Project description:Abstract: A large part of the nitrogen in forest soils is found in recalcitrant organic matter-protein complexes. Ectomycorrhizal fungi are thought to have a key role in the decomposition and mobilization of nitrogen from such complexes. The knowledge on the functional mechanisms of these processes, and how they are regulated by carbon from the host plant and the availability of more easily available forms of nitrogen sources are limited. We used spectroscopic analyses and transcriptome profiling to examine how the presence/absence of glucose and ammonium regulates the decomposition and mobilization of nitrogen from litter material by the ectomycorrhizal fungus Paxillus involutus. Amendments of glucose triggered the assimilation of nitrogen and the decomposition of the litter material. Concomitantly, the expression of genes encoding enzymes involved in oxidative (i.e. Fenton chemistry) degradation of polysaccharides and polyphenols, peptidases, nitrogen transporters and enzymes in pathways of the nitrogen and carbon metabolism were upregulated in concert. Addition of ammonium had minute effects on both the expression of transcripts and decomposition of litter material, and only when glucose was present. Based on the spectroscopic analyses, three major types of chemical modifications of the litter material were observed. Each of them was correlated with the expression of specific sets of genes encoding extracellular enzymes. Our data suggests that the expression of the decomposition and nitrogen assimilation machinery of ectomycorrhizal fungi can be firmly regulated by the host carbon supply, i.e. priming, and that the availability of inorganic nitrogen as such has limited effects on the saprotrophic activities. Rineau F, Shah F., Smits M.M., Persson P., Johansson T., Carleer R., Troein C., Tunlid A. (2013) Carbon availability triggers the decomposition of plant litter and assimilation of nitrogen by an ectomycorrhizal fungus (submitted) A one-chip study (data from 12 subarrays collected from a 12-plex Nimblegen microarray (ID 467991) using total RNA recovered from three separate glass-bead cultures of Paxillus involutus (ATCC200175) after amendments of various soil-derived substrates. Transcriptome profiling to examine how the presence/absence of glucose and ammonium regulates the decomposition and mobilization of nitrogen from litter material by the ectomycorrhizal fungus Paxillus involutus.
Project description:Abstract: A large part of the nitrogen in forest soils is found in recalcitrant organic matter-protein complexes. Ectomycorrhizal fungi are thought to have a key role in the decomposition and mobilization of nitrogen from such complexes. The knowledge on the functional mechanisms of these processes, and how they are regulated by carbon from the host plant and the availability of more easily available forms of nitrogen sources are limited. We used spectroscopic analyses and transcriptome profiling to examine how the presence/absence of glucose and ammonium regulates the decomposition and mobilization of nitrogen from litter material by the ectomycorrhizal fungus Paxillus involutus. Amendments of glucose triggered the assimilation of nitrogen and the decomposition of the litter material. Concomitantly, the expression of genes encoding enzymes involved in oxidative (i.e. Fenton chemistry) degradation of polysaccharides and polyphenols, peptidases, nitrogen transporters and enzymes in pathways of the nitrogen and carbon metabolism were upregulated in concert. Addition of ammonium had minute effects on both the expression of transcripts and decomposition of litter material, and only when glucose was present. Based on the spectroscopic analyses, three major types of chemical modifications of the litter material were observed. Each of them was correlated with the expression of specific sets of genes encoding extracellular enzymes. Our data suggests that the expression of the decomposition and nitrogen assimilation machinery of ectomycorrhizal fungi can be firmly regulated by the host carbon supply, i.e. priming, and that the availability of inorganic nitrogen as such has limited effects on the saprotrophic activities. Rineau F, Shah F., Smits M.M., Persson P., Johansson T., Carleer R., Troein C., Tunlid A. (2013) Carbon availability triggers the decomposition of plant litter and assimilation of nitrogen by an ectomycorrhizal fungus (submitted)
