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Kim B, Nguyen MV, Park J, Kim YS, Han JW, Lee JY, Jeon J, Son H, Choi GJ, Kim H. Edeine B 1 produced by Brevibacillus brevis reduces the virulence of a plant pathogenic fungus by inhibiting mitochondrial respiration. mBio 2024; 15:e0135124. [PMID: 38860787 PMCID: PMC11253638 DOI: 10.1128/mbio.01351-24] [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: 05/03/2024] [Accepted: 05/06/2024] [Indexed: 06/12/2024] Open
Abstract
Plant pathogenic fungi cause serious diseases, which result in the loss of crop yields and reduce the quality of crops worldwide. To counteract the escalating risks of chemical fungicides, interest in biological control agents to manage plant diseases has significantly increased. In this study, we comprehensively screened microbial culture filtrates using a yeast screening system to find microbes exhibiting respiratory inhibition activity. Consequently, we found a soil-borne microbe Brevibacillus brevis HK544 strain exhibiting a respiration inhibitory activity and identified edeine B1 (EB1) from the culture filtrate of HK544 as the active compound of the respiration inhibition activity. Furthermore, against a plant pathogenic fungus Fusarium graminearum, our results showed that EB1 has effects on multiple aspects of respiration with the downregulation of most of the mitochondrial-related genes based on transcriptome analysis, differential EB1-sensitivity from targeted mutagenesis, and the synergistic effects of EB1 with electron transport chain complex inhibitors. With the promising plant disease control efficacy of B. brevis HK544 producing EB1, our results suggest that B. brevis HK544 has potential as a biocontrol agent for Fusarium head blight.IMPORTANCEAs a necrotrophic fungus, Fusarium graminearum is a highly destructive pathogen causing severe diseases in cereal crops and mycotoxin contamination in grains. Although chemical control is considered the primary approach to control plant disease caused by F. graminearum, fungicide-resistant strains have been detected in the field after long-term continuous application of fungicides. Moreover, applying chemical fungicides that trigger mycotoxin biosynthesis is a great concern for many researchers. Biocontrol of Fusarium head blight (FHB) by biological control agents (BCAs) represents an alternative approach and could be used as part of the integrated management of FHB and mycotoxin production. The most extensive studies on bacterial BCAs-fungal communications in agroecosystems have focused on antibiosis. Although many BCAs in agricultural ecology have already been used for fungal disease control, the molecular mechanisms of antibiotics produced by BCAs remain to be elucidated. Here, we found a potential BCA (Brevibacillus brevis HK544) with a strong antifungal activity based on the respiration inhibition activity with its active compound edeine B1 (EB1). Furthermore, our results showed that EB1 secreted by HK544 suppresses the expression of the mitochondria-related genes of F. graminearum, subsequently suppressing fungal development and the virulence of F. graminearum. In addition, EB1 exhibited a synergism with complex I inhibitors such as rotenone and fenazaquin. Our work extends our understanding of how B. brevis HK544 exhibits antifungal activity and suggests that the B. brevis HK544 strain could be a valuable source for developing new crop protectants to control F. graminearum.
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Affiliation(s)
- Bomin Kim
- Center for Eco-friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, South Korea
- Department of Medicinal Chemistry and Pharmacology, University of Science and Technology, Daejeon, South Korea
| | - Minh Van Nguyen
- Center for Eco-friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, South Korea
- Department of Medicinal Chemistry and Pharmacology, University of Science and Technology, Daejeon, South Korea
| | - Jiyeun Park
- Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea
| | - Yeong Seok Kim
- Center for Eco-friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, South Korea
- Department of Medicinal Chemistry and Pharmacology, University of Science and Technology, Daejeon, South Korea
| | - Jae Woo Han
- Center for Eco-friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, South Korea
| | - Joo-Youn Lee
- Therapeutics and Biotechnology Division, Korea Research Institute of Chemical Technology, Daejeon, South Korea
| | - Junhyun Jeon
- Department of Biotechnology, Yeungnam University, Gyeongsan, South Korea
| | - Hokyoung Son
- Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea
| | - Gyung Ja Choi
- Center for Eco-friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, South Korea
- Department of Medicinal Chemistry and Pharmacology, University of Science and Technology, Daejeon, South Korea
| | - Hun Kim
- Center for Eco-friendly New Materials, Korea Research Institute of Chemical Technology, Daejeon, South Korea
- Department of Medicinal Chemistry and Pharmacology, University of Science and Technology, Daejeon, South Korea
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2
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Wang M, Zhang W, Lu J, Huo Y, Wang J. The Effects of Antofine on the Morphological and Physiological Characteristics of Phytophthora capsici. Molecules 2024; 29:1965. [PMID: 38731455 PMCID: PMC11085548 DOI: 10.3390/molecules29091965] [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: 02/26/2024] [Revised: 04/23/2024] [Accepted: 04/23/2024] [Indexed: 05/13/2024] Open
Abstract
Phytophthora capsici is an important plant pathogenic oomycete that causes great losses to vegetable production around the world. Antofine is an important alkaloid isolated from Cynanchum komarovii Al. Iljinski and exhibits significant antifungal activity. In this study, the effect of antofine on the mycelial growth, morphology, and physiological characteristics of P. capsici was investigated using colorimetry. Meanwhile, the activity of mitochondrial respiratory chain complexes of P. capsici was evaluated following treatment with a 30% effective concentration (EC30), as well as EC50 and EC70, of antofine for 0, 12, 24, and 48 h. The results showed that antofine had a significant inhibitory effect against P. capsici, with an EC50 of 5.0795 μg/mL. After treatment with antofine at EC50 and EC70, the mycelia were rough, less full, and had obvious depression; they had an irregular protrusion structure; and they had serious wrinkles. In P. capsici, oxalic acid and exopolysaccharide contents decreased significantly, while cell membrane permeability and glycerol content increased when treated with antofine. Reactive oxygen species (ROS) entered a burst state in P. capsici after incubation with antofine for 3 h, and fluorescence intensity was 2.43 times higher than that of the control. The activities of the mitochondrial respiratory chain complex II, III, I + III, II + III, V, and citrate synthase in P. capsici were significantly inhibited following treatment with antofine (EC50 and EC70) for 48 h compared to the control. This study revealed that antofine is likely to affect the pathways related to the energy metabolism of P. capsici and thus affect the activity of respiratory chain complexes. These results increase our understanding of the action mechanism of antofine against P. capsici.
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Affiliation(s)
- Mei Wang
- College of Life Science, Yulin University, Yulin 719000, China; (W.Z.); (J.L.); (Y.H.)
| | - Weirong Zhang
- College of Life Science, Yulin University, Yulin 719000, China; (W.Z.); (J.L.); (Y.H.)
| | - Jiaojiao Lu
- College of Life Science, Yulin University, Yulin 719000, China; (W.Z.); (J.L.); (Y.H.)
| | - Yanbo Huo
- College of Life Science, Yulin University, Yulin 719000, China; (W.Z.); (J.L.); (Y.H.)
| | - Jing Wang
- College of Chemistry and Chemical Engineering, Yulin University, Yulin 719000, China;
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3
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Edrich ESM, Duvenage L, Gourlay CW. Alternative Oxidase - Aid or obstacle to combat the rise of fungal pathogens? BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2024; 1865:149031. [PMID: 38195037 DOI: 10.1016/j.bbabio.2024.149031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 11/16/2023] [Accepted: 01/03/2024] [Indexed: 01/11/2024]
Abstract
Fungal pathogens present a growing threat to both humans and global health security alike. Increasing evidence of antifungal resistance in fungal populations that infect both humans and plant species has increased reliance on combination therapies and shown the need for new antifungal therapeutic targets to be investigated. Here, we review the roles of mitochondria and fungal respiration in pathogenesis and discuss the role of the Alternative Oxidase enzyme (Aox) in both human fungal pathogens and phytopathogens. Increasing evidence exists for Aox within mechanisms that underpin fungal virulence. Aox also plays important roles in adaptability that may prove useful within dual targeted fungal-specific therapeutic approaches. As improved fungal specific mitochondrial and Aox inhibitors are under development we may see this as an emerging target for future approaches to tackling the growing challenge of fungal infection.
