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Title: The ectomycorrhizal fungus Paxillus involutus converts organic matter in plant litter using a trimmed brown-rot mechanism involving Fenton chemistry
Authors: Rineau, Francois
Roth, Doris
Shah, Firoz
Smits, Mark 
Johansson, Tomas
Canback, Bjorn
Olsen, Peter Bjarke
Persson, Per
Grell, Morten Nedergaard
Lindquist, Erika
Grigoriev, Igor V.
Lange, Lene
Tunlid, Anders
Issue Date: 2012
Source: ENVIRONMENTAL MICROBIOLOGY, 14 (6), p. 1477-1487
Abstract: Soils in boreal forests contain large stocks of carbon. Plants are the main source of this carbon through tissue residues and root exudates. A major part of the exudates are allocated to symbiotic ectomycorrhizal fungi. In return, the plant receives nutrients, in particular nitrogen from the mycorrhizal fungi. To capture the nitrogen, the fungi must at least partly disrupt the recalcitrant organic matterprotein complexes within which the nitrogen is embedded. This disruption process is poorly characterized. We used spectroscopic analyses and transcriptome profiling to examine the mechanism by which the ectomycorrhizal fungus Paxillus involutus degrades organic matter when acquiring nitrogen from plant litter. The fungus partially degraded polysaccharides and modified the structure of polyphenols. The observed chemical changes were consistent with a hydroxyl radical attack, involving Fenton chemistry similar to that of brown-rot fungi. The set of enzymes expressed by Pa. involutus during the degradation of the organic matter was similar to the set of enzymes involved in the oxidative degradation of wood by brown-rot fungi. However, Pa. involutus lacked transcripts encoding extracellular enzymes needed for metabolizing the released carbon. The saprotrophic activity has been reduced to a radical-based biodegradation system that can efficiently disrupt the organic matterprotein complexes and thereby mobilize the entrapped nutrients. We suggest that the released carbon then becomes available for further degradation and assimilation by commensal microbes, and that these activities have been lost in ectomycorrhizal fungi as an adaptation to symbiotic growth on host photosynthate. The interdependence of ectomycorrhizal symbionts and saprophytic microbes would provide a key link in the turnover of nutrients and carbon in forest ecosystems.
Notes: [Rineau, Francois; Shah, Firoz; Johansson, Tomas; Canback, Bjorn; Tunlid, Anders] Microbial Ecol Grp, Dept Biol, SE-22362 Lund, Sweden. [Roth, Doris; Grell, Morten Nedergaard; Lange, Lene] Aalborg Univ, Dept Biotechnol & Chem, DK-2750 Ballerup, Denmark. [Smits, Mark] Hasselt Univ, Ctr Environm Sci, B-3590 Diepenbeek, Limburg, Belgium. [Olsen, Peter Bjarke] Novozymes, DK-2880 Bagsvaerd, Denmark. [Persson, Per] Umea Univ, Dept Chem, SE-90187 Umea, Sweden. [Lindquist, Erika; Grigoriev, Igor V.] US DOE, Joint Genome Inst, Walnut Creek, CA 94598 USA.
Keywords: Microbiology
Document URI:
ISSN: 1462-2912
e-ISSN: 1462-2920
DOI: 10.1111/j.1462-2920.2012.02736.x
ISI #: 000304866600011
Category: A1
Type: Journal Contribution
Validations: ecoom 2013
Appears in Collections:Research publications

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