zhang, Rui Zhao, Shanzhi LinAbstract:Salt stress is an important environmental cue impeding poplar nitrogen nutrition. Here, we characterized the impact of salinity on proton-driven nitrate fluxes in ectomycorrhizal roots and the importance of a Hartig net for nitrate uptake. We employed two Paxillus involutus strains for root colonization: MAJ, which forms typical ectomycorrhizal structures (mantle and Hartig net), and NAU, colonizing roots with a thin, loose hyphal sheath. Fungus-colonized and noncolonized Populus × canescens were exposed to sodium chloride and used to measure root surface pH, nitrate (NO3 - ) flux and transcription of NO3 - transporters (NRTs; PcNRT1.1, -1.2, -2.1), and plasmalemma proton ATPases (HAs; PcHA4, -8, -11). Paxillus colonization enhanced root NO3 - uptake, decreased surface pH, and stimulated NRTs and HA4 of the host regardless the presence or absence of a Hartig net. Under salt stress, noncolonized roots exhibited strong net NO3 - efflux, whereas beneficial effects of fungal colonization on surface pH and HAs prevented NO3 - loss. Inhibition of HAs abolished NO3 - influx under all conditions. We found that stimulation of HAs was crucial for the beneficial influence of ectomycorrhiza on NO3 - uptake, whereas the presence of a Hartig net was not required for improved NO3 - translocation. Mycorrhizas may contribute to host adaptation to salt-affected environments by keeping up NO3 - nutrition.
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peroxidase activity in poplar inoculated with compatible and incompetent isolates of Paxillus involutus
Hayati Journal of Biosciences, 2007Co-Authors: Abdul Gafur, Andres Schutzendubel, Andrea PolleAbstract:Peroxidase activity of the hybrid poplar Populus x canescens (Ait.) Sm. (= P. tremula L. x P. alba L.) inoculated with compatible and incompetent isolates of Paxillus involutus (Batsch) Fr. was investigated. Screening of the ectomycorrhizal fungal isolates was initiated with exploration of mycelial growth characteristics and mycorrhizal ability in vitro with poplar. Both traits varied within the fungus although they did not seem to be genetically correlated. While isolates SCO1, NAU, and 031 grew faster than others, only isolates MAJ, SCO1, and 031 were able to form ectomycorrhiza with poplar. Isolates MAJ (compatible) and NAU (incompetent) were subsequently selected for further experiments. Activity of peroxidase, one of the defense-related enzymes, was examined in pure culture and short root components of compatible and incompetent interactions between poplar and P. involutus. Peroxidase activities increased significantly in poplar inoculated with incompetent isolate of the fungus compared to control, while induction of the same enzyme was not detected in compatible associations. Key words: ectomycorrhiza, Paxillus involutus, peroxidase, plant defense, poplar
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Paxillus involutus mycorrhiza attenuate nacl stress responses in the salt sensitive hybrid poplar populus canescens
Mycorrhiza, 2007Co-Authors: Rosemarie Langenfeldheyser, Ph Tachd, C F Lu, Eberhard Fritz, Tanja Dučić, Abdul Gafur, Andrea PolleAbstract:In order to characterise the effect of ectomycorrhiza on Na+-responses of the salt-sensitive poplar hybrid Populus × canescens, growth and stress responses of Paxillus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because total biomass was greater and leaves accumulated less Na+ than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the influence of mycorrhization on the subcellular localisation of Na+ and Cl− in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained higher Na+ and Cl− concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H2O2 in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H2O2 formation in cortical cells of both non-mycorrhizal and mycorrhizal poplar and stimulated peroxidase but not superoxide dismutase activities. This shows that mature ectomycorrhiza was unable to suppress salt-induced oxidative stress. Element analyses suggest that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na+ and increased supply with K+.