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Affiliation(s)
| | - Lucian Duvenage
- CMM AFRICA Medical Mycology Research Unit, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Campbell W Gourlay
- Kent Fungal Group, School of Biosciences, University of Kent, Kent CT2 9HY, UK.
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4
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Ren W, Wang Z, Lian S, Dong X, Li B, Liu N. Molecular and Biochemical Characterization of Field Resistant Isolates of Glomerella cingulata to Pyraclostrobin in China. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:3960-3966. [PMID: 36821832 DOI: 10.1021/acs.jafc.2c08846] [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: 06/18/2023]
Abstract
Glomerella leaf spot (GLS) caused by Glomerella cingulata is a destructive disease that results in severe defoliation and fruit spots in apples worldwide. The compound of pyraclostrobin and tebuconazole was registered in 2018 in China to control GLS. In 2020, the high-level resistance of G. cingulata to pyraclostrobin was found in the field in Shandong Province, with a resistance frequency of 4.8%. Except for a significant decrease in virulence, there was no fitness penalty in mycelial growth, sporulation, and stress tolerance of G. cingulata associated with the resistance to pyraclostrobin. No cross-resistance was detected between pyraclostrobin and tebuconazole or bromothalonil. The point mutation GGT (G) → GCT (A) at codon 143 in the Cytochrome b (Cytb) gene was identified in the pyraclostrobin-resistant isolates. Molecular docking analysis suggested that G143A significantly alters the affinity of pyraclostrobin to the Cytb protein. Based on the point mutation (G143A) in the Cytb gene, a cleaved amplified polymorphic sequences method was developed to detect pyraclostrobin resistance in G. cingulata populations. Results of this study will provide valuable information for the scientific management of GLS.
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Affiliation(s)
- Weichao Ren
- Key Laboratory of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China
| | - Zhongqiang Wang
- Key Laboratory of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China
| | - Sen Lian
- Key Laboratory of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China
| | - Xiangli Dong
- Key Laboratory of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China
| | - Baohua Li
- Key Laboratory of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China
| | - Na Liu
- Key Laboratory of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China
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Matsuzaki Y, Kiguchi S, Suemoto H, Iwahashi F. Antifungal activity of metyltetraprole against the existing QoI-resistant isolates of various plant pathogenic fungi: Metyltetraprole against QoI-R isolates. PEST MANAGEMENT SCIENCE 2020; 76:1743-1750. [PMID: 31769927 PMCID: PMC7204873 DOI: 10.1002/ps.5697] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 10/31/2019] [Accepted: 11/22/2019] [Indexed: 05/21/2023]
Abstract
BACKGROUND Metyltetraprole is a novel quinol oxidation site of Complex III inhibitor (QoI) fungicide that inhibits mitochondrial electron transport at the Qo site of the cytochrome bc1 complex. Previous reports have demonstrated that it is also active against the QoI-resistant (QoI-R) isolates of Zymoseptoria tritici and Pyrenophora teres with the mutations G143A and F129L in their cytochrome b gene, respectively. Further studies on cross-resistance between metyltetraprole and existing QoIs were performed using an increased number of isolates of Z. tritici, P. teres, Ramularia collo-cygni, Pyrenophora tritici-repentis, and several other plant pathogenic fungi. RESULTS Differences in the EC50 values between the wild-type and QoI-R isolates with the mutations G143A or F129L were always smaller for metyltetraprole compared to those for the existing QoIs, and they were never greater than five in terms of resistance factor. The 2-year field experiments showed that the metyltetraprole treatment did not increase the percentage of QoI-R isolates likely to harbor the G143A mutation in a Z. tritici population. CONCLUSION The unique behavior of metyltetraprole against the existing QoI-R isolates was confirmed for all tested pathogen species. Our results provide important information to establish a fungicide resistance management strategy using metyltetraprole in combination or alternation with other fungicides. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Yuichi Matsuzaki
- Health and Crop Sciences Research LaboratorySumitomo Chemical Co., Ltd.TakarazukaJapan
| | - So Kiguchi
- Health and Crop Sciences Research LaboratorySumitomo Chemical Co., Ltd.TakarazukaJapan
| | - Haruka Suemoto
- Health and Crop Sciences Research LaboratorySumitomo Chemical Co., Ltd.TakarazukaJapan
| | - Fukumatsu Iwahashi
- Health and Crop Sciences Research LaboratorySumitomo Chemical Co., Ltd.TakarazukaJapan
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Wang L, Ren X, Guo W, Wang D, Han L, Feng J. Oxidative Stress and Apoptosis of Gaeumannomyces graminis ( Get) Induced by Carabrone. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:10448-10457. [PMID: 31453693 DOI: 10.1021/acs.jafc.9b02951] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Carabrone is isolated from Carpesium macrocephalum Franch. et Sav, which has good fungicidal activity, especially for Gaeumannomyces graminis (Get). According to previous studies, we speculated that carabrone targets the mitochondrial enzyme complex III of Get. To elucidate the mode of action, we used carabrone to induce oxidative stress and apoptosis in Get. Incubation with carabrone reduced the burst of reactive oxygen species (ROS) and mitochondrial membrane potential, as well as phosphatidylserine release. Carabrone caused ROS accumulation in mycelia by inhibiting the activity of antioxidase enzymes, among which inhibition of glutathione reductase (GR) activity was most obvious. The catalytic center of GR consists of l-cysteine residues that react with the α-methylene-γ-butyrolactone active site of carabrone. Additionally, a positive TUNEL reaction led to diffusion of the DNA electrophoresis band and upregulation of Ggmet1 and Ggmet2. We propose that carabrone inhibits antioxidant enzymes and promotes ROS overproduction, which causes membrane hyperpermeability, release of apoptotic factors, activation of the mitochondria-mediated apoptosis pathway, and fungal cell apoptosis.
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Affiliation(s)
- Lanying Wang
- Research and Development Center of Biorational Pesticide , Northwest A&F University , Yangling 712100 , Shaanxi , China
- Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests , Hainan University , Ministry of Education, Haikou 570228 , Hainan , China
| | - Xingyu Ren
- Research and Development Center of Biorational Pesticide , Northwest A&F University , Yangling 712100 , Shaanxi , China
| | - Wenhui Guo
- Research and Development Center of Biorational Pesticide , Northwest A&F University , Yangling 712100 , Shaanxi , China
| | - Delong Wang
- Research and Development Center of Biorational Pesticide , Northwest A&F University , Yangling 712100 , Shaanxi , China
| | - Lirong Han
- Research and Development Center of Biorational Pesticide , Northwest A&F University , Yangling 712100 , Shaanxi , China
| | - Juntao Feng
- Research and Development Center of Biorational Pesticide , Northwest A&F University , Yangling 712100 , Shaanxi , China
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Baggio JS, Peres NA, Amorim L. Sensitivity of Botrytis cinerea Isolates from Conventional and Organic Strawberry Fields in Brazil to Azoxystrobin, Iprodione, Pyrimethanil, and Thiophanate-Methyl. PLANT DISEASE 2018; 102:1803-1810. [PMID: 30125196 DOI: 10.1094/pdis-08-17-1221-re] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Botrytis fruit rot, caused by Botrytis cinerea, is one of the most important strawberry diseases worldwide, and fungicide applications are often used to manage the disease in commercial production. Isolates of B. cinerea were collected from conventional and organic strawberry fields in four Brazilian States from 2013 to 2015 and their sensitivity to the main single-site mode-of action fungicides used in Brazil was tested. Resistance to azoxystrobin, iprodione, pyrimethanil, and thiophanate-methyl was found and values for effective concentration that inhibited mycelial growth by 50% were higher than 71.9, 1.2, 5.0, and 688 µg/ml, respectively, regardless the production system. Resistance to these fungicides was observed in 87.5, 76.6, 23.4, and 92.2% of isolates from conventional fields and 31.4, 22.9, 14.3, and 51.4% of isolates from organic fields, respectively. Moreover, frequencies of isolates with multiple fungicide resistance to the four active ingredients were 20.6 and 2.8% whereas 6.3 and 27.8% were sensitive to the four fungicides for conventional and organic areas, respectively. Molecular analyses of the cytochrome b, β-tubulin, and bos1 genes revealed the presence of G143A; E198A; and I365 N/S, Q369P, or N373S mutations, respectively, in resistant isolates of B. cinerea. Field rates of fungicides sprayed preventively to inoculated strawberry fruit failed to control disease caused by the respective resistant isolates.
