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Chen Y, Yao Z, Zhao L, Yu M, Chen B, Zou C. Redundant and Distinct Roles of Two 14-3-3 Proteins in Fusarium sacchari, Pathogen of Sugarcane Pokkah Boeng Disease. J Fungi (Basel) 2024; 10:257. [PMID: 38667928 PMCID: PMC11051555 DOI: 10.3390/jof10040257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 03/14/2024] [Accepted: 03/23/2024] [Indexed: 04/28/2024] Open
Abstract
Fusarium sacchari, a key pathogen of sugarcane, is responsible for the Pokkah boeng disease (PBD) in China. The 14-3-3 proteins have been implicated in critical developmental processes, including dimorphic transition, signal transduction, and carbon metabolism in various phytopathogenic fungi. However, their roles are poorly understood in F. sacchari. This study focused on the characterization of two 14-3-3 protein-encoding genes, FsBmh1 and FsBmh2, within F. sacchari. Both genes were found to be expressed during the vegetative growth stage, yet FsBmh1 was repressed at the sporulation stage in vitro. To elucidate the functions of these genes, the deletion mutants ΔFsBmh1 and ΔFsBmh2 were generated. The ΔFsBmh2 exhibited more pronounced phenotypic defects, such as impaired hyphal branching, septation, conidiation, spore germination, and colony growth, compared to the ΔFsBmh1. Notably, both knockout mutants showed a reduction in virulence, with transcriptome analysis revealing changes associated with the observed phenotypes. To further investigate the functional interplay between FsBmh1 and FsBmh2, we constructed and analyzed mutants with combined deletion and silencing (ΔFsBmh/siFsBmh) as well as overexpression (O-FsBmh). The combinations of ΔFsBmh1/siFsBmh2 or ΔFsBmh2/siFsBmh1 displayed more severe phenotypes than those with single allele deletions, suggesting a functional redundancy between the two 14-3-3 proteins. Yeast two-hybrid (Y2H) assays identified 20 proteins with pivotal roles in primary metabolism or diverse biological functions, 12 of which interacted with both FsBmh1 and FsBmh2. Three proteins were specifically associated with FsBmh1, while five interacted exclusively with FsBmh2. In summary, this research provides novel insights into the roles of FsBmh1 and FsBmh2 in F. sacchari and highlights potential targets for PBD management through the modulation of FsBmh functions.
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Affiliation(s)
- Yuejia Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Ministry & Province Co-Sponsored Center of Collaborative Innovation for Sugarcane Industry, College of Life Science and Technology, Guangxi University, Nanning 530004, China; (Y.C.); (M.Y.)
| | - Ziting Yao
- Plant Protection Research Institute, Guangxi Academy of Agriculture Science, Nanning 530007, China;
| | - Lixian Zhao
- Guangxi Key Laboratory of Sugarcane Biology, College of Agriculture, Guangxi University, Nanning 530004, China;
| | - Mei Yu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Ministry & Province Co-Sponsored Center of Collaborative Innovation for Sugarcane Industry, College of Life Science and Technology, Guangxi University, Nanning 530004, China; (Y.C.); (M.Y.)
| | - Baoshan Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Ministry & Province Co-Sponsored Center of Collaborative Innovation for Sugarcane Industry, College of Life Science and Technology, Guangxi University, Nanning 530004, China; (Y.C.); (M.Y.)
- Guangxi Key Laboratory of Sugarcane Biology, College of Agriculture, Guangxi University, Nanning 530004, China;
| | - Chengwu Zou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Ministry & Province Co-Sponsored Center of Collaborative Innovation for Sugarcane Industry, College of Life Science and Technology, Guangxi University, Nanning 530004, China; (Y.C.); (M.Y.)