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Paxillus involutus mycorrhiza attenuate nacl stress responses in the salt sensitive hybrid poplar
2007Co-Authors: C F Lu, Eberhard Fritz, Abdul Gafur, Andrea PolleAbstract:In order to characterise the effect of ectomycor- rhiza on Na + -responses of the salt-sensitive poplar hybrid Populus×canescens, growth and stress responses of Pax- illus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because total biomass was greater and leaves accumulated less Na + than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the influence of mycorrhization on the subcel- lular localisation of Na + and Cl − in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained higher Na + and Cl − concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H2O2 in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H2O2 formation in cortical cells of both non- mycorrhizal and mycorrhizal poplar and stimulated perox- idase but not superoxide dismutase activities. This shows that mature ectomycorrhiza was unable to suppress salt- induced oxidative stress. Element analyses suggest that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na + and increased supply with K + .
Abdul Gafur - One of the best experts on this subject based on the ideXlab platform.
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peroxidase activity in poplar inoculated with compatible and incompetent isolates of Paxillus involutus
Hayati Journal of Biosciences, 2007Co-Authors: Abdul Gafur, Andres Schutzendubel, Andrea PolleAbstract:Peroxidase activity of the hybrid poplar Populus x canescens (Ait.) Sm. (= P. tremula L. x P. alba L.) inoculated with compatible and incompetent isolates of Paxillus involutus (Batsch) Fr. was investigated. Screening of the ectomycorrhizal fungal isolates was initiated with exploration of mycelial growth characteristics and mycorrhizal ability in vitro with poplar. Both traits varied within the fungus although they did not seem to be genetically correlated. While isolates SCO1, NAU, and 031 grew faster than others, only isolates MAJ, SCO1, and 031 were able to form ectomycorrhiza with poplar. Isolates MAJ (compatible) and NAU (incompetent) were subsequently selected for further experiments. Activity of peroxidase, one of the defense-related enzymes, was examined in pure culture and short root components of compatible and incompetent interactions between poplar and P. involutus. Peroxidase activities increased significantly in poplar inoculated with incompetent isolate of the fungus compared to control, while induction of the same enzyme was not detected in compatible associations. Key words: ectomycorrhiza, Paxillus involutus, peroxidase, plant defense, poplar
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Paxillus involutus mycorrhiza attenuate nacl stress responses in the salt sensitive hybrid poplar populus canescens
Mycorrhiza, 2007Co-Authors: Rosemarie Langenfeldheyser, Ph Tachd, C F Lu, Eberhard Fritz, Tanja Dučić, Abdul Gafur, Andrea PolleAbstract:In order to characterise the effect of ectomycorrhiza on Na+-responses of the salt-sensitive poplar hybrid Populus × canescens, growth and stress responses of Paxillus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because total biomass was greater and leaves accumulated less Na+ than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the influence of mycorrhization on the subcellular localisation of Na+ and Cl− in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained higher Na+ and Cl− concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H2O2 in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H2O2 formation in cortical cells of both non-mycorrhizal and mycorrhizal poplar and stimulated peroxidase but not superoxide dismutase activities. This shows that mature ectomycorrhiza was unable to suppress salt-induced oxidative stress. Element analyses suggest that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na+ and increased supply with K+.
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Paxillus involutus mycorrhiza attenuate nacl stress responses in the salt sensitive hybrid poplar
2007Co-Authors: C F Lu, Eberhard Fritz, Abdul Gafur, Andrea PolleAbstract:In order to characterise the effect of ectomycor- rhiza on Na + -responses of the salt-sensitive poplar hybrid Populus×canescens, growth and stress responses of Pax- illus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because total biomass was greater and leaves accumulated less Na + than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the influence of mycorrhization on the subcel- lular localisation of Na + and Cl − in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained higher Na + and Cl − concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H2O2 in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H2O2 formation in cortical cells of both non- mycorrhizal and mycorrhizal poplar and stimulated perox- idase but not superoxide dismutase activities. This shows that mature ectomycorrhiza was unable to suppress salt- induced oxidative stress. Element analyses suggest that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na + and increased supply with K + .
Anders Tunlid - One of the best experts on this subject based on the ideXlab platform.
