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Jiang C, Zhang S, Zhang Q, Tao Y, Wang C, Xu JR. FgSKN7 and FgATF1 have overlapping functions in ascosporogenesis, pathogenesis and stress responses in Fusarium graminearum. Environ Microbiol 2014; 17:1245-60. [PMID: 25040476 DOI: 10.1111/1462-2920.12561] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 06/28/2014] [Indexed: 11/30/2022]
Abstract
Fusarium head blight caused by Fusarium graminearum is one of the most destructive diseases of wheat and barley. Deoxynivalenol (DON) produced by the pathogen is an important mycotoxins and virulence factor. Because oxidative burst is a common defense response and reactive oxygen species (ROS) induces DON production, in this study, we characterized functional relationships of three stress-related transcription factor genes FgAP1, FgATF1 and FgSKN7. Although all of them played a role in tolerance to oxidative stress, deletion of FgAP1 or FgATF1 had no significant effect on DON production. In contrast, Fgskn7 mutants were reduced in DON production and defective in H2 O2 -induced TRI gene expression. The Fgap1 mutant had no detectable phenotype other than increased sensitivity to H2 O2 and Fgap1 Fgatf1 and Fgap1 Fgskn7 mutants lacked additional or more severe phenotypes than the single mutants. The Fgatf1, but not Fgskn7, mutant was significantly reduced in virulence and delayed in ascospore release. The Fgskn7 Fgatf1 double mutant had more severe defects in growth, conidiation and virulence than the Fgatf1 or Fgskn7 mutant. Instead of producing four-celled ascospores, it formed eight small, single-celled ascospores in each ascus. Therefore, FgSKN7 and FgATF1 must have overlapping functions in intracellular ROS signalling for growth, development and pathogenesis in F. graminearum.
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Affiliation(s)
- Cong Jiang
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwestern A&F University, Yangling, Shaanxi, 712100, China; Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, 47907, USA
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252
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Finiti I, de la O Leyva M, Vicedo B, Gómez-Pastor R, López-Cruz J, García-Agustín P, Real MD, González-Bosch C. Hexanoic acid protects tomato plants against Botrytis cinerea by priming defence responses and reducing oxidative stress. MOLECULAR PLANT PATHOLOGY 2014; 15:550-62. [PMID: 24320938 PMCID: PMC6638872 DOI: 10.1111/mpp.12112] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Treatment with the resistance priming inducer hexanoic acid (Hx) protects tomato plants from Botrytis cinerea by activating defence responses. To investigate the molecular mechanisms underlying hexanoic acid-induced resistance (Hx-IR), we compared the expression profiles of three different conditions: Botrytis-infected plants (Inf), Hx-treated plants (Hx) and Hx-treated + infected plants (Hx+Inf). The microarray analysis at 24 h post-inoculation showed that Hx and Hx+Inf plants exhibited the differential expression and priming of many Botrytis-induced genes. Interestingly, we found that the activation by Hx of other genes was not altered by the fungus at this time point. These genes may be considered to be specific targets of the Hx priming effect and may help to elucidate its mechanisms of action. It is noteworthy that, in Hx and Hx+Inf plants, there was up-regulation of proteinase inhibitor genes, DNA-binding factors, enzymes involved in plant hormone signalling and synthesis, and, remarkably, the genes involved in oxidative stress. Given the relevance of the oxidative burst occurring in plant-pathogen interactions, the effect of Hx on this process was studied in depth. We showed by specific staining that reactive oxygen species (ROS) accumulation in Hx+Inf plants was reduced and more restricted around infection sites. In addition, these plants showed higher ratios of reduced to oxidized glutathione and ascorbate, and normal levels of antioxidant activities. The results obtained indicate that Hx protects tomato plants from B. cinerea by regulating and priming Botrytis-specific and non-specific genes, preventing the harmful effects of oxidative stress produced by infection.
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Affiliation(s)
- Ivan Finiti
- Departamento de Bioquímica y Biología Molecular, Instituto de Agroquímica y Tecnología de los Alimentos (IATA, CSIC), Universidad de Valencia, Avda. Agustín Escardino 7, 46980, Paterna, Valencia, Spain
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253
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Hogan D, Wheeler RT. The complex roles of NADPH oxidases in fungal infection. Cell Microbiol 2014; 16:1156-67. [PMID: 24905433 DOI: 10.1111/cmi.12320] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 05/27/2014] [Accepted: 05/29/2014] [Indexed: 12/21/2022]
Abstract
NADPH oxidases play key roles in immunity and inflammation that go beyond the production of microbicidal reactive oxygen species (ROS). The past decade has brought a new appreciation for the diversity of roles played by ROS in signalling associated with inflammation and immunity. NADPH oxidase activity affects disease outcome during infections by human pathogenic fungi, an important group of emerging and opportunistic pathogens that includes Candida, Aspergillus and Cryptococcus species. Here we review how alternative roles of NADPH oxidase activity impact fungal infection and how ROS signalling affects fungal physiology. Particular attention is paid to roles for NADPH oxidase in immune migration, immunoregulation in pulmonary infection, neutrophil extracellular trap formation, autophagy and inflammasome activity. These recent advances highlight the power and versatility of spatiotemporally controlled redox regulation in the context of infection, and point to a need to understand the molecular consequences of NADPH oxidase activity in the cell.
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Affiliation(s)
- Deborah Hogan
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
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254
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Espinosa F, Garrido I, Ortega A, Casimiro I, Álvarez-Tinaut MC. Redox activities and ROS, NO and phenylpropanoids production by axenically cultured intact olive seedling roots after interaction with a mycorrhizal or a pathogenic fungus. PLoS One 2014; 9:e100132. [PMID: 24967716 PMCID: PMC4072634 DOI: 10.1371/journal.pone.0100132] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 05/22/2014] [Indexed: 12/29/2022] Open
Abstract
Roots of intact olive seedlings, axenically cultured, were alternatively placed in contact with Rhizophagus irregularis (mycorrhizal) or Verticillim dahliae (pathogenic) fungi. MeJA treatments were also included. In vivo redox activities in the apoplast of the intact roots (anion superoxide generation, superoxide dismutase and peroxidase activities) were measured. All our results showed that apoplastic redox activities of intact seedling roots in contact with the compatible mycorrhizal fungus were clearly attenuated in comparison with the pathogenic fungus or treated with MeJA, even at the early stages of treatment used. Total phenolics, flavonoids and phenylpropanoid glycosides were also quantified. Roots in contact with the mycorrhizal fungus did not enhance the biosynthesis of phenolic compounds with respect to controls, while those in contact with the pathogenic one significantly enhanced the biosynthesis of all phenolic fractions measured. Reactive oxygen species and nitric oxid accumulation in roots were examined by fluorescence microscopy. All of them presented much higher accumulation in roots in contact with the pathogenic than with the mycorrhizal fungus. Altogether these results indicate that intact olive seedling roots clearly differentiated between mycorrhizal and pathogenic fungi, attenuating defense reactions against the first to facilitate its establishment, while inducing a strong and sustained defense reaction against the second. Both reactive oxygen and nitrogen species seemed to be involved in these responses from the first moments of contact. However, further investigations are required to clarify the proposed crosstalk between them and their respective roles in these responses since fluorescence images of roots revealed that reactive oxygen species were mainly accumulated in the apoplast (congruently with the measured redox activities in this compartment) while nitric oxid was mainly stored in the cytosol.
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Affiliation(s)
- Francisco Espinosa
- Departamento de Biología Vegetal, Ecología y Ciencias de la Tierra, Universidad de Extremadura, Avenida Elvas s/n, Badajoz, Spain
| | - Inmaculada Garrido
- Departamento de Biología Vegetal, Ecología y Ciencias de la Tierra, Universidad de Extremadura, Avenida Elvas s/n, Badajoz, Spain
| | - Alfonso Ortega
- Departamento de Biología Vegetal, Ecología y Ciencias de la Tierra, Universidad de Extremadura, Avenida Elvas s/n, Badajoz, Spain
| | - Ilda Casimiro
- Departamento de Anatomía, Biología Celular y Zoología, Universidad de Extremadura, Avenida Elvas s/n, Badajoz, Spain
| | - Mª Carmen Álvarez-Tinaut
- Departamento de Biología Vegetal, Ecología y Ciencias de la Tierra, Universidad de Extremadura, Avenida Elvas s/n, Badajoz, Spain
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255
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Nagygyörgy E, Kovács B, Leiter É, Miskei M, Pócsi I, Hornok L, Ádám A. Toxicity of abiotic stressors to Fusarium species: differences in hydrogen peroxide and fungicide tolerance. Acta Microbiol Immunol Hung 2014; 61:189-208. [PMID: 24939687 DOI: 10.1556/amicr.61.2014.2.9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Stress sensitivity of three related phytopathogenic Fusarium species (Fusarium graminearum, Fusarium oxysporum and Fusarium verticillioides) to different oxidative, osmotic, cell wall, membrane, fungicide stressors and an antifungal protein (PAF) were studied in vitro. The most prominent and significant differences were found in oxidative stress tolerance: all the three F. graminearum strains showed much higher sensitivity to hydrogen peroxide and, to a lesser extent, to menadione than the other two species. High sensitivity of F. verticillioides strains was also detectable to an azole drug, Ketoconazole. Surprisingly, no or limited differences were observed in response to other oxidative, osmotic and cell wall stressors. These results indicate that fungal oxidative stress response and especially the response to hydrogen peroxide (this compound is involved in a wide range of plant-fungus interactions) might be modified on niche-specific manner in these phylogenetically related Fusarium species depending on their pathogenic strategy. Supporting the increased hydrogen peroxide sensitivity of F. graminearum, genome-wide analysis of stress signal transduction pathways revealed the absence one CatC-type catalase gene in F. graminearum in comparison to the other two species.
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Affiliation(s)
- Emese Nagygyörgy
- 1 Hungarian Academy of Sciences Plant Protection Institute, Centre for Agricultural Research H-1525 Budapest P.O. Box 102 Hungary
| | - Barbara Kovács
- 2 University of Debrecen Department of Microbial Biotechnology and Cell Biology, Faculty of Sciences H-4032 Debrecen Egyetem tér 1 Hungary
| | - Éva Leiter
- 2 University of Debrecen Department of Microbial Biotechnology and Cell Biology, Faculty of Sciences H-4032 Debrecen Egyetem tér 1 Hungary
| | - Márton Miskei
- 2 University of Debrecen Department of Microbial Biotechnology and Cell Biology, Faculty of Sciences H-4032 Debrecen Egyetem tér 1 Hungary
| | - István Pócsi
- 2 University of Debrecen Department of Microbial Biotechnology and Cell Biology, Faculty of Sciences H-4032 Debrecen Egyetem tér 1 Hungary
| | - László Hornok
- 3 Szent István University Mycology Group of the Hungarian Academy of Sciences, Institute of Plant Protection H-2103 Gödöllő Páter K. u. 1 Hungary
| | - Attila Ádám
- 1 Hungarian Academy of Sciences Plant Protection Institute, Centre for Agricultural Research H-1525 Budapest P.O. Box 102 Hungary
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256
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Lalève A, Fillinger S, Walker AS. Fitness measurement reveals contrasting costs in homologous recombinant mutants of Botrytis cinerea resistant to succinate dehydrogenase inhibitors. Fungal Genet Biol 2014; 67:24-36. [DOI: 10.1016/j.fgb.2014.03.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 03/20/2014] [Accepted: 03/21/2014] [Indexed: 01/22/2023]
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257
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Sun Y, Wang C, Yang B, Wu F, Hao X, Liang W, Niu F, Yan J, Zhang H, Wang B, Deyholos MK, Jiang YQ. Identification and functional analysis of mitogen-activated protein kinase kinase kinase (MAPKKK) genes in canola (Brassica napus L.). JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:2171-88. [PMID: 24604738 PMCID: PMC3991747 DOI: 10.1093/jxb/eru092] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Mitogen-activated protein kinase (MAPK) signalling cascades, consisting of three types of reversibly phosphorylated kinases (MAPKKK, MAPKK, and MAPK), are involved in important processes including plant immunity and hormone responses. The MAPKKKs comprise the largest family in the MAPK cascades, yet only a few of these genes have been associated with physiological functions, even in the model plant Arabidopsis thaliana. Canola (Brassica napus L.) is one of the most important oilseed crops in China and worldwide. To explore MAPKKK functions in biotic and abiotic stress responses in canola, 66 MAPKKK genes were identified and 28 of them were cloned. Phylogenetic analysis of these canola MAPKKKs with homologous genes from representative species classified them into three groups (A-C), comprising four MAPKKKs, seven ZIKs, and 17 Raf genes. A further 15 interaction pairs between these MAPKKKs and the downstream BnaMKKs were identified through a yeast two-hybrid assay. The interactions were further validated through bimolecular fluorescence complementation (BiFC) analysis. In addition, by quantitative real-time reverse transcription-PCR, it was further observed that some of these BnaMAPKKK genes were regulated by different hormone stimuli, abiotic stresses, or fungal pathogen treatments. Interestingly, two novel BnaMAPKKK genes, BnaMAPKKK18 and BnaMAPKKK19, which could elicit hypersensitive response (HR)-like cell death when transiently expressed in Nicotiana benthamiana leaves, were successfully identified. Moreover, it was found that BnaMAPKKK19 probably mediated cell death through BnaMKK9. Overall, the present work has laid the foundation for further characterization of this important MAPKKK gene family in canola.
