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Nitrogen acquisition from mineral-associated proteins by an ectomycorrhizal fungus

Wang, Tao LU ; Tian, Zhaomo LU ; Tunlid, Anders LU and Persson, Per LU (2020) In New Phytologist
Abstract

In nitrogen (N)-limited boreal forests, trees depend on the decomposing activity of their ectomycorrhizal (ECM) fungal symbionts to access soil N. A large fraction of this N exists as proteinaceous compounds associated with mineral particles. However, it is not known if ECM fungi can access these mineral-associated proteins; accordingly, possible acquisition mechanisms have not been investigated. With tightly controlled isotopic, spectroscopic, and chromatographic experiments, we quantified and analyzed the mechanisms of N acquisition from iron oxide mineral-associated proteins by Paxillus involutus, a widespread ECM fungus in boreal forests. The fungus acquired N from the mineral-associated proteins. The collective results indicated a... (More)

In nitrogen (N)-limited boreal forests, trees depend on the decomposing activity of their ectomycorrhizal (ECM) fungal symbionts to access soil N. A large fraction of this N exists as proteinaceous compounds associated with mineral particles. However, it is not known if ECM fungi can access these mineral-associated proteins; accordingly, possible acquisition mechanisms have not been investigated. With tightly controlled isotopic, spectroscopic, and chromatographic experiments, we quantified and analyzed the mechanisms of N acquisition from iron oxide mineral-associated proteins by Paxillus involutus, a widespread ECM fungus in boreal forests. The fungus acquired N from the mineral-associated proteins. The collective results indicated a proteolytic mechanism involving formation of the crucial enzyme–substrate complexes at the mineral surfaces. Hence, the enzymes hydrolyzed the mineral-associated proteins without initial desorption of the proteins. The proteolytic activity was suppressed by adsorption of proteases to the mineral particles. This process was counteracted by fungal secretion of mineral-surface-reactive compounds that decreased the protease–mineral interactions and thereby promoted the formation of enzyme–substrate complexes. The ability of ECM fungi to simultaneously generate extracellular proteases and surface-reactive metabolites suggests that they can play an important role in unlocking the large N pool of mineral-associated proteins to trees in boreal forests.

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organization
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Contribution to journal
publication status
epub
subject
keywords
boreal forests, decomposition and N acquisition, ectomycorrhizal (ECM) fungi, iron oxides, mineral-associated organic nitrogen, Paxillus involutus, secondary metabolites, soil proteins
in
New Phytologist
publisher
Wiley-Blackwell
external identifiers
  • pmid:32279319
  • scopus:85084488124
ISSN
0028-646X
DOI
10.1111/nph.16596
language
English
LU publication?
yes
id
0cbc4e2a-1df4-4cfd-be21-4c582c0bfa53
date added to LUP
2020-06-10 15:35:57
date last changed
2020-09-16 04:46:17
@article{0cbc4e2a-1df4-4cfd-be21-4c582c0bfa53,
  abstract     = {<p>In nitrogen (N)-limited boreal forests, trees depend on the decomposing activity of their ectomycorrhizal (ECM) fungal symbionts to access soil N. A large fraction of this N exists as proteinaceous compounds associated with mineral particles. However, it is not known if ECM fungi can access these mineral-associated proteins; accordingly, possible acquisition mechanisms have not been investigated. With tightly controlled isotopic, spectroscopic, and chromatographic experiments, we quantified and analyzed the mechanisms of N acquisition from iron oxide mineral-associated proteins by Paxillus involutus, a widespread ECM fungus in boreal forests. The fungus acquired N from the mineral-associated proteins. The collective results indicated a proteolytic mechanism involving formation of the crucial enzyme–substrate complexes at the mineral surfaces. Hence, the enzymes hydrolyzed the mineral-associated proteins without initial desorption of the proteins. The proteolytic activity was suppressed by adsorption of proteases to the mineral particles. This process was counteracted by fungal secretion of mineral-surface-reactive compounds that decreased the protease–mineral interactions and thereby promoted the formation of enzyme–substrate complexes. The ability of ECM fungi to simultaneously generate extracellular proteases and surface-reactive metabolites suggests that they can play an important role in unlocking the large N pool of mineral-associated proteins to trees in boreal forests.</p>},
  author       = {Wang, Tao and Tian, Zhaomo and Tunlid, Anders and Persson, Per},
  issn         = {0028-646X},
  language     = {eng},
  month        = {04},
  publisher    = {Wiley-Blackwell},
  series       = {New Phytologist},
  title        = {Nitrogen acquisition from mineral-associated proteins by an ectomycorrhizal fungus},
  url          = {http://dx.doi.org/10.1111/nph.16596},
  doi          = {10.1111/nph.16596},
  year         = {2020},
}