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- Title
Fenton reaction facilitates organic nitrogen acquisition by an ectomycorrhizal fungus.
- Authors
Op De Beeck, Michiel; Troein, Carl; Peterson, Carsten; Persson, Per; Tunlid, Anders
- Abstract
Summary: 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 (˙OH), produced by the ectomycorrhizal fungus <italic>Paxillus involutus</italic> during growth on SOM, are involved in liberating organic N. <italic>Paxillus involutus</italic> was grown for 7 d on N‐containing or N‐free substrates that represent major organic compounds of SOM. ˙OH production, ammonium assimilation, and proteolytic activity were measured daily. ˙OH production was strongly induced when <italic>P. involutus</italic> 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 ˙OH production occurs in a burst, regulated mainly by ammonium and ferric iron concentrations. We propose that the production of ˙OH 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.
- Subjects
ECTOMYCORRHIZAL fungi; NITROGEN in agriculture; HUMUS; ORGANIC compounds; PROTEOLYSIS; PLANTS
- Publication
New Phytologist, 2018, Vol 218, Issue 1, p335
- ISSN
0028-646X
- Publication type
Article
- DOI
10.1111/nph.14971