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Affiliation(s)
- Yun Sun
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
- * These authors contributed equally to this work
| | - Chen Wang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
- * These authors contributed equally to this work
| | - Bo Yang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
- * These authors contributed equally to this work
| | - Feifei Wu
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Xueyu Hao
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Wanwan Liang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Fangfang Niu
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Jingli Yan
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Hanfeng Zhang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Boya Wang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
| | - Michael K. Deyholos
- Department of Biological Sciences, University of Alberta, Edmonton T6G 2E9, Canada
| | - Yuan-Qing Jiang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China
- To whom correspondence should be addressed. E-mail: or
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258
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Beys-da-Silva WO, Santi L, Berger M, Calzolari D, Passos DO, Guimarães JA, Moresco JJ, Yates JR. Secretome of the biocontrol agent metarhizium anisopliae induced by the cuticle of the cotton pest Dysdercus peruvianus reveals new insights into infection. J Proteome Res 2014; 13:2282-96. [PMID: 24702058 PMCID: PMC4012838 DOI: 10.1021/pr401204y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
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Metarhizium anisopliae is an entomopathogenic
fungus that has evolved specialized strategies to infect insect hosts.
Here we analyzed secreted proteins related to Dysdercus peruvianus infection. Using shotgun proteomics, abundance changes in 71 proteins
were identified after exposure to host cuticle. Among these proteins
were classical fungal effectors secreted by pathogens to degrade physical
barriers and alter host physiology. These include lipolytic enzymes,
Pr1A, B, C, I, and J proteases, ROS-related proteins, oxidorreductases,
and signaling proteins. Protein interaction networks were generated
postulating interesting candidates for further studies, including
Pr1C, based on possible functional interactions. On the basis of these
results, we propose that M. anisopliae is degrading
host components and actively secreting proteins to manage the physiology
of the host. Interestingly, the secretion of these factors occurs
in the absence of a host response. The findings presented here are
an important step in understanding the host–pathogen interaction
and developing more efficient biocontrol of D. peruvianus by M. anisopliae.
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Affiliation(s)
- Walter O Beys-da-Silva
- Department of Chemical Physiology and ‡Department of Cell and Molecular Biology, The Scripps Research Institute , 10550 North Torrey Pines Road, La Jolla, California 92037, United States
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259
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Tran VT, Braus-Stromeyer SA, Kusch H, Reusche M, Kaever A, Kühn A, Valerius O, Landesfeind M, Aßhauer K, Tech M, Hoff K, Pena-Centeno T, Stanke M, Lipka V, Braus GH. Verticillium transcription activator of adhesion Vta2 suppresses microsclerotia formation and is required for systemic infection of plant roots. THE NEW PHYTOLOGIST 2014; 202:565-581. [PMID: 24433459 DOI: 10.1111/nph.12671] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 12/03/2013] [Indexed: 05/05/2023]
Abstract
Six transcription regulatory genes of the Verticillium plant pathogen, which reprogrammed nonadherent budding yeasts for adhesion, were isolated by a genetic screen to identify control elements for early plant infection. Verticillium transcription activator of adhesion Vta2 is highly conserved in filamentous fungi but not present in yeasts. The Magnaporthe grisea ortholog conidiation regulator Con7 controls the formation of appressoria which are absent in Verticillium species. Vta2 was analyzed by using genetics, cell biology, transcriptomics, secretome proteomics and plant pathogenicity assays. Nuclear Vta2 activates the expression of the adhesin-encoding yeast flocculin genes FLO1 and FLO11. Vta2 is required for fungal growth of Verticillium where it is a positive regulator of conidiation. Vta2 is mandatory for accurate timing and suppression of microsclerotia as resting structures. Vta2 controls expression of 270 transcripts, including 10 putative genes for adhesins and 57 for secreted proteins. Vta2 controls the level of 125 secreted proteins, including putative adhesins or effector molecules and a secreted catalase-peroxidase. Vta2 is a major regulator of fungal pathogenesis, and controls host-plant root infection and H2 O2 detoxification. Verticillium impaired in Vta2 is unable to colonize plants and induce disease symptoms. Vta2 represents an interesting target for controlling the growth and development of these vascular pathogens.
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Affiliation(s)
- Van-Tuan Tran
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Grisebachstr. 8, D-37077, Göttingen, Germany
- Department of Microbiology, Faculty of Biology, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam
| | - Susanna A Braus-Stromeyer
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Grisebachstr. 8, D-37077, Göttingen, Germany
| | - Harald Kusch
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Grisebachstr. 8, D-37077, Göttingen, Germany
| | - Michael Reusche
- Department of Plant Cell Biology, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, D-37077, Göttingen, Germany
| | - Alexander Kaever
- Department of Bioinformatics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Goldschmidtstr. 1, D-37077, Göttingen, Germany
| | - Anika Kühn
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Grisebachstr. 8, D-37077, Göttingen, Germany
| | - Oliver Valerius
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Grisebachstr. 8, D-37077, Göttingen, Germany
| | - Manuel Landesfeind
- Department of Bioinformatics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Goldschmidtstr. 1, D-37077, Göttingen, Germany
| | - Kathrin Aßhauer
- Department of Bioinformatics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Goldschmidtstr. 1, D-37077, Göttingen, Germany
| | - Maike Tech
- Department of Bioinformatics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Goldschmidtstr. 1, D-37077, Göttingen, Germany
| | - Katharina Hoff
- Institute for Mathematics and Computer Science, Ernst-Moritz-Arndt-University Greifswald, Walther-Rathenau-Straße 47, D-17487, Greifswald, Germany
| | - Tonatiuh Pena-Centeno
- Institute for Mathematics and Computer Science, Ernst-Moritz-Arndt-University Greifswald, Walther-Rathenau-Straße 47, D-17487, Greifswald, Germany
| | - Mario Stanke
- Institute for Mathematics and Computer Science, Ernst-Moritz-Arndt-University Greifswald, Walther-Rathenau-Straße 47, D-17487, Greifswald, Germany
| | - Volker Lipka
- Department of Plant Cell Biology, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, D-37077, Göttingen, Germany
| | - Gerhard H Braus
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August-University Göttingen, Grisebachstr. 8, D-37077, Göttingen, Germany
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260
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The transcription factor BcLTF1 regulates virulence and light responses in the necrotrophic plant pathogen Botrytis cinerea. PLoS Genet 2014; 10:e1004040. [PMID: 24415947 PMCID: PMC3886904 DOI: 10.1371/journal.pgen.1004040] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 11/01/2013] [Indexed: 01/16/2023] Open
Abstract
Botrytis cinerea is the causal agent of gray mold diseases in a range of dicotyledonous plant species. The fungus can reproduce asexually by forming macroconidia for dispersal and sclerotia for survival; the latter also participate in sexual reproduction by bearing the apothecia after fertilization by microconidia. Light induces the differentiation of conidia and apothecia, while sclerotia are exclusively formed in the absence of light. The relevance of light for virulence of the fungus is not obvious, but infections are observed under natural illumination as well as in constant darkness. By a random mutagenesis approach, we identified a novel virulence-related gene encoding a GATA transcription factor (BcLTF1 for light-responsive TF1) with characterized homologues in Aspergillus nidulans (NsdD) and Neurospora crassa (SUB-1). By deletion and over-expression of bcltf1, we confirmed the predicted role of the transcription factor in virulence, and discovered furthermore its functions in regulation of light-dependent differentiation, the equilibrium between production and scavenging of reactive oxygen species (ROS), and secondary metabolism. Microarray analyses revealed 293 light-responsive genes, and that the expression levels of the majority of these genes (66%) are modulated by BcLTF1. In addition, the deletion of bcltf1 affects the expression of 1,539 genes irrespective of the light conditions, including the overexpression of known and so far uncharacterized secondary metabolism-related genes. Increased expression of genes encoding alternative respiration enzymes, such as the alternative oxidase (AOX), suggest a mitochondrial dysfunction in the absence of bcltf1. The hypersensitivity of Δbctlf1 mutants to exogenously applied oxidative stress - even in the absence of light - and the restoration of virulence and growth rates in continuous light by antioxidants, indicate that BcLTF1 is required to cope with oxidative stress that is caused either by exposure to light or arising during host infection. Both fungal pathogens and their host plants respond to light, which represents an important environmental cue. Unlike plants using light for energy generation, filamentous fungi use light, or its absence, as a general signal for orientation (night/day, underground/on the surface). Therefore, dependent on the ecological niche of the fungus, light may control the development of reproductive structures (photomorphogenesis), the dispersal of propagules (phototropism of reproductive structures) and the circadian rhythm. As in other organisms, fungi have to protect themselves against the detrimental effects of light, i.e. the damage to macromolecules by emerging singlet oxygen. Adaptive responses are the accumulation of pigments, especially in the reproductive and survival structures such as spores, sclerotia and fruiting bodies. Light is sensed by fungal photoreceptors leading to quick responses on the transcriptional level, and is furthermore considered to result in the accumulation of reactive oxygen species (ROS). In this study, we provide evidence that an unbalanced ROS homoeostasis (generation outweighs detoxification) caused by the deletion of the light-responsive transcription factor BcLTF1 impairs the ability of the necrotrophic pathogen Botrytis cinerea to grow in the presence of additional oxidative stress arising during illumination or during infection of the host.