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Affiliation(s)
- Juliana S Baggio
- Departamento de Fitopatologia, ESALQ, University of Sao Paulo, CEP 13418-900, Piracicaba, SP, Brazil
| | - Natalia A Peres
- Gulf Coast Research and Education Center, University of Florida, Wimauma
| | - Lilian Amorim
- Departmento de Fitopatologia, ESALQ, University of São Paulo, CEP 13418-900 Piracicaba, SP, Brazil
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Young DH, Wang NX, Meyer ST, Avila‐Adame C. Characterization of the mechanism of action of the fungicide fenpicoxamid and its metabolite UK-2A. PEST MANAGEMENT SCIENCE 2018; 74:489-498. [PMID: 28960782 PMCID: PMC5813142 DOI: 10.1002/ps.4743] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 08/31/2017] [Accepted: 09/22/2017] [Indexed: 05/04/2023]
Abstract
BACKGROUND Fenpicoxamid is a new fungicide for control of Zymoseptoria tritici, and is a derivative of the natural product UK-2A. Its mode of action and target site interactions have been investigated. RESULTS UK-2A strongly inhibited cytochrome c reductase, whereas fenpicoxamid was much less active, consistent with UK-2A being the fungicidally active species generated from fenpicoxamid by metabolism. Both compounds caused rapid loss of mitochondrial membrane potential in Z. tritici spores. In Saccharomyces cerevisiae, amino acid substitutions N31K, G37C and L198F at the Qi quinone binding site of cytochrome b reduced sensitivity to fenpicoxamid, UK-2A and antimycin A. Activity of fenpicoxamid was not reduced by the G143A exchange responsible for strobilurin resistance. A docking pose for UK-2A at the Qi site overlaid that of antimycin A. Activity towards Botrytis cinerea was potentiated by salicylhydroxamic acid, showing an ability of alternative respiration to mitigate activity. Fungitoxicity assays against Z. tritici field isolates showed no cross-resistance to strobilurin, azole or benzimidazole fungicides. CONCLUSION Fenpicoxamid is a Qi inhibitor fungicide that provides a new mode of action for Z. tritici control. Mutational and modeling studies suggest that the active species UK-2A binds at the Qi site in a similar, but not identical, fashion to antimycin A. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Affiliation(s)
| | - Nick X Wang
- Dow AgroSciencesDiscovery ResearchIndianapolisINUSA
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9
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Wang L, Zhang Y, Wang D, Wang M, Wang Y, Feng J. Mitochondrial Signs and Subcellular Imaging Provide Insight into the Antifungal Mechanism of Carabrone against Gaeumannomyces graminis var. tritici. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:81-90. [PMID: 29232953 DOI: 10.1021/acs.jafc.7b03913] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Carabrone, a botanical bicyclic sesquiterpenic lactone, has broad-spectrum antifungal activity and is particularly efficient against the devastating phytopathogen Gaeumannomyces graminis var. tritici (Ggt). The antifungal mechanism of carabrone against Ggt, however, remains unclear. The main objective of this study was to investigate the subcellular localization of carabrone in Ggt to gain a better understanding of its mechanism of action. When Ggt was exposed to carabrone (EC50 value of 28.45 μg/mL) for 7 days, a decline in mitochondrial concentration together with some obvious alternations in mitochondrial structure, including hazy outlines, medullary transitions, excess accumulation of unclear settlings, and vacuolar degeneration, were observed, indicating that carbrone may act on the mitochondria directly. A fluorescent conjugate (TTY) was thus designed and synthesized as a surrogate of carabrone that possessed comparable antifungal activity against Ggt (EC50 of 33.68 μg/mL). Additionally, a polyclonal antibody specific to carabrone and with a high titer (256 000) was also prepared by immunizing mice. Subsequently, two imaging techniques, the use of the fluorescent conjugate (FC) and immunofluorescence (IF), were applied to determine the subcellular localization of carabrone. Both FC and IF fluorescent signals demonstrated its mitochondrial localization with a Pearson's coefficient of 0.83 for FC and 0.86 for IF. These results imply that carabrone exerts its antifungal activity against Ggt by interfering with mitochondrial function.
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Affiliation(s)
- Lanying Wang
- Research and Development Center of Biorational Pesticide, Northwest A&F University , Yangling 712100, Shaanxi, China
- Institute of Tropical Agriculture and Forestry, Hainan University , Haikou 570228, Hainan, China
| | - Yunfei Zhang
- Research and Development Center of Biorational Pesticide, Northwest A&F University , Yangling 712100, Shaanxi, China
| | - Delong Wang
- Research and Development Center of Biorational Pesticide, Northwest A&F University , Yangling 712100, Shaanxi, China
| | - Mei Wang
- Research and Development Center of Biorational Pesticide, Northwest A&F University , Yangling 712100, Shaanxi, China
| | - Yong Wang
- Research and Development Center of Biorational Pesticide, Northwest A&F University , Yangling 712100, Shaanxi, China
| | - Juntao Feng
- Research and Development Center of Biorational Pesticide, Northwest A&F University , Yangling 712100, Shaanxi, China
- Engineering and Research Center of Biological Pesticide of Shaanxi Province , Yangling 712100, Shaanxi, China
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10
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Wang M, Wang L, Han L, Zhang X, Feng J. The effect of carabrone on mitochondrial respiratory chain complexes inGaeumannomyces graminis. J Appl Microbiol 2017; 123:1100-1110. [DOI: 10.1111/jam.13554] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 07/07/2017] [Accepted: 07/27/2017] [Indexed: 01/01/2023]
Affiliation(s)
- M. Wang
- Research and Development Center of Biorational Pesticide; Northwest A&F University; Yangling 712100 Shaanxi China
| | - L. Wang
- Research and Development Center of Biorational Pesticide; Northwest A&F University; Yangling 712100 Shaanxi China
| | - L. Han
- Research and Development Center of Biorational Pesticide; Northwest A&F University; Yangling 712100 Shaanxi China
| | - X. Zhang
- Research and Development Center of Biorational Pesticide; Northwest A&F University; Yangling 712100 Shaanxi China
- Engineering and Research Center of Biological Pesticide of Shaanxi Province; Yangling 712100 Shaanxi China
| | - J. Feng
- Research and Development Center of Biorational Pesticide; Northwest A&F University; Yangling 712100 Shaanxi China
- Engineering and Research Center of Biological Pesticide of Shaanxi Province; Yangling 712100 Shaanxi China
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11
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Chen SN, Shang Y, Wang Y, Schnabel G, Lin Y, Yin LF, Luo CX. Sensitivity of Monilinia fructicola from Peach Farms in China to Four Fungicides and Characterization of Isolates Resistant to Carbendazim and Azoxystrobin. PLANT DISEASE 2014; 98:1555-1560. [PMID: 30699783 DOI: 10.1094/pdis-11-13-1145-re] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Brown rot of peach caused by Monilinia fructicola can cause considerable preharvest and postharvest losses in China. Fungicides are increasingly utilized to minimize such losses. Eighty isolates of M. fructicola were collected from commercial peach orchards located in five provinces in China and the sensitivity to carbendazim, azoxystrobin, tebuconazole, and boscalid was determined. Resistance to carbendazim was detected only in the Yunnan province in 15 of 16 isolates. Characterization of carbendazim-resistant isolates revealed stable resistance, no fitness penalty, and negative cross resistance to diethofencarb. Resistant isolates produced disease symptoms on detached fruit sprayed with label rates of formulated carbendazim and possessed the amino acid mutation E198A in β-tubulin. Resistance to azoxystrobin was detected in 3 of 10 isolates from Fujian. In contrast to carbendazim resistance, however, azoxystrobin resistance was unstable, associated with a fitness penalty, and not associated with mutations in the target gene cytochrome b. The concentration at which mycelial growth is inhibited 50% (EC50) values of the azoxystrobin-sensitive isolates were 0.02 to 1.94 μg/ml, with a mean value of 0.54 μg/ml. All isolates were sensitive to tebuconazole, with a mean EC50 value of 0.03 μg/ml. The EC50 values for boscalid were 0.01 to 3.85 μg/ml, with a mean value of 1.02 μg/ml. Our results indicate that methyl benzimidazole carbamates (MBCs), quionon outside inhibitors, demethylation inhibitor fungicides, and succinate dehydrogenase inhibitors are likely to be very effective in controlling brown rot in many peach production areas in China, but that resistance to MBCs is emerging.
