Interaction between the Ectomycorrhizal Fungus Paxillus involutus, Damping-off Fungi and Pinus resinosa Seedlings

Seedlings of Pinus resinosa Ait. grown in test tubes were inoculated with the ectomycorrhizal fungus Paxillus involutus Fr. Oxalic acid was identified as one of the ethanol-soluble fungistatic and (or) fungitoxic components of the rhizosphere after fractionation by high performance liquid chromatography, paper chromatography, and gel filtration. Simultaneous inoculation of P. resinosa seedlings with authentic oxalic acid and a spore suspension of Fusarium oxysporum f.sp. pini protected the seedlings against Fusarium root rot and decreased the sporulation of F. oxysporum in the rhizosphere when compared with controls lacking oxalic acid. Quantitation of oxalic acid showed a five fold increase in production by Pax. involutus in tubes containing P. resinosa seedlings when compared with tubes lacking seedlings. The synthesis of oxalic acid by Pax. involutus is, therefore, stimulated by P. resinosa root exudate.

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Early effects of the ectomycorrhizal fungus Paxillus involutus on the root rot organism Fusarium associated with Pinus resinosa

Canadian Journal of Botany ◽

10.1139/b90-204 ◽

1990 ◽

Vol 68 (7) ◽

pp. 1589-1596 ◽

Cited By ~ 6

Author(s):

M. L. Farquhar ◽

R. L. Peterson

Keyword(s):

Pinus Resinosa ◽

Ectomycorrhizal Fungus ◽

Test Tube ◽

Disease Suppression ◽

Wall Material ◽

Paxillus Involutus ◽

Calcofluor White ◽

Cytoplasmic Inclusions ◽

Early Effects ◽

Root Tissues

Infection of Pinus resinosa Ait. seedlings in a sterile test tube culture system by Fusarium oxysporum f.sp. pini Schlecht. emend. Snyd. & Hans., which was determined microscopically by the presence of the fungus within root tissues, was significantly reduced within the first 6 days of infection after prior inoculation with the ectomycorrhizal fungus Paxillus involutus (Batsch) Fr. Hyphae and conidia of the pathogen were swollen and filled with osmiophilic material when P. involutus was also present in the rhizosphere of P. resinosa seedlings. Germination of F. oxysporum conidia was suppressed when they were placed in holes in P. involutus cultures on modified Melin Norkrans medium in Petri plates but was restored with removal of conidia from plates. Suppressed, ungerminated conidia had thick cell walls and large cytoplasmic inclusions. Staining using Calcofluor White M2R New revealed changes in the binding properties of septal wall material. Key words: Paxillus, Fusarium, ectomycorrhiza, disease suppression, anatomy.

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Interaction between the ectomycorrhizal fungus Paxillus involutus and Pinus resinosa induces resistance to Fusarium oxysporum

Canadian Journal of Botany ◽

10.1139/b88-080 ◽

1988 ◽

Vol 66 (3) ◽

pp. 558-562 ◽

Cited By ~ 61

Author(s):

Luc C. Duchesne ◽

R. L. Peterson ◽

Brian E. Ellis

Keyword(s):

Fusarium Oxysporum ◽

Seedling Survival ◽

Pathogenic Fungus ◽

Pinus Resinosa ◽

Ectomycorrhizal Fungus ◽

Antibiotic Activity ◽

Disease Suppression ◽

Paxillus Involutus ◽

Subsequent Infection ◽

Fivefold Increase

Inoculation of Pinus resinosa Ait. seedlings with the ectomycorrhizal fungus Paxillus involutus Fr. resulted in a 47% increase in resistance to subsequent infection by the root pathogenic fungus Fusarium oxysporum f.sp. pini as compared with control seedlings. This increase in seedling survival was associated with a sixfold decrease in the sporulation of F. oxysporum in the rhizosphere of seedlings inoculated with Pax. involutus when compared with the rhizosphere of control seedlings. Extraction and bioassay of the seedling rhizosphere and seedling tissues indicated that inoculation with Pax. involutus led to a fivefold increase in antibiotic activity in the rhizosphere of the seedlings treated with Pax. involutus. Most or all of the fungitoxicity was localized in the rhizosphere. Disease suppression by Pax. involutus in P. resinosa is, therefore, associated with an increase of fungitoxic chemicals in the rhizosphere of seedlings.

