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Fernandes C, Casadevall A, Gonçalves T. Mechanisms of Alternaria pathogenesis in animals and plants. FEMS Microbiol Rev 2023; 47:fuad061. [PMID: 37884396 DOI: 10.1093/femsre/fuad061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 09/18/2023] [Accepted: 10/25/2023] [Indexed: 10/28/2023] Open
Abstract
Alternaria species are cosmopolitan fungi darkly pigmented by melanin that infect numerous plant species causing economically important agricultural spoilage of various food crops. Alternaria spp. also infect animals, being described as entomopathogenic fungi but also infecting warm-blooded animals, including humans. Their clinical importance in human health, as infection agents, lay in the growing number of immunocompromised patients. Moreover, Alternaria spp. are considered some of the most abundant and potent sources of airborne sensitizer allergens causing allergic respiratory diseases, as severe asthma. Among the numerous strategies deployed by Alternaria spp. to attack their hosts, the production of toxins, carrying critical concerns to public health as food contaminant, and the production of hydrolytic enzymes such as proteases, can be highlighted. Alternaria proteases also trigger allergic symptoms in individuals with fungal sensitization, acting as allergens and facilitating antigen access to the host subepithelium. Here, we review the current knowledge about the mechanisms of Alternaria pathogenesis in plants and animals, the strategies used by Alternaria to cope with the host defenses, and the involvement Alternaria allergens and mechanisms of sensitization.
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Affiliation(s)
- Chantal Fernandes
- CNC-UC - Center for Neuroscience and Cell Biology of Coimbra, Rua Larga, 3004-504 Coimbra, Portugal
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Wolfe Street, Room E5132, Baltimore, Maryland 21205, USA
| | - Teresa Gonçalves
- CNC-UC - Center for Neuroscience and Cell Biology of Coimbra, Rua Larga, 3004-504 Coimbra, Portugal
- FMUC - Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504 Coimbra, Portugal
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Charpentier T, Viault G, Le Ray AM, Bataillé-Simoneau N, Helesbeux JJ, Blon N, Bastide F, Marchi M, Aligon S, Bruguière A, Dinh CP, Benbelkacem Z, Dallery JF, Simoneau P, Richomme P, Guillemette T. Natural Products Targeting the Fungal Unfolded Protein Response as an Alternative Crop Protection Strategy. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:13706-13716. [PMID: 37697453 DOI: 10.1021/acs.jafc.3c03602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/13/2023]
Abstract
Discovering new solutions for crop protection is a major challenge for the next decades as a result of the ecotoxicological impact of classical fungicides, the emergence of fungicide resistances, and the consequence of climate change on pathogen distribution. Previous work on fungal mutants deficient in the unfolded protein response (UPR) supported that targeting this pathway is a promising plant disease control strategy. In particular, we showed that the UPR is involved in fungal virulence by altering cell protection against host defense compounds, such as phytoalexins and phytoanticipins. In this study, we evaluated natural products targeting fungal IRE1 protein (UPR effector) and consequently increasing fungal susceptibility to plant defenses. Developing an in vitro cell-based screening assay allowed for the identification of seven potential IRE1 inhibitors with a focus on polyhydroxylated prenylated xanthones. Inhibition of hac1 mRNA splicing, which is mediated by IRE1, was then validated for the most active compound, namely, γ-mangostin 3. To study the mode of interaction between the binding site of IRE1 and active xanthones, molecular docking was also undertaken, revealing similar and novel interactions between the known inhibitor and the binding site. Eventually, active xanthones applied at subtoxic doses induced a significant reduction in necrosis size for leaves of Brassica oleracea inoculated with Alternaria brassicicola and Botrytis cinerea.
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Affiliation(s)
- Thomas Charpentier
- Université Angers, SONAS, SFR QUASAV, F-49000 Angers, France
- Université Angers, Institut Agro, INRAE, IRHS, SFR QUASAV, 49070 Beaucouzé, France
| | | | | | | | | | - Nadège Blon
- Université Angers, SONAS, SFR QUASAV, F-49000 Angers, France
| | - Franck Bastide
- Université Angers, Institut Agro, INRAE, IRHS, SFR QUASAV, 49070 Beaucouzé, France
| | - Muriel Marchi
- Université Angers, Institut Agro, INRAE, IRHS, SFR QUASAV, 49070 Beaucouzé, France
| | - Sophie Aligon
- Université Angers, Institut Agro, INRAE, IRHS, SFR QUASAV, 49070 Beaucouzé, France
| | | | - Chau Phi Dinh
- Université Angers, SONAS, SFR QUASAV, F-49000 Angers, France
| | | | - Jean-Felix Dallery
- Université Angers, Institut Agro, INRAE, IRHS, SFR QUASAV, 49070 Beaucouzé, France
| | - Philippe Simoneau
- Université Angers, Institut Agro, INRAE, IRHS, SFR QUASAV, 49070 Beaucouzé, France
| | - Pascal Richomme
- Université Angers, SONAS, SFR QUASAV, F-49000 Angers, France
| | - Thomas Guillemette
- Université Angers, Institut Agro, INRAE, IRHS, SFR QUASAV, 49070 Beaucouzé, France
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Lin S, Chen X, Xie L, Zhang Y, Zeng F, Long Y, Ren L, Qi X, Wei J. Biocontrol potential of lipopeptides produced by Paenibacillus polymyxa AF01 against Neoscytalidium dimidiatum in pitaya. Front Microbiol 2023; 14:1188722. [PMID: 37266020 PMCID: PMC10231640 DOI: 10.3389/fmicb.2023.1188722] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 04/28/2023] [Indexed: 06/03/2023] Open
Abstract
Pitaya canker, caused by Neoscytalidium dimidiatum, is one of the most important fungal diseases that cause significant losses in production. To replace chemical pesticides, the use of biocontrol strains to manage plant diseases has been the focus of research. In this study, the bacterial strain AF01, identified as Paenibacillus polymyxa, exhibited significant antifungal effects against N. dimidiatum and four other pitaya fungal pathogens. The strain P. polymyxa AF01 produces 13 fusaricidins, which directly inhibit mycelial growth, spore germination and germ tube elongation by causing the membrane integrity and cell ultrastructure to incur irreversible damage. Pot experiment and yield test confirmed that AF01 provided preservative effects by reducing the disease index. In comparison to the untreated control groups, RNA-seq data showed that P. polymyxa AF01 selectively blocked some transcription and translation processes and inhibited RNA and DNA structural dynamics, energy production and conversion, and signal transduction, particularly cell wall biosynthesis, changes in membrane permeability, and impairment of protein biosynthesis. Thus, P. polymyxa AF01 could be potentially useful as a suitable biocontrol agent for pitaya canker.
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Affiliation(s)
- Shanyu Lin
- College of Agriculture, Guangxi University, Nanning, China
- Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China Ministry of Agriculture and Rural Affairs, Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Plant Protection Research Institute, Guangxi Academy of Agricultural Science, Nanning, Guangxi, China
| | - Xiaohang Chen
- Baise Agricultural Scientific Research Institute, Baise, China
| | - Ling Xie
- Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China Ministry of Agriculture and Rural Affairs, Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Plant Protection Research Institute, Guangxi Academy of Agricultural Science, Nanning, Guangxi, China
| | - Yan Zhang
- Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China Ministry of Agriculture and Rural Affairs, Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Plant Protection Research Institute, Guangxi Academy of Agricultural Science, Nanning, Guangxi, China
| | - Fenghua Zeng
- Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China Ministry of Agriculture and Rural Affairs, Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Plant Protection Research Institute, Guangxi Academy of Agricultural Science, Nanning, Guangxi, China
| | - Yanyan Long
- Key Laboratory of Green Prevention and Control on Fruits and Vegetables in South China Ministry of Agriculture and Rural Affairs, Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Plant Protection Research Institute, Guangxi Academy of Agricultural Science, Nanning, Guangxi, China
| | - Liyun Ren
- College of Agricultural Engineering, Guangxi Vocational University of Agriculture, Nanning, China
| | - Xiuling Qi
- College of Agricultural Engineering, Guangxi Vocational University of Agriculture, Nanning, China
| | - Jiguang Wei
- College of Agriculture, Guangxi University, Nanning, China
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O’Boyle NM, Helesbeux JJ, Meegan MJ, Sasse A, O’Shaughnessy E, Qaisar A, Clancy A, McCarthy F, Marchand P. 30th Annual GP 2A Medicinal Chemistry Conference. Pharmaceuticals (Basel) 2023; 16:432. [PMID: 36986531 PMCID: PMC10056312 DOI: 10.3390/ph16030432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 01/16/2023] [Indexed: 03/14/2023] Open
Abstract
The Group for the Promotion of Pharmaceutical Chemistry in Academia (GP2A) held their 30th annual conference in August 2022 in Trinity College Dublin, Ireland. There were 9 keynote presentations, 10 early career researcher presentations and 41 poster presentations.
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Affiliation(s)
- Niamh M. O’Boyle
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | | | - Mary J. Meegan
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Astrid Sasse
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Elizabeth O’Shaughnessy
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Alina Qaisar
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Aoife Clancy
- School of Pharmacy and Pharmaceutical Sciences, Panoz Institute and Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland
| | - Florence McCarthy
- School of Chemistry and ABCRF, University College Cork, T12 K8AF Cork, Ireland
| | - Pascal Marchand
- Cibles et Médicaments des Infections et de l’Immunité, IICiMed, Nantes Université, UR 1155, F-44000 Nantes, France
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Lv Y, Yang H, Wang J, Wei S, Zhai H, Zhang S, Hu Y. Afper1 contributes to cell development and aflatoxin biosynthesis in Aspergillus flavus. Int J Food Microbiol 2022; 377:109828. [PMID: 35843028 DOI: 10.1016/j.ijfoodmicro.2022.109828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 06/22/2022] [Accepted: 07/02/2022] [Indexed: 11/28/2022]
Abstract
Aspergillus flavus contaminates crops and produces carcinogenic aflatoxins that pose severe threat to food safety and human health. To identify potential targets to control aflatoxin contamination, we characterized a novel Afper1 protein, which regulates cell development and secondary metabolite biosynthesis in A. flavus. Afper1 is localized in the nucleus and is required for hyphal growth, conidial and sclerotial production, and responses to osmotic stress and essential oils such as cinnamaldehyde and thymol. More importantly, aflatoxin production was impaired in the Afper1 deletion mutant. Proteomics analysis revealed that extracellular hydrolases and proteins involved in conidial development, endoplasmic reticulum (ER) homeostasis, and aflatoxin biosynthesis were differentially regulated in ΔAfper1. Unexpectedly, enzymes participated in reactive oxygen species (ROS) scavenging, including catalase (catA, catB) and superoxide dismutase (sodM) were significantly downregulated, and the ROS accumulation and sensitivity to hydrogen peroxide were confirmed experimentally. Additionally, Afper1 deletion significantly upregulated heterochromatin protein HepA and downregulated acetyltransferases involved in heterochromatin formation. Accompanying ROS accumulation and chromatin remodeling, proteins related to aflatoxins, ustiloxin B and gliotoxin were downregulated. These results implied that Afper1 deletion affected chromatin remodeling and disturbed ER homeostasis, leading to ROS accumulation, and ultimately resulting in defective growth and impaired secondary metabolite biosynthesis.
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Affiliation(s)
- Yangyong Lv
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China.
| | - Haojie Yang
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Jing Wang
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Shan Wei
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Huanchen Zhai
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Shuaibing Zhang
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China
| | - Yuansen Hu
- College of Biological Engineering, Henan University of Technology, People's Republic of China; Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, People's Republic of China.
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Nguyen NH, Trotel-Aziz P, Clément C, Jeandet P, Baillieul F, Aziz A. Camalexin accumulation as a component of plant immunity during interactions with pathogens and beneficial microbes. PLANTA 2022; 255:116. [PMID: 35511374 DOI: 10.1007/s00425-022-03907-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 04/26/2022] [Indexed: 06/14/2023]
Abstract
This review provides an overview on the role of camalexin in plant immunity taking into account various plant-pathogen and beneficial microbe interactions, regulation mechanisms and the contribution in basal and induced plant resistance. In a hostile environment, plants evolve complex and sophisticated defense mechanisms to counteract invading pathogens and herbivores. Several lines of evidence support the assumption that secondary metabolites like phytoalexins which are synthesized de novo, play an important role in plant defenses and contribute to pathogens' resistance in a wide variety of plant species. Phytoalexins are synthesized and accumulated in plants upon pathogen challenge, root colonization by beneficial microbes, following treatment with chemical elicitors or in response to abiotic stresses. Their protective properties against pathogens have been reported in various plant species as well as their contribution to human health. Phytoalexins are synthesized through activation of particular sets of genes encoding specific pathways. Camalexin (3'-thiazol-2'-yl-indole) is the primary phytoalexin produced by Arabidopsis thaliana after microbial infection or abiotic elicitation and an iconic representative of the indole phytoalexin family. The synthesis of camalexin is an integral part of cruciferous plant defense mechanisms. Although the pathway leading to camalexin has been largely elucidated, the regulatory networks that control the induction of its biosynthetic steps by pathogens with different lifestyles or by beneficial microbes remain mostly unknown. This review thus presents current knowledge regarding camalexin biosynthesis induction during plant-pathogen and beneficial microbe interactions as well as in response to microbial compounds and provides an overview on its regulation and interplay with signaling pathways. The contribution of camalexin to basal and induced plant resistance and its detoxification by some pathogens to overcome host resistance are also discussed.