- Guangxi Key Laboratory of Sugarcane Biology, College of Agriculture, Guangxi University, Nanning 530004, China;
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Rivera Pérez CA, Janz D, Schneider D, Daniel R, Polle A. Transcriptional Landscape of Ectomycorrhizal Fungi and Their Host Provides Insight into N Uptake from Forest Soil. mSystems 2022; 7:e0095721. [PMID: 35089084 PMCID: PMC8725588 DOI: 10.1128/msystems.00957-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 11/29/2021] [Indexed: 01/05/2023] Open
Abstract
Mineral nitrogen (N) is a major nutrient showing strong fluctuations in the environment due to anthropogenic activities. The acquisition and translocation of N to forest trees are achieved mainly by highly diverse ectomycorrhizal fungi (EMF) living in symbioses with their host roots. Here, we examined colonized root tips to characterize the entire root-associated fungal community by DNA metabarcoding-Illumina sequencing of the fungal internal transcribed spacer 2 (ITS2) molecular marker and used RNA sequencing to target metabolically active fungi and the plant transcriptome after N application. The study was conducted with beech (Fagus sylvatica L.), a dominant tree species in central Europe, grown in native forest soil. We demonstrate strong enrichment of 15N from nitrate or ammonium in the ectomycorrhizal roots by stable-isotope labeling. The relative abundance of the EMF members in the fungal community was correlated with their transcriptional abundances. The fungal metatranscriptome covered Kyoto Encyclopedia of Genes and Genomes (KEGG) and Eukaryotic Orthologous Groups (KOG) categories similar to those of model fungi and did not reveal significant changes related to N metabolization but revealed species-specific transcription patterns, supporting trait stability. In contrast to the resistance of the fungal metatranscriptome, the transcriptome of the host exhibited dedicated nitrate- or ammonium-responsive changes with the upregulation of transporters and enzymes required for nitrate reduction and a drastic enhancement of glutamine synthetase transcript levels, indicating the channeling of ammonium into the pathway for plant protein biosynthesis. Our results support that naturally assembled fungal communities living in association with the tree roots buffer nutritional signals in their own metabolism but do not shield plants from high environmental N levels. IMPORTANCE Although EMF are well known for their role in supporting tree N nutrition, the molecular mechanisms underlying N flux from the soil solution into the host through the ectomycorrhizal pathway remain widely unknown. Furthermore, ammonium and nitrate availability in the soil solution is subject to frequent oscillations that create a dynamic environment for the tree roots and associated microbes during N acquisition. Therefore, it is important to understand how root-associated mycobiomes and the tree roots handle these fluctuations. We studied the responses of the symbiotic partners by screening their transcriptomes after a sudden environmental flux of nitrate or ammonium. We show that the fungi and the host respond asynchronously, with the fungi displaying resistance to increased nitrate or ammonium and the host dynamically metabolizing the supplied N sources. This study provides insights into the molecular mechanisms of the symbiotic partners operating under N enrichment in a multidimensional symbiotic system.
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Affiliation(s)
- Carmen Alicia Rivera Pérez
- Forest Botany and Tree Physiology, Büsgen Institute, Georg-August University of Göttingen, Göttingen, Germany
| | - Dennis Janz
- Forest Botany and Tree Physiology, Büsgen Institute, Georg-August University of Göttingen, Göttingen, Germany
| | - Dominik Schneider
- Department of Genomic and Applied Microbiology, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
- Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
| | - Rolf Daniel
- Department of Genomic and Applied Microbiology, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
- Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
| | - Andrea Polle
- Forest Botany and Tree Physiology, Büsgen Institute, Georg-August University of Göttingen, Göttingen, Germany
