Ectomycorrhizal [i]Cortinarius[/i] species participate in enzymatic oxidation of humus in northern forest ecosystems

• Published in: New Phytologist
• Main Authors: Bodeker, Inga T. M., Clemmensen, Karina E., de Boer, Wietse, Martin, Francis, Olson, Ake, Lindahl, Bjorn D.
• Other Authors: Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences (SLU), Department of Forest Mycology and Plant Pathology, Department of Microbial Ecology, Royal Netherlands Academy of Arts and Sciences (KNAW), Interactions Arbres-Microorganismes (IAM), Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL), Swedish University of Agricultural Sciences; Swedish Research Council FORMAS; Office of Science of the US Department of Energy DE-AC02-05CH11231, French National Research Agency through the Clusters of Excellence ARBRE ANR-11-LABX-0002-01
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: carbon sequestration; Class II peroxidases; decomposition; ectomycorrhizal fungi; high throughput sequencing; nitrogen limitation; priming effect; transcription; [SDV]Life Sciences [q-bio]; Arctic
• Online Access: https://hal.science/hal-01268762; https://doi.org/10.1111/nph.12791

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.