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Affiliation(s)
- Ngoc Huu Nguyen
- Induced Resistance and Plant Bioprotection, USC INRAE 1488, University of Reims, UFR Sciences, Campus Moulin de la Housse, 51687 Cedex 02, Reims, France
- Department of Plant Biology, Faculty of Agriculture and Forestry, Tay Nguyen University, 567 Le Duan, Buon Ma Thuot, Daklak, Vietnam
| | - Patricia Trotel-Aziz
- Induced Resistance and Plant Bioprotection, USC INRAE 1488, University of Reims, UFR Sciences, Campus Moulin de la Housse, 51687 Cedex 02, Reims, France
| | - Christophe Clément
- Induced Resistance and Plant Bioprotection, USC INRAE 1488, University of Reims, UFR Sciences, Campus Moulin de la Housse, 51687 Cedex 02, Reims, France
| | - Philippe Jeandet
- Induced Resistance and Plant Bioprotection, USC INRAE 1488, University of Reims, UFR Sciences, Campus Moulin de la Housse, 51687 Cedex 02, Reims, France
| | - Fabienne Baillieul
- Induced Resistance and Plant Bioprotection, USC INRAE 1488, University of Reims, UFR Sciences, Campus Moulin de la Housse, 51687 Cedex 02, Reims, France
| | - Aziz Aziz
- Induced Resistance and Plant Bioprotection, USC INRAE 1488, University of Reims, UFR Sciences, Campus Moulin de la Housse, 51687 Cedex 02, Reims, France.
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Guirao-Abad JP, Weichert M, Askew DS. Cell death induction in Aspergillus fumigatus: accentuating drug toxicity through inhibition of the unfolded protein response (UPR). CURRENT RESEARCH IN MICROBIAL SCIENCES 2022; 3:100119. [PMID: 35909601 PMCID: PMC9325865 DOI: 10.1016/j.crmicr.2022.100119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/25/2022] [Accepted: 02/17/2022] [Indexed: 01/18/2023] Open
Abstract
The UPR is an adaptive stress response network that is tightly linked to the ability of Aspergillus fumigatus, and other pathogenic fungi, to sustain viability in the presence of adverse environmental conditions, including the stress of infection. In this review, we summarize the evidence that supports the concept of targeting the A. fumigatus UPR as a strategy to reduce the ability of the fungus to withstand stress.
One of the most potent opportunistic fungal pathogens of humans is Aspergillus fumigatus, an environmental mold that causes a life-threatening pneumonia with a high rate of morbidity and mortality. Despite advances in therapy, issues of drug toxicity and antifungal resistance remain an obstacle to effective therapy. This underscores the need for more information on fungal pathways that could be pharmacologically manipulated to either reduce the viability of the fungus during infection, or to unleash the fungicidal potential of current antifungal drugs. In this review, we summarize the emerging evidence that the ability of A. fumigatus to sustain viability during stress relies heavily on an adaptive signaling pathway known as the unfolded protein response (UPR), thereby exposing a vulnerability in this fungus that has strong potential for future therapeutic intervention.
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Unravelling the Initial Triggers of Botrytis cinerea Infection: First Description of Its Surfactome. J Fungi (Basel) 2021; 7:jof7121021. [PMID: 34947003 PMCID: PMC8708654 DOI: 10.3390/jof7121021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 11/20/2021] [Accepted: 11/26/2021] [Indexed: 11/17/2022] Open
Abstract
Botrytis cinerea is a critically important phytopathogenic fungus, causing devastating crop losses; signal transduction cascades mediate the “dialogue” among the fungus, plant, and environment. Surface proteins play important roles as front-line receptors. We report the first description of the surfactome of a filamentous fungus. To obtain a complete view of these cascades during infection of B. cinerea, its surfactome has been described by optimization of the “shaving” process and LC–MS/MS at two different infection stages, and with both rapid and late responses to environmental changes. The best results were obtained using PBS buffer in the “shaving” protocol. The surfactome obtained comprises 1010 identified proteins. These have been categorized by gene ontology and protein–protein interactions to reveal new potential pathogenicity/virulence factors. From these data, the percentage of total proteins predicted for the genome of the fungus represented by proteins identified in this and other proteomics studies is calculated at 54%, a big increase over the previous 12%. The new data may be crucial for understanding better its biological activity and pathogenicity. Given its extensive exposure to plants and environmental conditions, the surfactome presents innumerable opportunities for interactions between the fungus and external elements, which should offer the best targets for fungicide development.
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Yang L, Wei Z, Li S, Xiao R, Xu Q, Ran Y, Ding W. Plant secondary metabolite, daphnetin reduces extracellular polysaccharides production and virulence factors of Ralstonia solanacearum. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2021; 179:104948. [PMID: 34802533 DOI: 10.1016/j.pestbp.2021.104948] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/18/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
Plants deploy a variety of secondary metabolites to fend off pathogen attack. Certain plants could accumulate coumarins in response to infection of bacteria, fungi, virus and oomycetes. Although coumarins are generally considered toxic to microbes, the exact mechanisms are often unknown. Here, we showed that a plant secondary metabolite daphnetin functions primarily by inhibiting Ralstonia solanacearum extracellular polysaccharides (EPS) production and biofilm formation in vitro, through suppressing genes expression of xpsR, epsE, epsB and lexM. Indeed, daphnetin significantly impaired virulence of R. solanacearum on tobacco plants. Transcriptional analysis suggested that daphnetin suppresses EPS synthesis cluster genes expression through transcriptional regulator XpsR. And daphnetin alter mainly virulence factors genes involved in type III secretion system, and type IV secretion system. R. solanacearum lacking EPS synthesis genes (epsB and epsC) that do not produce EPS, showed less virulence on tobacco plants. Molecular docking results indicated that the critical residues of domain in the binding pocket of the EpsB protein interact with daphnetin via conventional hydrogen bonding and hydrophobic interactions. Collectively, we found that daphnetin has potential as a novel virulence inhibitor of R. solanacearum, directly regulates EPS synthesis genes expression.
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Affiliation(s)
- Liang Yang
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University, Chongqing 400715, China
| | - Zhouling Wei
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University, Chongqing 400715, China
| | - Shili Li
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University, Chongqing 400715, China
| | - Rui Xiao
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University, Chongqing 400715, China
| | - Qinqin Xu
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University, Chongqing 400715, China
| | - Yuao Ran
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University, Chongqing 400715, China
| | - Wei Ding
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University, Chongqing 400715, China.
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Pleiotropic Effects of the P5-Type ATPase SpfA on Stress Response Networks Contribute to Virulence in the Pathogenic Mold Aspergillus fumigatus. mBio 2021; 12:e0273521. [PMID: 34663092 PMCID: PMC8524344 DOI: 10.1128/mbio.02735-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aspergillus fumigatus is a human-pathogenic mold that extracts nutrients from the environment or from host tissues by secreting hydrolytic enzymes. The ability of A. fumigatus to adjust secretion levels in proportion to demand relies on the assistance of the unfolded protein response (UPR), an adaptive stress response pathway that regulates the unique protein-folding environment of the endoplasmic reticulum (ER). The P5-type ATPase Spf1 has recently been implicated in a novel mechanism of ER homeostasis that involves correcting errors in ER-membrane protein targeting. However, the contribution of this protein to the biology of A. fumigatus is unknown. Here, we employed a gene knockout and RNA sequencing strategy to determine the functional role of the A. fumigatus gene coding for the orthologous P5 ATPase SpfA. The data reveal that the spfA gene is induced by ER stress in a UPR-dependent manner. In the absence of spfA, the A. fumigatus transcriptome shifts toward a profile of altered redox and lipid balance, in addition to a signature of ER stress that includes srcA, encoding a second P-type ATPase in the ER. A ΔspfA deletion mutant showed increased sensitivity to ER stress, oxidative stress, and antifungal drugs that target the cell wall or plasma membrane. The combined loss of spfA and srcA exacerbated these phenotypes and attenuated virulence in two animal infection models. These findings demonstrate that the ER-resident ATPases SpfA and SrcA act jointly to support diverse adaptive functions of the ER that are necessary for fitness in the host environment. IMPORTANCE The fungal UPR is an adaptive signaling pathway in the ER that buffers fluctuations in ER stress but also serves as a virulence regulatory hub in species of pathogenic fungi that rely on secretory pathway homeostasis for pathogenicity. This study demonstrates that the gene encoding the ER-localized P5-type ATPase SpfA is a downstream target of the UPR in the pathogenic mold A. fumigatus and that it works together with a second ER-localized P-type ATPase, SrcA, to support ER homeostasis, oxidative stress resistance, susceptibility to antifungal drugs, and virulence of A. fumigatus.
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Starke J, Harting R, Maurus I, Leonard M, Bremenkamp R, Heimel K, Kronstad JW, Braus GH. Unfolded Protein Response and Scaffold Independent Pheromone MAP Kinase Signaling Control Verticillium dahliae Growth, Development, and Plant Pathogenesis. J Fungi (Basel) 2021; 7:jof7040305. [PMID: 33921172 PMCID: PMC8071499 DOI: 10.3390/jof7040305] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/12/2021] [Accepted: 04/12/2021] [Indexed: 12/13/2022] Open
Abstract
Differentiation, growth, and virulence of the vascular plant pathogen Verticillium dahliae depend on a network of interconnected cellular signaling cascades. The transcription factor Hac1 of the endoplasmic reticulum-associated unfolded protein response (UPR) is required for initial root colonization, fungal growth, and vascular propagation by conidiation. Hac1 is essential for the formation of microsclerotia as long-time survival resting structures in the field. Single endoplasmic reticulum-associated enzymes for linoleic acid production as precursors for oxylipin signal molecules support fungal growth but not pathogenicity. Microsclerotia development, growth, and virulence further require the pheromone response mitogen-activated protein kinase (MAPK) pathway, but without the Ham5 scaffold function. The MAPK phosphatase Rok1 limits resting structure development of V.dahliae, but promotes growth, conidiation, and virulence. The interplay between UPR and MAPK signaling cascades includes several potential targets for fungal growth control for supporting disease management of the vascular pathogen V.dahliae.
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Affiliation(s)
- Jessica Starke
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, 37077 Göttingen, Germany; (J.S.); (R.H.); (I.M.); (M.L.); (R.B.); (K.H.)
| | - Rebekka Harting
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, 37077 Göttingen, Germany; (J.S.); (R.H.); (I.M.); (M.L.); (R.B.); (K.H.)
| | - Isabel Maurus
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, 37077 Göttingen, Germany; (J.S.); (R.H.); (I.M.); (M.L.); (R.B.); (K.H.)
| | - Miriam Leonard
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, 37077 Göttingen, Germany; (J.S.); (R.H.); (I.M.); (M.L.); (R.B.); (K.H.)
| | - Rica Bremenkamp
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, 37077 Göttingen, Germany; (J.S.); (R.H.); (I.M.); (M.L.); (R.B.); (K.H.)
| | - Kai Heimel
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, 37077 Göttingen, Germany; (J.S.); (R.H.); (I.M.); (M.L.); (R.B.); (K.H.)
| | - James W. Kronstad
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada;
| | - Gerhard H. Braus
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics and Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, 37077 Göttingen, Germany; (J.S.); (R.H.); (I.M.); (M.L.); (R.B.); (K.H.)