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Affiliation(s)
- S N Chen
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Y Shang
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Y Wang
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - G Schnabel
- School of Agricultural, Forest and Environmental Sciences, Clemson University, Clemson, SC 29634
| | - Y Lin
- College of Plant Science and Technology and the Key Lab of Crop Disease Monitoring & Safety Control in Hubei Province, Huazhong Agricultural University
| | - L F Yin
- College of Plant Science and Technology and the Key Lab of Crop Disease Monitoring & Safety Control in Hubei Province, Huazhong Agricultural University
| | - C X Luo
- College of Plant Science and Technology and the Key Lab of Crop Disease Monitoring & Safety Control in Hubei Province, Huazhong Agricultural University
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Xu C, Hou Y, Wang J, Yang G, Liang X, Zhou M. Activity of a novel strobilurin fungicide benzothiostrobin against Sclerotinia sclerotiorum. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2014; 115:32-38. [PMID: 25307463 DOI: 10.1016/j.pestbp.2014.08.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/10/2014] [Accepted: 08/12/2014] [Indexed: 06/04/2023]
Abstract
Benzothiostrobin is a novel strobilurin fungicide. In this study, baseline sensitivity of Sclerotinia sclerotiorum (Lib.) de Bary to benzothiostrobin was determined using 100 strains collected during 2012 and 2013 from different geographical regions in Jiangsu Province of China, and the average EC50 value was 0.0218 (± 0.0111)μg/mL for mycelial growth. After benzothiostrobin treatment, hyphae were contorted with offshoot of top increasing and cell membrane permeability increased markedly, while sclerotial production and oxalic acid content significantly decreased. Benzothiostrobin strongly inhibited mycelial respiration within 12h and the oxygen consumption of the mycelia could not be inhibited after 24h. On detached rapeseed leaves, the protective and curative activity test of benzothiostrobin suggested that benzothiostrobin had good control efficiency against S. sclerotiorum, and protective activity was better than curative activity. These results will contribute to us evaluating the potential of the new strobilurin fungicide benzothiostrobin for management of diseases caused by S. sclerotiorum and understanding the mode of action of benzothiostrobin against S. sclerotiorum.
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Affiliation(s)
- Congying Xu
- College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Pesticide, Jiangsu Province, Nanjing 210095, China.
| | - Yiping Hou
- College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Pesticide, Jiangsu Province, Nanjing 210095, China
| | - Jianxin Wang
- College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Pesticide, Jiangsu Province, Nanjing 210095, China
| | - Guangfu Yang
- College of Chemisty, Central China Normal University, Hubei Province, Wuhan 430079, China
| | - Xiaoyu Liang
- College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Pesticide, Jiangsu Province, Nanjing 210095, China
| | - Mingguo Zhou
- College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Pesticide, Jiangsu Province, Nanjing 210095, China.
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Frederick ZA, Villani SM, Cooley DR, Biggs AR, Raes JJ, Cox KD. Prevalence and Stability of Qualitative QoI Resistance in Populations of Venturia inaequalis in the Northeastern United States. PLANT DISEASE 2014; 98:1122-1130. [PMID: 30708794 DOI: 10.1094/pdis-10-13-1042-re] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Quinone-outside-inhibitor (QoI) fungicides are a safe and effective means of managing apple scab caused by Venturia inaequalis. To determine the prevalence of both quantitative (partial) and qualitative (complete) QoI resistance in V. inaequalis in the northeastern United States, we sampled single-lesion conidial isolates (n = 4,481) from 120 commercial and research orchards from 2004 to 2011 with a range of exposure to QoI fungicides from none to several applications a year. In all, 67% of these orchard populations of V. inaequalis were sensitive to QoI fungicides, 28% exhibited QoI practical resistance, and 5% were not sensitive QoI fungicides but had not become practically resistant. Isolates with qualitative QoI resistance, conferred by the G143A cytochrome b gene mutation, were found in 13 of the 34 QoI-resistant orchard populations. To evaluate the stability of the G143A mutation, 27 isolates were selected from different orchard populations to represent the scope of regional populations. These isolates were subcultured continuously in the presence or absence of the QoI fungicide trifloxystrobin. All isolates that initially possessed qualitative resistance maintained the resistant genotype (G143A) for six transfers over 6 months in both the absence and presence of trifloxystrobin. Given the observed QoI resistance in orchard populations of V. inaequalis and the stability of the G143A mutation in individual isolates, apple scab management paradigms must encompass strategies to limit selection of QoI resistance in the sensitive orchard populations remaining in the region.
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Affiliation(s)
- Zachary A Frederick
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, NY 14456
| | - Sara M Villani
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, NY 14456
| | - Daniel R Cooley
- Department Plant, Soil, and Insect Science, University of Massachusetts, Amherst 01003
| | - Alan R Biggs
- Kearneysville Tree Fruit Research and Education Center, West Virginia University, Kearneysville 25443
| | - Jessica J Raes
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University
| | - Kerik D Cox
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University
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Abstract
Philasterides dicentrarchi causes a severe disease in turbot, and at present there are no drugs available to treat infected fish. We have previously demonstrated that, in addition to the classical respiratory pathway, P. dicentrarchi possesses an alternative mitochondrial respiratory pathway that is cyanide-insensitive and salicylhydroxamic acid (SHAM)-sensitive. In this study, we found that during the initial phase of growth in normoxia, ciliate respiration is sensitive to the natural polyphenol resveratrol (RESV) and to Antimycin A (AMA). However, under hypoxic conditions, the parasite utilizes AMA-insensitive respiration, which is completely inhibited by RESV and by the antioxidant propyl gallate (PG), an alternative oxidase (AOX) inhibitor. PG caused significantly dose-dependent inhibition of the in vitro growth of the parasite under normoxia and hypoxia and an over-expression of heat shock proteins of the Hsp70 subfamily. RESV and PG may affect the protective role of the AOX against mitochondrial oxidative stress, leading to an impaired mitochondrial membrane potential and mitochondrial dysfunction, which the parasite attempts to neutralize by increasing the expression of Hsp70. In view of the antiparasitic effects induced by AOX inhibitors and the absence of AOX in their host, this enzyme constitutes a potential target for the development of new drugs against scuticociliatosis.
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Xu T, Wang YT, Liang WS, Yao F, Li YH, Li DR, Wang H, Wang ZY. Involvement of alternative oxidase in the regulation of sensitivity of Sclerotinia sclerotiorum to the fungicides azoxystrobin and procymidone. J Microbiol 2013; 51:352-8. [DOI: 10.1007/s12275-013-2534-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 01/17/2013] [Indexed: 11/30/2022]
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De Miccolis Angelini RM, Rotolo C, Masiello M, Pollastro S, Ishii H, Faretra F. Genetic analysis and molecular characterisation of laboratory and field mutants of Botryotinia fuckeliana (Botrytis cinerea) resistant to QoI fungicides. PEST MANAGEMENT SCIENCE 2012; 68:1231-1240. [PMID: 22488841 DOI: 10.1002/ps.3281] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 11/28/2011] [Accepted: 01/25/2012] [Indexed: 05/31/2023]
Abstract
BACKGROUND QoI fungicides, inhibitors of mitochondrial respiration, are considered to be at high risk of resistance development. In several phytopathogenic fungi, resistance is caused by mutations (most frequently G143A) in the mitochondrial cytochrome b (cytb) gene. The genetic and molecular basis of QoI resistance were investigated in laboratory and field mutants of Botryotinia fuckeliana (de Bary) Whetz. exhibiting in vitro reduced sensitivity to trifloxystrobin. RESULTS B. fuckeliana mutants highly resistant to trifloxystrobin were obtained in the laboratory by spontaneous mutations in wild-type strains, or from naturally infected plants on a medium amended with 1-3 mg L(-1) trifloxystrobin and 2 mM salicylhydroxamic acid, an inhibitor of alternative oxidase. No point mutations were detected, either in the complete nucleotide sequences of the cytb gene or in those of the aox and Rieske protein genes of laboratory mutants, whereas all field mutants carried the G143A mutation in the mitochondrial cytb gene. QoI resistance was always maternally inherited in ascospore progeny of sexual crosses of field mutants with sensitive reference strains. CONCLUSIONS The G143A mutation in cytb gene is confirmed to be responsible for field resistance to QoIs in B. fuckeliana. Maternal inheritance of resistance to QoIs in progeny of sexual crosses confirmed that it is caused by extranuclear genetic determinants. In laboratory mutants the heteroplasmic state of mutated mitochondria could likely hamper the G143A detection, otherwise other gene(s) underlying different mechanisms of resistance could be involved.