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261
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New insights into the roles of NADPH oxidases in sexual development and ascospore germination in Sordaria macrospora. Genetics 2014; 196:729-44. [PMID: 24407906 DOI: 10.1534/genetics.113.159368] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
NADPH oxidase (NOX)-derived reactive oxygen species (ROS) act as signaling determinants that induce different cellular processes. To characterize NOX function during fungal development, we utilized the genetically tractable ascomycete Sordaria macrospora. Genome sequencing of a sterile mutant led us to identify the NADPH oxidase encoding nox1 as a gene required for fruiting body formation, regular hyphal growth, and hyphal fusion. These phenotypes are shared by nor1, lacking the NOX regulator NOR1. Further phenotypic analyses revealed a high correlation between increased ROS production and hyphal fusion deficiencies in nox1 and other sterile mutants. A genome-wide transcriptional profiling analysis of mycelia and isolated protoperithecia from wild type and nox1 revealed that nox1 inactivation affects the expression of genes related to cytoskeleton remodeling, hyphal fusion, metabolism, and mitochondrial respiration. Genetic analysis of nox2, lacking the NADPH oxidase 2 gene, nor1, and transcription factor deletion mutant ste12, revealed a strict melanin-dependent ascospore germination defect, indicating a common genetic pathway for these three genes. We report that gsa3, encoding a G-protein α-subunit, and sac1, encoding cAMP-generating adenylate cyclase, act in a separate pathway during the germination process. The finding that cAMP inhibits ascospore germination in a melanin-dependent manner supports a model in which cAMP inhibits NOX2 activity, thus suggesting a link between both pathways. Our results expand the current knowledge on the role of NOX enzymes in fungal development and provide a frame to define upstream and downstream components of the NOX signaling pathways in fungi.
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262
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Abstract
Gene transfer has been identified as a prevalent and pervasive phenomenon and an important source of genomic innovation in bacteria. The role of gene transfer in microbial eukaryotes seems to be of a reduced magnitude but in some cases can drive important evolutionary innovations, such as new functions that underpin the colonization of different niches. The aim of this review is to summarize published cases that support the hypothesis that horizontal gene transfer (HGT) has played a role in the evolution of phytopathogenic traits in fungi and oomycetes. Our survey of the literature identifies 46 proposed cases of transfer of genes that have a putative or experimentally demonstrable phytopathogenic function. When considering the life-cycle steps through which a pathogen must progress, the majority of the HGTs identified are associated with invading, degrading, and manipulating the host. Taken together, these data suggest HGT has played a role in shaping how fungi and oomycetes colonize plant hosts.
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Affiliation(s)
- Darren Soanes
- Biosciences, University of Exeter, Exeter, EX4 4QD, United Kingdom;
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263
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Turrà D, Segorbe D, Di Pietro A. Protein kinases in plant-pathogenic fungi: conserved regulators of infection. ANNUAL REVIEW OF PHYTOPATHOLOGY 2014; 52:267-88. [PMID: 25090477 DOI: 10.1146/annurev-phyto-102313-050143] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Phytopathogenic fungi have evolved an amazing diversity of infection modes and nutritional strategies, yet the signaling pathways that govern pathogenicity are remarkably conserved. Protein kinases (PKs) catalyze the reversible phosphorylation of proteins, regulating a variety of cellular processes. Here, we present an overview of our current understanding of the different classes of PKs that contribute to fungal pathogenicity on plants and of the mechanisms that regulate and coordinate PK activity during infection-related development. In addition to the well-studied PK modules, such as MAPK (mitogen-activated protein kinase) and cAMP (cyclic adenosine monophosphate)-PKA (protein kinase A) cascades, we also discuss new PK pathways that have emerged in recent years as key players of pathogenic development and disease. Understanding how conserved PK signaling networks have been recruited during the evolution of fungal pathogenicity not only advances our knowledge of the highly elaborate infection process but may also lead to the development of novel strategies for the control of plant disease.
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Affiliation(s)
- David Turrà
- Departamento de Genética and Campus de Excelencia Agroalimentario (ceiA3), Universidad de Córdoba, 14071 Córdoba, Spain; , ,
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264
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Aranega-Bou P, de la O Leyva M, Finiti I, García-Agustín P, González-Bosch C. Priming of plant resistance by natural compounds. Hexanoic acid as a model. FRONTIERS IN PLANT SCIENCE 2014; 5:488. [PMID: 25324848 PMCID: PMC4181288 DOI: 10.3389/fpls.2014.00488] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 09/03/2014] [Indexed: 05/18/2023]
Abstract
Some alternative control strategies of currently emerging plant diseases are based on the use of resistance inducers. This review highlights the recent advances made in the characterization of natural compounds that induce resistance by a priming mechanism. These include vitamins, chitosans, oligogalacturonides, volatile organic compounds, azelaic and pipecolic acid, among others. Overall, other than providing novel disease control strategies that meet environmental regulations, natural priming agents are valuable tools to help unravel the complex mechanisms underlying the induced resistance (IR) phenomenon. The data presented in this review reflect the novel contributions made from studying these natural plant inducers, with special emphasis placed on hexanoic acid (Hx), proposed herein as a model tool for this research field. Hx is a potent natural priming agent of proven efficiency in a wide range of host plants and pathogens. It can early activate broad-spectrum defenses by inducing callose deposition and the salicylic acid (SA) and jasmonic acid (JA) pathways. Later it can prime pathogen-specific responses according to the pathogen's lifestyle. Interestingly, Hx primes redox-related genes to produce an anti-oxidant protective effect, which might be critical for limiting the infection of necrotrophs. Our Hx-IR findings also strongly suggest that it is an attractive tool for the molecular characterization of the plant alarmed state, with the added advantage of it being a natural compound.
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Affiliation(s)
- Paz Aranega-Bou
- Departamento de Bioquímica y Biología Molecular, Universitat de Valencia, Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones CientíficasValencia, Spain
| | - Maria de la O Leyva
- Departamento de Bioquímica y Biología Molecular, Universitat de Valencia, Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones CientíficasValencia, Spain
| | - Ivan Finiti
- Departamento de Bioquímica y Biología Molecular, Universitat de Valencia, Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones CientíficasValencia, Spain
| | - Pilar García-Agustín
- Grupo de Bioquímica y Biotecnología, Área de Fisiología Vegetal, Departamento de Ciencias Agrarias y del Medio Natural, Escola Superior de Tecnologia i Ciències Experimentals, Universitat Jaume ICastellón, Spain
| | - Carmen González-Bosch
- Departamento de Bioquímica y Biología Molecular, Universitat de Valencia, Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones CientíficasValencia, Spain
- *Correspondence: Carmen González-Bosch, Departamento de Bioquímica y Biología Molecular, Universitat de Valencia, Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones Científicas, Avenida Agustín Escardino 7, 46980 Paterna, Valencia, Spain e-mail:
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265
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Samalova M, Meyer AJ, Gurr SJ, Fricker MD. Robust anti-oxidant defences in the rice blast fungus Magnaporthe oryzae confer tolerance to the host oxidative burst. THE NEW PHYTOLOGIST 2014; 201:556-573. [PMID: 24117971 DOI: 10.1111/nph.12530] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/20/2013] [Indexed: 05/22/2023]
Abstract
Plants respond to pathogen attack via a rapid burst of reactive oxygen species (ROS). However, ROS are also produced by fungal metabolism and are required for the development of infection structures in Magnaporthe oryzae. To obtain a better understanding of redox regulation in M. oryzae, we measured the amount and redox potential of glutathione (E(GSH)), as the major cytoplasmic anti-oxidant, the rates of ROS production, and mitochondrial activity using multi-channel four-dimensional (x,y,z,t) confocal imaging of Grx1-roGFP2 and fluorescent reporters during spore germination, appressorium formation and infection. High levels of mitochondrial activity and ROS were localized to the growing germ tube and appressorium, but E(GSH) was highly reduced and tightly regulated during development. Furthermore, germlings were extremely resistant to external H2O2 exposure ex planta. EGSH remained highly reduced during successful infection of the susceptible rice cultivar CO39. By contrast, there was a dramatic reduction in the infection of resistant (IR68) rice, but the sparse hyphae that did form also maintained a similar reduced E(GSH). We conclude that M. oryzae has a robust anti-oxidant defence system and maintains tight control of EGSH despite substantial oxidative challenge. Furthermore, the magnitude of the host oxidative burst alone does not stress the pathogen sufficiently to prevent infection in this pathosystem.
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Affiliation(s)
- Marketa Samalova
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Andreas J Meyer
- INRES, Universität Bonn, Friedrich-Ebert-Allee 144, D-53113, Bonn, Germany
| | - Sarah J Gurr
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
- Biosciences, University of Exeter, Devon, EX4 4QD, UK
| | - Mark D Fricker
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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266
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Mu D, Li C, Zhang X, Li X, Shi L, Ren A, Zhao M. Functions of the nicotinamide adenine dinucleotide phosphate oxidase family inGanoderma lucidum: an essential role in ganoderic acid biosynthesis regulation, hyphal branching, fruiting body development, and oxidative-stress resistance. Environ Microbiol 2013; 16:1709-28. [DOI: 10.1111/1462-2920.12326] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 11/01/2013] [Indexed: 12/27/2022]
Affiliation(s)
- Dashuai Mu
- College of Life Sciences; Nanjing Agricultural University; Nanjing China
| | - Chenyang Li
- College of Life Sciences; Nanjing Agricultural University; Nanjing China
| | - Xuchen Zhang
- College of Life Sciences; Nanjing Agricultural University; Nanjing China
| | - Xiongbiao Li
- College of Life Sciences; Nanjing Agricultural University; Nanjing China
| | - Liang Shi
- College of Life Sciences; Nanjing Agricultural University; Nanjing China
| | - Ang Ren
- College of Life Sciences; Nanjing Agricultural University; Nanjing China
| | - Mingwen Zhao
- College of Life Sciences; Nanjing Agricultural University; Nanjing China
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267
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Montibus M, Ducos C, Bonnin-Verdal MN, Bormann J, Ponts N, Richard-Forget F, Barreau C. The bZIP transcription factor Fgap1 mediates oxidative stress response and trichothecene biosynthesis but not virulence in Fusarium graminearum. PLoS One 2013; 8:e83377. [PMID: 24349499 PMCID: PMC3861502 DOI: 10.1371/journal.pone.0083377] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 11/01/2013] [Indexed: 11/22/2022] Open
Abstract
Redox sensing is of primary importance for fungi to cope with oxidant compounds found in their environment. Plant pathogens are particularly subject to the oxidative burst during the primary steps of infection. In the budding yeast Saccharomyces cerevisiae, it is the transcription factor Yap1 that mediates the response to oxidative stress via activation of genes coding for detoxification enzymes. In the cereal pathogen Fusarium graminearum, Fgap1 a homologue of Yap1 was identified and its role was investigated. During infection, this pathogen produces mycotoxins belonging to the trichothecenes family that accumulate in the grains. The global regulation of toxin biosynthesis is not completely understood. However, it is now clearly established that an oxidative stress activates the production of toxins by F. graminearum. The involvement of Fgap1 in this activation was investigated. A deleted mutant and a strain expressing a truncated constitutive form of Fgap1 were constructed. None of the mutants was affected in pathogenicity. The deleted mutant showed higher level of trichothecenes production associated with overexpression of Tri genes. Moreover activation of toxin accumulation in response to oxidative stress was no longer observed. Regarding the mutant with the truncated constitutive form of Fgap1, toxin production was strongly reduced. Expression of oxidative stress response genes was not activated in the deleted mutant and expression of the gene encoding the mitochondrial superoxide dismutase MnSOD1 was up-regulated in the mutant with the truncated constitutive form of Fgap1. Our results demonstrate that Fgap1 plays a key role in the link between oxidative stress response and F. graminearum secondary metabolism.