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Boonchaisri S, Stevenson T, Dias DA. Utilization of GC-MS untargeted metabolomics to assess the delayed response of glufosinate treatment of transgenic herbicide resistant (HR) buffalo grasses (Stenotaphrum secundatum L.). Metabolomics 2020; 16:22. [PMID: 31989303 DOI: 10.1007/s11306-020-1644-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 01/22/2020] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Herbicide resistant (HR) buffalo grasses were genetically engineered to resist the non-selective herbicide, glufosinate in order to facilitate a modern, 'weeding program' which is highly effective in terms of minimizing costs and labor. The resistant trait was conferred by an insertion of the pat gene to allow for the production of the enzyme phosphinothricin acetyltransferase (PAT) to detoxify the glufosinate inhibitive effect. To date, there are only a few reports using metabolomics as well as molecular characterizations published for glufosinate-resistant crops with no reports on HR turfgrass. Therefore, for the first time, this study examines the metabolome of glufosinate-resistant buffalo grasses which not only will be useful to future growers but also the scientific community. OBJECTIVE A major aim of this present work is to characterize and evaluate the metabolic alterations which may arise from a genetic transformation of HR buffalo grasses by comprehensively using gas chromatography-mass spectrometry (GC-MS) based untargeted metabolomics. METHODS Eight-week old plants of 4 HR buffalo grasses, (93-1A, 93-2B, 93-3C and 93-5A) and 3 wild type varieties (WT 8-4A, WT 9-1B and WT 9-1B) were selected for physiological, molecular and metabolomics experiments. Plants were either sprayed with 1, 5, 10 and 15% v/v of glufosinate to evaluate the visual injuries or submerged in 5% v/v of glufosinate 3 days prior to a GC-MS based untargeted metabolomics analysis. In contrast, the control group was treated with distilled water. Leaves were extracted in 1:1 methanol:water and then analysed, using an in-house GC-MS untargeted workflow. RESULTS Results identified 199 metabolites with only 6 of them (cis-aconitic acid, allantoin, cellobiose, glyceric acid, maltose and octadecanoic acid) found to be statistically significant (p < 0.05) between the HR and wild type buffalo grass varieties compared to the control experiment. Among these metabolites, unusual accumulation of allantoin was prominent and was an unanticipated effect of the pat gene insertion. As expected, glufosinate treatment caused significant metabolic alterations in the sensitive wild type, with the up-regulation of several amino acids (e.g. phenylalanine and isoleucine) which was likely due to glufosinate-induced senescence. The aminoacyl-tRNA biosynthetic pathway was identified as the most significant enriched pathway as a result of glufosinate effects because a number of its intermediates were amino acids. CONCLUSION HR buffalo grasses were very similar to its wild type comparator based on a comprehensive GC-MS based untargeted metabolomics and therefore, should guarantee the safe use of these HR buffalo grasses. The current metabolomics analyses not only confirmed the effects of glufosinate to up-regulate free amino acid pools in the sensitive wild type but also several alterations in sugar, sugar phosphate and organic acid metabolism have been reported.
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Affiliation(s)
| | - Trevor Stevenson
- School of Science, RMIT University, Bundoora, VIC, 3083, Australia
| | - Daniel A Dias
- School of Health and Biomedical Sciences, Discipline of Laboratory Medicine, RMIT University, PO Box 71, Bundoora, VIC, 3083, Australia.
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Nehls U, Plassard C. Nitrogen and phosphate metabolism in ectomycorrhizas. THE NEW PHYTOLOGIST 2018; 220:1047-1058. [PMID: 29888395 DOI: 10.1111/nph.15257] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 05/01/2018] [Indexed: 05/23/2023]
Abstract
1047 I. Introduction 1047 II. Mobilization of soil N/P by ECM fungi 1048 III. N/P uptake 1048 IV. N/P assimilation 1049 V. N/P storage and remobilization 1049 VI. Hyphal N/P efflux at the plant-fungus interface 1052 VII. Conclusion and research needs 1054 Acknowledgements 1055 References 1055 SUMMARY: Nutrient homeostasis is essential for fungal cells and thus tightly adapted to the local demand in a mycelium with hyphal specialization. Based on selected ectomycorrhizal (ECM) fungal models, we outlined current concepts of nitrogen and phosphate nutrition and their limitations, and included knowledge from Baker's yeast when major gaps had to be filled. We covered the entire pathway from nutrient mobilization, import and local storage, distribution within the mycelium and export at the plant-fungus interface. Even when nutrient import and assimilation were broad issues for ECM fungi, we focused mainly on nitrate and organic phosphorus uptake, as other nitrogen/phosphorus (N/P) sources have been covered by recent reviews. Vacuolar N/P storage and mobilization represented another focus point of this review. Vacuoles are integrated into cellular homeostasis and central for an ECM mycelium at two locations: soil-growing hyphae and hyphae of the plant-fungus interface. Vacuoles are also involved in long-distance transport. We further discussed potential mechanisms of bidirectional long-distance nutrient transport (distances from millimetres to metres). A final focus of the review was N/P export at the plant-fungus interface, where we compared potential efflux mechanisms and pathways, and discussed their prerequisites.