- Correspondence: ; Tel.: +49-(0)551-39-33771
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N’Guyen GQ, Raulo R, Porquier A, Iacomi B, Pelletier S, Renou JP, Bataillé-Simoneau N, Campion C, Hamon B, Kwasiborski A, Colou J, Benamar A, Hudhomme P, Macherel D, Simoneau P, Guillemette T. Responses of the Necrotrophic Fungus Alternaria brassisicola to the Indolic Phytoalexin Brassinin. FRONTIERS IN PLANT SCIENCE 2021; 11:611643. [PMID: 33552104 PMCID: PMC7860980 DOI: 10.3389/fpls.2020.611643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 12/17/2020] [Indexed: 06/12/2023]
Abstract
Alternaria brassicicola causes black spot disease in Brassicaceae. During host infection, this necrotrophic fungus is exposed to various antimicrobial compounds, such as the phytoalexin brassinin which is produced by many cultivated Brassica species. To investigate the cellular mechanisms by which this compound causes toxicity and the corresponding fungal adaptive strategies, we first analyzed fungal transcriptional responses to short-term exposure to brassinin and then used additional functional approaches. This study supports the hypothesis that indolic phytoalexin primarily targets mitochondrial functions in fungal cells. Indeed, we notably observed that phytoalexin treatment of A. brassicicola disrupted the mitochondrial membrane potential and resulted in a significant and rapid decrease in the oxygen consumption rates. Secondary effects, such as Reactive oxygen species production, changes in lipid and endoplasmic reticulum homeostasis were then found to be induced. Consequently, the fungus has to adapt its metabolism to protect itself against the toxic effects of these molecules, especially via the activation of high osmolarity glycerol and cell wall integrity signaling pathways and by induction of the unfolded protein response.
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Affiliation(s)
| | - Roxane Raulo
- Institut Charles Viollette – EA 7394, Université de Lille, INRA, ISA, Université d’Artois, Université du Littoral Côte d’Opale, Lille, France
| | | | | | - Sandra Pelletier
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
| | - Jean-Pierre Renou
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
| | | | - Claire Campion
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
| | - Bruno Hamon
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
| | | | - Justine Colou
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
| | - Abdelilah Benamar
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
| | | | - David Macherel
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
| | - Philippe Simoneau
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
| | - Thomas Guillemette
- UNIV Angers, Institut Agro, INRAE, IRHS, SFR 4207 QuaSaV, Angers, France
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13
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Wang W, Yang J, Zhang J, Liu YX, Tian C, Qu B, Gao C, Xin P, Cheng S, Zhang W, Miao P, Li L, Zhang X, Chu J, Zuo J, Li J, Bai Y, Lei X, Zhou JM. An Arabidopsis Secondary Metabolite Directly Targets Expression of the Bacterial Type III Secretion System to Inhibit Bacterial Virulence. Cell Host Microbe 2020; 27:601-613.e7. [PMID: 32272078 DOI: 10.1016/j.chom.2020.03.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 12/19/2019] [Accepted: 02/17/2020] [Indexed: 10/24/2022]
Abstract
Plants deploy a variety of secondary metabolites to fend off pathogen attack. Although defense compounds are generally considered toxic to microbes, the exact mechanisms are often unknown. Here, we show that the Arabidopsis defense compound sulforaphane (SFN) functions primarily by inhibiting Pseudomonas syringae type III secretion system (TTSS) genes, which are essential for pathogenesis. Plants lacking the aliphatic glucosinolate pathway, which do not accumulate SFN, were unable to attenuate TTSS gene expression and exhibited increased susceptibility to P. syringae strains that cannot detoxify SFN. Chemoproteomics analyses showed that SFN covalently modified the cysteine at position 209 of HrpS, a key transcription factor controlling TTSS gene expression. Site-directed mutagenesis and functional analyses further confirmed that Cys209 was responsible for bacterial sensitivity to SFN in vitro and sensitivity to plant defenses conferred by the aliphatic glucosinolate pathway. Collectively, these results illustrate a previously unknown mechanism by which plants disarm a pathogenic bacterium.
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Affiliation(s)
- Wei Wang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jing Yang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Lifeomics, Beijing 102206, China
| | - Jian Zhang
- Department of Chemical Biology, College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Synthetic and Functional Biomolecules Center and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - Yong-Xin Liu
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China
| | - Caiping Tian
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Lifeomics, Beijing 102206, China
| | - Baoyuan Qu
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China
| | - Chulei Gao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Peiyong Xin
- National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Shujing Cheng
- National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenjing Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pei Miao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lei Li
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Xiaojuan Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China
| | - Jinfang Chu
- National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Jianru Zuo
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiayang Li
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yang Bai
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China; CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), Beijing 100101, China
| | - Xiaoguang Lei
- Department of Chemical Biology, College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Synthetic and Functional Biomolecules Center and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China.
| | - Jian-Min Zhou
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China.
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14
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A Human IRE1 Inhibitor Blocks the Unfolded Protein Response in the Pathogenic Fungus Aspergillus fumigatus and Suggests Noncanonical Functions within the Pathway. mSphere 2020; 5:5/5/e00879-20. [PMID: 33087521 PMCID: PMC7580959 DOI: 10.1128/msphere.00879-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The unfolded protein response (UPR) is a signaling pathway that maintains endoplasmic reticulum (ER) homeostasis, with functions that overlap virulence mechanisms in the human-pathogenic mold Aspergillus fumigatus. The canonical pathway centers on HacA, its master transcriptional regulator. Translation of this protein requires the removal of an unconventional intron from the cytoplasmic mRNA of the hacA gene, which is achieved by an RNase domain located in the ER-transmembrane stress sensor IreA. Here, we show that targeting this RNase activity with a small-molecule inhibitor effectively blocked UPR activation, resulting in effects that mirror the consequences of genetic deletion of the RNase domain. However, these phenotypes were surprisingly narrow in scope relative to those associated with a complete deletion of the hacA gene. These findings expand the understanding of UPR signaling in this species by supporting the existence of noncanonical functions for the unspliced hacA mRNA in ER stress response. The unfolded protein response (UPR) is a signaling network that maintains homeostasis of the endoplasmic reticulum (ER). In the human-pathogenic fungus Aspergillus fumigatus, the UPR is initiated by activation of an endoribonuclease (RNase) domain in the ER transmembrane stress sensor IreA, which splices the downstream mRNA hacAu into its active form, hacAi, encoding the master transcriptional regulator of the pathway. Small-molecule inhibitors against IRE1, the human ortholog of IreA, have been developed for anticancer therapy, but their effects on the fungal UPR are unexplored. Here, we demonstrate that the IRE1 RNase inhibitor 4μ8C prevented A. fumigatus from increasing the levels of hacAi mRNA, thereby blocking induction of downstream UPR target gene expression. Treatment with 4μ8C had minimal effects on growth in minimal medium but severely impaired growth on a collagen substrate that requires high levels of hydrolytic enzyme secretion, mirroring the phenotype of other fungal UPR mutants. 4μ8C also increased sensitivity to carvacrol, a natural compound that disrupts ER integrity in fungi, and hygromycin B, which correlated with reduced expression of glycosylation-related genes. Interestingly, treatment with 4μ8C was unable to induce all of the phenotypes attributed to the loss of the canonical UPR in a ΔhacA mutant but showed remarkable similarity to the phenotype of an RNase-deficient IreA mutant that is also unable to generate the hacAi mRNA. These results establish proof of principle that pharmacological inhibition of the canonical UPR pathway is feasible in A. fumigatus and support a noncanonical role for the hacAu mRNA in ER stress response. IMPORTANCE The unfolded protein response (UPR) is a signaling pathway that maintains endoplasmic reticulum (ER) homeostasis, with functions that overlap virulence mechanisms in the human-pathogenic mold Aspergillus fumigatus. The canonical pathway centers on HacA, its master transcriptional regulator. Translation of this protein requires the removal of an unconventional intron from the cytoplasmic mRNA of the hacA gene, which is achieved by an RNase domain located in the ER-transmembrane stress sensor IreA. Here, we show that targeting this RNase activity with a small-molecule inhibitor effectively blocked UPR activation, resulting in effects that mirror the consequences of genetic deletion of the RNase domain. However, these phenotypes were surprisingly narrow in scope relative to those associated with a complete deletion of the hacA gene. These findings expand the understanding of UPR signaling in this species by supporting the existence of noncanonical functions for the unspliced hacA mRNA in ER stress response.
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15
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Functional Coupling between the Unfolded Protein Response and Endoplasmic Reticulum/Golgi Ca 2+-ATPases Promotes Stress Tolerance, Cell Wall Biosynthesis, and Virulence of Aspergillus fumigatus. mBio 2020; 11:mBio.01060-20. [PMID: 32487759 PMCID: PMC7267887 DOI: 10.1128/mbio.01060-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Many species of pathogenic fungi deploy the unfolded protein response (UPR) to expand the folding capacity of the endoplasmic reticulum (ER) in proportion to the demand for virulence-related proteins that traffic through the secretory pathway. Although Ca2+ plays a pivotal role in ER function, the mechanism by which transcriptional upregulation of the protein folding machinery is coordinated with Ca2+ homeostasis is incompletely understood. In this study, we investigated the link between the UPR and genes encoding P-type Ca2+-ATPases in the human-pathogenic mold Aspergillus fumigatus We demonstrate that acute ER stress increases transcription of the srcA gene, encoding a member of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) family, as well as that of pmrA, encoding a secretory pathway Ca2+-ATPase (SPCA) in the Golgi membrane. Loss of the UPR transcription factor HacA prevented the induction of srcA and pmrA transcription during ER stress, defining these ER/Golgi Ca2+ pumps as novel downstream targets of this pathway. While deletion of srcA alone caused no major deficiencies, a ΔsrcA/ΔpmrA mutant displayed a severe polarity defect, was hypersensitive to ER stress, and showed attenuated virulence. In addition, cell wall analyses revealed a striking reduction in mannose levels in the absence of both Ca2+ pumps. The ΔhacA mutant was hypersensitive to agents that block calcineurin-dependent signaling, consistent with a functional coupling between the UPR and Ca2+ homeostasis. Together, these findings demonstrate that the UPR integrates the need for increased levels of chaperone and folding enzymes with an influx of Ca2+ into the secretory pathway to support fungal growth, stress adaptation, and pathogenicity.IMPORTANCE The UPR is an intracellular signal transduction pathway that maintains homeostasis of the ER. The pathway is also tightly linked to the expression of virulence-related traits in diverse species of human-pathogenic and plant-pathogenic fungal species, including the predominant mold pathogen infecting humans, Aspergillus fumigatus Despite advances in the understanding of UPR signaling, the linkages and networks that are governed by this pathway are not well defined. In this study, we revealed that the UPR is a major driving force for stimulating Ca2+ influx at the ER and Golgi membranes and that the coupling between the UPR and Ca2+ import is important for virulence, cell wall biosynthesis, and resistance to antifungal compounds that inhibit Ca2+ signaling.
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16
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Schmitz L, Kronstad JW, Heimel K. Conditional gene expression reveals stage-specific functions of the unfolded protein response in the Ustilago maydis-maize pathosystem. MOLECULAR PLANT PATHOLOGY 2020; 21:258-271. [PMID: 31802604 PMCID: PMC6988420 DOI: 10.1111/mpp.12893] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Ustilago maydis is a model organism for the study of biotrophic plant-pathogen interactions. The sexual and pathogenic development of the fungus are tightly connected since fusion of compatible haploid sporidia is prerequisite for infection of the host plant, maize (Zea mays). After plant penetration, the unfolded protein response (UPR) is activated and required for biotrophic growth. The UPR is continuously active throughout all stages of pathogenic development in planta. However, since development of UPR deletion mutants stops directly after plant penetration, the role of an active UPR at later stages of development remained to be determined. Here, we established a gene expression system for U. maydis that uses endogenous, conditionally active promoters to either induce or repress expression of a gene of interest during different stages of plant infection. Integration of the expression constructs into the native genomic locus and removal of resistance cassettes were required to obtain a wild-type-like expression pattern. This indicates that genomic localization and chromatin structure are important for correct promoter activity and gene expression. By conditional expression of the central UPR regulator, Cib1, in U. maydis, we show that a functional UPR is required for continuous plant defence suppression after host infection and that U. maydis relies on a robust control system to prevent deleterious UPR hyperactivation.
