title: Ectomycorrhizal Cortinarius species participate in enzymatic oxidation of humus in northern forest ecosystems.
abstract: In northern forests, belowground sequestration of nitrogen (N) in complex organic pools restricts nutrient availability to plants. Oxidative extracellular enzymes produced by ectomycorrhizal fungi may aid plant N acquisition by providing access to N in macromolecular complexes. We test the hypotheses that ectomycorrhizal Cortinarius species produce Mn-dependent peroxidases, and that the activity of these enzymes declines at elevated concentrations of inorganic N. In a boreal pine forest and a sub-arctic birch forest, Cortinarius DNA was assessed by 454-sequencing of ITS amplicons and related to Mn-peroxidase activity in humus samples with- and without previous N amendment. Transcription of Cortinarius Mn-peroxidase genes was investigated in field samples. Phylogenetic analyses of Cortinarius peroxidase amplicons and genome sequences were performed. We found a significant co-localization of high peroxidase activity and DNA from Cortinarius species. Peroxidase activity was reduced by high ammonium concentrations. Amplification of mRNA sequences indicated transcription of Cortinarius Mn-peroxidase genes under field conditions. The Cortinarius glaucopus genome encodes 11 peroxidases - a number comparable to many white-rot wood decomposers. These results support the hypothesis that some ectomycorrhizal fungi--Cortinarius species in particular--may play an important role in decomposition of complex organic matter, linked to their mobilization of organically bound N.
authors.affiliation: Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007, Uppsala, Sweden; Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Box 49, 230 53, Alnarp, Sweden.
authors.forename: Inga T M
authors.initials: IT
authors.lastname: Bödeker
authors.forename: Karina E
authors.initials: KE
authors.lastname: Clemmensen
authors.forename: Wietse
authors.initials: W
authors.lastname: de Boer
authors.forename: Francis
authors.initials: F
authors.lastname: Martin
authors.forename: Åke
authors.initials: Å
authors.lastname: Olson
authors.forename: Björn D
authors.initials: BD
authors.lastname: Lindahl
mesh_terms: D029662:Betula / Q000382:microbiology; D055363:Cortinarius / Q000201:enzymology* / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D065928:Forests; D038821:Mycorrhizae / Q000201:enzymology* / Q000235:genetics; D009584:Nitrogen / Q000378:metabolism; D058458:Nitrogen Cycle; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D028223:Pinus / Q000382:microbiology; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer; D012987:Soil; D010544:Peroxidases; C051129:manganese peroxidase; D009584:Nitrogen
keywords: Class II peroxidases; carbon sequestration; decomposition; ectomycorrhizal fungi; high throughput sequencing; nitrogen limitation; priming effect; transcription