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Chen Y, Cao Y, Jiao C, Sun X, Gai Y, Zhu Z, Li H. The Alternaria alternata StuA transcription factor interacting with the pH-responsive regulator PacC for the biosynthesis of host-selective toxin and virulence in citrus. Microbiol Spectr 2023; 11:e0233523. [PMID: 37812002 PMCID: PMC10715145 DOI: 10.1128/spectrum.02335-23] [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: 06/04/2023] [Accepted: 08/19/2023] [Indexed: 10/10/2023] Open
Abstract
IMPORTANCE In this study, we used Alternaria alternata as a biological model to report the role of StuA in phytopathogenic fungi. Our findings indicated that StuA is required for Alternaria citri toxin (ACT) biosynthesis and fungal virulence. In addition, StuA physically interacts with PacC. Disruption of stuA or pacC led to decreased expression of seven toxin biosynthetic genes (ACCT) and toxin production. PacC could recognize and bind to the promoter regions of ACTT6 and ACTTR. Our results revealed a previously unrecognized (StuA-PacC)→ACTTR module for the biosynthesis of ACT in A. alternata, which also provides a framework for the study of StuA in other fungi.
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Affiliation(s)
- Yanan Chen
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou, China
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang Agriculture & Forestry University, Hangzhou, China
| | - Yingzi Cao
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Chen Jiao
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Xuepeng Sun
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang Agriculture & Forestry University, Hangzhou, China
| | - Yunpeng Gai
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou, China
| | - Zengrong Zhu
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou, China
- Hainan Institute, Zhejiang University, Sanya, China
| | - Hongye Li
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou, China
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Rovetto EI, Luz C, La Spada F, Meca G, Riolo M, Cacciola SO. Diversity of Mycotoxins and Other Secondary Metabolites Recovered from Blood Oranges Infected by Colletotrichum, Alternaria, and Penicillium Species. Toxins (Basel) 2023; 15:407. [PMID: 37505676 PMCID: PMC10467077 DOI: 10.3390/toxins15070407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 06/12/2023] [Accepted: 06/19/2023] [Indexed: 07/29/2023] Open
Abstract
This study identified secondary metabolites produced by Alternaria alternata, Colletotrichum gloeosporioides, and Penicillium digitatum in fruits of two blood orange cultivars before harvest. Analysis was performed by UHPLC-Q-TOF-MS. Three types of fruits were selected, asymptomatic, symptomatic showing necrotic lesions caused by hail, and mummified. Extracts from peel and juice were analyzed separately. Penicillium digitatum was the prevalent species recovered from mummified and hail-injured fruits. Among 47 secondary metabolites identified, 16, 18, and 13 were of A. alternata, C. gloeosporioides, and P. digitatum, respectively. Consistently with isolations, indicating the presence of these fungi also in asymptomatic fruits, the metabolic profiles of the peel of hail-injured and asymptomatic fruits did not differ substantially. Major differences were found in the profiles of juice from hail-injured and mummified fruits, such as a significant higher presence of 5,4-dihydroxy-3,7,8-trimethoxy-6C-methylflavone and Atrovenetin, particularly in the juice of mummified fruits of the Tarocco Lempso cultivar. Moreover, the mycotoxins patulin and Rubratoxin B were detected exclusively in mummified fruits. Patulin was detected in both the juice and peel, with a higher relative abundance in the juice, while Rubratoxin B was detected only in the juice. These findings provide basic information for evaluating and preventing the risk of contamination by mycotoxins in the citrus fresh fruit supply chain and juice industry.
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Affiliation(s)
- Ermes Ivan Rovetto
- Department of Agriculture, Food and Environment, University of Catania, 95123 Catania, Italy; (E.I.R.); (F.L.S.)
| | - Carlos Luz
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy, University of Valencia, Burjassot, 460100 València, Spain; (C.L.); (G.M.)
| | - Federico La Spada
- Department of Agriculture, Food and Environment, University of Catania, 95123 Catania, Italy; (E.I.R.); (F.L.S.)
| | - Giuseppe Meca
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy, University of Valencia, Burjassot, 460100 València, Spain; (C.L.); (G.M.)
| | - Mario Riolo
- Department of Agriculture, Food and Environment, University of Catania, 95123 Catania, Italy; (E.I.R.); (F.L.S.)