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Affiliation(s)
- Lara Schmitz
- Institute for Microbiology and GeneticsDepartment of Molecular Microbiology and GeneticsGöttingen Center for Molecular Biosciences (GZMB)University of GöttingenGrisebachstr. 8D‐37077GöttingenGermany
- International Research Training Group 2172 PRoTECTGöttingen, VancouverGermany
| | - James W. Kronstad
- International Research Training Group 2172 PRoTECTGöttingen, VancouverGermany
- Michael Smith LaboratoriesDepartment of Microbiology and ImmunologyUniversity of British ColumbiaVancouverBCV6T 1Z4Canada
| | - Kai Heimel
- Institute for Microbiology and GeneticsDepartment of Molecular Microbiology and GeneticsGöttingen Center for Molecular Biosciences (GZMB)University of GöttingenGrisebachstr. 8D‐37077GöttingenGermany
- International Research Training Group 2172 PRoTECTGöttingen, VancouverGermany
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17
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Proteomic study of the membrane components of signalling cascades of Botrytis cinerea controlled by phosphorylation. Sci Rep 2019; 9:9860. [PMID: 31285484 PMCID: PMC6614480 DOI: 10.1038/s41598-019-46270-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 06/26/2019] [Indexed: 12/19/2022] Open
Abstract
Protein phosphorylation and membrane proteins play an important role in the infection of plants by phytopathogenic fungi, given their involvement in signal transduction cascades. Botrytis cinerea is a well-studied necrotrophic fungus taken as a model organism in fungal plant pathology, given its broad host range and adverse economic impact. To elucidate relevant events during infection, several proteomics analyses have been performed in B. cinerea, but they cover only 10% of the total proteins predicted in the genome database of this fungus. To increase coverage, we analysed by LC-MS/MS the first-reported overlapped proteome in phytopathogenic fungi, the "phosphomembranome" of B. cinerea, combining the two most important signal transduction subproteomes. Of the 1112 membrane-associated phosphoproteins identified, 64 and 243 were classified as exclusively identified or overexpressed under glucose and deproteinized tomato cell wall conditions, respectively. Seven proteins were found under both conditions, but these presented a specific phosphorylation pattern, so they were considered as exclusively identified or overexpressed proteins. From bioinformatics analysis, those differences in the membrane-associated phosphoproteins composition were associated with various processes, including pyruvate metabolism, unfolded protein response, oxidative stress response, autophagy and cell death. Our results suggest these proteins play a significant role in the B. cinerea pathogenic cycle.
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18
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Pinter N, Hach CA, Hampel M, Rekhter D, Zienkiewicz K, Feussner I, Poehlein A, Daniel R, Finkernagel F, Heimel K. Signal peptide peptidase activity connects the unfolded protein response to plant defense suppression by Ustilago maydis. PLoS Pathog 2019; 15:e1007734. [PMID: 30998787 PMCID: PMC6490947 DOI: 10.1371/journal.ppat.1007734] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 04/30/2019] [Accepted: 03/27/2019] [Indexed: 11/18/2022] Open
Abstract
The corn smut fungus Ustilago maydis requires the unfolded protein response (UPR) to maintain homeostasis of the endoplasmic reticulum (ER) during the biotrophic interaction with its host plant Zea mays (maize). Crosstalk between the UPR and pathways controlling pathogenic development is mediated by protein-protein interactions between the UPR regulator Cib1 and the developmental regulator Clp1. Cib1/Clp1 complex formation results in mutual modification of the connected regulatory networks thereby aligning fungal proliferation in planta, efficient effector secretion with increased ER stress tolerance and long-term UPR activation in planta. Here we address UPR-dependent gene expression and its modulation by Clp1 using combinatorial RNAseq/ChIPseq analyses. We show that increased ER stress resistance is connected to Clp1-dependent alterations of Cib1 phosphorylation, protein stability and UPR gene expression. Importantly, we identify by deletion screening of UPR core genes the signal peptide peptidase Spp1 as a novel key factor that is required for establishing a compatible biotrophic interaction between U. maydis and its host plant maize. Spp1 is dispensable for ER stress resistance and vegetative growth but requires catalytic activity to interfere with the plant defense, revealing a novel virulence specific function for signal peptide peptidases in a biotrophic fungal/plant interaction. Biotrophic pathogens establish compatible interactions with their host to cause disease. A critical step in this process is the suppression of plant defense responses by secreted effector proteins. In the maize infecting fungus Ustilago maydis expression of effector encoding genes is coordinately upregulated at defined stages of pathogenic development in so-called effector waves. Efficient secretion of the multitude of effectors relies on the unfolded protein response (UPR) to maintain homeostasis of the endoplasmic reticulum. Activation of the UPR is connected to the control of fungal proliferation through direct protein-protein interactions between the UPR regulator Cib1 and the developmental regulator Clp1. Here, we show that this interaction leads to functional modification of Cib1 and modulation of UPR gene expression to adapt the UPR for long-term activity in the plant. Within a core set of UPR regulated genes we identify the signal peptide peptidase Spp1 as a key factor for fungal virulence. We show that Spp1 requires its conserved catalytic activity to suppress the plant defense and cause disease. The virulence specific function of Spp1 does not involve pathways previously known to be associated with Spp1-like proteins or plant defense suppression, suggesting a novel role for Spp1 substrates in biotrophic interactions.
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Affiliation(s)
- Niko Pinter
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
| | - Christina Andrea Hach
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
| | - Martin Hampel
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
| | - Dmitrij Rekhter
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
| | - Krzysztof Zienkiewicz
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
- Service Unit for Metabolomics and Lipidomics, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
| | - Ivo Feussner
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
- Service Unit for Metabolomics and Lipidomics, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
| | - Anja Poehlein
- Department of Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, University of Göttingen, Göttingen, Germany
| | - Rolf Daniel
- Department of Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, University of Göttingen, Göttingen, Germany
| | - Florian Finkernagel
- Center for Tumor Biology and Immunology (ZTI), Institute of Molecular Biology and Tumor Research (IMT), Marburg, Germany
| | - Kai Heimel
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Göttingen Center for Molecular Biosciences (GZMB), University of Göttingen, Göttingen, Germany
- * E-mail:
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19
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Zhang H, Li Y, Dickman MB, Wang Z. Cytoprotective Co-chaperone BcBAG1 Is a Component for Fungal Development, Virulence, and Unfolded Protein Response (UPR) of Botrytis cinerea. Front Microbiol 2019; 10:685. [PMID: 31024482 PMCID: PMC6467101 DOI: 10.3389/fmicb.2019.00685] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 03/19/2019] [Indexed: 11/25/2022] Open
Abstract
The Bcl-2 associated athanogene (BAG) family is an evolutionarily conserved group of co-chaperones that confers stress protection against a variety of cellular insults extending from yeasts, plants to humans. Little is known, however, regarding the biological role of BAG proteins in phytopathogenic fungi. Here, we identified the unique BAG gene (BcBAG1) from the necrotrophic fungal pathogen, Botrytis cinerea. BcBAG1 is the homolog of Arabidopsis thaliana AtBAG4, and ectopic expression of BcBAG1 in atbag4 knock-out mutants restores salt tolerance. BcBAG1 deletion mutants (ΔBcbag1) exhibited decreased conidiation, enhanced melanin accumulation and lost the ability to develop sclerotia. Also, BcBAG1 disruption blocked fungal conidial germination and successful penetration, leading to a reduced virulence in host plants. BcBAG1 contains BAG (BD) domain at C-terminus and ubiquitin-like (UBL) domain at N-terminus. Complementation assays indicated that BD can largely restored pathogenicity of ΔBcbag1. Abiotic stress assays showed ΔBcbag1 was more sensitive than the wild-type strain to NaCl, calcofluor white, SDS, tunicamycin, dithiothreitol (DTT), heat and cold stress, suggesting BcBAG1 plays a cytoprotective role during salt stress, cell wall stress, and ER stress. BcBAG1 negatively regulated the expression of BcBIP1, BcIRE1 and the splicing of BcHAC1 mRNA, which are core regulators of unfolded protein response (UPR) during ER stress. Moreover, BcBAG1 interacted with HSP70-type chaperones, BcBIP1 and BcSKS2. In summary, this work demonstrates that BcBAG1 is pleiotropic and not only essential for fungal development, hyphal melanization, and virulence, but also required for response to multiple abiotic stresses and UPR pathway of B. cinerea.
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Affiliation(s)
- Honghong Zhang
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China.,Institute for Plant Genomics and Biotechnology, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX, United States.,Department of Plant Pathology and Microbiology, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX, United States
| | - Yurong Li
- Institute for Plant Genomics and Biotechnology, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX, United States.,Department of Plant Pathology and Microbiology, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX, United States
| | - Martin B Dickman
- Institute for Plant Genomics and Biotechnology, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX, United States.,Department of Plant Pathology and Microbiology, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX, United States
| | - Zonghua Wang
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China.,Institute of Oceanography, Minjiang University, Fuzhou, China
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Evolutionarily Conserved and Divergent Roles of Unfolded Protein Response (UPR) in the Pathogenic Cryptococcus Species Complex. Sci Rep 2018; 8:8132. [PMID: 29802329 PMCID: PMC5970146 DOI: 10.1038/s41598-018-26405-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 05/10/2018] [Indexed: 01/01/2023] Open
Abstract
The unfolded protein response (UPR) pathway, consisting of the evolutionarily conserved Ire1 kinase/endonuclease and the bZIP transcription factor Hxl1, is critical for the pathogenicity of Cryptococcus neoformans; however, its role remains unknown in other pathogenic Cryptococcus species. Here, we investigated the role of the UPR pathway in C. deuterogattii, which causes pneumonia and systemic cryptococcosis, even in immunocompetent individuals. In response to ER stress, C. deuterogattii Ire1 triggers unconventional splicing of HXL1 to induce the expression of UPR target genes such as KAR2, DER1, ALG7, and ERG29. Furthermore, C. deuterogattii Ire1 is required for growth at mammalian body temperature, similar to C. neoformans Ire1. However, deletion of HXL1 does not significantly affect the growth of C. deuterogattii at 37 °C, which is in contrast to the indispensable role of HXL1 in the growth of C. neoformans at 37 °C. Nevertheless, both C. deuterogattii ire1Δ and hxl1Δ mutants are avirulent in a murine model of systemic cryptococcosis, suggesting that a non-thermotolerance phenotypic trait also contributes to the role of the UPR pathway in the virulence of pathogenic Cryptococcus species. In conclusion, the UPR pathway plays redundant and distinct roles in the virulence of members of the pathogenic Cryptococcus species complex.
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van der Does HC, Rep M. Adaptation to the Host Environment by Plant-Pathogenic Fungi. ANNUAL REVIEW OF PHYTOPATHOLOGY 2017; 55:427-450. [PMID: 28645233 DOI: 10.1146/annurev-phyto-080516-035551] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Many fungi can live both saprophytically and as endophyte or pathogen inside a living plant. In both environments, complex organic polymers are used as sources of nutrients. Propagation inside a living host also requires the ability to respond to immune responses of the host. We review current knowledge of how plant-pathogenic fungi do this. First, we look at how fungi change their global gene expression upon recognition of the host environment, leading to secretion of effectors, enzymes, and secondary metabolites; changes in metabolism; and defense against toxic compounds. Second, we look at what is known about the various cues that enable fungi to sense the presence of living plant cells. Finally, we review literature on transcription factors that participate in gene expression in planta or are suspected to be involved in that process because they are required for the ability to cause disease.
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Affiliation(s)
| | - Martijn Rep
- Molecular Plant Pathology, University of Amsterdam, 1098XH Amsterdam, The Netherlands;
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Pigné S, Zykwinska A, Janod E, Cuenot S, Kerkoud M, Raulo R, Bataillé-Simoneau N, Marchi M, Kwasiborski A, N'Guyen G, Mabilleau G, Simoneau P, Guillemette T. A flavoprotein supports cell wall properties in the necrotrophic fungus Alternaria brassicicola. Fungal Biol Biotechnol 2017; 4:1. [PMID: 28955470 PMCID: PMC5611651 DOI: 10.1186/s40694-016-0029-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 12/21/2016] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Flavin-dependent monooxygenases are involved in key biological processes as they catalyze a wide variety of chemo-, regio- and enantioselective oxygenation reactions. Flavoprotein monooxygenases are frequently encountered in micro-organisms, most of which require further functional and biocatalytic assessment. Here we investigated the function of the AbMak1 gene, which encodes a group A flavin monooxygenase in the plant pathogenic fungus Alternaria brassicicola, by generating a deficient mutant and examining its phenotype. RESULTS Functional analysis indicates that the AbMak1 protein is involved in cell wall biogenesis and influences the melanization process. We documented a significant decrease in melanin content in the Δabmak1 strain compared to the wild-type and complemented strains. We investigated the cell wall morphology and physical properties in the wild-type and transformants using electron and atomic force microscopy. These approaches confirmed the aberrant morphology of the conidial wall structure in the Δabmak1 strain which had an impact on hydrophilic adhesion and conidial surface stiffness. However, there was no significant impairment in growth, conidia formation, pathogenicity or susceptibility to various environmental stresses in the Δabmak1 strain. CONCLUSION This study sheds new light on the function of a fungal flavin-dependent monooxygenase, which plays an important role in melanization.