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Affiliation(s)
- Mathilde Montibus
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
- * E-mail:
| | - Christine Ducos
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
| | | | - Jorg Bormann
- University of Hamburg, Biocenter Klein Flottbek, Department of Molecular Phytopathology and Genetics, Hamburg, Germany
| | - Nadia Ponts
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
| | - Florence Richard-Forget
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
| | - Christian Barreau
- Institut National de la Recherche Agronomique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
- Centre National de la Recherche Scientifique, Unité de Recherche 1264 MycSA, Villenave d’Ornon, France
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268
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Van Buyten E, Höfte M. Pythium species from rice roots differ in virulence, host colonization and nutritional profile. BMC PLANT BIOLOGY 2013; 13:203. [PMID: 24314036 PMCID: PMC3878986 DOI: 10.1186/1471-2229-13-203] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 11/29/2013] [Indexed: 05/20/2023]
Abstract
BACKGROUND Progressive yield decline in Philippine aerobic rice fields has been recently associated with three closely related Pythium spp., P. arrhenomanes, P. graminicola and P. inflatum. To understand their differential virulence towards rice seedlings, we conducted a comparative survey in which three isolates each of P. arrhenomanes, P. graminicola and P. inflatum were selected to investigate host colonization, host responses and carbon utilization profiles using histopathological analyses, phenoarrays, DNA quantifications and gene expression studies. RESULTS The isolate of the most virulent species, P. arrhenomanes, quickly colonized the outer and inner root tissues of rice seedlings, including the xylem, by which it possibly blocked the water transport and induced severe stunting, wilting and seedling death. The lower virulence of the tested P. graminicola and P. inflatum isolates seemed to be reflected in slower colonization processes, limited invasion of the vascular stele and less systemic spread, in which cell wall fortification appeared to play a role. Progressive hyphal invasions triggered the production of reactive oxygen species (ROS) and phenolic compounds, which was the strongest for the P. arrhenomanes isolate and was delayed or much weaker upon inoculation with the P. inflatum isolate. The necrosis marker OsJamyb seemed faster and stronger induced by the most virulent isolates. Although the isolate of P. inflatum was nutritionally the most versatile, the most virulent Pythium isolate appeared physiologically more adapted to its host, evidenced by its broad amino acid utilization profile, including D-amino acids, L-threonine and hydroxyl-L-proline. The latter two compounds have been implicated in plant defense and their use by P. arrhenomanes could therefore represent a part of its virulence strategy. CONCLUSIONS This study illustrates that the differential virulence of rice-pathogenic P. arrhenomanes, P. graminicola and P. inflatum isolates is related to their root colonization capacity, the intensity of induced root responses and their ability to utilize amino acids in their colonization niche. Accordingly, this paper presents important knowledge concerning rice root infections by oomycetes, which could be helpful to further disentangle virulence tactics of soil-borne pathogens.
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Affiliation(s)
- Evelien Van Buyten
- Laboratory of Phytopathology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
| | - Monica Höfte
- Laboratory of Phytopathology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
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269
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De Coninck B, Carron D, Tavormina P, Willem L, Craik DJ, Vos C, Thevissen K, Mathys J, Cammue BPA. Mining the genome of Arabidopsis thaliana as a basis for the identification of novel bioactive peptides involved in oxidative stress tolerance. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:5297-307. [PMID: 24043855 DOI: 10.1093/jxb/ert295] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Although evidence has accumulated on the role of plant peptides in the response to external conditions, the number of peptide-encoding genes in the genome is still underestimated. Using tiling arrays, we identified 176 unannotated transcriptionally active regions (TARs) in Arabidopsis thaliana that were induced upon oxidative stress generated by the herbicide paraquat (PQ). These 176 TARs could be translated into 575 putative oxidative stress-induced peptides (OSIPs). A high-throughput functional assay was used in the eukaryotic model organism Saccharomyces cerevisiae allowing us to test for bioactive peptides that increase oxidative stress tolerance. In this way, we identified three OSIPs that, upon overexpression in yeast, resulted in a significant rise in tolerance to hydrogen peroxide (H2O2). For one of these peptides, the decapeptide OSIP108, exogenous application to H2O2-treated yeast also resulted in significantly increased survival. OSIP108 is contained within a pseudogene and is induced in A. thaliana leaves by both the reactive oxygen species-inducer PQ and the necrotrophic fungal pathogen Botrytis cinerea. Moreover, infiltration and overexpression of OSIP108 in A. thaliana leaves resulted in increased tolerance to treatment with PQ. In conclusion, the identification and characterization of OSIP108 confirms the validity of our high-throughput approach, based on tiling array analysis in A. thaliana and functional screening in yeast, to identify bioactive peptides.
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Affiliation(s)
- Barbara De Coninck
- Centre for Microbial and Plant Genetics, KU Leuven, 3001 Heverlee, Belgium
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270
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Van Nguyen T, Kröger C, Bönnighausen J, Schäfer W, Bormann J. The ATF/CREB transcription factor Atf1 is essential for full virulence, deoxynivalenol production, and stress tolerance in the cereal pathogen Fusarium graminearum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:1378-1394. [PMID: 23945004 DOI: 10.1094/mpmi-04-13-0125-r] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Fusarium graminearum is a necrotrophic plant pathogen of cereals that produces mycotoxins such as deoxynivalenol (DON) and zearalenone (ZEA) in grains. The stress-activated mitogen-activated protein kinase FgOS-2 is a central regulator in F. graminearum and controls, among others, virulence and DON and ZEA production. Here, we characterized the ATF/CREB-activating transcription factor FgAtf1, a regulator that functions downstream of FgOS-2. We created deletion and overexpression mutants of Fgatf1, the latter being also in an FgOS-2 deletion mutant. FgAtf1 localizes to the nucleus and appears to interact with FgOS-2 under osmotic stress conditions. Deletion mutants in Fgatf1 (ΔFgatf1) are more sensitive to osmotic stress and less sensitive to oxidative stress compared with the wild type. Furthermore, sexual reproduction is delayed. ΔFgatf1 strains produced higher amounts of DON under in vitro induction conditions than that of the wild type. However, during wheat infection, DON production by ΔFgatf1 is strongly reduced. The ΔFgatf1 strains displayed strongly reduced virulence to wheat and maize. Interestingly, constitutive expression of Fgatf1 in the wild type led to hypervirulence on wheat, maize, and Brachypodium distachyon. Moreover, constitutive expression of Fgatf1 in the ΔFgOS-2 mutant background almost complements ΔFgOS-2-phenotypes. These data suggest that FgAtf1 may be the most important transcription factor regulated by FgOS-2.
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271
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Zhang N, MohdZainudin NAI, Scher K, Condon BJ, Horwitz BA, Turgeon BG. Iron, oxidative stress, and virulence: roles of iron-sensitive transcription factor Sre1 and the redox sensor ChAp1 in the maize pathogen Cochliobolus heterostrophus. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:1473-1485. [PMID: 23980626 DOI: 10.1094/mpmi-02-13-0055-r] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The gene SRE1, encoding the GATA transcription factor siderophore biosynthesis repressor (Sre1), was identified in the genome of the maize pathogen Cochliobolus heterostrophus and deleted. Mutants were altered in sensitivity to iron, oxidative stress, and virulence to the host. To gain insight into mechanisms of this combined regulation, genetic interactions among SRE1 (the nonribosomal peptide synthetase encoding gene NPS6, which is responsible for extracellular siderophore biosynthesis) and ChAP1 (encoding a transcription factor regulating redox homeostasis) were studied. To identify members of the Sre1 regulon, expression of candidate iron and oxidative stress-related genes was assessed in wild-type (WT) and sre1 mutants using quantitative reverse-transcription polymerase chain reaction. In sre1 mutants, NPS6 and NPS2 genes, responsible for siderophore biosynthesis, were derepressed under iron replete conditions, whereas the high-affinity reductive iron uptake pathway associated gene, FTR1, was not, in contrast to outcomes with other well-studied fungal models. C. heterostrophus L-ornithine-N(5)- monooxygenase (SIDA2), ATP-binding cassette (ABC6), catalase (CAT1), and superoxide dismutase (SOD1) genes were also derepressed under iron-replete conditions in sre1 mutants. Chap1nps6 double mutants were more sensitive to oxidative stress than either Chap1 or nps6 single mutants, while Chap1sre1 double mutants showed a modest increase in resistance compared with single Chap1 mutants but were much more sensitive than sre1 mutants. These findings suggest that the NPS6 siderophore indirectly contributes to redox homeostasis via iron sequestration, while Sre1 misregulation may render cells more sensitive to oxidative stress. The double-mutant phenotypes are consistent with a model in which iron sequestration by NPS6 defends the pathogen against oxidative stress. C. heterostrophus sre1, nps6, Chap1, Chap1nps6, and Chap1sre1 mutants are all reduced in virulence toward the host, compared with the WT.
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272
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Shalaby S, Larkov O, Lamdan NL, Horwitz BA. Genetic interaction of the stress response factors ChAP1 and Skn7 in the maize pathogen Cochliobolus heterostrophus. FEMS Microbiol Lett 2013; 350:83-9. [PMID: 24164316 DOI: 10.1111/1574-6968.12314] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 10/16/2013] [Accepted: 10/22/2013] [Indexed: 11/27/2022] Open
Abstract
The transcription factors ChAP1 and Skn7 of the maize pathogen Cochliobolus heterostrophus are orthologs of Yap1 and Skn7 in yeast, where they are predicted to work together in a complex. Previous work showed that in C. heterostrophus, as in yeast, ChAP1 accumulates in the nucleus in response to reactive oxygen species (ROS). The expression of genes whose products counteract oxidative stress depends on ChAP1, as shown by impaired ability of a Δchap1 mutant to induce these 'antioxidant' genes. In this study, we found that under oxidative stress, antioxidant gene expression is also partially impaired in the Δskn7 mutant but to a milder extent than in the Δchap1 mutant, whereas in the double mutant - Δchap1-Δskn7 - none of the tested genes was induced, with the exception of one catalase gene, CAT2. Both single mutants are capable of infecting the plant, showing similar virulence to the WT. The double mutant, however, showed clearly decreased virulence, pointing to additive contributions of ChAP1 and Skn7. Possible mechanisms are discussed, including additive regulation of gene expression by oxidative stress.
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Affiliation(s)
- Samer Shalaby
- Department of Biology, Technion - Israel Institute of Technology, Haifa, Israel
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273
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Bento T, Torres L, Fialho M, Bononi V. Growth inhibition and antioxidative response of wood decay fungi exposed to plant extracts of Casearia
species. Lett Appl Microbiol 2013; 58:79-86. [DOI: 10.1111/lam.12159] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 08/28/2013] [Accepted: 09/09/2013] [Indexed: 11/26/2022]
Affiliation(s)
- T.S. Bento
- Instituto de Botânica de São Paulo; Núcleo de Pesquisa em Micologia; São Paulo Brazil
| | - L.M.B. Torres
- Instituto de Botânica de São Paulo; Núcleo de Pesquisa em Fisiologia e Bioquímica de Plantas; São Paulo Brazil
| | - M.B. Fialho
- Instituto de Botânica de São Paulo; Núcleo de Pesquisa em Fisiologia e Bioquímica de Plantas; São Paulo Brazil
| | - V.L.R. Bononi
- Instituto de Botânica de São Paulo; Núcleo de Pesquisa em Micologia; São Paulo Brazil
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274
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Ronen M, Shalaby S, Horwitz BA. Role of the transcription factor ChAP1 in cytoplasmic redox homeostasis: imaging with a genetically encoded sensor in the maize pathogen Cochliobolus heterostrophus. MOLECULAR PLANT PATHOLOGY 2013; 14:786-90. [PMID: 23745603 PMCID: PMC6638657 DOI: 10.1111/mpp.12047] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The redox-sensitive transcription factor ChAP1 [Cochliobolus heterostrophus YAP1 (Yeast Activator Protein 1) orthologue] of C. heterostrophus is required for oxidative stress tolerance. It is not known, however, to what extent the intracellular redox state changes on exposure of the fungus to oxidants, and whether ChAP1 is involved in the return of the cell to redox homeostasis. In order to answer these questions, we expressed a ratiometric redox-sensitive fluorescent protein sensor, pHyper, in C. heterostrophus. The fluorescence ratio was sensitive to extracellular hydrogen peroxide (H2O2) concentrations that had been shown previously to inhibit the germination of conidia and growth of the pathogen in culture. chap1 mutants showed a slower return to redox homeostasis than the wild-type on exposure to H2O2. Plant extracts that mimic oxidants in their ability to promote nuclear retention of ChAP1 reduced, rather than oxidized, the fungal cells. This result is consistent with other data suggesting that ChAP1 responds to plant-derived signals other than oxidants. pHyper should be a useful reporter of the intracellular redox state in filamentous fungi.