- Laboratory of Food Chemistry and Toxicology, Faculty of Pharmacy, University of Valencia, Burjassot, 460100 València, Spain; (C.L.); (G.M.)
| | - Santa Olga Cacciola
- Department of Agriculture, Food and Environment, University of Catania, 95123 Catania, Italy; (E.I.R.); (F.L.S.)
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Meng S, Huang S, Liu J, Gai Y, Li M, Duan S, Zhang S, Sun X, Yang Q, Wang Y, Xu K, Ma H. Histone Methylation Is Required for Virulence, Conidiation, and Multi-Stress Resistance of Alternaria alternata. Front Microbiol 2022; 13:924476. [PMID: 35783406 PMCID: PMC9245015 DOI: 10.3389/fmicb.2022.924476] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 05/24/2022] [Indexed: 11/22/2022] Open
Abstract
Histone methylation, which is critical for transcriptional regulation and various biological processes in eukaryotes, is a reversible dynamic process regulated by histone methyltransferases (HMTs) and histone demethylases (HDMs). This study determined the function of 5 HMTs (AaDot1, AaHMT1, AaHnrnp, AaSet1, and AaSet2) and 1 HDMs (AaGhd2) in the phytopathogenic fungus Alternaria alternata by analyzing targeted gene deletion mutants. The vegetative growth, conidiation, and pathogenicity of ∆AaSet1 and ∆AaSet2 were severely inhibited indicating that AaSet1 and AaSet2 play critical roles in cell development in A. alternata. Multiple stresses analysis revealed that both AaSet1 and AaSet2 were involved in the adaptation to cell wall interference agents and osmotic stress. Meanwhile, ∆AaSet1 and ∆AaSet2 displayed serious vegetative growth defects in sole carbon source medium, indicating that AaSet1 and AaSet2 play an important role in carbon source utilization. In addition, ∆AaSet2 colony displayed white in color, while the wild-type colony was dark brown, indicating AaSet2 is an essential gene for melanin biosynthesis in A. alternata. AaSet2 was required for the resistance to oxidative stress. On the other hand, all of ∆AaDot1, ∆AaHMT1, and ∆AaGhd2 mutants displayed wild-type phenotype in vegetative growth, multi-stress resistance, pathogenicity, carbon source utilization, and melanin biosynthesis. To explore the regulatory mechanism of AaSet1 and AaSet2, RNA-seq of these mutants and wild-type strain was performed. Phenotypes mentioned above correlated well with the differentially expressed genes in ∆AaSet1 and ∆AaSet2 according to the KEGG and GO enrichment results. Overall, our study provides genetic evidence that defines the central role of HMTs and HDMs in the pathological and biological functions of A. alternata.
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Affiliation(s)
- Shuai Meng
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, China
| | - Suya Huang
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, China
| | - Jinhua Liu
- Natural Medicine Institute of Zhejiang YangShengTang Co., LTD, Hangzhou, China
| | - Yunpeng Gai
- School of Grassland Science, Beijing Forestry University, Beijing, China
| | - Min Li
- China-USA Citrus Huanglongbing Joint Laboratory (GNU-UF Joint Lab), National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Shuo Duan
- China-USA Citrus Huanglongbing Joint Laboratory (GNU-UF Joint Lab), National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China
| | - Shuting Zhang
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, China
| | - Xuepeng Sun
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, China
| | - Qi Yang
- Linyi Inspection and Testing Center, Linyi, China
| | - Yuchun Wang
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, China
| | - Kai Xu
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, China
| | - Haijie Ma
- Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, China
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Falter C, Reumann S. The essential role of fungal peroxisomes in plant infection. MOLECULAR PLANT PATHOLOGY 2022; 23:781-794. [PMID: 35001508 PMCID: PMC9104257 DOI: 10.1111/mpp.13180] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 12/06/2021] [Accepted: 12/06/2021] [Indexed: 06/09/2023]
Abstract
Several filamentous fungi are ecologically and economically important plant pathogens that infect a broad variety of crops. They cause high annual yield losses and contaminate seeds and fruits with mycotoxins. Not only powerful infection structures and detrimental toxins, but also cell organelles, such as peroxisomes, play important roles in plant infection. In this review, we summarize recent research results that revealed novel peroxisomal functions of filamentous fungi and highlight the importance of peroxisomes for infection of host plants. Central for fungal virulence are two primary metabolic pathways, fatty acid β-oxidation and the glyoxylate cycle, both of which are required to produce energy, acetyl-CoA, and carbohydrates. These are ultimately needed for the synthesis of cell wall polymers and for turgor generation in infection structures. Most novel results stem from different routes of secondary metabolism and demonstrate that peroxisomes produce important precursors and house various enzymes needed for toxin production and melanization of appressoria. All these peroxisomal functions in fungal virulence might represent elegant targets for improved crop protection.
