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Fenton reaction facilitates organic nitrogen acquisition by an ectomycorrhizal fungus

Author:
  • Michiel Op De Beeck
  • Carl Troein
  • Carsten Peterson
  • Per Persson
  • Anders Tunlid
Publishing year: 2018-01-03
Language: English
Pages: 335-343
Publication/Series: New Phytologist
Volume: 218
Issue: 1
Document type: Journal article
Publisher: Wiley-Blackwell

Abstract english

Boreal trees rely on their ectomycorrhizal fungal symbionts to acquire growth-limiting nutrients, such as nitrogen (N), which mainly occurs as proteins complexed in soil organic matter (SOM). The mechanisms for liberating this N are unclear as ectomycorrhizal fungi have lost many genes encoding lignocellulose-degrading enzymes present in their saprotrophic ancestors. We hypothesized that hydroxyl radicals (bullOH), produced by the ectomycorrhizal fungus Paxillus involutus during growth on SOM, are involved in liberating organic N. Paxillus involutus was grown for 7 d on N-containing or N-free substrates that represent major organic compounds of SOM. bullOH production, ammonium assimilation, and proteolytic activity were measured daily. bullOH production was strongly induced when P. involutus switched from ammonium to protein as the main N source. Extracellular proteolytic activity was initiated shortly after the oxidation. Oxidized protein substrates induced higher proteolytic activity than unmodified proteins. Dynamic modeling predicted that bullOH production occurs in a burst, regulated mainly by ammonium and ferric iron concentrations. We propose that the production of bullOH and extracellular proteolytic enzymes are regulated by similar nutritional signals. Oxidation works in concert with proteolysis, improving N liberation from proteins in SOM. Organic N mining by ectomycorrhizal fungi has, until now, only been attributed to proteolysis.

Keywords

  • Microbiology
  • Botany
  • Fenton reaction
  • Nitrogen (N)
  • Paxillus involutus
  • Proteolysis
  • Soil organic matter (SOM)

Other

Published
  • MICCS - Molecular Interactions Controlling soil Carbon Sequestration
  • ISSN: 0028-646X
Anders Tunlid
E-mail: anders [dot] tunlid [at] biol [dot] lu [dot] se

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