Nitrogen acquisition from mineral-associated proteins by an ectomycorrhizal fungus

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@article{0cbc4e2a1df44cfdbe214c582c0bfa53,
title = "Nitrogen acquisition from mineral-associated proteins by an ectomycorrhizal fungus",
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 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.",
keywords = "boreal forests, decomposition and N acquisition, ectomycorrhizal (ECM) fungi, iron oxides, mineral-associated organic nitrogen, Paxillus involutus, secondary metabolites, soil proteins",
author = "Tao Wang and Zhaomo Tian and Anders Tunlid and Per Persson",
year = "2020",
month = "4",
day = "12",
doi = "10.1111/nph.16596",
language = "English",
journal = "New Phytologist",
issn = "1469-8137",
publisher = "Wiley-Blackwell",

}