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the carbon starvation response of the ectomycorrhizal fungus Paxillus involutus
FEMS Microbiology Ecology, 2015Co-Authors: Magnus Ellstrom, Firoz Shah, Dag Ahren, Tomas Johansson, Per Persson, Anders TunlidAbstract:The amounts of carbon allocated to the fungal partner in ectomycorrhizal associations can vary substantially depending on the plant growth and the soil nutrient conditions, and the fungus may frequently be confronted with limitations in carbon. We used chemical analysis and transcriptome profiling to examine the physiological response of the ectomycorrhizal fungus Paxillus involutus to carbon starvation during axenic cultivation. Carbon starvation induced a decrease in the biomass. Concomitantly, ammonium, cell wall material (chitin) and proteolytic enzymes were released into the medium, which suggest autolysis. Compared with the transcriptome of actively growing hyphae, about 45% of the transcripts analyzed were differentially regulated during C-starvation. Induced during starvation were transcripts encoding extracellular enzymes such as peptidases, chitinases and laccases. In parallel, transcripts of N-transporters were upregulated, which suggest that some of the released nitrogen compounds were re-assimilated by the mycelium. The observed changes suggest that the carbon starvation response in P. involutus is associated with complex cellular changes that involves autolysis, recycling of intracellular compounds by autophagy and reabsorption of the extracellular released material. The study provides molecular markers that can be used to examine the role of autolysis for the turnover and survival of the ectomycorrhizal mycelium in soils.
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variation in host specificity and gene content in strains from genetically isolated lineages of the ectomycorrhizal fungus Paxillus involutus s lat
Mycorrhiza, 2009Co-Authors: Jenny Hedh, Tomas Johansson, Anders TunlidAbstract:Ectomycorrhizal fungi are known to vary in host range. Some fungi can enter into symbiosis with multiple plant species, while others have restricted host ranges. The aim of this study was to examine variation in host specificity among strains from the basidiomycete Paxillus involutus s. lat. Recent studies have shown that this fungus consists of at least four genetically isolated lineages, phylogenetic species (PS) I (which corresponds to the morphological species Paxillus obscurosporus), PS II (P. involutus s. str.), PS III (Paxillus validus), and PS IV (not yet supported by any reference material). Thirty-five Paxillus strains of PS I to IV were examined in microcosms for their capacity to infect birch (Betula pendula) and spruce (Picea abies). Seventeen strains were compatible and formed mycorrhizae with both tree species. Seven strains were incompatible with both birch and spruce. The gene content in three pairs of incompatible and compatible strains PS I, II, and III were compared using microarray-based comparative genomic hybridizations. Of 4,113 P. involutus gene representatives analyzed, 390 varied in copy numbers in at least one of the three pairwise comparisons. Only three reporters showed significant changes in all three pairwise comparisons, and none of these were changed in a similar way in three comparisons. Our data indicate that changes in host range have occurred frequently and independently among strains in P. obscurosporus, P. involutus s. str., and P. validus. No evidence was obtained demonstrating that these changes have been associated with the gain or loss of similar genes in these three species.
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evolution of nucleotide sequences and expression patterns of hydrophobin genes in the ectomycorrhizal fungus Paxillus involutus
New Phytologist, 2007Co-Authors: Balaji Rajashekar, Tomas Johansson, Peter Samson, Anders TunlidAbstract:Hydrophobins are small, secreted proteins that play important roles in the development of pathogenic and symbiotic fungi. Evolutionary mechanisms generating sequence and expression divergence among members in hydrophobin gene families are largely unknown. Seven hydrophobin (hyd) genes and one hyd pseudogene were isolated from strains of the ectomycorrhizal fungus Paxillus involutus. Sequences were analysed using phylogenetic methods. Expression profiles were inferred from microarray experiments. The hyd genes included both young (recently diverged) and old duplicates. Some young hyd genes exhibited an initial phase of enhanced sequence evolution owing to relaxed or positive selection. There was no significant association between sequence divergence and variation in expression levels. However, three hyd genes displayed a shift in the expression levels or an altered tissue specificity following duplication. The Paxillus hyd genes evolve according to the so-called birth-and-death model in which some duplicates are maintained for a long time, whereas others are inactivated through mutations. The role of subfunctionalization and/or neofunctionalization for preserving the hyd duplicates in the genome is discussed. (Less)
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evolution of nucleotide sequences and expression patterns of hydrophobin genes in the ectomycorrhizal fungus Paxillus involutus
New Phytologist, 2007Co-Authors: Balaji Rajashekar, Tomas Johansson, Peter Samson, Anders TunlidAbstract:Hydrophobins are small, secreted proteins that play important roles in the development of pathogenic and symbiotic fungi. Evolutionary mechanisms generating sequence and expression divergence among members in hydrophobin gene families are largely unknown. Seven hydrophobin (hyd) genes and one hyd pseudogene were isolated from strains of the ectomycorrhizal fungus Paxillus involutus. Sequences were analysed using phylogenetic methods. Expression profiles were inferred from microarray experiments. The hyd genes included both young (recently diverged) and old duplicates. Some young hyd genes exhibited an initial phase of enhanced sequence evolution owing to relaxed or positive selection. There was no significant association between sequence divergence and variation in expression levels. However, three hyd genes displayed a shift in the expression levels or an altered tissue specificity following duplication. The Paxillus hyd genes evolve according to the so-called birth-and-death model in which some duplicates are maintained for a long time, whereas others are inactivated through mutations. The role of subfunctionalization and/or neofunctionalization for preserving the hyd duplicates in the genome is discussed.