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Affiliation(s)
- Mordechai Ronen
- Department of Plant Sciences, Tel Aviv University, Ramat Aviv 69978, Israel
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275
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Schürmann J, Buttermann D, Herrmann A, Giesbert S, Tudzynski P. Molecular characterization of the NADPH oxidase complex in the ergot fungus Claviceps purpurea: CpNox2 and CpPls1 are important for a balanced host-pathogen interaction. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:1151-64. [PMID: 23777432 DOI: 10.1094/mpmi-03-13-0064-r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Reactive oxygen species producing NADPH oxidase (Nox) complexes are involved in defense reactions in animals and plants while they trigger infection-related processes in pathogenic fungi. Knowledge about the composition and localization of these complexes in fungi is limited; potential components identified thus far include two to three catalytical subunits, a regulatory subunit (NoxR), the GTPase Rac, the scaffold protein Bem1, and a tetraspanin-like membrane protein (Pls1). We showed that, in the biotrophic grass-pathogen Claviceps purpurea, the catalytical subunit CpNox1 is important for infection. Here, we present identification of major Nox complex partners and a functional analysis of CpNox2 and the tetraspanin CpPls1. We show that, as in other fungi, Nox complexes are important for formation of sclerotia; CpRac is, indeed, a complex partner because it interacts with CpNoxR, and CpNox1/2 and CpPls1 are associated with the endoplasmatic reticulum. However, unlike in all other fungi, Δcppls1 is more similar to Δcpnox1 than to Δcpnox2, and CpNox2 is not essential for infection. In contrast, Δcpnox2 shows even more pronounced disease symptoms, indicating that Cpnox2 controls the infection process and moderates damage to the host. These data confirm that fungal Nox complexes have acquired specific functions dependent of the lifestyle of the pathogen.
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276
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Gupta S, Bhar A, Chatterjee M, Das S. Fusarium oxysporum f.sp. ciceri race 1 induced redox state alterations are coupled to downstream defense signaling in root tissues of chickpea (Cicer arietinum L.). PLoS One 2013; 8:e73163. [PMID: 24058463 PMCID: PMC3772884 DOI: 10.1371/journal.pone.0073163] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 07/17/2013] [Indexed: 12/22/2022] Open
Abstract
Reactive oxygen species are known to play pivotal roles in pathogen perception, recognition and downstream defense signaling. But, how these redox alarms coordinate in planta into a defensive network is still intangible. Present study illustrates the role of Fusarium oxysporum f.sp ciceri Race1 (Foc1) induced redox responsive transcripts in regulating downstream defense signaling in chickpea. Confocal microscopic studies highlighted pathogen invasion and colonization accompanied by tissue damage and deposition of callose degraded products at the xylem vessels of infected roots of chickpea plants. Such depositions led to the clogging of xylem vessels in compatible hosts while the resistant plants were devoid of such obstructions. Lipid peroxidation assays also indicated fungal induced membrane injury. Cell shrinkage and gradual nuclear adpression appeared as interesting features marking fungal ingress. Quantitative real time polymerase chain reaction exhibited differential expression patterns of redox regulators, cellular transporters and transcription factors during Foc1 progression. Network analysis showed redox regulators, cellular transporters and transcription factors to coordinate into a well orchestrated defensive network with sugars acting as internal signal modulators. Respiratory burst oxidase homologue, cationic peroxidase, vacuolar sorting receptor, polyol transporter, sucrose synthase, and zinc finger domain containing transcription factor appeared as key molecular candidates controlling important hubs of the defense network. Functional characterization of these hub controllers may prove to be promising in understanding chickpea-Foc1 interaction and developing the case study as a model for looking into the complexities of wilt diseases of other important crop legumes.
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Affiliation(s)
- Sumanti Gupta
- Division of Plant Biology, Bose Institute, Kolkata, West Bengal, India
| | - Anirban Bhar
- Division of Plant Biology, Bose Institute, Kolkata, West Bengal, India
| | - Moniya Chatterjee
- Division of Plant Biology, Bose Institute, Kolkata, West Bengal, India
| | - Sampa Das
- Division of Plant Biology, Bose Institute, Kolkata, West Bengal, India
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277
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Bischof R, Fourtis L, Limbeck A, Gamauf C, Seiboth B, Kubicek CP. Comparative analysis of the Trichoderma reesei transcriptome during growth on the cellulase inducing substrates wheat straw and lactose. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:127. [PMID: 24016404 PMCID: PMC3847502 DOI: 10.1186/1754-6834-6-127] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 09/04/2013] [Indexed: 05/05/2023]
Abstract
BACKGROUND Renewable lignocellulosic biomass is an advantageous resource for the production of second generation biofuels and other biorefinery products. In Middle Europe, wheat straw is one of the most abundant low-cost sources of lignocellulosic biomass. For its efficient use, an efficient mix of cellulases and hemicellulases is required. In this paper, we investigated how cellulase production by T. reesei on wheat straw compares to that on lactose, the only soluble and also cheap inducing carbon source for enzyme production. RESULTS We have examined and compared the transcriptome of T. reesei growing on wheat straw and lactose as carbon sources under otherwise similar conditions. Gene expression on wheat straw exceeded that on lactose, and 1619 genes were found to be only induced on wheat straw but not on lactose. They comprised 30% of the CAZome, but were also enriched in genes associated with phospholipid metabolism, DNA synthesis and repair, iron homeostatis and autophagy. Two thirds of the CAZome was expressed both on wheat straw as well as on lactose, but 60% of it at least >2-fold higher on the former. Major wheat straw specific genes comprised xylanases, chitinases and mannosidases. Interestingly, the latter two CAZyme families were significantly higher expressed in a strain in which xyr1 encoding the major regulator of cellulase and hemicellulase biosynthesis is non-functional. CONCLUSIONS Our data reveal several major differences in the transcriptome between wheat straw and lactose which may be related to the higher enzyme formation on the former and their further investigation could lead to the development of methods for increasing enzyme production on lactose.
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Affiliation(s)
- Robert Bischof
- Austrian Centre of Industrial Biotechnology (ACIB) GmBH c/o Institute of Chemical Engineering, University of Technology of Vienna, Gumpendorferstraβe 1a, Vienna A-1060, Austria
| | - Lukas Fourtis
- Institute of Chemical Engineering, University of Technology of Vienna, Gumpendorferstraβe 1a, Vienna A-1060, Austria
| | - Andreas Limbeck
- Institute of Chemical Technologies and Analytics, University of Technology of Vienna, Getreidemarkt 9, Vienna A-1060, Austria
| | - Christian Gamauf
- Biotech & Renewables Center, Clariant GmbH, München 81477, Germany
| | - Bernhard Seiboth
- Austrian Centre of Industrial Biotechnology (ACIB) GmBH c/o Institute of Chemical Engineering, University of Technology of Vienna, Gumpendorferstraβe 1a, Vienna A-1060, Austria
- Institute of Chemical Engineering, University of Technology of Vienna, Gumpendorferstraβe 1a, Vienna A-1060, Austria
| | - Christian P Kubicek
- Austrian Centre of Industrial Biotechnology (ACIB) GmBH c/o Institute of Chemical Engineering, University of Technology of Vienna, Gumpendorferstraβe 1a, Vienna A-1060, Austria
- Institute of Chemical Engineering, University of Technology of Vienna, Gumpendorferstraβe 1a, Vienna A-1060, Austria
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278
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Yang SL, Chung KR. Similar and distinct roles of NADPH oxidase components in the tangerine pathotype of Alternaria alternata. MOLECULAR PLANT PATHOLOGY 2013; 14:543-556. [PMID: 23527595 PMCID: PMC6638896 DOI: 10.1111/mpp.12026] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The fungal nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) complex, which has been implicated in the production of low-level reactive oxygen species (ROS), contains mainly NoxA, NoxB (gp91(phox) homologues) and NoxR (p67(phox) homologue). Here, we report the developmental and pathological functions of NoxB and NoxR in the tangerine pathotype of Alternaria alternata. Loss-of-function genetics revealed that all three Nox components are required for the accumulation of cellular hydrogen peroxide (H₂O₂). Alternaria alternata strains lacking NoxA, NoxB or NoxR also displayed an increased sensitivity to H₂O₂ and many ROS-generating oxidants. These phenotypes are highly similar to those previously seen for the Δyap1 mutant lacking a YAP1 transcriptional regulator and for the Δhog1 mutant lacking a HOG1 mitogen-activated protein (MAP) kinase, implicating a possible link among them. A fungal strain carrying a NoxA NoxB or NoxA NoxR double mutation was more sensitive to the test compounds than the strain mutated at a single gene, implicating a synergistic function among Nox components. The ΔnoxB mutant strain failed to produce any conidia; both ΔnoxA and ΔnoxR mutant strains showed a severe reduction in sporulation. Mutant strains carrying defective NoxB had higher chitin content than the wild-type and were insensitive to calcofluor white, Congo red and the fungicides vinclozolin and fludioxonil. Virulence assays revealed that all three Nox components are required for the elaboration of the penetration process. The inability to penetrate the citrus host, observed for Δnox mutants, could be overcome by wounding and by reacquiring a dominant Nox gene. The A. alternata NoxR did not influence the expression of NoxB, but negatively regulated NoxA. Importantly, the expression of both YAP1 and HOG1 genes, whose products are involved in resistance to ROS, was down-regulated in fungi carrying defective NoxA, NoxB or NoxR. Our results highlight the requirement of Nox in ROS resistance and provide insights into its critical role in regulating both YAP1 and HOG1 in A. alternata.