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Affiliation(s)
- Christian Falter
- Plant Biochemistry and Infection BiologyInstitute of Plant Science and MicrobiologyUniversität HamburgHamburgGermany
| | - Sigrun Reumann
- Plant Biochemistry and Infection BiologyInstitute of Plant Science and MicrobiologyUniversität HamburgHamburgGermany
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Wang H, Guo Y, Luo Z, Gao L, Li R, Zhang Y, Kalaji HM, Qiang S, Chen S. Recent Advances in Alternaria Phytotoxins: A Review of Their Occurrence, Structure, Bioactivity and Biosynthesis. J Fungi (Basel) 2022; 8:jof8020168. [PMID: 35205922 PMCID: PMC8878860 DOI: 10.3390/jof8020168] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/06/2022] [Accepted: 02/07/2022] [Indexed: 12/04/2022] Open
Abstract
Alternaria is a ubiquitous fungal genus in many ecosystems, consisting of species and strains that can be saprophytic, endophytic, or pathogenic to plants or animals, including humans. Alternaria species can produce a variety of secondary metabolites (SMs), especially low molecular weight toxins. Based on the characteristics of host plant susceptibility or resistance to the toxin, Alternaria phytotoxins are classified into host-selective toxins (HSTs) and non-host-selective toxins (NHSTs). These Alternaria toxins exhibit a variety of biological activities such as phytotoxic, cytotoxic, and antimicrobial properties. Generally, HSTs are toxic to host plants and can cause severe economic losses. Some NHSTs such as alternariol, altenariol methyl-ether, and altertoxins also show high cytotoxic and mutagenic activities in the exposed human or other vertebrate species. Thus, Alternaria toxins are meaningful for drug and pesticide development. For example, AAL-toxin, maculosin, tentoxin, and tenuazonic acid have potential to be developed as bioherbicides due to their excellent herbicidal activity. Like altersolanol A, bostrycin, and brefeldin A, they exhibit anticancer activity, and ATX V shows high activity to inhibit the HIV-1 virus. This review focuses on the classification, chemical structure, occurrence, bioactivity, and biosynthesis of the major Alternaria phytotoxins, including 30 HSTs and 50 NHSTs discovered to date.
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Affiliation(s)
- He Wang
- Weed Research Laboratory, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China; (H.W.); (Y.G.); (Z.L.); (L.G.); (Y.Z.); (S.Q.)
| | - Yanjing Guo
- Weed Research Laboratory, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China; (H.W.); (Y.G.); (Z.L.); (L.G.); (Y.Z.); (S.Q.)
| | - Zhi Luo
- Weed Research Laboratory, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China; (H.W.); (Y.G.); (Z.L.); (L.G.); (Y.Z.); (S.Q.)
| | - Liwen Gao
- Weed Research Laboratory, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China; (H.W.); (Y.G.); (Z.L.); (L.G.); (Y.Z.); (S.Q.)
| | - Rui Li
- Agricultural and Animal Husbandry Ecology and Resource Protection Center, Ordos Agriculture and Animal Husbandry Bureau, Ordos 017010, China;
| | - Yaxin Zhang
- Weed Research Laboratory, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China; (H.W.); (Y.G.); (Z.L.); (L.G.); (Y.Z.); (S.Q.)
| | - Hazem M. Kalaji
- Department of Plant Physiology, Institute of Biology, Warsaw University of Life Sciences SGGW, 159 Nowoursynowska 159, 02-776 Warsaw, Poland;
- Institute of Technology and Life Sciences—National Research Institute, Falenty, Al. Hrabska 3, 05-090 Raszyn, Poland
| | - Sheng Qiang
- Weed Research Laboratory, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China; (H.W.); (Y.G.); (Z.L.); (L.G.); (Y.Z.); (S.Q.)
| | - Shiguo Chen
- Weed Research Laboratory, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China; (H.W.); (Y.G.); (Z.L.); (L.G.); (Y.Z.); (S.Q.)