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Affiliation(s)
- Sandrine Pigné
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 49071 Beaucouzé, France
| | - Agata Zykwinska
- UMR 6502, Institut des Matériaux Jean Rouxel, 2, Rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France.,Present Address: Laboratoire Ecosystèmes Microbiens et Molécules Marines pour les Biotechnologies, IFREMER, Rue de l'île d'Yeu, BP 21105, 44311 Nantes Cedex 3, France
| | - Etienne Janod
- UMR 6502, Institut des Matériaux Jean Rouxel, 2, Rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France
| | - Stéphane Cuenot
- UMR 6502, Institut des Matériaux Jean Rouxel, 2, Rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France
| | - Mohammed Kerkoud
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 49071 Beaucouzé, France
| | - Roxane Raulo
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 49071 Beaucouzé, France
| | | | - Muriel Marchi
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 49071 Beaucouzé, France
| | - Anthony Kwasiborski
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 49071 Beaucouzé, France
| | - Guillaume N'Guyen
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 49071 Beaucouzé, France
| | - Guillaume Mabilleau
- Plateforme SCIAM, Institut de Biologie en Santé, CHU, Université d'Angers, 4, Rue Larrey, 49933 Angers Cedex, France
| | - Philippe Simoneau
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 49071 Beaucouzé, France
| | - Thomas Guillemette
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 49071 Beaucouzé, France
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Unfolded Protein Response (UPR) Regulator Cib1 Controls Expression of Genes Encoding Secreted Virulence Factors in Ustilago maydis. PLoS One 2016; 11:e0153861. [PMID: 27093436 PMCID: PMC4836707 DOI: 10.1371/journal.pone.0153861] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 04/05/2016] [Indexed: 11/27/2022] Open
Abstract
The unfolded protein response (UPR), a conserved eukaryotic signaling pathway to ensure protein homeostasis in the endoplasmic reticulum (ER), coordinates biotrophic development in the corn smut fungus Ustilago maydis. Exact timing of UPR activation is required for virulence and presumably connected to the elevated expression of secreted effector proteins during infection of the host plant Zea mays. In the baker’s yeast Saccharomyces cerevisiae, expression of UPR target genes is induced upon binding of the central regulator Hac1 to unfolded protein response elements (UPREs) in their promoters. While a role of the UPR in effector secretion has been described previously, we investigated a potential UPR-dependent regulation of genes encoding secreted effector proteins. In silico prediction of UPREs in promoter regions identified the previously characterized effector genes pit2 and tin1-1, as bona fide UPR target genes. Furthermore, direct binding of the Hac1-homolog Cib1 to the UPRE containing promoter fragments of both genes was confirmed by quantitative chromatin immunoprecipitation (qChIP) analysis. Targeted deletion of the UPRE abolished Cib1-dependent expression of pit2 and significantly affected virulence. Furthermore, ER stress strongly increased Pit2 expression and secretion. This study expands the role of the UPR as a signal hub in fungal virulence and illustrates, how biotrophic fungi can coordinate cellular physiology, development and regulation of secreted virulence factors.
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Lo Presti L, López Díaz C, Turrà D, Di Pietro A, Hampel M, Heimel K, Kahmann R. A conserved co-chaperone is required for virulence in fungal plant pathogens. THE NEW PHYTOLOGIST 2016; 209:1135-1148. [PMID: 26487566 DOI: 10.1111/nph.13703] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 09/04/2015] [Indexed: 06/05/2023]
Abstract
The maize pathogenic fungus Ustilago maydis experiences endoplasmic reticulum (ER) stress during plant colonization and relies on the unfolded protein response (UPR) to cope with this stress. We identified the U. maydis co-chaperone, designated Dnj1, as part of this conserved cellular response to ER stress. ∆dnj1 cells are sensitive to the ER stressor tunicamycin and display a severe virulence defect in maize infection assays. A dnj1 mutant allele unable to stimulate the ATPase activity of chaperones phenocopies the null allele. A Dnj1-mCherry fusion protein localizes in the ER and interacts with the luminal chaperone Bip1. The Fusarium oxysporum Dnj1 ortholog contributes to the virulence of this fungal pathogen in tomato plants. Unlike the human ortholog, F. oxysporum Dnj1 partially rescues the virulence defect of the Ustilago dnj1 mutant. By enabling the fungus to restore ER homeostasis and maintain a high secretory activity, Dnj1 contributes to the establishment of a compatible interaction with the host. Dnj1 orthologs are present in many filamentous fungi, but are absent in budding and fission yeasts. We postulate a conserved and essential role during virulence for this class of co-chaperones.
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Affiliation(s)
- Libera Lo Presti
- Max Planck Institute for Terrestrial Microbiology, Karl-von Frisch-Strasse 10, 35043, Marburg, Germany
| | - Cristina López Díaz
- Departamento de Genética, Campus de Excelencia Internacional Agroalimentario ceiA3, Universidad de Córdoba, 14071, Cordoba, Spain
| | - David Turrà
- Departamento de Genética, Campus de Excelencia Internacional Agroalimentario ceiA3, Universidad de Córdoba, 14071, Cordoba, Spain
| | - Antonio Di Pietro
- Departamento de Genética, Campus de Excelencia Internacional Agroalimentario ceiA3, Universidad de Córdoba, 14071, Cordoba, Spain
| | - Martin Hampel
- Department of Molecular Microbiology and Genetics, Georg-August-Universität Göttingen, Grisebachstraße 8, 37077, Göttingen, Germany
| | - Kai Heimel
- Department of Molecular Microbiology and Genetics, Georg-August-Universität Göttingen, Grisebachstraße 8, 37077, Göttingen, Germany
| | - Regine Kahmann
- Max Planck Institute for Terrestrial Microbiology, Karl-von Frisch-Strasse 10, 35043, Marburg, Germany
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Unfolded protein response is required for Aspergillus oryzae growth under conditions inducing secretory hydrolytic enzyme production. Fungal Genet Biol 2015; 85:1-6. [DOI: 10.1016/j.fgb.2015.10.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Revised: 10/19/2015] [Accepted: 10/20/2015] [Indexed: 12/27/2022]
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Hansenula polymorpha Hac1p Is Critical to Protein N-Glycosylation Activity Modulation, as Revealed by Functional and Transcriptomic Analyses. Appl Environ Microbiol 2015; 81:6982-93. [PMID: 26231645 DOI: 10.1128/aem.01440-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Accepted: 07/23/2015] [Indexed: 12/13/2022] Open
Abstract
Aggregation of misfolded protein in the endoplasmic reticulum (ER) induces a cellular protective response to ER stress, the unfolded protein response (UPR), which is mediated by a basic leucine zipper (bZIP) transcription factor, Hac1p/Xbp1. In this study, we identified and studied the molecular functions of a HAC1 homolog from the thermotolerant yeast Hansenula polymorpha (HpHAC1). We found that the HpHAC1 mRNA contains a nonconventional intron of 177 bp whose interaction with the 5' untranslated region is responsible for the translational inhibition of the HpHAC1 mRNA. The H. polymorpha hac1-null (Hphac1Δ) mutant strain grew slowly, even under normal growth conditions, and was less thermotolerant than the wild-type (WT) strain. The mutant strain was also more sensitive to cell wall-perturbing agents and to the UPR-inducing agents dithiothreitol (DTT) and tunicamycin (TM). Using comparative transcriptome analysis of the WT and Hphac1Δ strains treated with DTT and TM, we identified HpHAC1-dependent core UPR targets, which included genes involved in protein secretion and processing, particularly those required for N-linked protein glycosylation. Notably, different glycosylation and processing patterns of the vacuolar glycoprotein carboxypeptidase Y were observed in the WT and Hphac1Δ strains. Moreover, overexpression of active HpHac1p significantly increased the N-linked glycosylation efficiency and TM resistance. Collectively, our results suggest that the function of HpHac1p is important not only for UPR induction but also for efficient glycosylation in H. polymorpha.
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Montenegro-Montero A, Goity A, Larrondo LF. The bZIP Transcription Factor HAC-1 Is Involved in the Unfolded Protein Response and Is Necessary for Growth on Cellulose in Neurospora crassa. PLoS One 2015; 10:e0131415. [PMID: 26132395 PMCID: PMC4488935 DOI: 10.1371/journal.pone.0131415] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 06/02/2015] [Indexed: 12/15/2022] Open
Abstract
High protein secretion capacity in filamentous fungi requires an extremely efficient system for protein synthesis, folding and transport. When the folding capacity of the endoplasmic reticulum (ER) is exceeded, a pathway known as the unfolded protein response (UPR) is triggered, allowing cells to mitigate and cope with this stress. In yeast, this pathway relies on the transcription factor Hac1, which mediates the up-regulation of several genes required under these stressful conditions. In this work, we identified and characterized the ortholog of the yeast HAC1 gene in the filamentous fungus Neurospora crassa. We show that its mRNA undergoes an ER stress-dependent splicing reaction, which in N. crassa removes a 23 nt intron and leads to a change in the open reading frame. By disrupting the N. crassa hac-1 gene, we determined it to be crucial for activating UPR and for proper growth in the presence of ER stress-inducing chemical agents. Neurospora is naturally found growing on dead plant material, composed primarily by lignocellulose, and is a model organism for the study of plant cell wall deconstruction. Notably, we found that growth on cellulose, a substrate that requires secretion of numerous enzymes, imposes major demands on ER function and is dramatically impaired in the absence of hac-1, thus broadening the range of physiological functions of the UPR in filamentous fungi. Growth on hemicellulose however, another carbon source that necessitates the secretion of various enzymes for its deconstruction, is not impaired in the mutant nor is the amount of proteins secreted on this substrate, suggesting that secretion, as a whole, is unaltered in the absence of hac-1. The characterization of this signaling pathway in N. crassa will help in the study of plant cell wall deconstruction by fungi and its manipulation may result in important industrial biotechnological applications.
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Affiliation(s)
- Alejandro Montenegro-Montero
- Millennium Nucleus for Fungal Integrative and Synthetic Biology, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alejandra Goity
- Millennium Nucleus for Fungal Integrative and Synthetic Biology, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Luis F. Larrondo
- Millennium Nucleus for Fungal Integrative and Synthetic Biology, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail:
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Calmes B, Morel-Rouhier M, Bataillé-Simoneau N, Gelhaye E, Guillemette T, Simoneau P. Characterization of glutathione transferases involved in the pathogenicity of Alternaria brassicicola. BMC Microbiol 2015; 15:123. [PMID: 26081847 PMCID: PMC4470081 DOI: 10.1186/s12866-015-0462-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 06/03/2015] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Glutathione transferases (GSTs) represent an extended family of multifunctional proteins involved in detoxification processes and tolerance to oxidative stress. We thus anticipated that some GSTs could play an essential role in the protection of fungal necrotrophs against plant-derived toxic metabolites and reactive oxygen species that accumulate at the host-pathogen interface during infection. RESULTS Mining the genome of the necrotrophic Brassica pathogen Alternaria brassicicola for glutathione transferase revealed 23 sequences, 17 of which could be clustered into the main classes previously defined for fungal GSTs and six were 'orphans'. Five isothiocyanate-inducible GSTs from five different classes were more thoroughly investigated. Analysis of their catalytic properties revealed that two GSTs, belonging to the GSTFuA and GTT1 classes, exhibited GSH transferase activity with isothiocyanates (ITC) and peroxidase activity with cumene hydroperoxide, respectively. Mutant deficient for these two GSTs were however neither more susceptible to ITC nor less aggressive than the wild-type parental strain. By contrast mutants deficient for two other GSTs, belonging to the Ure2pB and GSTO classes, were distinguished by their hyper-susceptibility to ITC and low aggressiveness against Brassica oleracea. In particular AbGSTO1 could participate in cell tolerance to ITC due to its glutathione-dependent thioltransferase activity. The fifth ITC-inducible GST belonged to the MAPEG class and although it was not possible to produce the soluble active form of this protein in a bacterial expression system, the corresponding deficient mutant failed to develop normal symptoms on host plant tissues. CONCLUSIONS Among the five ITC-inducible GSTs analyzed in this study, three were found essential for full aggressiveness of A. brassicicola on host plant. This, to our knowledge is the first evidence that GSTs might be essential virulence factors for fungal necrotrophs.
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Affiliation(s)
- Benoit Calmes
- Université d'Angers, UMR 1345 IRHS, SFR 4207 QUASAV, 2 Bd Lavoisier, Angers cedex, F-49045, France.
- INRA, UMR 1345 IRHS, 42 rue Georges Morel, Beaucouzé Cedex, F-49071, France.
- Agrocampus-Ouest, UMR 1345 IRHS, 2 rue le Nôtre, Angers cedex, F-49045, France.
| | - Mélanie Morel-Rouhier
- Université de Lorraine, UMR1136 Interactions Arbres-Microorganismes, Vandoeuvre-lès, F-54500, Nancy, France.
- INRA, UMR1136 Interactions Arbres-Microorganismes, F-54280, Champenoux, France.
| | - Nelly Bataillé-Simoneau
- Université d'Angers, UMR 1345 IRHS, SFR 4207 QUASAV, 2 Bd Lavoisier, Angers cedex, F-49045, France.
- INRA, UMR 1345 IRHS, 42 rue Georges Morel, Beaucouzé Cedex, F-49071, France.