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Affiliation(s)
- Uwe Nehls
- Botany, University of Bremen, Bremen, 28359, Germany
| | - Claude Plassard
- Eco & Sols, Université de Montpellier, INRA, CIRAD, IRD, Montpellier SupAgro, Montpellier, 34060, France
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Khouja H, Daghino S, Abbà S, Boutaraa F, Chalot M, Blaudez D, Martino E, Perotto S. OmGOGAT-disruption in the ericoid mycorrhizal fungus Oidiodendron maius induces reorganization of the N pathway and reduces tolerance to heavy-metals. Fungal Genet Biol 2014; 71:1-8. [DOI: 10.1016/j.fgb.2014.08.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 08/01/2014] [Accepted: 08/07/2014] [Indexed: 10/24/2022]
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Downes DJ, Davis MA, Kreutzberger SD, Taig BL, Todd RB. Regulation of the NADP-glutamate dehydrogenase gene gdhA in Aspergillus nidulans by the Zn(II)2Cys6 transcription factor LeuB. Microbiology (Reading) 2013; 159:2467-2480. [DOI: 10.1099/mic.0.071514-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Damien J. Downes
- Department of Genetics, University of Melbourne, Parkville, VIC 3010, Australia
- Department of Plant Pathology, Kansas State University, 4024 Throckmorton Plant Sciences Center, Manhattan, KS 66506, USA
| | - Meryl A. Davis
- Department of Genetics, University of Melbourne, Parkville, VIC 3010, Australia
| | | | - Brendan L. Taig
- Department of Genetics, University of Melbourne, Parkville, VIC 3010, Australia
| | - Richard B. Todd
- Department of Genetics, University of Melbourne, Parkville, VIC 3010, Australia
- Department of Plant Pathology, Kansas State University, 4024 Throckmorton Plant Sciences Center, Manhattan, KS 66506, USA
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Shah F, Rineau F, Canbäck B, Johansson T, Tunlid A. The molecular components of the extracellular protein-degradation pathways of the ectomycorrhizal fungus Paxillus involutus. THE NEW PHYTOLOGIST 2013; 200:875-887. [PMID: 23902518 PMCID: PMC4282482 DOI: 10.1111/nph.12425] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 06/25/2013] [Indexed: 05/20/2023]
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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Affiliation(s)
- Firoz Shah
- Department of Biology, Microbial Ecology Group, Lund UniversityEcology Building, SE-223 62, Lund, Sweden
| | - Francois Rineau
- Department of Biology, Microbial Ecology Group, Lund UniversityEcology Building, SE-223 62, Lund, Sweden
| | - Björn Canbäck
- Department of Biology, Microbial Ecology Group, Lund UniversityEcology Building, SE-223 62, Lund, Sweden
| | - Tomas Johansson
- Department of Biology, Microbial Ecology Group, Lund UniversityEcology Building, SE-223 62, Lund, Sweden
| | - Anders Tunlid
- Department of Biology, Microbial Ecology Group, Lund UniversityEcology Building, SE-223 62, Lund, Sweden
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Rineau F, Shah F, Smits MM, Persson P, Johansson T, Carleer R, Troein C, Tunlid A. Carbon availability triggers the decomposition of plant litter and assimilation of nitrogen by an ectomycorrhizal fungus. THE ISME JOURNAL 2013; 7:2010-22. [PMID: 23788332 PMCID: PMC3965319 DOI: 10.1038/ismej.2013.91] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 04/19/2013] [Accepted: 04/23/2013] [Indexed: 11/17/2022]
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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Affiliation(s)
- F Rineau
- Environmental Biology Group, Centre for Environmental Sciences, Hasselt University, Agoralaan, Diepenbeek, Belgium
| | - F Shah
- Department of Biology, Microbial Ecology Group, Ecology Building, Lund, Sweden
| | - M M Smits
- Environmental Biology Group, Centre for Environmental Sciences, Hasselt University, Agoralaan, Diepenbeek, Belgium
| | - P Persson