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screening for rapidly evolving genes in the ectomycorrhizal fungus Paxillus involutus using cdna microarrays
Molecular Ecology, 2005Co-Authors: Antoine Le Quere, Andres Schutzendubel, Kasper Astrup Eriksen, Bjorn Canback, Tomas Johansson, Balaji Rajashekar, Anders TunlidAbstract:We have examined the variations in gene content and sequence divergence that could be associated with symbiotic adaptations in the ectomycorrhizal fungus Paxillus involutus and the closely related species Paxillus filamentosus. Strains with various abilities to form mycorrhizae were analysed by comparative genomic hybridizations using a cDNA microarray containing 1076 putative unique genes of P. involutus. To screen for genes diverging at an enhanced and presumably non-neutral rate, we implemented a simple rate test using information from both the variations in hybridizations signal and data on sequence divergence of the arrayed genes relative to the genome of Coprinus cinereus. C. cinereus is a free-living saprophyte and is the closest evolutionary relative to P. involutus that has been fully sequenced. Approximately 17% of the genes investigated were detected as rapidly diverging within Paxillus. Furthermore, 6% of the genes varied in copy numbers between the analysed strains. Genome rearrangements associated with this variation including duplications and deletions may also play a role in adaptive evolution. The cohort of divergent and duplicated genes showed an over-representation of either orphans, genes whose products are located at membranes, or genes encoding for components of stress/defence reactions. Some of the identified genomic changes may be associated with the variation in host specificity of ectomycorrhizal fungi. The proposed procedure could be generally applicable to screen for rapidly evolving genes in closely related strains or species where at least one has been sequenced or characterized by expressed sequence tag analysis.
Michel Chalot - One of the best experts on this subject based on the ideXlab platform.
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cadmium responsive thiols in the ectomycorrhizal fungus Paxillus involutus
Applied and Environmental Microbiology, 2004Co-Authors: Mikael Courbot, Laurent Diez, Roberta Ruotolo, Michel Chalot, Pierre LeroyAbstract:Molecular and cellular mechanisms underlying the sustained metal tolerance of ectomycorrhizal fungi are largely unknown. Some of the main mechanisms involved in metal detoxification appear to involve the chelation of metal ions in the cytosol with thiol-containing compounds, such as glutathione, phytochelatins, or metallothioneins. We used an improved high-performance liquid chromatography method for the simultaneous measurement of thiol-containing compounds from cysteine and its derivatives (γ-glutamylcysteine, glutathione) to higher-molecular-mass compounds (phytochelatins). We found that glutathione and γ-glutamylcysteine contents increased when the ectomycorrhizal fungus Paxillus involutus was exposed to cadmium. An additional compound with a 3-kDa molecular mass, most probably related to a metallothionein, increased drastically in mycelia exposed to cadmium. The relative lack of phytochelatins and the presence of a putative metallothionein suggest that ectomycorrhizal fungi may use a different means to tolerate heavy metals, such as Cd, than do their plant hosts.
