Carbon availability triggers the decomposition of plant litter and assimilation of nitrogen by an ectomycorrhizal fungus

• Published in: The ISME Journal Vol. 7; no. 10; pp. 2010 - 2022
• Main Authors: Rineau, F, Shah, F, Smits, M M, Persson, P, Johansson, T, Carleer, R, Troein, C, Tunlid, A
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-10-2013; Nature Publishing Group
• Subjects: 631/326/193; 631/326/47; Agaricales - enzymology; Agaricales - genetics; Agaricales - metabolism; Ammonium; Biofysiks; Biologi; Biological Sciences; Biomedical and Life Sciences; Biophysics; Carbon; Carbon - metabolism; Carbon - pharmacology; carbon and nitrogen cycling; carbon availability; Chemical Sciences; Decomposition; Earth and Related Environmental Sciences; Ecology; ectomycorrhiza; Enzymes; Enzymes - genetics; Enzymes - metabolism; Evolutionary Biology; Forest soils; Gene Expression Profiling; Gene Expression Regulation, Fungal - drug effects; Geovetenskap och miljövetenskap; Glucose; Kemi; Life Sciences; Litter; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Mycorrhizae - enzymology; Mycorrhizae - genetics; Mycorrhizae - metabolism; Natural Sciences; Naturvetenskap; Nitrogen - metabolism; Nitrogen - pharmacology; nitrogen assimilation; Nitrogen sources; Organic matter; organic matter degradation; Original; original-article; Paxillus involutus; Plants - metabolism; Plants - microbiology; Saccharides; Soil - chemistry; Soil Microbiology; Spectroscopy, Fourier Transform Infrared; ectomycorrhiza; carbon availability; carbon and nitrogen cycling; organic matter degradation; nitrogen assimilation
• ISSN: 1751-7362; 1751-7370; 1751-7370
• DOI: 10.1038/ismej.2013.91

The majority of nitrogen in forest soils is found in organic matter–protein complexes. Ectomycorrhizal fungi (EMF) are thought to have a key role in decomposing and mobilizing nitrogen from such complexes. However, little is known about the mechanisms governing these processes, how they are regulated by the carbon in the host plant and the availability of more easily available forms of nitrogen sources. Here we used spectroscopic analyses and transcriptome profiling to examine how the presence or absence of glucose and/or ammonium regulates decomposition of litter material and nitrogen mobilization by the ectomycorrhizal fungus
Paxillus involutus
. We found that the assimilation of nitrogen and the decomposition of the litter material are triggered by the addition of glucose. Glucose addition also resulted in upregulation of the expression of genes encoding enzymes involved in oxidative degradation of polysaccharides and polyphenols, peptidases, nitrogen transporters and enzymes in pathways of the nitrogen and carbon metabolism. In contrast, the addition of ammonium to organic matter had relatively minor effects on the expression of transcripts and the decomposition of litter material, occurring only when glucose was present. On the basis of spectroscopic analyses, three major types of chemical modifications of the litter material were observed, each correlated with the expression of specific sets of genes encoding extracellular enzymes. Our data suggest that the expression of the decomposition and nitrogen assimilation processes of EMF can be tightly regulated by the host carbon supply and that the availability of inorganic nitrogen as such has limited effects on saprotrophic activities.