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Later events in suppression of Fusarium root rot of red pine seedlings by the ectomycorrhizal fungus Paxillus involutus

Canadian Journal of Botany ◽

10.1139/b91-177 ◽

1991 ◽

Vol 69 (6) ◽

pp. 1372-1383 ◽

Cited By ~ 12

Author(s):

M. L. Farquhar ◽

R. L. Peterson

Keyword(s):

Pinus Resinosa ◽

Ectomycorrhizal Fungus ◽

Red Pine ◽

Disease Suppression ◽

Host Cells ◽

Paxillus Involutus ◽

Free System ◽

Primary Roots ◽

Pine Seedlings ◽

Rooting Medium

Colonization of primary roots of red pine (Pinus resinosa Ait.) seedlings by two isolates of the fungal pathogen Fusarium oxysporum Schlecht. emend Snyd. & Hans. f.sp. pini in a sterile, soil-free system and a nonsterile rooting medium was suppressed for 2 months if the roots were exposed to the ectomycorrhizal fungus Paxillus involutus (Batsch.) Fr. for 1 week before being inoculated with the pathogen. Roots of protected seedlings harboured only a few hyphae of the pathogen. These were either vacuolated or filled with slightly electron-dense substances and did not penetrate host cells. In contrast, roots of seedlings not inoculated by P. involutus were extensively colonized by F. oxysporum, and host tissue vacuolation and disorganization occurred. Papillae, consisting of either small protuberances or elongate projections, were infrequently formed in response to infection. Chlamydospores of F. oxysporum that formed in the sterile system had numerous lipid deposits and amorphous thick walls but few mitochondria and little endoplasmic reticulum. Key words: biological control, ectomycorrhiza, Fusarium, Pinus resinosa, disease suppression.

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Secretion of Iron(III)-Reducing Metabolites during Protein Acquisition by the Ectomycorrhizal Fungus Paxillus involutus

Microorganisms ◽

10.3390/microorganisms9010035 ◽

2020 ◽

Vol 9 (1) ◽

pp. 35

Author(s):

Firoz Shah ◽

Markus Gressler ◽

Susan Nehzati ◽

Michiel Op De Beeck ◽

Luigi Gentile ◽

...

Keyword(s):

Fenton Reaction ◽

Ectomycorrhizal Fungus ◽

Paxillus Involutus ◽

Environmental Cues ◽

Rapid Reduction ◽

Fenton Chemistry ◽

X Ray ◽

Solid Iron ◽

X Ray Absorption ◽

Step Mechanism

The ectomycorrhizal fungus Paxillus involutus decomposes proteins using a two-step mechanism, including oxidation and proteolysis. Oxidation involves the action of extracellular hydroxyl radicals (•OH) generated by the Fenton reaction. This reaction requires the presence of iron(II). Here, we monitored the speciation of extracellular iron and the secretion of iron(III)-reducing metabolites during the decomposition of proteins by P. involutus. X-ray absorption spectroscopy showed that extracellular iron was mainly present as solid iron(III) phosphates and oxides. Within 1 to 2 days, these compounds were reductively dissolved, and iron(II) complexes were formed, which remained in the medium throughout the incubation. HPLC and mass spectrometry detected five extracellular iron(III)-reducing metabolites. Four of them were also secreted when the fungus grew on a medium containing ammonium as the sole nitrogen source. NMR identified the unique iron(III)-reductant as the diarylcyclopentenone involutin. Involutin was produced from day 2, just before the elevated •OH production, preceding the oxidation of BSA. The other, not yet fully characterized iron(III)-reductants likely participate in the rapid reduction and dissolution of solid iron(III) complexes observed on day one. The production of these metabolites is induced by other environmental cues than for involutin, suggesting that they play a role beyond the Fenton chemistry associated with protein oxidation.

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Cadmium-Responsive Thiols in the Ectomycorrhizal Fungus Paxillus involutus

Applied and Environmental Microbiology ◽

10.1128/aem.70.12.7413-7417.2004 ◽

2004 ◽

Vol 70 (12) ◽

pp. 7413-7417 ◽

Cited By ~ 97

Author(s):

Mikael Courbot ◽

Laurent Diez ◽

Roberta Ruotolo ◽

Michel Chalot ◽

Pierre Leroy

Keyword(s):

Molecular Mass ◽

Ectomycorrhizal Fungi ◽

High Performance ◽

Metal Tolerance ◽

Ectomycorrhizal Fungus ◽

Paxillus Involutus ◽

Cellular Mechanisms ◽

Chromatography Method ◽

Relative Lack ◽

Liquid Chromatography Method

ABSTRACT 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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