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Affiliation(s)
- Siwy Ling Yang
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences-IFAS, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
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279
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Karányi Z, Holb I, Hornok L, Pócsi I, Miskei M. FSRD: fungal stress response database. DATABASE-THE JOURNAL OF BIOLOGICAL DATABASES AND CURATION 2013; 2013:bat037. [PMID: 23757396 PMCID: PMC3678302 DOI: 10.1093/database/bat037] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Adaptation to different types of environmental stress is a common part of life for today's fungi. A deeper understanding of the organization, regulation and evolution of fungal stress response systems may lead to the development of novel antifungal drugs and technologies or the engineering of industrial strains with elevated stress tolerance. Here we present the Fungal Stress Response Database (http://internal.med.unideb.hu/fsrd) aimed to stimulate further research on stress biology of fungi. The database incorporates 1985 fungal stress response proteins with verified physiological function(s) and their orthologs identified and annotated in 28 species including human and plant pathogens, as well as important industrial fungi. The database will be extended continuously to cover other fully sequenced fungal species. Our database, as a starting point for future stress research, facilitates the analysis of literature data on stress and the identification of ortholog groups of stress response proteins in newly sequenced fungal genomes. Database URL: http://internal.med.unideb.hu/fsrd
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Affiliation(s)
- Zsolt Karányi
- Department of Medicine, Medical and Health Science Center, University of Debrecen, H-4032 Debrecen Nagyerdei krt. 98, Hungary
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280
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Simon UK, Polanschütz LM, Koffler BE, Zechmann B. High resolution imaging of temporal and spatial changes of subcellular ascorbate, glutathione and H₂O₂ distribution during Botrytis cinerea infection in Arabidopsis. PLoS One 2013; 8:e65811. [PMID: 23755284 PMCID: PMC3673919 DOI: 10.1371/journal.pone.0065811] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 05/03/2013] [Indexed: 11/23/2022] Open
Abstract
In order to study the mechanisms behind the infection process of the necrotrophic fungus Botrytis cinerea, the subcellular distribution of hydrogen peroxide (H₂O₂) was monitored over a time frame of 96 h post inoculation (hpi) in Arabidopsis thaliana Col-0 leaves at the inoculation site (IS) and the area around the IS which was defined as area adjacent to the inoculation site (AIS). H₂O₂ accumulation was correlated with changes in the compartment-specific distribution of ascorbate and glutathione and chloroplast fine structure. This study revealed that the severe breakdown of the antioxidative system, indicated by a drop in ascorbate and glutathione contents at the IS at later stages of infection correlated with an accumulation of H₂O₂ in chloroplasts, mitochondria, cell walls, nuclei and the cytosol which resulted in the development of chlorosis and cell death, eventually visible as tissue necrosis. A steady increase of glutathione contents in most cell compartments within infected tissues (up to 600% in chloroplasts at 96 hpi) correlated with an accumulation of H₂O₂ in chloroplasts, mitochondria and cell walls at the AIS indicating that high glutathione levels could not prevent the accumulation of reactive oxygen species (ROS) which resulted in chlorosis. Summing up, this study reveals the intracellular sequence of events during Botrytis cinerea infection and shows that the breakdown of the antioxidative system correlated with the accumulation of H₂O₂ in the host cells. This resulted in the degeneration of the leaf indicated by severe changes in the number and ultrastructure of chloroplasts (e.g. decrease of chloroplast number, decrease of starch and thylakoid contents, increase of plastoglobuli size), chlorosis and necrosis of the leaves.
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Affiliation(s)
- Uwe K. Simon
- Institute of Plant Sciences, University of Graz, Graz, Austria
| | | | | | - Bernd Zechmann
- Institute of Plant Sciences, University of Graz, Graz, Austria
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281
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Zhu J, Yu X, Xie B, Gu X, Zhang Z, Li S. Transcriptomic profiling-based mutant screen reveals three new transcription factors mediating menadione resistance in Neurospora crassa. Fungal Biol 2013; 117:422-30. [DOI: 10.1016/j.funbio.2013.04.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 04/10/2013] [Accepted: 04/11/2013] [Indexed: 11/26/2022]
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282
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Delaye L, García-Guzmán G, Heil M. Endophytes versus biotrophic and necrotrophic pathogens—are fungal lifestyles evolutionarily stable traits? FUNGAL DIVERS 2013. [DOI: 10.1007/s13225-013-0240-y] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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283
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Xu L, Chen W. Random T-DNA mutagenesis identifies a Cu/Zn superoxide dismutase gene as a virulence factor of Sclerotinia sclerotiorum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:431-41. [PMID: 23252459 DOI: 10.1094/mpmi-07-12-0177-r] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Agrobacterium-mediated transformation (AMT) was used to identify potential virulence factors in Sclerotinia sclerotiorum. Screening AMT transformants identified two mutants showing significantly reduced virulence. The mutants showed growth rate, sclerotial formation, and oxalate production similar to that of the wild type. The mutation was due to a single T-DNA insertion at 212 bp downstream of the Cu/Zn superoxide dismutase (SOD) gene (SsSOD1, SS1G_00699). Expression levels of SsSOD1 were significantly increased under oxidative stresses or during plant infection in the wild-type strain but could not be detected in the mutant. SsSOD1 functionally complemented the Cu/Zn SOD gene in a Δsod1 Saccharomyces cerevisiae mutant. The SOD mutant had increased sensitivity to heavy metal toxicity and oxidative stress in culture and reduced ability to detoxify superoxide in infected leaves. The mutant also had reduced expression levels of other known pathogenicity genes such as endo-polygalacturanases sspg1 and sspg3. The functions of SsSOD1 were further confirmed by SsSOD1-deletion mutation. Like the AMT insertion mutant, the SsSOD1-deletion mutant exhibited normal growth rate, sclerotial formation, oxalate production, increased sensitivity to metal and oxidative stress, and reduced virulence. These results suggest that SsSOD1, while not being required for saprophytic growth and completion of the life cycle, plays critical roles in detoxification of reactive oxygen species during host-pathogen interactions and is an important virulence factor of Sclerotinia sclerotiorum.
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Affiliation(s)
- Liangsheng Xu
- Department of Plant Pathology, Washington State University, Pullman, WA, USA
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284
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The NADPH oxidase complexes in Botrytis cinerea: evidence for a close association with the ER and the tetraspanin Pls1. PLoS One 2013; 8:e55879. [PMID: 23418468 PMCID: PMC3572182 DOI: 10.1371/journal.pone.0055879] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 01/03/2013] [Indexed: 01/27/2023] Open
Abstract
NADPH oxidases (Nox) are major enzymatic systems that generate reactive-oxygen species (ROS) in multicellular eukaryotes. In several fungi they have been shown to be involved in sexual differentiation and pathogenicity. However, in contrast to the well characterized mammalian systems, basic information on the composition, recruitment, and localization of fungal Nox complexes and on the molecular mechanisms of their cellular effects are still lacking. Here we give a detailed analysis of components of the Nox complexes in the gray mold fungus Botrytis cinerea. It had previously been shown that the two catalytic transmembrane subunits BcNoxA and B are important for development of sclerotia and for full virulence, with BcNoxA being involved in spreading of lesions and BcNoxB in penetration; BcNoxR functions as a regulator of both subunits. Here we present evidence (using for the first time a functional GFP fusion able to complement the ΔbcnoxA mutant) that BcNoxA localizes mainly to the ER and at the plasma membrane; BcNoxB shows a similar localization pattern, while the regulator BcNoxR is found in vesicles throughout the hyphae and at the hyphal tip. To identify possible interaction partners, which could be involved in the localization or recruitment of the Nox complexes, we functionally characterized the tetraspanin Pls1, a transmembrane protein, which had been suggested to be a NoxB-interacting partner in the saprophyte Podospora anserina. Knock-out experiments and GFP fusions substantiate a link between BcNoxB and BcPls1 because both deletion mutants have overlapping phenotypes (especially a defect in penetration), and the proteins show a similar localization pattern (ER). However, in contrast to the corresponding protein in P. anserina BcPls1 is important for female fertility, but not for ascospore germination.
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285
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NADPH oxidases regulate septin-mediated cytoskeletal remodeling during plant infection by the rice blast fungus. Proc Natl Acad Sci U S A 2013; 110:3179-84. [PMID: 23382235 DOI: 10.1073/pnas.1217470110] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The rice blast fungus Magnaporthe oryzae infects plants with a specialized cell called an appressorium, which uses turgor to drive a rigid penetration peg through the rice leaf cuticle. Here, we show that NADPH oxidases (Nox) are necessary for septin-mediated reorientation of the F-actin cytoskeleton to facilitate cuticle rupture and plant cell invasion. We report that the Nox2-NoxR complex spatially organizes a heteroligomeric septin ring at the appressorium pore, required for assembly of a toroidal F-actin network at the point of penetration peg emergence. Maintenance of the cortical F-actin network during plant infection independently requires Nox1, a second NADPH oxidase, which is necessary for penetration hypha elongation. Organization of F-actin in appressoria is disrupted by application of antioxidants, whereas latrunculin-mediated depolymerization of appressorial F-actin is competitively inhibited by reactive oxygen species, providing evidence that regulated synthesis of reactive oxygen species by fungal NADPH oxidases directly controls septin and F-actin dynamics.
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286
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Ambrose KV, Belanger FC. SOLiD-SAGE of endophyte-infected red fescue reveals numerous effects on host transcriptome and an abundance of highly expressed fungal secreted proteins. PLoS One 2012; 7:e53214. [PMID: 23285269 PMCID: PMC3532157 DOI: 10.1371/journal.pone.0053214] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 11/27/2012] [Indexed: 11/19/2022] Open
Abstract
One of the most important plant-fungal symbiotic relationships is that of cool season grasses with endophytic fungi of the genera Epichloë and Neotyphodium. These associations often confer benefits, such as resistance to herbivores and improved drought tolerance, to the hosts. One benefit that appears to be unique to fine fescue grasses is disease resistance. As a first step towards understanding the basis of the endophyte-mediated disease resistance in Festuca rubra we carried out a SOLiD-SAGE quantitative transcriptome comparison of endophyte-free and Epichloë festucae-infected F. rubra. Over 200 plant genes involved in a wide variety of physiological processes were statistically significantly differentially expressed between the two samples. Many of the endophyte expressed genes were surprisingly abundant, with the most abundant fungal tag representing over 10% of the fungal mapped tags. Many of the abundant fungal tags were for secreted proteins. The second most abundantly expressed fungal gene was for a secreted antifungal protein and is of particular interest regarding the endophyte-mediated disease resistance. Similar genes in Penicillium and Aspergillus spp. have been demonstrated to have antifungal activity. Of the 10 epichloae whole genome sequences available, only one isolate of E. festucae and Neotyphodium gansuense var inebrians have an antifungal protein gene. The uniqueness of this gene in E. festucae from F. rubra, its transcript abundance, and the secreted nature of the protein, all suggest it may be involved in the disease resistance conferred to the host, which is a unique feature of the fine fescue-endophyte symbiosis.
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Affiliation(s)
- Karen V. Ambrose
- Department of Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey, United States of America
| | - Faith C. Belanger
- Department of Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey, United States of America
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287
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Chung KR. Stress Response and Pathogenicity of the Necrotrophic Fungal Pathogen Alternaria alternata. SCIENTIFICA 2012; 2012:635431. [PMID: 24278721 PMCID: PMC3820455 DOI: 10.6064/2012/635431] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 10/03/2012] [Indexed: 05/07/2023]
Abstract
The production of host-selective toxins by the necrotrophic fungus Alternaria alternata is essential for the pathogenesis. A. alternata infection in citrus leaves induces rapid lipid peroxidation, accumulation of hydrogen peroxide (H2O2), and cell death. The mechanisms by which A. alternata avoids killing by reactive oxygen species (ROS) after invasion have begun to be elucidated. The ability to coordinate of signaling pathways is essential for the detoxification of cellular stresses induced by ROS and for pathogenicity in A. alternata. A low level of H2O2, produced by the NADPH oxidase (NOX) complex, modulates ROS resistance and triggers conidiation partially via regulating the redox-responsive regulators (YAP1 and SKN7) and the mitogen-activated protein (MAP) kinase (HOG1) mediated pathways, which subsequently regulate the genes required for the biosynthesis of siderophore, an iron-chelating compound. Siderophore-mediated iron acquisition plays a key role in ROS detoxification because of the requirement of iron for the activities of antioxidants (e.g., catalase and SOD). Fungal strains impaired for the ROS-detoxifying system severely reduce the virulence on susceptible citrus cultivars. This paper summarizes the current state of knowledge of signaling pathways associated with cellular responses to multidrugs, oxidative and osmotic stress, and fungicides, as well as the pathogenicity/virulence in the tangerine pathotype of A. alternata.