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transcriptomic responses to cadmium in the ectomycorrhizal fungus Paxillus involutus
FEBS Letters, 2004Co-Authors: Christophe Jacob, Mikael Courbot, Francis Martin, Annick Brun, Michel ChalotAbstract:Abstract The molecular mechanisms underlying the response of ectomycorrhizal fungi to heavy metals in general and cadmium in particular remain poorly understood. We screened 2040 arrayed cDNAs of the ectomycorrhizal fungus Paxillus involutus to identify cadmium-responsive genes by using differential hybridization. Forty nine (2.4%) of the 2040 cDNAs were differentially expressed, among which transcripts coding a laccase, an aconitase, and a metallothionein were upregulated by 3.9-, 3.7- and 2.8-fold, respectively, whereas genes coding hydrophobins and threonine dehydratase were strongly downregulated. Our results suggest that complexation of cadmium by phenolic compounds, or by complexing peptides such as metallothioneins, is probably key determinant of the cellular response to cadmium in P. involutus . In addition, the present study suggests that the synthesis of hydrophobins may be efficiently reduced, thus redirecting Cys to the manufacture of Cys-enriched compounds.
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metabolism of n 15 alanine in the ectomycorrhizal fungus Paxillus involutus
Experimental Mycology, 1995Co-Authors: Michel Chalot, Roger D. Finlay, Hans Ek, Bengt SoderstromAbstract:Alanine metabolism in the ectomycorrhizal fungus Paxillus involutus was investigated using [N-15]alanine. Short-term exposure of mycelial discs to [N-15]alanine showed that the greatest flow of N-15 was to glutamate and to aspartate. Levels of enrichment were as high as 15-20% for glutamate and 13-18% for aspartate, whereas that of alanine reached 30%. Label was also detected in the amino-N of glutamine and in serine and glycine, although at lower levels. Preincubation of mycelia with aminooxyacetate, an inhibitor of transamination reactions, resulted in complete inhibition of the flow of the label to glutamate, aspartate, and amino-N of glutamine, whereas [N-15]alanine rapidly accumulated. This evidence indicates the direct involvement of alanine aminotransferase for translocation of N-15 from alanine to glutamate. Alanine may be a convenient reservoir of both nitrogen and carbon. (C) 1995 Academic Press, Inc. (Less)
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factors affecting amino acid uptake by the ectomycorrhizal fungus Paxillus involutus
Fungal Biology, 1995Co-Authors: Michel Chalot, Roger D. Finlay, Minnamaarit Kytoviita, Annick Brun, Bengt SoderstromAbstract:Factors affecting amino acid uptake by the ectomycorrhizal fungus Paxillus involutus were investigated using tracer kinetic experiments. Amino acid uptake by P. involutus was dependent on the pH of the incubation medium. Uptake of L-glutamate and L-glutamine had a distinct pH optimum around pH 4.0 and declined sharply between pH 4.5 and 6.4. Uptake of alanine and aspartate was also highest at low pH values (3-4) but declined more slowly with increasing pH. Total uptake of labelled amino acids was unaffected by 0.05 or 0.5 mM ammonium while 5 mM ammonium decreased amino acid uptake. Nitrate or glucose did not significantly affect amino acid uptake but glucose greatly increased the proportion of carbon that was respired. Uptake of the different amino acids decreased by a factor of 4 to 10 with increasing age (1-5 wk) and the proportion of absorbed C-14 that was respired increased with age. Changes in the size of the total amino acid pool were inversely related to those in the rate of uptake and the pool increased steadily with age. The implications of the ability of P. involutus to take up amino acids are discussed. (Less)
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respiration of 14c alanine by the ectomycorrhizal fungus Paxillus involutus
Fems Microbiology Letters, 1994Co-Authors: Michel Chalot, Roger D. Finlay, Annick Brun, Bengt SoderstromAbstract:The ectomycorrhizal fungus Paxillus involutus efficiently took up exogenously supplied [14C]alanine and rapidly converted it to pyruvate, citrate, succinate, fumarate and to CO2, thus providing direct evidence for the utilisation of alanine as a respiratory substrate. [14C]alanine was further actively metabolised to glutamate, glutamine and aspartate. Exposure to aminooxyacetate completely suppressed 14CO2 evolution and greatly reduced the flow of carbon from [14C]alanine to tricarboxylic acid cycle intermediates and amino acids, suggesting that alanine aminotransferase plays a pivotal role in alanine metabolism in Paxillus involutus.
