| 1. |
- Braesel, Jana, et al.
(författare)
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Three Redundant Synthetases Secure Redox-Active Pigment Production in the Basidiomycete Paxillus involutus.
- 2015
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Ingår i: Chemistry and Biology. - : Elsevier BV. - 1879-1301 .- 1074-5521. ; 22:10, s. 1325-1334
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Tidskriftsartikel (refereegranskat)abstract
- The symbiotic fungus Paxillus involutus serves a critical role in maintaining forest ecosystems, which are carbon sinks of global importance. P. involutus produces involutin and other 2,5-diarylcyclopentenone pigments that presumably assist in the oxidative degradation of lignocellulose via Fenton chemistry. Their precise biosynthetic pathways, however, remain obscure. Using a combination of biochemical, genetic, and transcriptomic analyses, in addition to stable-isotope labeling with synthetic precursors, we show that atromentin is the key intermediate. Atromentin is made by tridomain synthetases of high similarity: InvA1, InvA2, and InvA5. An inactive atromentin synthetase, InvA3, gained activity after a domain swap that replaced its native thioesterase domain with that of InvA5. The found degree of multiplex biosynthetic capacity is unprecedented with fungi, and highlights the great importance of the metabolite for the producer.
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| 2. |
- Ellström, Magnus, et al.
(författare)
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The carbon starvation response of the ectomycorrhizal fungus Paxillus involutus.
- 2015
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941. ; 91:4
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Tidskriftsartikel (refereegranskat)abstract
- The amounts of carbon allocated to the fungal partner in ectomycorrhizal associations can vary substantially depending on the plant growth and the soil nutrient conditions, and the fungus may frequently be confronted with limitations in carbon. We used chemical analysis and transcriptome profiling to examine the physiological response of the ectomycorrhizal fungus Paxillus involutus to carbon starvation during axenic cultivation. Carbon starvation induced a decrease in the biomass. Concomitantly, ammonium, cell-wall material (chitin) and proteolytic enzymes were released into the medium, which suggest autolysis. Compared with the transcriptome of actively growing hyphae, about 45% of the transcripts analyzed were differentially regulated during C-starvation. Induced during starvation were transcripts encoding extracellular enzymes such as peptidases, chitinases, and laccases. In parallel, transcripts of N-transporters were upregulated, which suggest that some of the released nitrogen compounds were re-assimilated by the mycelium. The observed changes suggest that the carbon-starvation response in P. involutus is associated with complex cellular changes that involves autolysis, recycling of intracellular compounds by autophagy and reabsorption of the extracellular released material. The study provides molecular markers that can be used to examine the role of autolysis for the turnover and survival of the ectomycorrhizal mycelium in soils.
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| 3. |
- 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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| 4. |
- Ramasamy, Lakshmana Kumar, et al.
(författare)
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Secure Smart Wearable Computing through Artificial Intelligence-Enabled Internet of Things and Cyber-Physical Systems for Health Monitoring
- 2022
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Ingår i: Sensors. - : MDPI. - 1424-8220. ; 22:3
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Tidskriftsartikel (refereegranskat)abstract
- The functionality of the Internet is continually changing from the Internet of Computers (IoC) to the “Internet of Things (IoT)”. Most connected systems, called Cyber-Physical Systems (CPS), are formed from the integration of numerous features such as humans and the physical environment, smart objects, and embedded devices and infrastructure. There are a few critical problems, such as security risks and ethical issues that could affect the IoT and CPS. When every piece of data and device is connected and obtainable on the network, hackers can obtain it and utilise it for different scams. In medical healthcare IoT-CPS, everyday medical and physical data of a patient may be gathered through wearable sensors. This paper proposes an AI-enabled IoT-CPS which doctors can utilise to discover diseases in patients based on AI. AI was created to find a few disorders such as Diabetes, Heart disease and Gait disturbances. Each disease has various symptoms among patients or elderly. Dataset is retrieved from the Kaggle repository to execute AI-enabled IoT-CPS technology. For the classification, AI-enabled IoT-CPS Algorithm is used to discover diseases. The experimental results demonstrate that compared with existing algorithms, the proposed AI-enabled IoT-CPS algorithm detects patient diseases and fall events in elderly more efficiently in terms of Accuracy, Precision, Recall and F-measure.
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| 5. |
- Rineau, F., et al.