Project description:Abstract: Proteins contribute to a major part of the organic nitrogen in forest soils. This nitrogen is mobilized and becomes available to trees as a result of the depolymerizing activities of symbiotic ectomycorrhizal fungi. The mechanisms by which these fungi depolymerize proteins and assimilate the released nitrogen are poorly characterized. Biochemical analysis and transcriptome profiling were performed to examine the proteolytic machinery and the uptake system of the ectomycorrhizal basidiomycete Paxillus involutus during the assimilation of organic nitrogen from various protein sources and extracts of organic matter. All substrates induced secretion of peptidase activity with an acidic pH optimum, mostly contributed by aspartic peptidases. The peptidase activity was transiently repressed by ammonium. Transcriptional analysis revealed a large number of extracellular endo- and exopeptidases. The expression levels of these peptidases were regulated in parallel with transporters and enzymes involved in the assimilation and metabolism of the released peptides and amino acids. For the first time the molecular components of the protein degradation pathways of an ectomycorrhizal fungus are described. The data suggest that the transcripts encoding these components are regulated in response to the chemical properties and the availability of the protein substrates. Firoz Shah, Francois Rineau, Björn Canbäck, Tomas Johansson and Anders Tunlid (2013) The molecular components of the extracellular protein-degradation pathways of the ectomycorrhizal fungus Paxillus involutus (submitted)
Project description:In this study, examinations were performed on how the ECM fungus Paxillus involutus degrade complex, plant and litter material by using elemental analyses, FTIR spectroscopy, pyrolysis-GC/MS, and synchronous fluorescence spectroscopy together with microarray analyses screening 12,214 gene models, derived from 454 sequenced cDNA libraries. Rineau, F., Roth, D., Shah, F., Smits, M., Johansson, T., Canbäck, B., Bjarke Olsen, P., Persson, P., Nedergaard Grell, M., Lange, L., & Tunlid, A. (201X) Expression levels tune enzymatic exploitation of plant litter material by ectomycorrhizal fungi (manuscript in preparation).
Project description:Abstract: Proteins contribute to a major part of the organic nitrogen in forest soils. This nitrogen is mobilized and becomes available to trees as a result of the depolymerizing activities of symbiotic ectomycorrhizal fungi. The mechanisms by which these fungi depolymerize proteins and assimilate the released nitrogen are poorly characterized. Biochemical analysis and transcriptome profiling were performed to examine the proteolytic machinery and the uptake system of the ectomycorrhizal basidiomycete Paxillus involutus during the assimilation of organic nitrogen from various protein sources and extracts of organic matter. All substrates induced secretion of peptidase activity with an acidic pH optimum, mostly contributed by aspartic peptidases. The peptidase activity was transiently repressed by ammonium. Transcriptional analysis revealed a large number of extracellular endo- and exopeptidases. The expression levels of these peptidases were regulated in parallel with transporters and enzymes involved in the assimilation and metabolism of the released peptides and amino acids. For the first time the molecular components of the protein degradation pathways of an ectomycorrhizal fungus are described. The data suggest that the transcripts encoding these components are regulated in response to the chemical properties and the availability of the protein substrates. Firoz Shah, Francois Rineau, Björn Canbäck, Tomas Johansson and Anders Tunlid (2013) The molecular components of the extracellular protein-degradation pathways of the ectomycorrhizal fungus Paxillus involutus (submitted) A one-chip study (data from 9 subarrays collected from a 12-plex Nimblegen microarray (ID: 461228)) using total RNA recovered from glass-bead cultures of Paxillus involutus (ATCC200175) after amendments of 3 different substrates (3 replicates of each).