Rosemarie Langenfeldheyser - One of the best experts on this subject based on the ideXlab platform.
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effect of nacl on growth and ion relations in two salt tolerant strains of Paxillus involutus
Forestry Studies in China, 2008Co-Authors: Hua Zhang, Cunfu Lu, Lisi Li, Meijuan Wang, Ruigang Wang, Shaoliang Chen, Yanjun Lu, Yunxia Zhang, Jing Li, Rosemarie LangenfeldheyserAbstract:The effect of NaCl on growth, biomass and ion relations of two salt-tolerant isolates of Paxillus involutus, MAJ and NAU were investigated. The two Paxillus strains were exposed to the following concentrations of NaCl: 0, 100, 200 and 500 mmol·L−1. Growth of MAJ and NAU was enhanced by 100 mmol·L−1 NaCl but severely inhibited at the concentration of 500 mmol·L−1. NAU exhibited a greater capacity to exclude Na+ and Cl− under all salinity levels, whereas the salt-includer MAJ had a higher capacity in nutrient uptake under salt stress. The ratios Na+/K+, Na+/Ca2+ and Na+/Mg2+ in NaCl-treated MAJ and NAU did not increase at levels of 100 and 200 mmol·L−1 NaCl but markedly increased at 500 mmol·L−1. This suggests that the two strains, especially MAJ, enhanced nutrient uptake corresponding to the increased Na+ influx at moderate salinity. We conclude that both MAJ and NAU are able to tolerate 500 mmol·L−1 NaCl but there are species-specific differences in retaining ionic homeostasis in the two Paxillus strains. NAU is a salt-excluder, MAJ is a salt-includer but retains a high capacity in nutrient selectivity under saline conditions. Their definite mechanisms to enhance salt tolerance of mycorrhizal hosts need further study.
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Paxillus involutus mycorrhiza attenuate nacl stress responses in the salt sensitive hybrid poplar populus canescens
Mycorrhiza, 2007Co-Authors: Rosemarie Langenfeldheyser, Ph Tachd, C F Lu, Eberhard Fritz, Tanja Dučić, Abdul Gafur, Andrea PolleAbstract:In order to characterise the effect of ectomycorrhiza on Na+-responses of the salt-sensitive poplar hybrid Populus × canescens, growth and stress responses of Paxillus involutus (strain MAJ) were tested in liquid cultures in the presence of 20 to 500 mM NaCl, and the effects of mycorrhization on mineral nutrient accumulation and oxidative stress were characterised in mycorrhizal and non-mycorrhizal poplar seedlings exposed to 150 mM NaCl. Paxillus involutus was salt tolerant, showing biomass increases in media containing up to 500 mM NaCl after 4 weeks growth. Mycorrhizal mantle formation on poplar roots was not affected by 150 mM NaCl. Whole plant performance was positively affected by the fungus because total biomass was greater and leaves accumulated less Na+ than non-mycorrhizal plants. Energy dispersive X-ray microanalysis using transmission electron microscopy analysis of the influence of mycorrhization on the subcellular localisation of Na+ and Cl− in roots showed that the hyphal mantle did not diminish salt accumulation in root cell walls, indicating that mycorrhization did not provide a physical barrier against excess salinity. In the absence of salt stress, mycorrhizal poplar roots contained higher Na+ and Cl− concentrations than non-mycorrhizal poplar roots. Paxillus involutus hyphae produced H2O2 in the mantle but not in the Hartig net or in pure culture. Salt exposure resulted in H2O2 formation in cortical cells of both non-mycorrhizal and mycorrhizal poplar and stimulated peroxidase but not superoxide dismutase activities. This shows that mature ectomycorrhiza was unable to suppress salt-induced oxidative stress. Element analyses suggest that improved performance of mycorrhizal poplar under salt stress may result from diminished xylem loading of Na+ and increased supply with K+.