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Grahl N, Dinamarco TM, Willger SD, Goldman GH, Cramer RA. Aspergillus fumigatus mitochondrial electron transport chain mediates oxidative stress homeostasis, hypoxia responses and fungal pathogenesis. Mol Microbiol 2012; 84:383-99. [PMID: 22443190 DOI: 10.1111/j.1365-2958.2012.08034.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We previously observed that hypoxia is an important component of host microenvironments during pulmonary fungal infections. However, mechanisms of fungal growth in these in vivo hypoxic conditions are poorly understood. Here, we report that mitochondrial respiration is active in hypoxia (1% oxygen) and critical for fungal pathogenesis. We generated Aspergillus fumigatus alternative oxidase (aoxA) and cytochrome C (cycA) null mutants and assessed their ability to tolerate hypoxia, macrophage killing and virulence. In contrast to ΔaoxA, ΔcycA was found to be significantly impaired in conidia germination, growth in normoxia and hypoxia, and displayed attenuated virulence. Intriguingly, loss of cycA results in increased levels of AoxA activity, which results in increased resistance to oxidative stress, macrophage killing and long-term persistence in murine lungs. Thus, our results demonstrate a previously unidentified role for fungal mitochondrial respiration in the pathogenesis of aspergillosis, and lay the foundation for future research into its role in hypoxia signalling and adaptation.
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Affiliation(s)
- Nora Grahl
- Department of Immunology and Infectious Diseases, Montana State University, Bozeman, MT, USA
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Inoue K, Tsurumi T, Ishii H, Park P, Ikeda K. Cytological evaluation of the effect of azoxystrobin and alternative oxidase inhibitors in Botrytis cinerea. FEMS Microbiol Lett 2011; 326:83-90. [PMID: 22092932 DOI: 10.1111/j.1574-6968.2011.02438.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 10/09/2011] [Accepted: 10/10/2011] [Indexed: 11/29/2022] Open
Abstract
Azoxystrobin (AZ), a strobilurin-derived fungicide, is known to inhibit mitochondrial respiration in fungi by blocking the electron transport chain in the inner mitochondrial membrane. Germination was strongly inhibited when Botrytis cinerea spore suspension was treated with AZ and the alternative oxidase (AOX) inhibitors, salicylhydroxamic acid (SHAM) and n-propyl gallate. However, chemical death indicators trypan blue and propidium iodide showed that those spores were still alive. When the spore suspension in the AZ and SHAM solution was replaced with distilled water, the germination rate almost recovered, at least during the first 2 days of incubation with AZ and SHAM solution. No morphological alteration was detected in the cells treated with AZ and SHAM, especially in mitochondria, using transmission electron microscopy. Therefore, simultaneous application of AZ and AOX inhibitors has a fungistatic, rather than a fungicidal, action.
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Affiliation(s)
- Kanako Inoue
- Stress Cytology Laboratory, Graduate School of Agriculture, Kobe University, Kobe, Japan
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Exploring mechanisms of resistance to respiratory inhibitors in field strains of Botrytis cinerea, the causal agent of gray mold. Appl Environ Microbiol 2010; 76:6615-30. [PMID: 20693447 DOI: 10.1128/aem.00931-10] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Respiratory inhibitors are among the fungicides most widely used for disease control on crops. Most are strobilurins and carboxamides, inhibiting the cytochrome b of mitochondrial complex III and the succinate dehydrogenase of mitochondrial complex II, respectively. A few years after the approval of these inhibitors for use on grapevines, field isolates of Botrytis cinerea, the causal agent of gray mold, resistant to one or both of these classes of fungicide were recovered in France and Germany. However, little was known about the mechanisms underlying this resistance in field populations of this fungus. Such knowledge could facilitate resistance risk assessment. The aim of this study was to investigate the mechanisms of resistance occurring in B. cinerea populations. Highly specific resistance to strobilurins was correlated with a single mutation of the cytb target gene. Changes in its intronic structure may also have occurred due to an evolutionary process controlling selection for resistance. Specific resistance to carboxamides was identified for six phenotypes, with various patterns of resistance levels and cross-resistance. Several mutations specific to B. cinerea were identified within the sdhB and sdhD genes encoding the iron-sulfur protein and an anchor protein of the succinate dehydrogenase complex. Another as-yet-uncharacterized mechanism of resistance was also recorded. In addition to target site resistance mechanisms, multidrug resistance, linked to the overexpression of membrane transporters, was identified in strains with low to moderate resistance to several respiratory inhibitors. This diversity of resistance mechanisms makes resistance management difficult and must be taken into account when developing strategies for Botrytis control.
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Gong S, Hao J, Xia Y, Liu X, Li J. Inhibitory effect of bionic fungicide 2-allylphenol on Botrytis cinerea (Pers. ex Fr.) in vitro. PEST MANAGEMENT SCIENCE 2009; 65:1337-1343. [PMID: 19685448 DOI: 10.1002/ps.1820] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
BACKGROUND 2-Allylphenol is a registered fungicide in China to control fungal diseases on tomato, strawberry and apple. It is synthetic and structurally resembles the active ingredient ginkgol isolated from Ginkgo biloba L. bark. 2-Allylphenol has been used in China for 10 years. However, its biochemical mode of action remains unclear. An in vitro study was conducted on the biochemical mechanism of 2-allyphenol inhibiting Botrytis cinerea (Pers. ex Fr.). RESULTS The inhibition was approximately 3 times stronger when the fungus was grown on non-fermentable source, glycerol, than that on a fermentable carbon source, glucose. Inhibition of B. cinerea and Magnaporthe oryzae (Hebert) Barr mycelial growth was markedly potentiated in the presence of salicylhydroxamic acid (SHAM), an inhibitor of mitochondrial alternative oxidase. Furthermore, at 3 h after treatment with 2-allylphenol, oxygen consumption had recovered, but respiration was resistant to potassium cyanide and sensitive to SHAM, indicating that 2-allylphenol had the ability to induce cyanide-resistant respiration. The mycelium inhibited in the presence of 2-allylphenol grew vigorously after being transferred to a fungicide-free medium, indicating that 2-allylphenol is a fungistatic compound. Adenine nucleotide assay showed that 2-allylphenol depleted ATP content and decreased the energy charge values, which confirmed that 2-allylphenol is involved in the impairment of the ATP energy generation system. CONCLUSION These results suggested that 2-allylphenol induces cyanide-resistant respiration and causes ATP decrease, and inhibits respiration by an unidentified mechanism.
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Affiliation(s)
- Shuangjun Gong
- Department of Plant Pathology, College of Agriculture and Biotechnology, China Agricultural University, Beijing 100193, People's Republic of China
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Ishii H, Fountaine J, Chung WH, Kansako M, Nishimura K, Takahashi K, Oshima M. Characterisation of QoI-resistant field isolates of Botrytis cinerea from citrus and strawberry. PEST MANAGEMENT SCIENCE 2009; 65:916-922. [PMID: 19444805 DOI: 10.1002/ps.1773] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
BACKGROUND In 2004, field isolates of Botrytis cinerea Pers. ex Fr., resistant to strobilurin fungicides (QoIs), were first found in commercial citrus orchards in Wakayama Prefecture, Japan. Subsequently, QoI-resistant isolates of this fungus were also detected in plastic strawberry greenhouses in Saga, Ibaraki and Chiba prefectures, Japan. Biological and molecular characterisation of resistant isolates was conducted in this study. RESULTS QoI-resistant isolates of B. cinerea grew well on PDA plates containing kresoxim-methyl or azoxystrobin at 1 mg L(-1), supplemented with 1 mM of n-propyl gallate, an inhibitor of alternative oxidase, whereas the growth of sensitive isolates was strongly suppressed. Results from this in vitro test were in good agreement with those of fungus inoculation tests in vivo. In resistant isolates, the mutation at amino acid position 143 of the cytochrome b gene, known to be the cause of high QoI resistance in various fungal pathogens, was found, but only occasionally. The heteroplasmy of cytochrome b gene was confirmed, and the wild-type sequence often present in the majority of resistant isolates, indicating that the proportion of mutated cytochrome b gene was very low. CONCLUSION The conventional RFLP and sequence analyses of PCR-amplified cytochrome b gene are insufficient for molecular identification of QoI resistance in B. cinerea.