- Department of Chemistry, Umeå University, Umeå, Sweden
| | - T Johansson
- Department of Biology, Microbial Ecology Group, Ecology Building, Lund, Sweden
| | - R Carleer
- Applied and Analytical Chemistry, Hasselt University, Agoralaan, Diepenbeek, Belgium
| | - C Troein
- Department of Astronomy and Theoretical Physics, Lund University, Lund, Sweden
| | - A Tunlid
- Department of Biology, Microbial Ecology Group, Ecology Building, Lund, Sweden
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Abstract
AbstractBacteria and fungi from pristine soil, never exposed to glufosinate herbicide, were isolated and analyzed for glufosinate tolerance. Seven of the 15 tested isolates were sensitive to 1 mM glufosinate (an active ingredient of many nonselective contact herbicides), 5 were resistant to 4 mM glufosinate and 3 even to 8 mM glufosinate in liquid medium. None of the isolated microorganisms carried the gene for glufosinate resistance bar (bialaphos resistance) in its genome and at least in some of glufosinate-resistant isolates the increased glutamine synthetase level was detected as a possible resistance mechanism. The transfer of the bar glufosinate resistance gene from transgenic maize Bt 176 into glufosinate-sensitive soil bacterium Bacillus pumilus S1 was not detected under the laboratory conditions by a classical plate count method and PCR. The ecological risk of potential bar gene transfer from genetically modified plants into soil microcosms under natural circumstances is discussed.
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Alvarez M, Huygens D, Olivares E, Saavedra I, Alberdi M, Valenzuela E. Ectomycorrhizal fungi enhance nitrogen and phosphorus nutrition of Nothofagus dombeyi under drought conditions by regulating assimilative enzyme activities. PHYSIOLOGIA PLANTARUM 2009; 136:426-436. [PMID: 19470091 DOI: 10.1111/j.1399-3054.2009.01237.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Drought stress conditions (DC) reduce plant growth and nutrition, restraining the sustainable reestablishment of Nothofagus dombeyi in temperate south Chilean forest ecosystems. Ectomycorrhizal symbioses have been documented to enhance plant nitrogen (N) and phosphorus (P) uptake under drought, but the regulation of involved assimilative enzymes remains unclear. We studied 1-year-old N. dombeyi (Mirb.) Oerst. plants in association with the ectomycorrhizal fungi Pisolithus tinctorius (Pers.) Coker & Couch. and Descolea antartica Sing. In greenhouse experiments, shoot and root dry weights, mycorrhizal colonization, foliar N and P concentrations, and root enzyme activities [glutamate synthase (glutamine oxoglutarate aminotransferase (GOGAT), EC 1.4.1.13-14), glutamine synthetase (GS, EC 6.3.1.2), glutamate dehydrogenase (GDH, EC 1.4.1.2-4), nitrate reductase (NR, EC 1.6.6.1), and acid phosphomonoesterase (PME, EC 3.1.3.1-2)] were determined as a function of soil-water content. Inoculation of N. dombeyi with P. tinctorius and D. antartica significantly stimulated plant growth and increased plant foliar N and P concentrations, especially under DC. Ectomycorrhizal inoculation increased the activity of all studied enzymes relative to non-mycorrhizal plants under drought. We speculate that GDH is a key enzyme involved in the enhancement of ectomycorrhizal carbon (C) availability by fuelling the tricarboxylic acid (TCA) cycle under conditions of drought-induced carbon deficit. All studied assimilative enzymes of the ectomycorrhizal associations, involved in C, N, and P transfers, are closely interlinked and interdependent. The up-regulation of assimilative enzyme activities by ectomycorrhizal fungal root colonizers acts as a functional mechanism to increase seedling endurance to drought. We insist upon incorporating ectomycorrhizal inoculation in existing Chilean afforestation programs.
