| 1. |
- Courty, Pierre-Emmanuel, et al.
(författare)
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The role of ectomycorrhizal communities in forest ecosystem processes: New perspectives and emerging concepts
- 2010
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 42:5, s. 679-698
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Forskningsöversikt (refereegranskat)abstract
- The fungal symbionts forming ectomycorrhizas, as well as their associated bacteria, benefit forest trees in a number of ways although the most important is enhancing soil nutrient mobilization and uptake. This is reciprocated by the allocation of carbohydrates by the tree to the fungus through the root interface, making the relationship a mutualistic association. Many field observations suggest that ectomycorrhizal fungi contribute to a number of key ecosystem functions such as carbon cycling, nutrient mobilization from soil organic matter, nutrient mobilization from soil minerals, and linking trees through common mycorrhizal networks. Until now, it has been very difficult to study trees and their fungal associates in forest ecosystems and most of the work on ECM functioning has been done in laboratory or nursery conditions. In this review with discuss the possibility of working at another scale, in forest settings. Numerous new techniques are emerging that makes possible the in situ study of the functional diversity of ectomycorrhizal communities. This approach should help to integrate developing research on the functional ecology of ectomycorrhizas and their associated bacteria with the potential implications of such research for managing the effects of climate change on forests. (C) 2010 Elsevier Ltd. All rights reserved.
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| 2. |
- Kohler, Annegret, et al.
(författare)
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Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists.
- 2015
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 47:4, s. 176-410
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Tidskriftsartikel (refereegranskat)abstract
- To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a 'symbiosis toolkit', with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.
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| 3. |
- Rineau, Francois, et al.
(författare)
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Effects of Liming on Potential Oxalate Secretion and Iron Chelation of Beech Ectomycorrhizal Root Tips.
- 2010
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 1432-184X .- 0095-3628. ; 60, s. 331-339
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Tidskriftsartikel (refereegranskat)abstract
- Liming is used to counteract forest decline induced by soil acidification. It consists of Ca and Mg input to forest soil and not only restores tree mineral nutrition but also modifies the availability of nutrients in soil. Ectomycorrhizal (ECM) fungi are involved in mineral nutrient uptake by trees and can recover them through dissolution of mineral surface. Oxalate and siderophore secretion are considered as the main agents of mineral weathering by ECMs. Here, we studied the effects of liming on the potential oxalate secretion and iron complexation by individual beech ECM root tips. Results show that freshly excised Lactarius subdulcis root tips from limed plots presented a high potential oxalate exudation of 177 muM tip(-1) h(-1). As this ECM species distribution is very dense, it is likely that, in the field, oxalate concentrations in the vicinity of its clusters could be very high. This points out that not only extraradical mycelium but also ECM root tips of certain species can contribute significantly to mineral weathering. Nonmetric multidimensional scaling (NMDS) separated potential oxalate production by ECM root tips in limed and untreated plots, and this activity was mainly driven by L. subdulcis ECMs, but NMDS on potential activity of iron mobilization by ECM root tips did not show a difference between limed and untreated plots. As the mean oxalate secretion did not significantly correlated with the mean iron mobilization by ECM morphotype, we conclude that iron complexation was due to either other organic acids or to siderophores.
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| 4. |
- Rineau, Francois, et al.
(författare)
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Liming in a beech forest results in more mineral elements stored in the mantle of Lactarius subdulcis ectomycorrhizas.