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Affiliation(s)
- Hideo Ishii
- National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki 305-8604, Japan.
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Mendoza L, Espinoza P, Urzua A, Vivanco M, Cotoras M. In vitro antifungal activity of the diterpenoid 7 alpha-hydroxy-8(17)-labden-15-oic acid and its derivatives against Botrytis cinerea. Molecules 2009; 14:1966-79. [PMID: 19512998 PMCID: PMC6254283 DOI: 10.3390/molecules14061966] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 05/14/2009] [Accepted: 05/18/2009] [Indexed: 11/16/2022] Open
Abstract
We investigated the inhibitory effect of the natural diterpenoids, 7α-hydroxy-8(17)-labden-15-oic acid (salvic acid, 1), 7α-acetanoyloxy-8(17)-labden-15-oic acid (acetylsalvic acid, 2) and the hemisynthetic diterpenoids 7α-acyloxy-8(17)-labden-15-oic acids derivatives, 7α-propanoyloxy-8(17)-labden-15-oic acid (propanoylsalvic acid, 3), 7α-butanoyloxy-8(17)-labden-15-oic acid (butanoylsalvic acid, 4) and 7α-isopentanoyloxy-8(17)-labden-15-oic acid (isopentanoylsalvic acid, 5), against Botrytis cinerea. Diterpenoid fungitoxicity was assessed using the radial growth test method. All diterpenoids, with the exception of isopentenoylsalvic acid, inhibited the mycelial growth of B. cinerea in solid media. Shortest side-chain diterpenoids were more effective than the derivatives with longer chains in the inhibition of B. cinerea mycelial growth. The results suggest that hydrophobicity and structural features would be important factors in the antifungal effect of these diterpenoids. Studies on a possible action mechanism of natural diterpenoids, salvic acid and acetylsalvic acid, showed that these diterpenoids exerted their effect by a different mechanism. Salvic acid did not alter cytoplasmic membrane or cause respiratory chain inhibition. Instead, acetylsalvic acid affected the cytoplasmic membrane producing leakage of 260-nm absorbing compounds.
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Affiliation(s)
- Leonora Mendoza
- Facultad de Química y Biología, Universidad de Santiago de Chile, Avenida Bernardo O'Higgins 3363, Santiago, Chile.
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Živić M, Zakrzewska J, Stanić M, Cvetić T, Živanović B. Alternative respiration of fungus Phycomyces blakesleeanus. Antonie van Leeuwenhoek 2009; 95:207-17. [DOI: 10.1007/s10482-008-9304-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 12/22/2008] [Indexed: 10/21/2022]
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Schnabel G, Dait Q, Paradkar MR. Cloning and expression analysis of the ATP-binding cassette transporter gene MFABC1 and the alternative oxidase gene MfAOX1 from Monilinia fructicola. PEST MANAGEMENT SCIENCE 2003; 59:1143-1151. [PMID: 14561072 DOI: 10.1002/ps.744] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Brown rot, caused by Moniliniafructicola (G Wint) Honey, is a serious disease of peach in all commercial peach production areas in the USA, including South Carolina where it has been primarily controlled by pre-harvest application of 14-alpha demethylation (DMI) fungicides for more than 15 years. Recently, the Qo fungicide azoxystrobin was registered for brown rot control and is currently being investigated for its potential as a DMI fungicide rotation partner because of its different mode of action. In an effort to investigate molecular mechanisms of DMI and Qo fungicide resistance in M fructicola, the ABC transporter gene MfABC1 and the alternative oxidase gene MfAOX1 were cloned to study their potential role in conferring fungicide resistance. The MfABC1 gene was 4380 bp in length and contained one intron of 71 bp. The gene revealed high amino acid homologies with atrB from Aspergillus nidulans (Eidam) Winter, an ABC transporter conferring resistance to many fungicides, including DMI fungicides. MfABC1 gene expression was induced after myclobutanil and propiconazole treatment in isolates with low sensitivity to the same fungicides, and in an isolate with high sensitivity to propiconazole. The results suggest that the MfABC1 gene may be a DMI fungicide resistance determinant in M fructicola. The alternative oxidase gene MfAOX1 from M fructicola was cloned and gene expression was analyzed. The MfAOX1 gene was 1077 bp in length and contained two introns of 54 and 67 bp. The amino acid sequence was 63.8, 63.8 and 57.7% identical to alternative oxidases from Venturia inaequalis (Cooke) Winter, Aspergillus niger van Teighem and A nidulans, respectively. MfAOX1 expression in some but not all M fructicola isolates was induced in mycelia treated with azoxystrobin. Azoxystrobin at 2 microg ml(-1) significantly induced MfAOX1 expression in isolates with low MfAOX1 constitutive expression levels.
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Affiliation(s)
- Guido Schnabel
- Department of Plant Pathology and Physiology, 218 Long Hall, Clemson University, Clemson, SC 29634, USA.
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Kim YS, Dixon EW, Vincelli P, Farman ML. Field Resistance to Strobilurin (Q(o)I) Fungicides in Pyricularia grisea Caused by Mutations in the Mitochondrial Cytochrome b Gene. PHYTOPATHOLOGY 2003; 93:891-900. [PMID: 18943171 DOI: 10.1094/phyto.2003.93.7.891] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
ABSTRACT Gray leaf spot caused by Pyricularia grisea is a highly destructive disease of perennial ryegrass turf. Control of gray leaf spot is dependent on the use of preventative fungicide treatments. Strobilurin-based (Q(o)I) fungicides, which inhibit the cytochrome bc(1) respiratory complex, have proven to be very effective against gray leaf spot. However, in August 2000, disease was diagnosed in Q(o)I-treated perennial ryegrass turf on golf courses in Lexington, KY, Champaign, IL, and Bloomington, IL. To determine if resistance was due to a mutation in the fungicide target, the cytochrome b gene (CYTB) was amplified from baseline and resistant isolates. Nucleotide sequence analysis revealed an intronless coding region of 1,179 bp. Isolates that were resistant to Q(o)I fungicides possessed one of two different mutant alleles, each of which carried a single point mutation. The first mutant allele had a guanine-to-cytosine transition at nucleotide position +428, resulting in a replacement of glycine 143 by alanine (G143A). Mutant allele two exhibited a cytosine-to-adenine transversion at position +387, causing a phenylalanine-to-leucine change (F129L). Cleavable amplified polymorphic sequence analysis revealed that neither mutation was present in a collection of baseline isolates collected before Q(o)I fungicide use and indicated that suspected Q(o)I- resistant isolates found in 2001 in Indiana and Maryland possessed the F129L mutation. The Pyricularia grisea isolates possessing the G143A substitution were significantly more resistant to azoxystrobin and trifloxystrobin, in vitro, than those having F129L. DNA fingerprinting of resistant isolates revealed that the mutations occurred in just five genetic backgrounds, suggesting that field resistance to the Q(o)I fungicides in Pyricularia grisea is due to a small number of ancestral mutations.
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Wood PM, Hollomon DW. A critical evaluation of the role of alternative oxidase in the performance of strobilurin and related fungicides acting at the Qo site of complex III. PEST MANAGEMENT SCIENCE 2003; 59:499-511. [PMID: 12741518 DOI: 10.1002/ps.655] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Mitochondrial respiration conserves energy by linking NADH oxidation and electron-coupled proton translocation with ATP synthesis, through a core pathway involving three large protein complexes. Strobilurin fungicides block electron flow through one of these complexes (III), and disrupt energy supply. Despite an essential need for ATP throughout fungal disease development, strobilurins are largely preventative; indeed some diseases are not controlled at all, and several pathogens have quickly developed resistance. Target-site variation is not the only cause of these performance difficulties. Alternative oxidase (AOX) is a strobilurin-insensitive terminal oxidase that allows electrons from ubiquinol to bypass Complex III. Its synthesis is constitutive in some fungi but in many others is induced by inhibition of the main pathway. AOX provides a strobilurin-insensitive pathway for oxidation of NADH. Protons are pumped as electrons flow through Complex I, but energy conservation is less efficient than for the full respiratory chain. Salicylhydroxamic acid (SHAM) is a characteristic inhibitor of AOX, and several studies have explored the potentiation of strobilurin activity by SHAM. We present a kinetic-based model which relates changes in the extent of potentiation during different phases of disease development to a changing importance of energy efficiency. The model provides a framework for understanding the varying efficacy of strobilurin fungicides. In many cases, AOX can limit strobilurin effectiveness once an infection is established, but is unable to interfere significantly with strobilurin action during germination. A less stringent demand for energy efficiency during early disease development could lead to insensitivity towards this class of fungicides. This is discussed in relation to Botrytis cinerea, which is often poorly controlled by strobilurins. Mutations with a similar effect may explain evidence implicating AOX in resistance development in normally well-controlled plant pathogens, such as Venturia inaequalis.