- Agrocampus-Ouest, UMR 1345 IRHS, 2 rue le Nôtre, Angers cedex, F-49045, France.
| | - Eric Gelhaye
- Université de Lorraine, UMR1136 Interactions Arbres-Microorganismes, Vandoeuvre-lès, F-54500, Nancy, France.
- INRA, UMR1136 Interactions Arbres-Microorganismes, F-54280, Champenoux, France.
| | - Thomas Guillemette
- Université d'Angers, UMR 1345 IRHS, SFR 4207 QUASAV, 2 Bd Lavoisier, Angers cedex, F-49045, France.
- INRA, UMR 1345 IRHS, 42 rue Georges Morel, Beaucouzé Cedex, F-49071, France.
- Agrocampus-Ouest, UMR 1345 IRHS, 2 rue le Nôtre, Angers cedex, F-49045, France.
| | - Philippe Simoneau
- Université d'Angers, UMR 1345 IRHS, SFR 4207 QUASAV, 2 Bd Lavoisier, Angers cedex, F-49045, France.
- INRA, UMR 1345 IRHS, 42 rue Georges Morel, Beaucouzé Cedex, F-49071, France.
- Agrocampus-Ouest, UMR 1345 IRHS, 2 rue le Nôtre, Angers cedex, F-49045, France.
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How the necrotrophic fungus Alternaria brassicicola kills plant cells remains an enigma. EUKARYOTIC CELL 2015; 14:335-44. [PMID: 25681268 DOI: 10.1128/ec.00226-14] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Alternaria species are mainly saprophytic fungi, but some are plant pathogens. Seven pathotypes of Alternaria alternata use secondary metabolites of host-specific toxins as pathogenicity factors. These toxins kill host cells prior to colonization. Genes associated with toxin synthesis reside on conditionally dispensable chromosomes, supporting the notion that pathogenicity might have been acquired several times by A. alternata. Alternaria brassicicola, however, seems to employ a different mechanism. Evidence on the use of host-specific toxins as pathogenicity factors remains tenuous, even after a diligent search aided by full-genome sequencing and efficient reverse-genetics approaches. Similarly, no individual genes encoding lipases or cell wall-degrading enzymes have been identified as strong virulence factors, although these enzymes have been considered important for fungal pathogenesis. This review describes our current understanding of toxins, lipases, and cell wall-degrading enzymes and their roles in the pathogenesis of A. brassicicola compared to those of other pathogenic fungi. It also describes a set of genes that affect pathogenesis in A. brassicicola. They are involved in various cellular functions that are likely important in most organisms and probably indirectly associated with pathogenesis. Deletion or disruption of these genes results in weakly virulent strains that appear to be sensitive to the defense mechanisms of host plants. Finally, this review discusses the implications of a recent discovery of three important transcription factors associated with pathogenesis and the putative downstream genes that they regulate.
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Heimel K. Unfolded protein response in filamentous fungi-implications in biotechnology. Appl Microbiol Biotechnol 2014; 99:121-32. [PMID: 25384707 DOI: 10.1007/s00253-014-6192-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 10/24/2014] [Accepted: 10/27/2014] [Indexed: 01/16/2023]
Abstract
The unfolded protein response (UPR) represents a mechanism to preserve endoplasmic reticulum (ER) homeostasis that is conserved in eukaryotes. ER stress caused by the accumulation of potentially toxic un- or misfolded proteins in the ER triggers UPR activation and the induction of genes important for protein folding in the ER, ER expansion, and transport from and to the ER. Along with this adaptation, the overall capacity for protein secretion is markedly increased by the UPR. In filamentous fungi, various approaches to employ the UPR for improved production of homologous and heterologous proteins have been investigated. As the effects on protein production were strongly dependent on the expressed protein, generally applicable strategies have to be developed. A combination of transcriptomic approaches monitoring secretion stress and basic research on the UPR mechanism provided novel and important insight into the complex regulatory cross-connections between UPR signalling, cellular physiology, and developmental processes. It will be discussed how this increasing knowledge on the UPR might stimulate the development of novel strategies for using the UPR as a tool in biotechnology.
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Affiliation(s)
- Kai Heimel
- Institut für Mikrobiologie & Genetik, Georg-August-Universität, Grisebachstr. 8, 37077, Göttingen, Germany,
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32
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Tang W, Ru Y, Hong L, Zhu Q, Zuo R, Guo X, Wang J, Zhang H, Zheng X, Wang P, Zhang Z. System-wide characterization of bZIP transcription factor proteins involved in infection-related morphogenesis of Magnaporthe oryzae. Environ Microbiol 2014; 17:1377-96. [PMID: 25186614 DOI: 10.1111/1462-2920.12618] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 08/29/2014] [Accepted: 09/01/2014] [Indexed: 12/21/2022]
Abstract
The basic leucine zipper (bZIP) domain-containing transcription factors (TFs) function as key regulators of cellular growth and differentiation in eukaryotic organisms including fungi. We have previously identified MoAp1 and MoAtf1 as bZIP TFs in Magnaporthe oryzae and demonstrated that they regulate the oxidative stress response and are critical in conidiogenesis and pathogenicity. Studies of bZIP proteins could provide a novel strategy for controlling rice blast, but a systematic examination of the bZIP proteins has not been carried out. Here, we identified 19 additional bZIP TFs and characterized their functions. We found that the majority of these TFs exhibit active functions, most notably, in conidiogenesis. We showed that MoHac1 regulates the endoplasmic reticulum stress response through a conserved unfolded protein response pathway, MoMetR controls amino acid metabolism to govern growth and differentiation, and MoBzip10 governs appressorium function and invasive hyphal growth. Moreover, MoBzip5 participates in appressorium formation through a pathway distinct from that MoBzip10, and MoMeaB appears to exert a regulatory role through nutrient uptake and nitrogen utilization. Collectively, our results provide insights into shared and specific functions associated with each of these TFs and link the regulatory roles to the fungal growth, conidiation, appressorium formation, host penetration and pathogenicity.
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Affiliation(s)
- Wei Tang
- Department of Plant Pathology, College of Plant Protection, Key Laboratory of Integrated Management of Crop Diseases and Pests, Nanjing Agricultural University, Ministry of Education, Nanjing, 210095, China
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Abstract
The gateway to the secretory pathway is the endoplasmic reticulum (ER), an organelle that is responsible for the accurate folding, post-translational modification and final assembly of up to a third of the cellular proteome. When secretion levels are high, errors in protein biogenesis can lead to the accumulation of abnormally folded proteins, which threaten ER homeostasis. The unfolded protein response (UPR) is an adaptive signaling pathway that counters a buildup in misfolded and unfolded proteins by increasing the expression of genes that support ER protein folding capacity. Fungi, like other eukaryotic cells that are specialized for secretion, rely upon the UPR to buffer ER stress caused by fluctuations in secretory demand. However, emerging evidence is also implicating the UPR as a central regulator of fungal pathogenesis. In this review, we discuss how diverse fungal pathogens have adapted ER stress response pathways to support the expression of virulence-related traits that are necessary in the host environment.
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Affiliation(s)
- Karthik Krishnan
- Department of Pathology & Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45267-0529
| | - David S Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45267-0529
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34
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Malavazi I, Goldman GH, Brown NA. The importance of connections between the cell wall integrity pathway and the unfolded protein response in filamentous fungi. Brief Funct Genomics 2014; 13:456-70. [PMID: 25060881 DOI: 10.1093/bfgp/elu027] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the external environment, or within a host organism, filamentous fungi experience sudden changes in nutrient availability, osmolality, pH, temperature and the exposure to toxic compounds. The fungal cell wall represents the first line of defense, while also performing essential roles in morphology, development and virulence. A polarized secretion system is paramount for cell wall biosynthesis, filamentous growth, nutrient acquisition and interactions with the environment. The unique ability of filamentous fungi to secrete has resulted in their industrial adoption as fungal cell factories. Protein maturation and secretion commences in the endoplasmic reticulum (ER). The unfolded protein response (UPR) maintains ER functionality during exposure to secretion and cell wall stress. UPR, therefore, influences secretion and cell wall homeostasis, which in turn impacts upon numerous fungal traits important to pathogenesis and biotechnology. Subsequently, this review describes the relevance of the cell wall and UPR systems to filamentous fungal pathogens or industrial microbes and then highlights interconnections between the two systems. Ultimately, the possible biotechnological applications of an enhanced understanding of such regulatory systems in combating fungal disease, or the removal of natural bottlenecks in protein secretion in an industrial setting, are discussed.
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Krishnan K, Ren Z, Losada L, Nierman WC, Lu LJ, Askew DS. Polysome profiling reveals broad translatome remodeling during endoplasmic reticulum (ER) stress in the pathogenic fungus Aspergillus fumigatus. BMC Genomics 2014; 15:159. [PMID: 24568630 PMCID: PMC3943501 DOI: 10.1186/1471-2164-15-159] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 02/17/2014] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND The unfolded protein response (UPR) is a network of intracellular signaling pathways that supports the ability of the secretory pathway to maintain a balance between the load of proteins entering the endoplasmic reticulum (ER) and the protein folding capacity of the ER lumen. Current evidence indicates that several pathogenic fungi rely heavily on this pathway for virulence, but there is limited understanding of the mechanisms involved. The best known functional output of the UPR is transcriptional upregulation of mRNAs involved in ER homeostasis. However, this does not take into account mechanisms of translational regulation that involve differential loading of ribosomes onto mRNAs. In this study, a global analysis of transcript-specific translational regulation was performed in the pathogenic mold Aspergillus fumigatus to determine the nature and scope of the translational response to ER stress. RESULTS ER stress was induced by treating the fungus with dithiothreitol, tunicamycin, or a thermal up-shift. The mRNAs were then fractionated on the basis of ribosome occupancy into an under-translated pool (U) and a well-translated pool (W). The mRNAs were used to interrogate microarrays and the ratio of the hybridization signal (W/U) was used as an indicator of the relative translational efficiency of a mRNA under each condition. The largest category of translationally upregulated mRNAs during ER stress encoded proteins involved in translation. Components of the ergosterol and GPI anchor biosynthetic pathways also showed increased polysome association, suggesting an important role for translational regulation in membrane and cell wall homeostasis. ER stress induced limited remodeling of the secretory pathway translatome. However, a select group of transcription factors was translationally upregulated, providing a link to subsequent modification of the transcriptome. Finally, we provide evidence that one component of the ER stress translatome is a novel mRNA isoform from the yvc1 gene that is induced by ER stress in a UPR-dependent manner. CONCLUSIONS Together, these findings define a core set of mRNAs subject to translational control during the adaptive response to acute ER stress in A. fumigatus and reveal a remarkable breadth of functions that are needed to resolve ER stress in this organism.
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Affiliation(s)
| | | | | | | | | | - David S Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0529, USA.
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Guillemette T, Calmes B, Simoneau P. Impact of the UPR on the virulence of the plant fungal pathogen A. brassicicola. Virulence 2014; 5:357-64. [PMID: 24189567 PMCID: PMC3956514 DOI: 10.4161/viru.26772] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Revised: 10/10/2013] [Accepted: 10/10/2013] [Indexed: 11/19/2022] Open
Abstract
The fungal genus Alternaria contains many destructive plant pathogens, including Alternaria brassicicola, which causes black spot disease on a wide range of Brassicaceae plants and which is routinely used as a model necrotrophic pathogen in studies with Arabidopsis thaliana. During host infection, many fungal proteins that are critical for disease progression are processed in the endoplasmic reticulum (ER)/Golgi system and secreted in planta. The unfolded protein response (UPR) is an essential part of ER protein quality control that ensures efficient maturation of secreted and membrane-bound proteins in eukaryotes. This review highlights the importance of the UPR signaling pathway with respect to the ability of A. brassicicola to efficiently accomplish key steps of its pathogenic life cycle. Understanding the pathogenicity mechanisms that fungi uses during infection is crucial for the development of new antifungal therapies. Therefore the UPR pathway has emerged as a promising drug target for plant disease control.