(författare)
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Carbon availability triggers the decomposition of plant litter and assimilation of nitrogen by an ectomycorrhizal fungus
- 2013
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Ingår i: The ISME Journal. - : nternational Society for Microbial Ecology. - 1751-7362 .- 1751-7370. ; 7:10, s. 2010-2022
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
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| 7. |
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| 8. |
- Shah, Firoz
(författare)
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Insights into the Molecular Mechanisms of Litter Decomposition and Assimilation of Nitrogen by Ectomycorrhizal Fungi
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ectomycorrhizae is the dominant type of mycorrhiza found in association with tree roots in boreal and northern temperate forests. In this symbiosis, the fungal partner derives energy from photosynthates provided by the host trees and in return delivers soil-derived nutrients such as nitrogen (N). The majority of N in forest soils is embedded in recalcitrant 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 decomposing processes, how they are regulated by C and N availability, and the mechanisms of organic N uptake. The work described in the thesis uses spectroscopic methods, chemical analysis and transcriptome profiling to examine the mechanisms by which the model ectomycorrhizal fungus Paxillus involutus degrades soil organic matter (SOM) while assimilating the organic nitrogen from plant litter. Finally, the decomposing ability of seven other species of EMF was examined that differ in ecology and evolutionary history. The EMF P. involutus degraded SOM, while assimilating N, by a radical-based oxidation involving Fenton chemistry similar to the mechanism used by saprophytic brown-rot (BR) fungi. The key indications were the apparition of a C=O peak in the signature of cellulose, the side chain modifications of lignin residues, and the increase in the Fe3+-reducing activity in the culture filtrate. The set of enzymes expressed during the degradation of SOM was similar to the set of enzymes involved in the oxidative degradation of wood by BR fungi. Secondary metabolites are key components for Fe3+-reduction and the generation of Fenton reagent in BR oxidative degradation of lignocellulose. The Fe3+-reducing activity of P. involutus was caused by the pigment involutin. The saprotrophic activity of P. involutus is reduced to a radical-based biodegradation system that efficiently disrupts the organic matter and thereby mobilizes the entrapped N. The decomposition of plant litter and assimilation of nitrogen was triggered by the addition of glucose while ammonium addition had minor effects. P. involutus secreted peptidase activity, mostly contributed by aspartic peptidases while degrading proteins. The expression levels of extracellular peptidases were regulated in parallel with transporters and enzymes involved in the assimilation and metabolism of the released peptides and amino acids. Finally, all the examined EMF species catalyzes oxidative degradation of complex organic components in the litter extract with a mechanism similar to that of BR fungi. The ability to modify complex organic material by oxidation is not restricted to rapidly-growing, long-distance exploration types of EMF, but it is also found in slow-growing, medium- and short-distance EMF exploration types. All examined EMF species expresses distinctively different sets oxidative enzymes to oxidize the litter material. Thus, EMF can degrade plant litter by oxidative mechanisms similar to BR while variation in gene expression might reflect adaptations of the decomposing mechanisms to different environmental conditions.
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| 9. |
- Shah, Firoz, et al.
(författare)
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Involutin is a Fe3+ reductant Secreted by the Ectomycorrhizal Fungus Paxillus involutus during Fenton-based Decomposition of Organic Matter.
- 2015
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Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 81:24, s. 8427-8433
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Tidskriftsartikel (refereegranskat)abstract
- Ectomycorrhizal fungi play a key role in mobilizing nutrients embedded in recalcitrant organic matter complexes, thereby increasing nutrient accessibility to the host plant. Recent study have shown that during assimilation of nutrients, the ectomycorrhizal fungus Paxillus involutus decomposes organic matter using an oxidative mechanism involving Fenton chemistry (Fe(2+) + H2O2 + H(+) → Fe(3+) + •OH + H2O) similar to that of brown-rot wood-decaying fungi. In such fungi, secreted metabolites are one of the components that drive one-electron reductions of Fe(3+) and O2, generating Fenton chemistry reagents. Here, we investigated whether such a mechanism is also implemented by P. involutus during organic matter decomposition. Activity-guided purification was performed to isolate the Fe(3+)-reducing principle secreted by P. involutus during growth on maize compost extract. The Fe(3+)-reducing activity correlated with the presence of one compound. Mass spectrometry and NMR identified this compound as the diarylcyclopentenone involutin. A major part of the involutin produced by P. involutus during organic matter decomposition was secreted into the medium and the metabolite was not detected when the fungus was grown on a mineral nutrient medium. We also demonstrated that in the presence of H2O2, involutin has the capacity to drive an in vitro Fenton reaction via Fe(3+) reduction. Our results show that the mechanism for reducing Fe(3+) and generating hydroxyl radicals via Fenton chemistry by ectomycorrhizal fungi during organic matter decomposition is similar to that expressed by the evolutionarily related brown-rot saprotrophs during wood decay.
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| 10. |
- Shah, Firoz, et al.
(författare)
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Secretion of iron(III)-reducing metabolites during protein acquisition by the ectomycorrhizal fungus paxillus involutus
- 2021
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Ingår i: Microorganisms. - : MDPI AG. - 2076-2607. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- The ectomycorrhizal fungus Paxillus involutus decomposes proteins using a two-step mechanism, including oxidation and proteolysis. Oxidation involves the action of extracellular hydroxyl radicals (•OH) generated by the Fenton reaction. This reaction requires the presence of iron(II). Here, we monitored the speciation of extracellular iron and the secretion of iron(III)-reducing metabolites during the decomposition of proteins by P. involutus. X-ray absorption spectroscopy showed that extracellular iron was mainly present as solid iron(III) phosphates and oxides. Within 1 to 2 days, these compounds were reductively dissolved, and iron(II) complexes were formed, which remained in the medium throughout the incubation. HPLC and mass spectrometry detected five extracellular iron(III)-reducing metabolites. Four of them were also secreted when the fungus grew on a medium containing ammonium as the sole nitrogen source. NMR identified the unique iron(III)-reductant as the diarylcyclopentenone involutin. Involutin was produced from day 2, just before the elevated •OH production, preceding the oxidation of BSA. The other, not yet fully characterized iron(III)-reductants likely participate in the rapid reduction and dissolution of solid iron(III) complexes observed on day one. The production of these metabolites is induced by other environmental cues than for involutin, suggesting that they play a role beyond the Fenton chemistry associated with protein oxidation.
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| 11. |
- 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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| 12. |
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