- 2010
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Ingår i: Fungal Biology. - : Elsevier BV. - 1878-6146. ; 114:11-12, s. 1007-1014
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Tidskriftsartikel (refereegranskat)abstract
- Liming is a forest practice used to counteract forest decline induced by soil acidification. It consists of direct Ca and Mg input in forest soil and restores tree mineral nutrition, but also causes drastic changes in nutrient availability in soil. Ectomycorrhizal (ECM) fungi significantly contribute in nutrient uptake by trees, and can recover them through organic acid secretion or through enzymatic degradation of organic matter. The symbiotic fungi use their extraradical mycelium for nutrient uptake, and then store them into the ECM mantle. In this study we measured how liming influences element contents in the mantle of Lactarius subdulcis ECMs, an abundant and particularly active in oxalate and laccase secretion in beech stands. For this purpose we used SEM observation coupled with energy- (EDX) and wavelength-dispersive-X-ray microanalyses (WDX). Results showed that ECM mantles of this species presented significantly higher Ca, Mg, Mn, K, Si, Al and Fe contents in limed plots. The nutrient amounts of L. subdulcis ECMs were significantly different between individuals for all the elements, showing a differential storage ability between individuals. The storage role of the ECM mantle can be interpreted in two different ways: i) a detoxification role for Al or heavy metals and ii) an increased potential nutrient resource by the fungus, which can benefit the tree.
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| 5. |
- Rineau, Francois, et al.
(författare)
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Secreted enzymatic activities of ectomycorrhizal fungi as a case study of functional diversity and functional redundancy
- 2011
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Ingår i: Annals of Forest Science. - : Springer Science and Business Media LLC. - 1286-4560 .- 1297-966X. ; 68:1, s. 69-80
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Tidskriftsartikel (refereegranskat)abstract
- Introduction Many studies deal with taxonomic diversity (TD) or estimation of functional traits of ectomycorrhizal communities. However, to our knowledge, none of them has ever tried to calculate the functional diversity (FD) of those communities, which is of critical importance for the diversity and reliability of nutrient supply to the tree. Objectives Here, we propose to evaluate the functional diversity of ECM communities in their potential ability to mobilise nutrients from organic matter, in two different forest stands. Results Results show that in both forest stands: TD is strongly correlated with FD. ECM species are functionally redundant within the communities for their abilities to secrete organic matter degrading enzymes. The functional traits (enzymatic activities) of the studied ectomycorrhizal communities are not related within genera, nor within families or phylogenetically related groups of taxa. Some species show a wide phenotypic plasticity for their enzymatic profiles. Conclusion This study provides the first evidence of functional redundancy in ectomycorrhizal communities. More studies are now needed to evaluate the robustness of these results at wider ecosystem scales and using other relevant functional traits.
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| 6. |
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| 7. |
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| 8. |
- Shah, Firoz, et al.
(författare)
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The molecular components of the extracellular protein-degradation pathways of the ectomycorrhizal fungus Paxillus involutus.
- 2013
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 200:3, s. 875-887
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Tidskriftsartikel (refereegranskat)abstract
- Proteins contribute to a major part of the organic nitrogen (N) in forest soils. This N 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 N 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 N 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.
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| 9. |
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| 10. |
- Tunlid, Anders, et al.
(författare)
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Soil organic matter decomposition mechanisms in ectomycorrhizal fungi
- 2016
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Ingår i: Molecular Mycorrhizal Symbiosis. - Hoboken, NJ, USA : John Wiley & Sons, Inc.. - 9781118951415 - 9781118951446 ; , s. 257-275
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Bokkapitel (refereegranskat)abstract
- In boreal forests, ectomycorrhizal (ECM) fungi are found in soil layers containing decomposed litter and humus-rich soil organic matter (SOM). This chapter summarizes the present understanding of the mechanisms for oxidative decomposition of SOM and the hydrolysis and mobilization of organic N and P sources by ECM fungi. It discusses how these processes may influence the formation and stability of SOM, and the interactions with saprotrophic microorganisms in forest ecosystems. The chapter gives a brief introduction to litter decomposition mechanisms in saprotrophic fungi. To investigate experimentally the capacity of ECM fungi to decompose humic-rich SOM and the mechanisms underlying this decomposition, a series of experiments have been conducted using Paxillus involutus as a "model" species. ECM fungi have evolved from diverse nutritional backgrounds, including litter decomposers and WR and BR wood decayers. During these transitions, ECM lineages lost many genes related to saprotrophy. There is evidence that some ECM employ the Fenton reaction during SOM decomposition.
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