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Affiliation(s)
- Maricel Alvarez
- Universidad Austral de Chile, Instituto de Botánica, Valdivia, Chile.
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Cao T, Kim YM, Kav NNV, Strelkov SE. A proteomic evaluation of Pyrenophora tritici-repentis, causal agent of tan spot of wheat, reveals major differences between virulent and avirulent isolates. Proteomics 2009; 9:1177-96. [PMID: 19206107 DOI: 10.1002/pmic.200800475] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Pyrenophora tritici-repentis causes tan spot, an important foliar disease of wheat. The fungus produces multiple host-specific toxins, including Ptr ToxB, a chlorosis-inducing protein encoded by the ToxB gene. A homolog of ToxB is also found in avirulent isolates of the fungus. In order to improve understanding of the role of this homolog and evaluate the general pathogenic ability of P. tritici-repentis, we compared the proteomes of avirulent race 4 and virulent race 5 isolates of the pathogen. Western blotting analysis revealed the presence of Ptr ToxB in spore germination and culture fluids of race 5 but not race 4. A comprehensive proteome-level comparison by 2-DE indicated 133 differentially abundant proteins in the secretome (29 proteins) and mycelium (104 proteins) of races 4 and 5, of which 63 were identified by MS/MS. A number of the proteins found to be up-regulated in race 5 have been implicated in microbial virulence in other pathosystems, and included the secreted enzymes alpha-mannosidase and exo-beta-1,3-glucanase, heat-shock and BiP proteins, and various metabolic enzymes. These proteome-level differences suggest a reduced general pathogenic ability in race 4 of P. tritici-repentis, irrespective of toxin production. Such differences may reflect an adaptation to a saprophytic habit.
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Affiliation(s)
- Tiesen Cao
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
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Courty PE, Poletto M, Duchaussoy F, Buée M, Garbaye J, Martin F. Gene transcription in Lactarius quietus-Quercus petraea ectomycorrhizas from a forest soil. Appl Environ Microbiol 2008; 74:6598-605. [PMID: 18791033 PMCID: PMC2576711 DOI: 10.1128/aem.00584-08] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 08/29/2008] [Indexed: 11/20/2022] Open
Abstract
Extracting fungal mRNA from ectomycorrhizas (ECMs) and forest soil samples for monitoring in situ metabolic activities is a significant challenge when studying the role of ECMs in biogeochemical cycles. A robust, simple, rapid, and effective method was developed for extracting RNA from rhizospheric soil and ECMs by adapting previous grinding and lysis methods. The quality and yield of the extracted RNA were sufficient to be used for reverse transcription. RNA extracted from ECMs of Lactarius quietus in a 100-year-old oak stand was used to construct a cDNA library and sequence expressed sequence tags. The transcripts of many genes involved in primary metabolism and in the degradation of organic matter were found. The transcription levels of four targeted fungal genes (glutamine synthase, a general amino acid transporter, a tyrosinase, and N-acetylhexosaminidase) were measured by quantitative reverse transcription-PCR in ECMs and in the ectomycorrhizospheric soil (the soil surrounding the ECMs containing the extraradical mycelium) in forest samples. On average, levels of gene expression for the L. quietus ECM root tips were similar to those for the extraradical mycelium, although gene expression varied up to 10-fold among the samples. This study demonstrates that gene expression from ECMs and soil can be analyzed. These results provide new perspectives for investigating the role of ectomycorrhizal fungi in the functioning of forest ecosystems.