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Affiliation(s)
- Paul M Wood
- Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK.
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Ziogas BN, Markoglou AN, Tzima A. A non-Mendelian inheritance of resistance to strobilurin fungicides in Ustilago maydis. PEST MANAGEMENT SCIENCE 2002; 58:908-916. [PMID: 12233180 DOI: 10.1002/ps.543] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Mutants of Ustilago maydis (DC) Corda with high resistance to azoxystrobin (RF 164 to 4714, based on EC50 values), an inhibitor of mitochondrial electron transport at the cytochrome bc1 complex, were isolated in a mutation frequency of 2.3 x 10(-7) after nitrosoguanidine mutagenesis and selection on media containing 1 microgram ml-1 azoxystrobin in addition to 0.5 mM salicylhydroxamate (SHAM), a specific inhibitor of cyanide-resistant (alternative) respiration. Oxygen uptake in whole cells was strongly inhibited in the wild-type strains by azoxystrobin (1.5 micrograms ml-1) in addition to SHAM (1 mM), but not in the mutant isolates. Genetic analysis with nine such mutant isolates resulted in progeny phenotypes which did not follow Mendelian segregation, but satisfied the criteria of non-Mendelian (cytoplasmic) heredity. In crosses between three mutant isolates with the compatible wild-type strains, the sensitivity was inherited by progeny maternally from the wild-type parent strain (criterion of uniparental inheritance). In crosses between wild-type strains and remaining mutant isolates, a continuous distribution of sensitivity in the progeny was found (criterion of vegetative segregation). The third criterion of cytoplasmic resistance (criterion of intracellular selection) was fulfilled by experiments on the stability of resistance phenotypes. With two exceptions, a reduction of resistance was observed in the mutant strains when they were grown on inhibitor-free medium. Recovery of the high resistance level was observed after they were returned to the selection medium. Cross-resistance studies with other fungicides, which also inhibit electron transport through complex III of respiratory chain, showed that mutations for resistance to azoxystrobin were also responsible for reduced sensitivity to kresoxim-methyl (RF 18 to 1199) and to antimycin-A (RF 20 to 305), which act at the Qo and Qi sites of the cytochrome bc1 complex, respectively. Studies of the fitness of azoxystrobin-resistant isolates showed that these mutations appeared to be pleiotropic, having significant adverse effects on growth in liquid culture and pathogenicity on young corn plants.
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Affiliation(s)
- Basil N Ziogas
- Laboratory of Plant Pathology, Agricultural University of Athens, Votanikos, 118 55 Athens, Greece.
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Leroux P, Fritz R, Debieu D, Albertini C, Lanen C, Bach J, Gredt M, Chapeland F. Mechanisms of resistance to fungicides in field strains of Botrytis cinerea. PEST MANAGEMENT SCIENCE 2002; 58:876-88. [PMID: 12233177 DOI: 10.1002/ps.566] [Citation(s) in RCA: 210] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Field strains of Botrytis cinerea Pers ex Fr, the causal agent of grey mould diseases, were collected from French vineyards between 1993 and 2000. Several phenotypes have been characterized according to the inhibitory effects of fungicides towards germ-tube elongation and mycelial growth. Two types of benzimidazole-resistant strains (Ben R1 and Ben R2) could be detected; negative cross-resistance to phenylcarbamates (e.g. diethofencarb) was only found in Ben R1. Benzimidazole resistance was related to point mutations at codon 198 (Ben R1) or 200 (Ben R2) of the beta-tubulin gene. Most dicarboximide-resistant strains were also weakly resistant to aromatic hydrocarbon fungicides (e.g. dicloran) but remained sensitive to phenylpyrroles (e.g. fludioxonil). These resistant field strains (Imi R1) contained a single base pair mutation at position 365 in a two-component histidine kinase gene, probably involved in the fungal osmoregulation. Three anilinopyrimidine-resistant phenotypes have been identified. In the most resistant one (Ani R1), resistance was restricted to anilinopyrimidines, but no differences were observed in the amino-acid sequences of cystathionine beta-lyase (the potential target site of these fungicides) from Ani R1 or wild-type strains. In the two other phenotypes (Ani R2 and Ani R3), resistance extended to various other groups of fungicide, including dicarboximides, phenylpyrroles and sterol biosynthesis inhibitors. This multi-drug resistance was probably determined by over-production of ATP-binding cassette transporters. The hydroxyanilide fenhexamid is a novel botryticide whose primary target site is the 3-keto reductase involved in sterol C-4 demethylations. Apart from the multi-drug-resistant strain Ani R3, three other fenhexamid-resistant phenotypes have been recognized. For two of them (Hyd R1 and Hyd R2) fenhexamid-resistance seemed to result from P450-mediated detoxification. Reduced sensitivity of the target site could be the putative resistance mechanism operating in the third resistant phenotype (Hyd R3). Increased sensitivity to inhibitors of sterol 14 alpha-demethylase recorded in Hyd R1 strains was related to two amino-acid changes at positions 15 and 105 of this enzyme.
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Affiliation(s)
- Pierre Leroux
- INRA, Unité de Phytopharmacie et Médiateurs Chimiques, 78026 Versailles, France.
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Avila-Adame C, Köller W. Disruption of the alternative oxidase gene in Magnaporthe grisea and its impact on host infection. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2002; 15:493-500. [PMID: 12036280 DOI: 10.1094/mpmi.2002.15.5.493] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Plants and numerous fungi including Magnaporthe grisea protect mitochondria from interference by respiration inhibitors by expressing alternative oxidase, the enzymatic core of alternative respiration. The alternative oxidase gene AOXMg of M. grisea was disrupted. Several lines of evidence suggested that the disruption of AOXMg was sufficient to completely curb the expression of alternative respiration. In the infection of barley leaves, several AOXMg-minus and, thus, alternative respiration-deficient mutants of M. grisea retained their pathogenicity without significant impairment of virulence. However, differences between the wild-type strain and an AOXMg-minus mutant were apparent under oxidative stress conditions generated by the treatment of infected barley leaves with the commercial respiration inhibitor azoxystrobin. Symptom development was effectively suppressed on leaves infected with the alternative respiration-deficient mutant, while lesions on leaves infected with the wild-type strain continued to develop at much higher inhibitor doses. However, respective lesions rarely developed to the stage of full maturity. The results did not conform to a previous model implying that expression of alternative respiration is silenced during pathogenesis by the presence of constitutive plant antioxidants. Rather, alternative respiration provided protection from azoxystrobin during both saprophytic and infectious stages of the pathogen. The nature of similar oxidative stress conditions in the ecology of M. grisea remains an open question.
