Fungal taste for minerals: the ectomycorrhizal fungus Paxillus involutus triggers specific genes when extracting potassium from different silicates

AbstractSilicates make up about 90% of the Earth’s crust and constitute the main source of mineral nutrients for microorganisms and plants. Fungi can actively weather silicates to extract nutrients. However, it is unclear whether they are able to obtain the same amounts of nutrients and use the same mechanisms when tapping into different mineral sources. We performed a microcosm experiment using the ectomycorrhizal basidiomycetes Paxillus involutus and the silicates K-vermiculite, muscovite and phlogopite as only potassium sources, as they show a different resistance for the removal of K cations from the mineral structure. A combination of transcriptomic, elemental and SEM analyses showed that different minerals stimulated specific weathering mechanisms and led to a change in fungal genes expression. The differential expression of the fungal genes generated alternative chemical attacks on the minerals, resulting in a tailored dissolution and selective uptake of chemical elements according to the leachability of K from the silicate mineral. The K uptake capacity of the fungus was highest with vermiculite in comparison to growth on phlogopite and muscovite. The findings provide new insights into fungal-mineral interactions that will help to interpret key processes for the homeostasis of soil environments.

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

Journal of Phytopathology ◽

10.1111/j.1439-0434.1991.tb00113.x ◽

1991 ◽

Vol 132 (3) ◽

pp. 207-218 ◽

Cited By ~ 27

Author(s):

C. Chakravarty ◽

R. L. Peterson ◽

B. E. Ellis

Keyword(s):

Pinus Resinosa ◽

Ectomycorrhizal Fungus ◽

Paxillus Involutus ◽

Damping Off

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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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