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Affiliation(s)
- Kuang-Ren Chung
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL 32611, USA
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288
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Rastogi A, Pospíšil P. Production of hydrogen peroxide and hydroxyl radical in potato tuber during the necrotrophic phase of hemibiotrophic pathogen Phytophthora infestans infection. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2012; 117:202-6. [DOI: 10.1016/j.jphotobiol.2012.10.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Revised: 09/26/2012] [Accepted: 10/08/2012] [Indexed: 01/16/2023]
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289
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Cho K, Kim Y, Wi SJ, Seo JB, Kwon J, Chung JH, Park KY, Nam MH. Nontargeted metabolite profiling in compatible pathogen-inoculated tobacco (Nicotiana tabacum L. cv. Wisconsin 38) using UPLC-Q-TOF/MS. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2012; 60:11015-28. [PMID: 23072474 DOI: 10.1021/jf303702j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A biphasic reactive oxygen species (ROS) production has previously been observed in tobacco at 1 and 48 h after inoculation with the hemibiotrophic compatible pathogen, Phytophthora parasitica var. nicotianae (Ppn). To characterize the response of tobacco to biphasically produced ROS concerning the propagation of Ppn, ultraperformance liquid chromatography-quadrupole-time of flight/ mass spectrometry (UPLC-Q-TOF/MS) based metabolic profiling combined with multivariate statistical analysis was performed. Among the nonredundant 355 mass ions in ESI+ mode and 345 mass ions in ESI- mode that were selected as significantly changed by Ppn inoculation (|p(corr)| > 0.6 on S-plot of orthogonal partial least-squares discriminant analysis (OPLS-DA), fold-change > 2, and p < 0.05 in the independent two-sample t test), 76 mass ions were identified on the basis of their accurate mass ions and MS/MS spectra. Phenolic amino acids, phenylpropanoids, hydroxycinnamic acid amides, linoleic acid, linolenic acid, lysophospholipids, glycoglycerolipids, and trioxidized phospholipids were identified as having changed after Ppn inoculation. On the basis of their quantitative changes, the metabolic responses occurring at each phase of ROS production after Ppn inoculation were investigated in this study.
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Affiliation(s)
- Kyoungwon Cho
- Seoul Center, Korea Basic Science Institute (KBSI), Seoul 136-713, Republic of Korea
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290
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Tudzynski P, Heller J, Siegmund U. Reactive oxygen species generation in fungal development and pathogenesis. Curr Opin Microbiol 2012; 15:653-9. [PMID: 23123514 DOI: 10.1016/j.mib.2012.10.002] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 10/01/2012] [Accepted: 10/01/2012] [Indexed: 12/20/2022]
Abstract
Reactive oxygen species (ROS) generated by NADPH-dependent oxidases (Nox) have been shown to function as signaling molecules and to be essential for many differentiation processes in mammals and plants. There is growing evidence that ROS are important for many aspects of fungal life including vegetative hyphal growth, differentiation of conidial anastomosis tubes, fruiting body and infection structure formation, and for induction of apoptosis. Recent results from studies in fungal saprophytic and pathogenic model systems have shed new light on the role of Nox in cytoskeleton organization, the structure of Nox complexes and links to components of the apical complex, and the localization of Nox to the endoplasmic reticulum.
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Affiliation(s)
- Paul Tudzynski
- Institut für Biologie und Biotechnologie der Pflanzen, Westf. Wilhelms Universitaet, Schlossplatz 8, D-48143 Muenster, Germany.
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291
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Benhamou N, le Floch G, Vallance J, Gerbore J, Grizard D, Rey P. Pythium oligandrum: an example of opportunistic success. Microbiology (Reading) 2012; 158:2679-2694. [DOI: 10.1099/mic.0.061457-0] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Affiliation(s)
- Nicole Benhamou
- Centre de recherche en horticulture, Pavillon de l’ENVIROTRON, 2480 Boulevard Hochelga, Université Laval, QC G1V 0A6, Canada
| | - Gaêtan le Floch
- Université Européenne de Bretagne/Université de Brest, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, ESMISAB, 29 820 Plouzané, France
| | - Jessica Vallance
- Université de Bordeaux, ISVV, UMR1065 Santé et Agroécologie du Vignoble (SAVE), Bordeaux Sciences Agro, F-33140, Villenave d’Ornon, France et INRA, ISVV, UMR1065 SAVE, F-33140, Villenave d’Ornon, France
| | - Jonathan Gerbore
- Université de Bordeaux, ISVV, UMR1065 Santé et Agroécologie du Vignoble (SAVE), Bordeaux Sciences Agro, F-33140, Villenave d’Ornon, France et INRA, ISVV, UMR1065 SAVE, F-33140, Villenave d’Ornon, France
| | | | - Patrice Rey
- Université de Bordeaux, ISVV, UMR1065 Santé et Agroécologie du Vignoble (SAVE), Bordeaux Sciences Agro, F-33140, Villenave d’Ornon, France et INRA, ISVV, UMR1065 SAVE, F-33140, Villenave d’Ornon, France
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292
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Heller J, Meyer AJ, Tudzynski P. Redox-sensitive GFP2: use of the genetically encoded biosensor of the redox status in the filamentous fungus Botrytis cinerea. MOLECULAR PLANT PATHOLOGY 2012; 13:935-47. [PMID: 22524254 PMCID: PMC6638776 DOI: 10.1111/j.1364-3703.2012.00802.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The production of reactive oxygen species (ROS) is part of the defence reaction of plants against invading pathogens. The effect of ROS on filamentous fungi is still unclear. In this study, ratiometric redox-sensitive green fluorescent protein (roGFP) was introduced as a tool for in vivo measurement of the cellular redox status in filamentous fungi. A fungal expression system for roGFP2 was constructed. Expressed in Botrytis cinerea, roGFP2 reversibly responded to redox changes induced by incubation with H(2)O(2) or dithiothreitol, which was determined by confocal laser scanning microscopy imaging and fluorometry. As the sensor detects the redox potential of the cellular glutathione pool, it was used to analyse the kinetics of GSH (glutathione, reduced form) recovery after H(2)O(2) treatment. The transcription factor Bap1 is the main transcriptional regulator of H(2)O(2) -scavenging proteins in B. cinerea. When compared with the wild-type, GSH recovery in the Δbap1 deletion mutant was affected after repeated H(2)O(2) treatment. ROS and intracellular redox changes can be used by fungi for signalling purposes. In planta experiments, performed in this study, indicated that redox processes seem to be important for the differentiation of penetration structures. During the penetration of onion epidermal cells, the status of the cellular glutathione pool differed between appressoria-like structures and infecting hyphae, being reduced in the presence of infecting hyphae and more oxidized around appressoria-like structures.
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Affiliation(s)
- Jens Heller
- Institut fuer Biologie und Biotechnologie der Pflanzen, Westf. Wilhelms-Universitaet, Hindenburgplatz 55, D-48143 Muenster, Germany
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293
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Barna B, Fodor J, Harrach BD, Pogány M, Király Z. The Janus face of reactive oxygen species in resistance and susceptibility of plants to necrotrophic and biotrophic pathogens. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2012; 59:37-43. [PMID: 22321616 DOI: 10.1016/j.plaphy.2012.01.014] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 01/17/2012] [Indexed: 05/19/2023]
Abstract
Plant pathogens can be divided into biotrophs and necrotrophs according to their different life styles; biotrophs prefer living, while necrotrophs prefer dead cells for nutritional purposes. Therefore tissue necrosis caused by reactive oxygen species (ROS) during pathogen infection increases host susceptibility to necrotrophic, but resistance to biotrophic pathogen. Consequently, elevation of antioxidant capacity of plants enhances their tolerance to development of necroses caused by necrotrophic pathogens. Plant hormones can strongly influence induction of ROS and antioxidants, thereby influencing susceptibility or resistance of plants to pathogens. Pathogen-induced ROS themselves are considered as signaling molecules. Generally, salicylic acid (SA) signaling induces defense against biotrophic pathogens, whereas jasmonic acid (JA) against necrotrophic pathogens. Furthermore pathogens can modify plant's defense signaling network for their own benefit by changing phytohormone homeostasis. On the other hand, ROS are harmful also to the pathogens, consequently they try to defend themselves by elevating antioxidant activity and secreting ROS scavengers in the infected tissue. The Janus face nature of ROS and plant cell death on biotrophic and on necrotrophic pathogens is also supported by the experiments with BAX inhibitor-1 and the mlo mutation of Mlo gene in barley. It was found that ROS and elevated plant antioxidant activity play an important role in systemic acquired resistance (SAR) and induced systemic resistance (ISR), as well as in mycorrhiza induced abiotic and biotic stress tolerance of plants.
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Affiliation(s)
- B Barna
- Plant Protection Institute, Hungarian Academy of Sciences, P.O. Box 102, 1525 Budapest, Hungary.
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294
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Van Thuat N, Schäfer W, Bormann J. The stress-activated protein kinase FgOS-2 is a key regulator in the life cycle of the cereal pathogen Fusarium graminearum. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:1142-1156. [PMID: 22591226 DOI: 10.1094/mpmi-02-12-0047-r] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Fusarium graminearum is one of the most destructive pathogens of cereals and a threat to food and feed production worldwide. It is an ascomycetous plant pathogen and the causal agent of Fusarium head blight disease in small grain cereals and of cob rot disease in maize. Infection with F. graminearum leads to yield losses and mycotoxin contamination. Zearalenone (ZEA) and deoxynivalenol (DON) are hazardous mycotoxins; the latter is necessary for virulence toward wheat. Deletion mutants of the F. graminearum orthologue of the Saccharomyces cerevisiae Hog1 stress-activated protein kinase, FgOS-2 (ΔFgOS-2), showed drastically reduced in planta DON and ZEA production. However, ΔFgOS-2 produced even more DON than the wild type under in vitro conditions, whereas ZEA production was similar to that of the wild type. These deletion strains are dramatically reduced in pathogenicity toward maize and wheat. We constitutively expressed the fluorescent protein dsRed in the deletion strains and the wild type. Microscopic analysis revealed that ΔFgOS-2 is unable to reach the rachis node at the base of wheat spikelets. During vegetative growth, ΔFgOS-2 strains exhibit increased resistance against the phenylpyrrole fludioxonil. Growth of mutant colonies on agar plates supplemented with NaCl is reduced but conidia formation remained unchanged. However, germination of mutant conidia on osmotic media is severely impaired. Germ tubes are swollen and contain multiple nuclei. The deletion mutants completely fail to produce perithecia and ascospores. Furthermore, FgOS-2 also plays a role in reactive oxygen species (ROS)-related signaling. The transcription and activity of fungal catalases is modulated by FgOS-2. Among the genes regulated by FgOS-2, we found a putative calcium-dependent NADPH-oxidase (noxC) and the transcriptional regulator of ROS metabolism, atf1. The present study describes new aspects of stress-activated protein kinase signaling in F. graminearum.