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Affiliation(s)
- P E Courty
- UMR 1136, INRA-Nancy Université, Interactions Arbres/Microorganismes, INRA-Nancy, 54280 Champenoux, France.
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Nuutinen JT, Timonen S. Identification of nitrogen mineralization enzymes, L-amino acid oxidases, from the ectomycorrhizal fungi Hebeloma spp. and Laccaria bicolor. ACTA ACUST UNITED AC 2008; 112:1453-64. [PMID: 18675352 DOI: 10.1016/j.mycres.2008.06.023] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Revised: 01/28/2008] [Accepted: 06/16/2008] [Indexed: 10/21/2022]
Abstract
Amino acids are major nitrogen sources in soils and they harbour a central position in the nitrogen metabolism of cells. We determined whether Hebeloma spp. and Laccaria bicolor expressed the enzyme L-amino acid oxidase (LAO), which catalyses the oxidative deamination of the alpha-amino group of L-amino acids. We measured LAO activities from the mycelial extracts of seven laboratory-grown fungal strains with three methods, and we measured how LAO activities were expressed in one Hebeloma sp. strain grown on four nitrogen sources. Hebeloma spp. and L. bicolor converted L-phenylalanine, but not D-phenylalanine, to hydrogen peroxide, 2-oxoacid, and ammonia, suggesting that they expressed LAO enzymes. The enzymes utilized five out of seven tested L-amino acids as substrates. LAO activities were maximal at pH 8, where Michaelis constant (Km) values were 2-5mm. The LAO of Hebeloma sp. was expressed on every nitrogen source analysed, and the activities were the highest in mycelia grown in nitrogen-rich conditions. We suggest that LAO is a mechanism for cellular amino acid catabolism in Hebeloma spp. and L. bicolor. Many soil bacteria and fungi also express LAO enzymes that have broad substrate specificities. Therefore, LAO is a potential candidate for a mechanism that catalyses nitrogen mineralization from amino acids at the ecosystem level.
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Affiliation(s)
- Jaro T Nuutinen
- University of Helsinki, Department of Applied Biology, P.O. Box 27, FI-00014 University of Helsinki, Finland.
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Mohr KI, Tebbe CC. Field study results on the probability and risk of a horizontal gene transfer from transgenic herbicide-resistant oilseed rape pollen to gut bacteria of bees. Appl Microbiol Biotechnol 2007; 75:573-82. [PMID: 17273854 DOI: 10.1007/s00253-007-0846-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Revised: 01/02/2007] [Accepted: 01/04/2007] [Indexed: 10/23/2022]
Abstract
Bees are specifically subjected to intimate contacts with transgenic plants due to their feeding activities on pollen. In this study, the probability and ecological risk of a gene transfer from pollen to gut bacteria of bees was investigated with larvae of Apis mellifera (honeybee), Bombus terrestris (bumblebee), and Osmia bicornis (red mason bee), all collected at a flowering transgenic oilseed rape field. The plants were genetically engineered with the pat-gene, conferring resistance against glufosinate (syn. phosphinothricin), a glutamine-synthetase inhibitor in plants and microorganisms. Ninety-six bacterial strains were isolated and characterized by 16S rRNA gene sequencing, revealing that Firmicutes represented 58% of the isolates, Actinobacteria 31%, and Proteobacteria 11%, respectively. Of all isolates, 40% were resistant to 1 mM glufosinate, and 11% even to 10 mM. Resistant phenotypes were found in all phylogenetic groups. None of the resistant phenotypes carried the recombinant pat-gene in its genome. The threshold of detecting gene transfer in this field study was relatively insensitive due to the high background of natural glufosinate resistance. However, the broad occurrence of glufosinate-resistant bacteria from different phylogenetic groups suggests that rare events of horizontal gene transfer will not add significantly to natural bacterial glufosinate resistance.
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Affiliation(s)
- Kathrin I Mohr
- Institut für Agrarökologie, Bundesforschungsanstalt für Landwirtschaft (FAL), Bundesallee 50, 38116, Braunschweig, Germany
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