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Affiliation(s)
- Thomas Guillemette
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
| | - Benoit Calmes
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
| | - Philippe Simoneau
- Université d’Angers; UMR 1345 IRHS; SFR QUASAV; Angers, France
- INRA; UMR 1345 IRHS; Angers, France
- Agrocampus-Ouest; UMR 1345 IRHS; Angers, France
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Kubicek CP, Starr TL, Glass NL. Plant cell wall-degrading enzymes and their secretion in plant-pathogenic fungi. ANNUAL REVIEW OF PHYTOPATHOLOGY 2014; 52:427-51. [PMID: 25001456 DOI: 10.1146/annurev-phyto-102313-045831] [Citation(s) in RCA: 426] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Approximately a tenth of all described fungal species can cause diseases in plants. A common feature of this process is the necessity to pass through the plant cell wall, an important barrier against pathogen attack. To this end, fungi possess a diverse array of secreted enzymes to depolymerize the main structural polysaccharide components of the plant cell wall, i.e., cellulose, hemicellulose, and pectin. Recent advances in genomic and systems-level studies have begun to unravel this diversity and have pinpointed cell wall-degrading enzyme (CWDE) families that are specifically present or enhanced in plant-pathogenic fungi. In this review, we discuss differences between the CWDE arsenal of plant-pathogenic and non-plant-pathogenic fungi, highlight the importance of individual enzyme families for pathogenesis, illustrate the secretory pathway that transports CWDEs out of the fungal cell, and report the transcriptional regulation of expression of CWDE genes in both saprophytic and phytopathogenic fungi.
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Cheon SA, Jung KW, Bahn YS, Kang HA. The unfolded protein response (UPR) pathway in Cryptococcus. Virulence 2013; 5:341-50. [PMID: 24504058 DOI: 10.4161/viru.26774] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Unique and evolutionarily conserved signaling pathways allow an organism to sense, respond to, and adapt to internal and external environmental cues at its biological niche. In eukaryotic cells, the unfolded protein response (UPR) pathway regulates endoplasmic reticulum (ER) homeostasis upon exposure to environmental changes causing ER stress. The UPR pathway of Cryptococcus neoformans, an opportunistic fungal pathogen, which causes life-threatening meningoencephalitis in immunocompromised individuals, consists of the evolutionarily conserved Ire1 kinase, a unique bZIP transcription factor, Hxl1, and the ER-resident molecular chaperone Kar2/BiP. Although the Cryptococcus UPR pathway regulates ER stress, antifungal drug resistance, and virulence in an Ire1/Hxl1-dependent manner, Ire1 has Hxl1-independent roles in capsule biosynthesis and thermotolerance. In this review, we highlight the conserved and unique features of the Cryptococcus UPR pathway compared with other fungal UPR systems and its importance in the pathogenesis of cryptococcosis and discuss future challenges in this field.
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Affiliation(s)
- Seon Ah Cheon
- Department of Life Science; Research Center for Biomolecules and Biosystems; College of Natural Science; Chung-Ang University; Seoul, Korea; Department of Agricultural Biotechnology and Center for Fungal Pathogenesis; Seoul National University; Seoul, Korea
| | - Kwang-Woo Jung
- Department of Biotechnology; Center for Fungal Pathogenesis; Yonsei University; Seoul, Korea
| | - Yong-Sun Bahn
- Department of Biotechnology; Center for Fungal Pathogenesis; Yonsei University; Seoul, Korea
| | - Hyun Ah Kang
- Department of Life Science; Research Center for Biomolecules and Biosystems; College of Natural Science; Chung-Ang University; Seoul, Korea
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Pochon S, Simoneau P, Pigné S, Balidas S, Bataillé-Simoneau N, Campion C, Jaspard E, Calmes B, Hamon B, Berruyer R, Juchaux M, Guillemette T. Dehydrin-like proteins in the necrotrophic fungus Alternaria brassicicola have a role in plant pathogenesis and stress response. PLoS One 2013; 8:e75143. [PMID: 24098369 PMCID: PMC3788798 DOI: 10.1371/journal.pone.0075143] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 08/09/2013] [Indexed: 11/18/2022] Open
Abstract
In this study, the roles of fungal dehydrin-like proteins in pathogenicity and protection against environmental stresses were investigated in the necrotrophic seed-borne fungus Alternaria brassicicola. Three proteins (called AbDhn1, AbDhn2 and AbDhn3), harbouring the asparagine-proline-arginine (DPR) signature pattern and sharing the characteristic features of fungal dehydrin-like proteins, were identified in the A. brassicicola genome. The expression of these genes was induced in response to various stresses and found to be regulated by the AbHog1 mitogen-activated protein kinase (MAPK) pathway. A knock-out approach showed that dehydrin-like proteins have an impact mainly on oxidative stress tolerance and on conidial survival upon exposure to high and freezing temperatures. The subcellular localization revealed that AbDhn1 and AbDhn2 were associated with peroxisomes, which is consistent with a possible perturbation of protective mechanisms to counteract oxidative stress and maintain the redox balance in AbDhn mutants. Finally, we show that the double deletion mutant ΔΔabdhn1-abdhn2 was highly compromised in its pathogenicity. By comparison to the wild-type, this mutant exhibited lower aggressiveness on B. oleracea leaves and a reduced capacity to be transmitted to Arabidopsis seeds via siliques. The double mutant was also affected with respect to conidiation, another crucial step in the epidemiology of the disease.
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Affiliation(s)
- Stéphanie Pochon
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Philippe Simoneau
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Sandrine Pigné
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Samuel Balidas
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Nelly Bataillé-Simoneau
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Claire Campion
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Emmanuel Jaspard
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Benoît Calmes
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Bruno Hamon
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | - Romain Berruyer
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
| | | | - Thomas Guillemette
- Université d’Angers, UMR 1345 IRHS, SFR QUASAV, Angers, France
- INRA, UMR 1345 IRHS, Angers, France
- Agrocampus-Ouest, UMR 1345 IRHS, Angers, France
- * E-mail:
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Heimel K, Freitag J, Hampel M, Ast J, Bölker M, Kämper J. Crosstalk between the unfolded protein response and pathways that regulate pathogenic development in Ustilago maydis. THE PLANT CELL 2013; 25:4262-77. [PMID: 24179126 PMCID: PMC3877826 DOI: 10.1105/tpc.113.115899] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The unfolded protein response (UPR) is a conserved eukaryotic signaling pathway regulating endoplasmic reticulum (ER) homeostasis during ER stress, which results, for example, from an increased demand for protein secretion. Here, we characterize the homologs of the central UPR regulatory proteins Hac1 (for Homologous to ATF/CREB1) and Inositol Requiring Enzyme1 in the plant pathogenic fungus Ustilago maydis and demonstrate that the UPR is tightly interlinked with the b mating-type-dependent signaling pathway that regulates pathogenic development. Exact timing of UPR is required for virulence, since premature activation interferes with the b-dependent switch from budding to filamentous growth. In addition, we found crosstalk between UPR and the b target Clampless1 (Clp1), which is essential for cell cycle release and proliferation in planta. The unusual C-terminal extension of the U. maydis Hac1 homolog, Cib1 (for Clp1 interacting bZIP1), mediates direct interaction with Clp1. The interaction between Clp1 and Cib1 promotes stabilization of Clp1, resulting in enhanced ER stress tolerance that prevents deleterious UPR hyperactivation. Thus, the interaction between Cib1 and Clp1 constitutes a checkpoint to time developmental progression and increased secretion of effector proteins at the onset of biotrophic development. Crosstalk between UPR and the b mating-type regulated developmental program adapts ER homeostasis to the changing demands during biotrophy.
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Affiliation(s)
- Kai Heimel
- Georg-August-University Göttingen, Institute for Microbiology and Genetics, Department of Molecular Microbiology and Genetics, 37077 Goettingen, Germany
- Karlsruhe Institute of Technology, Institute for Applied Bioscience, Department of Genetics, 76187 Karlsruhe, Germany
| | - Johannes Freitag
- Philipps-University Marburg, Department of Biology, 35032 Marburg, Germany
- LOEWE Centre for Synthetic Microbiology (SYNMIKRO), 35032 Marburg, Germany
| | - Martin Hampel
- Georg-August-University Göttingen, Institute for Microbiology and Genetics, Department of Molecular Microbiology and Genetics, 37077 Goettingen, Germany
| | - Julia Ast
- Philipps-University Marburg, Department of Biology, 35032 Marburg, Germany
| | - Michael Bölker
- Philipps-University Marburg, Department of Biology, 35032 Marburg, Germany
- LOEWE Centre for Synthetic Microbiology (SYNMIKRO), 35032 Marburg, Germany
- Address correspondence to
| | - Jörg Kämper
- Karlsruhe Institute of Technology, Institute for Applied Bioscience, Department of Genetics, 76187 Karlsruhe, Germany
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Cho Y, Ohm RA, Grigoriev IV, Srivastava A. Fungal-specific transcription factor AbPf2 activates pathogenicity in Alternaria brassicicola. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:498-514. [PMID: 23617599 DOI: 10.1111/tpj.12217] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/17/2013] [Accepted: 04/22/2013] [Indexed: 06/02/2023]
Abstract
Alternaria brassicicola is a successful saprophyte and necrotrophic plant pathogen. To identify molecular determinants of pathogenicity, we created non-pathogenic mutants of a transcription factor-encoding gene, AbPf2. The frequency and timing of germination and appressorium formation on host plants were similar between the non-pathogenic ∆abpf2 mutants and wild-type A. brassicicola. The mutants were also similar in vitro to wild-type A. brassicicola in terms of vegetative growth, conidium production, and responses to a phytoalexin, reactive oxygen species and osmolites. The hyphae of the mutants grew slowly but did not cause disease symptoms on the surface of host plants. Transcripts of the AbPf2 gene increased exponentially soon after wild-type conidia contacted their host plants . A small amount of AbPf2 protein, as monitored using GFP fusions, was present in young, mature conidia. The protein level decreased during saprophytic growth, but increased and was located primarily in fungal nuclei during pathogenesis. Levels of the proteins and transcripts sharply decreased following colonization of host tissues beyond the initial infection site. When expression of the transcription factor was induced in the wild-type during early pathogenesis, 106 fungal genes were also induced in the wild-type but not in the ∆abpf2 mutants. Notably, 33 of the 106 genes encoded secreted proteins, including eight putative effector proteins. Plants inoculated with ∆abpf2 mutants expressed higher levels of genes associated with photosynthesis, the pentose phosphate pathway and primary metabolism, but lower levels of defense-related genes. Our results suggest that AbPf2 is an important regulator of pathogenesis, but does not affect other cellular processes in A. brassicicola.
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Affiliation(s)
- Yangrae Cho
- Plant and Environmental Protection Sciences, University of Hawaii at Manoa, 3190 Maile Way, St John 317, Honolulu, HI 96822, USA.
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Powers-Fletcher MV, Feng X, Krishnan K, Askew DS. Deletion of the sec4 homolog srgA from Aspergillus fumigatus is associated with an impaired stress response, attenuated virulence and phenotypic heterogeneity. PLoS One 2013; 8:e66741. [PMID: 23785510 PMCID: PMC3681910 DOI: 10.1371/journal.pone.0066741] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/10/2013] [Indexed: 01/04/2023] Open
Abstract
Small GTPases of the Rab family are master regulators of membrane trafficking, responsible for coordinating the sorting, packaging and delivery of membrane-bound vesicles to specific sites within eukaryotic cells. The contribution of these proteins to the biology of the human pathogenic fungus Aspergillus fumigatus has not been explored. In this study, we characterized the srgA gene, encoding a Rab GTPase closely related to Sec4. We found that a GFP-SrgA fusion protein accumulated preferentially at hyphal tips and mature condiophores. The radial growth of a ΔsrgA mutant was impaired on both rich and minimal medium, consistent with a role for SrgA in filamentous growth. In addition, the ΔsrgA mutant revealed dysmorphic conidiophores that produced conidia with heterogeneous morphology. The ΔsrgA mutant was hypersensitive to brefeldin A-mediated inhibition of vesicular trafficking and showed increased temperature sensitivity relative to wild type A. fumigatus. However, the most striking phenotype of this mutant was its phenotypic heterogeneity. Individual colonies isolated from the original ΔsrgA mutant showed variable morphology with colony sectoring. In addition, each isolate of the ΔsrgA mutant displayed divergent phenotypes with respect to thermotolerance, in vitro stress response and virulence in a Galleria mellonella infection model. Taken together, these results indicate that SrgA contributes to the asexual development and filamentous growth of A. fumigatus. However, the discordant phenotypes observed among individual isolates of the ΔsrgA mutant suggest that the absence of srgA exerts selective pressure for the acquisition of compensatory changes, such as second-site suppressor mutations.