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Affiliation(s)
- Cruz Avila-Adame
- Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456, USA
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Steinfeld U, Sierotzki H, Parisi S, Poirey S, Gisi U. Sensitivity of mitochondrial respiration to different inhibitors in Venturia inaequalis. PEST MANAGEMENT SCIENCE 2001; 57:787-796. [PMID: 11561403 DOI: 10.1002/ps.356] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The sensitivity of Venturia inaequalis field isolates to inhibitors of the cytochrome bc1 complex at the Qo site (QoIs) was characterised at the molecular, biochemical and physiological level, and compared to other respiration inhibitors. Comparison of a sensitive and a QoI-resistant isolate revealed very high resistance factors both in mycelium growth and spore germination assays. Cross-resistance was observed among QoIs such as trifloxystrobin, azoxystrobin, famoxadone, strobilurin B and myxothiazol. In the mycelium growth assay, antimycin A, an inhibitor of the cytochrome bc1 complex at the Qi site, was less active against the QoI-resistant than against the sensitive isolate. The mixture of QoIs with salicylhydroxamic acid (SHAM), an inhibitor of the alternative oxidase, exerted synergistic effects in the spore germination but not in the mycelium growth assay. Thus, the cytochrome and the alternative respiration pathways are assumed to play different roles, depending on the developmental stage of the fungus. Induction of alternative oxidase (AOX) by trifloxystrobin was observed in mycelium cells at the molecular level for the sensitive but not the resistant isolate. Following QoI treatment, respiration parameters such as oxygen consumption, ATP level, membrane potential and succinate dehydrogenase activity were only slightly reduced in Qo-resistant mycelium cells, and remained at much higher levels than in sensitive cells. In contrast, no difference was observed between sensitive and resistant isolates when NADH consumption was measured. Comparison of the cytochrome b (cyt b) gene of the sensitive and resistant isolates did not reveal any point mutations as is known to occur in resistant isolates of other plant pathogens. It is assumed that QoI resistance in V inaequalis may be based on a compensation of the energy deficiency following QoI application upstream of the NADH dehydrogenase of the respiratory chain.
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Affiliation(s)
- U Steinfeld
- Syngenta Crop Protection, Research Biology, 4332 Stein, Switzerland
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Mayer AM, Staples RC, Gil-ad NL. Mechanisms of survival of necrotrophic fungal plant pathogens in hosts expressing the hypersensitive response. PHYTOCHEMISTRY 2001; 58:33-41. [PMID: 11524110 DOI: 10.1016/s0031-9422(01)00187-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The hypersensitive response (HR), elicited when resistant hosts are infected by incompatible races of biotrophic fungi, has been researched extensively. New studies on host responses to necrotrophic fungi are beginning to show that when the HR occurs in hosts colonized by necrotrophs, fungal growth is accelerated rather than retarded. We review current knowledge about how necrotrophs survive in host plants in which the HR is expressed. We discuss how necrotrophs cope with the environmental factors formed as a result of the HR. Necrotrophs contain an array of enzymes, which can help in exploiting the hostile environment in order to colonize the host and to remove or inactivate active oxygen species (AOS). Among this array of enzymes are superoxide dismutase (SOD), peroxidases, catalase, and perhaps laccases and polyphenol oxidases. Of these, only SOD and catalase have been studied in any detail. The precise significance of SOD and catalase in host invasion and fungal resistance is still not adequately known. The importance of different peroxidases is also still far from clear. We speculate that AOS species may trigger the response of necrotrophs to the host environment.
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Affiliation(s)
- A M Mayer
- Department of Botany, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat Ram Campus, Jerusalem 91904, Israel.
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Joseph-Horne T, Hollomon DW, Wood PM. Fungal respiration: a fusion of standard and alternative components. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1504:179-95. [PMID: 11245784 DOI: 10.1016/s0005-2728(00)00251-6] [Citation(s) in RCA: 227] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In animals, electron transfer from NADH to molecular oxygen proceeds via large respiratory complexes in a linear respiratory chain. In contrast, most fungi utilise branched respiratory chains. These consist of alternative NADH dehydrogenases, which catalyse rotenone insensitive oxidation of matrix NADH or enable cytoplasmic NADH to be used directly. Many also contain an alternative oxidase that probably accepts electrons directly from ubiquinol. A few fungi lack Complex I. Although the alternative components are non-energy conserving, their organisation within the fungal electron transfer chain ensures that the transfer of electrons from NADH to molecular oxygen is generally coupled to proton translocation through at least one site. The alternative oxidase enables respiration to continue in the presence of inhibitors for ubiquinol:cytochrome c oxidoreductase and cytochrome c oxidase. This may be particularly important for fungal pathogens, since host defence mechanisms often involve nitric oxide, which, whilst being a potent inhibitor of cytochrome c oxidase, has no inhibitory effect on alternative oxidase. Alternative NADH dehydrogenases may avoid the active oxygen production associated with Complex I. The expression and activity regulation of alternative components responds to factors ranging from oxidative stress to the stage of fungal development.
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Affiliation(s)
- T Joseph-Horne
- Department of Biochemistry, School of Biomedical Sciences, University of Bristol, UK.
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Karaffa L, Váczy K, Sándor E, Biró S, Szentirmai A, Pócsi I. Cyanide-resistant alternative respiration is strictly correlated to intracellular peroxide levels in Acremonium chrysogenum. Free Radic Res 2001; 34:405-16. [PMID: 11328676 DOI: 10.1080/10715760100300341] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
A strict correlation between the intensity of the cyanide-resistant alternative respiratory pathway and the intracellular peroxide levels in the cephalosporin C producer filamentous fungus Acremonium chrysogenum was demonstrated. Intracellular peroxide levels increased in a dose-dependent manner after addition of H2O2 to the culture media. A similar phenomenon was observed due to the specific inhibition of catalase by salicylic acid. In both cases, cyanide-resistant respiration was markedly stimulated. On the other hand, both cyanide-resistant respiration and intracellular peroxide levels were effectively suppressed by the lipid peroxyl radical scavenger DL-alpha-tocopherol, which breaks lipid peroxidation chains effectively. Our findings firmly supported the assumption that there is a connection between the intracellular peroxide levels and the intensity of the alternative respiratory pathway in fungi.
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Affiliation(s)
- L Karaffa
- Department of Microbiology and Biotechnology Faculty of Sciences University of Debrecen P.O. Box 63, H-4010, Debrecen, Hungary.
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Joseph-Horne T, Babij J, Wood PM, Hollomon D, Sessions RB. New sequence data enable modelling of the fungal alternative oxidase and explain an absence of regulation by pyruvate. FEBS Lett 2000; 481:141-6. [PMID: 10996313 DOI: 10.1016/s0014-5793(00)01943-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Respiratory rates involving the alternative oxidase (AO) were studied in mitochondria from Tapesia acuformis. There was no evidence for regulation by pyruvate, in contrast with plant AO. The site of interaction of pyruvate with the plant AO is a conserved cysteine. The primary sequence was obtained for AO from Magnaporthe grisea and compared with four published sequences for fungal AO. In all cases this cysteine was absent. Sequence data were obtained for the C-terminal domain of a further five fungal AOs. In this region the fungal sequences were all consistent with a four-helix, di-iron binding structure as in the ferritin-fold family. A molecular model of this domain was deduced from the structure of Delta-9 desaturase. This is in general agreement with that developed for plant AOs, despite very low sequence identity between the two kingdoms. Further modelling indicated an appropriate active site for binding of ubiquinol, required in the AO redox reaction.
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Affiliation(s)
- T Joseph-Horne
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, UK
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Affourtit C, Heaney SP, Moore AL. Mitochondrial electron transfer in the wheat pathogenic fungus Septoria tritici: on the role of alternative respiratory enzymes in fungicide resistance. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1459:291-8. [PMID: 11004442 DOI: 10.1016/s0005-2728(00)00157-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Certain phytopathogenic fungi are able to express alternative NADH- and quinol-oxidising enzymes that are insensitive to inhibitors of the mitochondrial respiratory Complexes I and III. To assess the extent to which such enzymes confer tolerance to respiration-targeted fungicides, an understanding of mitochondrial electron transfer in these species is required. An isolation procedure has been developed which results in intact, active and coupled mitochondria from the wheat pathogen Septoria tritici, as evidenced by morphological and kinetic data. Exogenous NADH, succinate and malate/glutamate are readily oxidised, the latter activity being only partly (approx. 70%) sensitive to rotenone. Of particular importance was the finding that azoxystrobin (a strobilurin fungicide) potently inhibits fungal respiration at the level of Complex III. In some S. tritici strains investigated, a small but significant part of the respiratory activity (approx. 10%) is insensitive to antimycin A and azoxystrobin. Such resistant activity is sensitive to octyl gallate, a specific inhibitor of the plant alternative oxidase. This enzyme, however, could not be detected immunologically. On the basis of the above findings, a conceptual mitochondrial electron transfer chain is presented. Data are discussed in terms of developmental and environmental regulation of the composition of this chain.
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Affiliation(s)
- C Affourtit
- Department of Biochemistry, University of Sussex, Brighton, UK.
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