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Affiliation(s)
- Nguyen Van Thuat
- Department of Molecular Phytopathology and Genetics, University of Hamburg, Hamburg, Germany
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295
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Bahuguna RN, Joshi R, Shukla A, Pandey M, Kumar J. Thiamine primed defense provides reliable alternative to systemic fungicide carbendazim against sheath blight disease in rice (Oryza sativa L.). PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2012; 57:159-67. [PMID: 22705591 DOI: 10.1016/j.plaphy.2012.05.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 05/03/2012] [Indexed: 05/06/2023]
Abstract
A novel pathogen defense strategy by thiamine priming was evaluated for its efficacy against sheath blight pathogen, Rhizoctonia solani AG-1A, of rice and compared with that of systemic fungicide, carbendazim (BCM). Seeds of semidwarf, high yielding, basmati rice variety Vasumati were treated with thiamine (50 mM) and BCM (4 mM). The pot cultured plants were challenge inoculated with R. solani after 40 days of sowing and effect of thiamine and BCM on rice growth and yield traits was examined. Higher hydrogen peroxide content, total phenolics accumulation, phenylalanine ammonia lyase (PAL) activity and superoxide dismutase (SOD) activity under thiamine treatment displayed elevated level of systemic resistance, which was further augmented under challenging pathogen infection. High transcript level of phenylalanine ammonia lyase (PAL) and manganese superoxide dismutase (MnSOD) validated mode of thiamine primed defense. Though minimum disease severity was observed under BCM treatment, thiamine produced comparable results, with 18.12 per cent lower efficacy. Along with fortifying defense components and minor influence on photosynthetic pigments and nitrate reductase (NR) activity, thiamine treatment significantly reduced pathogen-induced loss in photosynthesis, stomatal conductance, chlorophyll fluorescence, NR activity and NR transcript level. Physiological traits affected under pathogen infection were found signatory for characterizing plant's response under disease and were detectable at early stage of infection. These findings provide a novel paradigm for developing alternative, environmentally safe strategies to control plant diseases.
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Affiliation(s)
- Rajeev Nayan Bahuguna
- Division of Plant Physiology, Indian Agricultural Research Institute, New Delhi, India.
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296
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Heller J, Ruhnke N, Espino JJ, Massaroli M, Collado IG, Tudzynski P. The mitogen-activated protein kinase BcSak1 of Botrytis cinerea is required for pathogenic development and has broad regulatory functions beyond stress response. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:802-16. [PMID: 22352714 DOI: 10.1094/mpmi-11-11-0299] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The mitogen-activated protein kinase (MAPK) BcSak1 of Botrytis cinerea is activated upon exposure to H(2)O(2) and, hence, might be involved in coping with oxidative stress during infection. However, beside osmotic and oxidative stress sensitivity, Δbcsak1 mutants have a pleiotropic phenotype, as they do not produce conidia and are unable to penetrate unwounded host tissue. In this study, the role of BcSak1 was investigated in the stress response and during infection of French beans by Botrytis cinerea. Using a macroarray approach, it was shown that BcSak1 is only marginally involved in the specific oxidative stress response. In fact, the induction of several genes after oxidative stress treatment is BcSak1-dependent, but most of these genes are also induced under conditions of osmotic stress. The majority of genes regulated by BcSak1 are not involved in the stress response at all. Using a translational fusion of BcSak1 to green fluorescent protein, it was shown clearly that the localization of this MAPK depends on the type of stress being applied; it associates rapidly to the nucleus only under osmotic stress. Therefore, a model is proposed in which BcSak1 acts in the cytosol by activation of one or more transcription factors under oxidative stress and, at the same time, it reacts to osmotic stress by migrating to the nucleus. Interestingly, the MAPK is also involved in the regulation of secondary metabolism, as the major phytotoxins secreted by this fungus are reduced in the Δbcsak1 deletion mutant. Experiments done in planta underlined the essential role of BcSak1 in the early stages of infection, when it translocates to the nucleus and then changes to cytosolic distribution during hyphal growth within the tissue.
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Affiliation(s)
- Jens Heller
- Institut fuer Biologie und Biotechnologie def Pflanzen, Westf. Wilhelms-Universitaet, Muenster, Germany
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297
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Scalliet G, Bowler J, Luksch T, Kirchhofer-Allan L, Steinhauer D, Ward K, Niklaus M, Verras A, Csukai M, Daina A, Fonné-Pfister R. Mutagenesis and functional studies with succinate dehydrogenase inhibitors in the wheat pathogen Mycosphaerella graminicola. PLoS One 2012; 7:e35429. [PMID: 22536383 PMCID: PMC3334918 DOI: 10.1371/journal.pone.0035429] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 03/16/2012] [Indexed: 02/03/2023] Open
Abstract
A range of novel carboxamide fungicides, inhibitors of the succinate dehydrogenase enzyme (SDH, EC 1.3.5.1) is currently being introduced to the crop protection market. The aim of this study was to explore the impact of structurally distinct carboxamides on target site resistance development and to assess possible impact on fitness. We used a UV mutagenesis approach in Mycosphaerella graminicola, a key pathogen of wheat to compare the nature, frequencies and impact of target mutations towards five subclasses of carboxamides. From this screen we identified 27 amino acid substitutions occurring at 18 different positions on the 3 subunits constituting the ubiquinone binding (Qp) site of the enzyme. The nature of substitutions and cross resistance profiles indicated significant differences in the binding interaction to the enzyme across the different inhibitors. Pharmacophore elucidation followed by docking studies in a tridimensional SDH model allowed us to propose rational hypotheses explaining some of the differential behaviors for the first time. Interestingly all the characterized substitutions had a negative impact on enzyme efficiency, however very low levels of enzyme activity appeared to be sufficient for cell survival. In order to explore the impact of mutations on pathogen fitness in vivo and in planta, homologous recombinants were generated for a selection of mutation types. In vivo, in contrast to previous studies performed in yeast and other organisms, SDH mutations did not result in a major increase of reactive oxygen species levels and did not display any significant fitness penalty. However, a number of Qp site mutations affecting enzyme efficiency were shown to have a biological impact in planta. Using the combined approaches described here, we have significantly improved our understanding of possible resistance mechanisms to carboxamides and performed preliminary fitness penalty assessment in an economically important plant pathogen years ahead of possible resistance development in the field.
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298
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Singh K, Nizam S, Sinha M, Verma PK. Comparative transcriptome analysis of the necrotrophic fungus Ascochyta rabiei during oxidative stress: insight for fungal survival in the host plant. PLoS One 2012; 7:e33128. [PMID: 22427966 PMCID: PMC3299738 DOI: 10.1371/journal.pone.0033128] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 02/10/2012] [Indexed: 11/18/2022] Open
Abstract
Localized cell death, known as the hypersensitive response (HR), is an important defense mechanism for neutralizing phytopathogens. The hallmark of the HR is an oxidative burst produced by the host plant. We aimed to identify genes of the necrotrophic chickpea blight fungus Ascochyta rabiei that are involved in counteracting oxidative stress. A subtractive cDNA library was constructed after menadione treatment, which resulted in the isolation of 128 unigenes. A reverse northern blot was used to compare transcript profiles after H(2)O(2), menadione and sodium nitroprusside treatments. A total of 70 unigenes were found to be upregulated by more than two-fold following menadione treatment at different time intervals. A large number of genes not previously associated with oxidative stress were identified, along with many stress-responsive genes. Differential expression patterns of several genes were validated by quantitative real-time PCR (qRT-PCR) and northern blotting. In planta qRT-PCR of several selected genes also showed differential expression patterns during infection and disease progression. These data shed light on the molecular responses of the phytopathogen A. rabiei to overcome oxidative and nitrosative stresses and advance the understanding of necrotrophic fungal pathogen survival mechanisms.
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Affiliation(s)
- Kunal Singh
- Plant Immunity Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
| | - Shadab Nizam
- Plant Immunity Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
| | - Manisha Sinha
- Plant Immunity Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
| | - Praveen K. Verma
- Plant Immunity Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
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299
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Vargas WA, Martín JMS, Rech GE, Rivera LP, Benito EP, Díaz-Mínguez JM, Thon MR, Sukno SA. Plant defense mechanisms are activated during biotrophic and necrotrophic development of Colletotricum graminicola in maize. PLANT PHYSIOLOGY 2012; 158:1342-58. [PMID: 22247271 PMCID: PMC3291271 DOI: 10.1104/pp.111.190397] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 01/11/2012] [Indexed: 05/18/2023]
Abstract
Hemibiotrophic plant pathogens first establish a biotrophic interaction with the host plant and later switch to a destructive necrotrophic lifestyle. Studies of biotrophic pathogens have shown that they actively suppress plant defenses after an initial microbe-associated molecular pattern-triggered activation. In contrast, studies of the hemibiotrophs suggest that they do not suppress plant defenses during the biotrophic phase, indicating that while there are similarities between the biotrophic phase of hemibiotrophs and biotrophic pathogens, the two lifestyles are not analogous. We performed transcriptomic, histological, and biochemical studies of the early events during the infection of maize (Zea mays) with Colletotrichum graminicola, a model pathosystem for the study of hemibiotrophy. Time-course experiments revealed that mRNAs of several defense-related genes, reactive oxygen species, and antimicrobial compounds all begin to accumulate early in the infection process and continue to accumulate during the biotrophic stage. We also discovered the production of maize-derived vesicular bodies containing hydrogen peroxide targeting the fungal hyphae. We describe the fungal respiratory burst during host infection, paralleled by superoxide ion production in specific fungal cells during the transition from biotrophy to a necrotrophic lifestyle. We also identified several novel putative fungal effectors and studied their expression during anthracnose development in maize. Our results demonstrate a strong induction of defense mechanisms occurring in maize cells during C. graminicola infection, even during the biotrophic development of the pathogen. We hypothesize that the switch to necrotrophic growth enables the fungus to evade the effects of the plant immune system and allows for full fungal pathogenicity.
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Affiliation(s)
- Walter A. Vargas
- Centro Hispanoluso de Investigaciones Agrarias, Department of Microbiology and Genetics, University of Salamanca, 37185 Villamayor, Spain
| | - José M. Sanz Martín
- Centro Hispanoluso de Investigaciones Agrarias, Department of Microbiology and Genetics, University of Salamanca, 37185 Villamayor, Spain
| | - Gabriel E. Rech
- Centro Hispanoluso de Investigaciones Agrarias, Department of Microbiology and Genetics, University of Salamanca, 37185 Villamayor, Spain
| | - Lina P. Rivera
- Centro Hispanoluso de Investigaciones Agrarias, Department of Microbiology and Genetics, University of Salamanca, 37185 Villamayor, Spain
| | - Ernesto P. Benito
- Centro Hispanoluso de Investigaciones Agrarias, Department of Microbiology and Genetics, University of Salamanca, 37185 Villamayor, Spain
| | - José M. Díaz-Mínguez
- Centro Hispanoluso de Investigaciones Agrarias, Department of Microbiology and Genetics, University of Salamanca, 37185 Villamayor, Spain
| | - Michael R. Thon
- Centro Hispanoluso de Investigaciones Agrarias, Department of Microbiology and Genetics, University of Salamanca, 37185 Villamayor, Spain
| | - Serenella A. Sukno
- Centro Hispanoluso de Investigaciones Agrarias, Department of Microbiology and Genetics, University of Salamanca, 37185 Villamayor, Spain
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300
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Abstract
Biotrophy is a pervasive trait that evolved independently in plant pathogenic fungi and oomycetes. Comparative genomics of the first sequenced biotrophic pathogens highlight remarkable convergences, including gene losses in the metabolism of inorganic nitrogen, inorganic sulfur, and thiamine, and genes encoding carbohydrate active enzymes and secondary metabolism enzymes. Some biotrophs, but not all, display marked increases in overall genome size because of a proliferation of retrotransposons. I argue here that the release of constraints on transposon activity is driven by the advantages conferred by the genetic variability that results from transposition, in particular by the creation and diversification of broad palettes of effector genes. Increases in genome size and gene losses are the consequences of this trade-off. Genes that are not necessary for growth on a plant disappeared, but we still do not know what lost functions make some of these pathogens obligate.
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Affiliation(s)
- Pietro D Spanu
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, United Kingdom.
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