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Affiliation(s)
- Margaret V. Powers-Fletcher
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Xizhi Feng
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Karthik Krishnan
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - David S. Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
- * E-mail:
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Calmes B, Guillemette T, Teyssier L, Siegler B, Pigné S, Landreau A, Iacomi B, Lemoine R, Richomme P, Simoneau P. Role of mannitol metabolism in the pathogenicity of the necrotrophic fungus Alternaria brassicicola. FRONTIERS IN PLANT SCIENCE 2013; 4:131. [PMID: 23717316 PMCID: PMC3652318 DOI: 10.3389/fpls.2013.00131] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 04/20/2013] [Indexed: 05/29/2023]
Abstract
In this study, the physiological functions of fungal mannitol metabolism in the pathogenicity and protection against environmental stresses were investigated in the necrotrophic fungus Alternaria brassicicola. Mannitol metabolism was examined during infection of Brassica oleracea leaves by sequential HPLC quantification of the major soluble carbohydrates and expression analysis of genes encoding two proteins of mannitol metabolism, i.e., a mannitol dehydrogenase (AbMdh), and a mannitol-1-phosphate dehydrogenase (AbMpd). Knockout mutants deficient for AbMdh or AbMpd and a double mutant lacking both enzyme activities were constructed. Their capacity to cope with various oxidative and drought stresses and their pathogenic behavior were evaluated. Metabolic and gene expression profiling indicated an increase in mannitol production during plant infection. Depending on the mutants, distinct pathogenic processes, such as leaf and silique colonization, sporulation, survival on seeds, were impaired by comparison to the wild-type. This pathogenic alteration could be partly explained by the differential susceptibilities of mutants to oxidative and drought stresses. These results highlight the importance of mannitol metabolism with respect to the ability of A. brassicicola to efficiently accomplish key steps of its pathogenic life cycle.
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Affiliation(s)
- Benoit Calmes
- SFR 4207 QUASAV, UMR 1345 IRHS, Université d'AngersAngers Cedex, France
- SFR 4207 QUASAV, INRA, UMR 1345 IRHSAngers Cedex, France
- SFR 4207 QUASAV, Agrocampus-Ouest, UMR 1345 IRHSAngers Cedex, France
| | - Thomas Guillemette
- SFR 4207 QUASAV, UMR 1345 IRHS, Université d'AngersAngers Cedex, France
- SFR 4207 QUASAV, INRA, UMR 1345 IRHSAngers Cedex, France
- SFR 4207 QUASAV, Agrocampus-Ouest, UMR 1345 IRHSAngers Cedex, France
| | - Lény Teyssier
- SFR 4207 QUASAV, UMR 1345 IRHS, Université d'AngersAngers Cedex, France
- SFR 4207 QUASAV, INRA, UMR 1345 IRHSAngers Cedex, France
- SFR 4207 QUASAV, Agrocampus-Ouest, UMR 1345 IRHSAngers Cedex, France
| | - Benjamin Siegler
- Plateforme d'Ingénierie et Analyses Moléculaires, Université d'AngersAngers Cedex, France
| | - Sandrine Pigné
- SFR 4207 QUASAV, UMR 1345 IRHS, Université d'AngersAngers Cedex, France
- SFR 4207 QUASAV, INRA, UMR 1345 IRHSAngers Cedex, France
- SFR 4207 QUASAV, Agrocampus-Ouest, UMR 1345 IRHSAngers Cedex, France
| | - Anne Landreau
- SONAS EA 921, SFR 4207, QUASAV UFR des Sciences Pharmaceutiques et d'Ingénierie de la Santé, Université d'AngersAngers Cedex, France
| | | | - Rémi Lemoine
- Ecologie, Biologie des Interactions, UMR 7267 CNRS/Université de PoitiersPoitiers, France
| | - Pascal Richomme
- SONAS EA 921, SFR 4207, QUASAV UFR des Sciences Pharmaceutiques et d'Ingénierie de la Santé, Université d'AngersAngers Cedex, France
| | - Philippe Simoneau
- SFR 4207 QUASAV, UMR 1345 IRHS, Université d'AngersAngers Cedex, France
- SFR 4207 QUASAV, INRA, UMR 1345 IRHSAngers Cedex, France
- SFR 4207 QUASAV, Agrocampus-Ouest, UMR 1345 IRHSAngers Cedex, France
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Effects of a defective endoplasmic reticulum-associated degradation pathway on the stress response, virulence, and antifungal drug susceptibility of the mold pathogen Aspergillus fumigatus. EUKARYOTIC CELL 2013; 12:512-9. [PMID: 23355008 DOI: 10.1128/ec.00319-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Proteins that are destined for release outside the eukaryotic cell, insertion into the plasma membrane, or delivery to intracellular organelles are processed and folded in the endoplasmic reticulum (ER). An imbalance between the level of nascent proteins entering the ER and the organelle's ability to manage that load results in the accumulation of unfolded proteins. Terminally unfolded proteins are disposed of by ER-associated degradation (ERAD), a pathway that transports the aberrant proteins across the ER membrane into the cytosol for proteasomal degradation. The ERAD pathway was targeted in the mold pathogen Aspergillus fumigatus by deleting the hrdA gene, encoding the A. fumigatus ortholog of Hrd1, the E3 ubiquitin ligase previously shown to contribute to ERAD in other species. Loss of HrdA was associated with impaired degradation of a folding-defective ERAD substrate, CPY*, as well as activation of the unfolded-protein response (UPR). The ΔhrdA mutant showed resistance to voriconazole and reduced thermotolerance but was otherwise unaffected by a variety of environmental stressors. A double-deletion mutant deficient in both HrdA and another component of the same ERAD complex, DerA, was defective in secretion and showed hypersensitivity to ER, thermal, and cell wall stress. However, the ΔhrdA ΔderA mutant remained virulent in mouse and insect infection models. These data demonstrate that HrdA and DerA support complementary ERAD functions that promote survival under conditions of ER stress but are dispensable for virulence in the host environment.
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Ahuja I, Kissen R, Bones AM. Phytoalexins in defense against pathogens. TRENDS IN PLANT SCIENCE 2012; 17:73-90. [PMID: 22209038 DOI: 10.1016/j.tplants.2011.11.002] [Citation(s) in RCA: 569] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 11/04/2011] [Accepted: 11/14/2011] [Indexed: 05/18/2023]
Abstract
Plants use an intricate defense system against pests and pathogens, including the production of low molecular mass secondary metabolites with antimicrobial activity, which are synthesized de novo after stress and are collectively known as phytoalexins. In this review, we focus on the biosynthesis and regulation of camalexin, and its role in plant defense. In addition, we detail some of the phytoalexins produced by a range of crop plants from Brassicaceae, Fabaceae, Solanaceae, Vitaceae and Poaceae. This includes the very recently identified kauralexins and zealexins produced by maize, and the biosynthesis and regulation of phytoalexins produced by rice. Molecular approaches are helping to unravel some of the mechanisms and reveal the complexity of these bioactive compounds, including phytoalexin action and metabolism.
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Affiliation(s)
- Ishita Ahuja
- Department of Biology, Norwegian University of Science and Technology, Realfagbygget, NO-7491 Trondheim, Norway.
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Powers-Fletcher MV, Jambunathan K, Brewer JL, Krishnan K, Feng X, Galande AK, Askew DS. Impact of the lectin chaperone calnexin on the stress response, virulence and proteolytic secretome of the fungal pathogen Aspergillus fumigatus. PLoS One 2011; 6:e28865. [PMID: 22163332 PMCID: PMC3233604 DOI: 10.1371/journal.pone.0028865] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 11/16/2011] [Indexed: 11/18/2022] Open
Abstract
Calnexin is a membrane-bound lectin chaperone in the endoplasmic reticulum (ER) that is part of a quality control system that promotes the accurate folding of glycoproteins entering the secretory pathway. We have previously shown that ER homeostasis is important for virulence of the human fungal pathogen Aspergillus fumigatus, but the contribution of calnexin has not been explored. Here, we determined the extent to which A. fumigatus relies on calnexin for growth under conditions of environmental stress and for virulence. The calnexin gene, clxA, was deleted from A. fumigatus and complemented by reconstitution with the wild type gene. Loss of clxA altered the proteolytic secretome of the fungus, but had no impact on growth rates in either minimal or complex media at 37°C. However, the ΔclxA mutant was growth impaired at temperatures above 42°C and was hypersensitive to acute ER stress caused by the reducing agent dithiothreitol. In contrast to wild type A. fumigatus, ΔclxA hyphae were unable to grow when transferred to starvation medium. In addition, depleting the medium of cations by chelation prevented ΔclxA from sustaining polarized hyphal growth, resulting in blunted hyphae with irregular morphology. Despite these abnormal stress responses, the ΔclxA mutant remained virulent in two immunologically distinct models of invasive aspergillosis. These findings demonstrate that calnexin functions are needed for growth under conditions of thermal, ER and nutrient stress, but are dispensable for surviving the stresses encountered in the host environment.
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Affiliation(s)
- Margaret V. Powers-Fletcher
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | | | - Jordan L. Brewer
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Karthik Krishnan
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Xizhi Feng
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Amit K. Galande
- SRI International, Harrisonburg, Virginia, United States of America
| | - David S. Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
- * E-mail:
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47
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Feng X, Krishnan K, Richie DL, Aimanianda V, Hartl L, Grahl N, Powers-Fletcher MV, Zhang M, Fuller KK, Nierman WC, Lu LJ, Latgé JP, Woollett L, Newman SL, Cramer RA, Rhodes JC, Askew DS. HacA-independent functions of the ER stress sensor IreA synergize with the canonical UPR to influence virulence traits in Aspergillus fumigatus. PLoS Pathog 2011; 7:e1002330. [PMID: 22028661 PMCID: PMC3197630 DOI: 10.1371/journal.ppat.1002330] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Accepted: 09/06/2011] [Indexed: 12/20/2022] Open
Abstract
Endoplasmic reticulum (ER) stress is a condition in which the protein folding capacity of the ER becomes overwhelmed by an increased demand for secretion or by exposure to compounds that disrupt ER homeostasis. In yeast and other fungi, the accumulation of unfolded proteins is detected by the ER-transmembrane sensor IreA/Ire1, which responds by cleaving an intron from the downstream cytoplasmic mRNA HacA/Hac1, allowing for the translation of a transcription factor that coordinates a series of adaptive responses that are collectively known as the unfolded protein response (UPR). Here, we examined the contribution of IreA to growth and virulence in the human fungal pathogen Aspergillus fumigatus. Gene expression profiling revealed that A. fumigatus IreA signals predominantly through the canonical IreA-HacA pathway under conditions of severe ER stress. However, in the absence of ER stress IreA controls dual signaling circuits that are both HacA-dependent and HacA-independent. We found that a ΔireA mutant was avirulent in a mouse model of invasive aspergillosis, which contrasts the partial virulence of a ΔhacA mutant, suggesting that IreA contributes to pathogenesis independently of HacA. In support of this conclusion, we found that the ΔireA mutant had more severe defects in the expression of multiple virulence-related traits relative to ΔhacA, including reduced thermotolerance, decreased nutritional versatility, impaired growth under hypoxia, altered cell wall and membrane composition, and increased susceptibility to azole antifungals. In addition, full or partial virulence could be restored to the ΔireA mutant by complementation with either the induced form of the hacA mRNA, hacAi, or an ireA deletion mutant that was incapable of processing the hacA mRNA, ireAΔ10. Together, these findings demonstrate that IreA has both HacA-dependent and HacA-independent functions that contribute to the expression of traits that are essential for virulence in A. fumigatus. Aspergillus fumigatus is the predominant mold pathogen of humans, responsible for life-threatening infections in patients with depressed immunity. The fungus is highly adapted for secretion, a feature that it uses to extract nutrients from the host environment. High rates of protein secretion can overwhelm the protein folding capacity of the endoplasmic reticulum (ER). The resulting ER stress is alleviated by the unfolded protein response (UPR), a signaling pathway that is triggered by the ER-membrane sensor IreA and executed by the downstream transcription factor HacA. This paper uncovers a novel role for IreA in the expression of multiple adaptive traits that allow the fungus to cope with stress conditions that are encountered during infection. Gene expression profiling of ΔireA and ΔhacA mutants revealed that IreA signals predominantly through the canonical IreA-HacA UPR pathway under extreme conditions of ER stress, but has unexpected HacA-dependent and HacA-independent functions even in the absence of ER stress. These findings establish IreA as an important regulator of A. fumigatus pathogenicity and suggest that therapeutic targeting of the dual functions of this protein could be an effective antifungal strategy.
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Affiliation(s)
- Xizhi Feng
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Karthik Krishnan
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Daryl L. Richie
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | | | - Lukas Hartl
- Unité des Aspergillus, Institut Pasteur, Paris, France
| | - Nora Grahl
- Department of Immunology & Infectious Diseases, Montana State University, Bozeman, Montana, United States of America
| | - Margaret V. Powers-Fletcher
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Minlu Zhang
- Division of Biomedical Informatics, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America
| | - Kevin K. Fuller
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - William C. Nierman
- The J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Long Jason Lu
- Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | | | - Laura Woollett
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Simon L. Newman
- Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Robert A. Cramer
- Department of Immunology & Infectious Diseases, Montana State University, Bozeman, Montana, United States of America
| | - Judith C. Rhodes
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - David S. Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
- * E-mail:
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