Project description:Abstract: Proteins contribute to a major part of the organic nitrogen in forest soils. This nitrogen is mobilized and becomes available to trees as a result of the depolymerizing activities of symbiotic ectomycorrhizal fungi. The mechanisms by which these fungi depolymerize proteins and assimilate the released nitrogen are poorly characterized. Biochemical analysis and transcriptome profiling were performed to examine the proteolytic machinery and the uptake system of the ectomycorrhizal basidiomycete Paxillus involutus during the assimilation of organic nitrogen from various protein sources and extracts of organic matter. All substrates induced secretion of peptidase activity with an acidic pH optimum, mostly contributed by aspartic peptidases. The peptidase activity was transiently repressed by ammonium. Transcriptional analysis revealed a large number of extracellular endo- and exopeptidases. The expression levels of these peptidases were regulated in parallel with transporters and enzymes involved in the assimilation and metabolism of the released peptides and amino acids. For the first time the molecular components of the protein degradation pathways of an ectomycorrhizal fungus are described. The data suggest that the transcripts encoding these components are regulated in response to the chemical properties and the availability of the protein substrates. Firoz Shah, Francois Rineau, Björn Canbäck, Tomas Johansson and Anders Tunlid (2013) The molecular components of the extracellular protein-degradation pathways of the ectomycorrhizal fungus Paxillus involutus (submitted)
Project description:Abstract: Proteins contribute to a major part of the organic nitrogen in forest soils. This nitrogen is mobilized and becomes available to trees as a result of the depolymerizing activities of symbiotic ectomycorrhizal fungi. The mechanisms by which these fungi depolymerize proteins and assimilate the released nitrogen are poorly characterized. Biochemical analysis and transcriptome profiling were performed to examine the proteolytic machinery and the uptake system of the ectomycorrhizal basidiomycete Paxillus involutus during the assimilation of organic nitrogen from various protein sources and extracts of organic matter. All substrates induced secretion of peptidase activity with an acidic pH optimum, mostly contributed by aspartic peptidases. The peptidase activity was transiently repressed by ammonium. Transcriptional analysis revealed a large number of extracellular endo- and exopeptidases. The expression levels of these peptidases were regulated in parallel with transporters and enzymes involved in the assimilation and metabolism of the released peptides and amino acids. For the first time the molecular components of the protein degradation pathways of an ectomycorrhizal fungus are described. The data suggest that the transcripts encoding these components are regulated in response to the chemical properties and the availability of the protein substrates. Firoz Shah, Francois Rineau, Björn Canbäck, Tomas Johansson and Anders Tunlid (2013) The molecular components of the extracellular protein-degradation pathways of the ectomycorrhizal fungus Paxillus involutus (submitted) A one-chip study (data from 12 subarrays collected from 12-plex Nimblegen microarray (IDs: 527896) using total RNA recovered from glass-bead cultures of Paxillus involutus (ATCC200175) after amendments of nitrogen (+/-NH4) to substrate followed by incubation for different periods of time (3 replicates of each).
Project description:Ectomycorrhizal fungi are dependent on host trees for carbon supply. In return ectomycorrhizal fungi supply trees with water and nutrients. It is known that when ectomycorrhizal fungi have exploited a nutrient rich patch in soil, the carbon allocation to mycelia in that patch is reduced, with the consequence of mycelia dying, but less is known of the dynamics of this senescence. We cultivated the ectomycorrhizal fungus Paxillus involutus in an axenic system. We collected growth and transcriptome data at different stages of carbon starvation during fungal growth. Carbon starvation induced a decrease in fungal biomass, which coincided with the release of NH4+ and the expression of genes connected with autophagy as well as protease and chitinase activity. Monoaromatic compounds, chitin and protease activity was detected in the liquid growth media during carbon starvation. The exudation of NH4+ and increase of monoaromatic compound during C starvation suggests senescence and autolysis of P. involutus. Together with the upregulation of genes involved in autophagy, chitinase and endopeptidase activity this points towards a controlled senescence including recycling of compounds originating from the fungi. Reduced C allocation to ectomycorrhizal mycelia in recently depleted nutrient patches in forest soils must be of ubiquitous nature. Understanding the mechanisms during exploitation of nutrients by ectomycorrhizal fungi is of great importance for understanding carbon and nutrient dynamics in forest soils. This is to our knowledge the first study describing the carbon starvation response in an ectomycorrhizal fungus.