- Correspondence: ; Tel.: +86-25-84395117
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Camiletti BX, Lichtemberg PS, Paredes JA, Carraro TA, Velascos J, Michailides TJ. Characterization, pathogenicity, and fungicide sensitivity of Alternaria isolates associated with preharvest fruit drop in California citrus. Fungal Biol 2022; 126:277-289. [DOI: 10.1016/j.funbio.2022.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/27/2022] [Accepted: 02/21/2022] [Indexed: 11/04/2022]
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He Y, Zhou J, Fu R, Liu Y, Wang Y, Liu H, Zhao J, Cui Y, Jiao B. The application of DNA-HRP functionalized AuNP probes in colorimetric detection of citrus-associated Alternaria genes. Talanta 2022; 237:122917. [PMID: 34736653 DOI: 10.1016/j.talanta.2021.122917] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 09/22/2021] [Accepted: 09/29/2021] [Indexed: 01/03/2023]
Abstract
The monitoring of the fungal genus Alternaria, which causes destructive brown spot disease in citruses worldwide and produces highly toxic mycotoxins, is extremely important to protect citrus and human health. In this work, we describe an ultrasensitive colorimetric method for the detection of genomic DNA of Alternaria from citrus fruit samples, using a system consisting of five groups of reporter probes. Each reporter probe is prepared by coupling recognition DNA and horseradish peroxidase (HRP) on the surface of gold nanoparticle (AuNP) through a convenient and low-cost freezing-assisted method. Meanwhile, the capture DNA is immobilized on magnetic bead (MB) via biotin-streptavidin reaction. Then, the capture DNA, target DNA, and five groups of AuNP-based reporter probes form a stable DNA-heptamer sandwich structure on the MB, and then HRP generates a blue signal for the subsequent colorimetric detection. It should be noted that AuNP with a large specific surface area drives abundant HRP anchoring, resulting in significant signal amplification. In addition, there are five groups of AuNP-based reporter probes, which further amplify the detection signal. As a result, the detection limit of the artificial target DNA is as low as 15.6 pM. Because the detection signal can be recorded visually without any special equipment, and its sensitivity is high, this method represents a suitable diagnostic tool for Alternaria genetic detection.
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Affiliation(s)
- Yue He
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China.
| | - Jing Zhou
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China
| | - Ruijie Fu
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China
| | - Yanlin Liu
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China
| | - Yiwen Wang
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China
| | - Haoran Liu
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China
| | - Jing Zhao
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China
| | - Yongliang Cui
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China
| | - Bining Jiao
- Laboratory of Quality & Safety Risk Assessment for Citrus Products (Chongqing), Ministry of Agriculture, Citrus Research Institute, Southwest University, Chongqing, 400712, PR China; National Citrus Engineering Research Center, Chongqing, 400712, PR China.
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Chen Y, Cao Y, Gai Y, Ma H, Zhu Z, Chung KR, Li H. Genome-Wide Identification and Functional Characterization of GATA Transcription Factor Gene Family in Alternaria alternata. J Fungi (Basel) 2021; 7:jof7121013. [PMID: 34946995 PMCID: PMC8706292 DOI: 10.3390/jof7121013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 11/18/2021] [Accepted: 11/23/2021] [Indexed: 12/19/2022] Open
Abstract
In the present study, we identified six GATA transcription factors (AaAreA, AaAreB, AaLreA, AaLreB, AaNsdD, and AaSreA) and characterized their functions in response to environmental stress and virulence in the tangerine pathotype of Alternaria alternata. The targeted gene knockout of each of the GATA-coding genes decreased the growth to varying degrees. The mutation of AaAreA, AaAreB, AaLreB, or AaNsdD decreased the conidiation. All the GATA transcription factors were found to be required for tolerance to cumyl hydroperoxide and tert-butyl-hydroperoxide (oxidants) and Congo red (a cell-wall-destructing agent). Pathogenicity assays assessed on detached citrus leaves revealed that mutations of AaAreA, AaLreA, AaLreB, or AaNsdD significantly decreased the fungal virulence. A comparative transcriptome analysis between the ∆AreA mutant and the wild-type strain revealed that the inactivation of AaAreA led to alterations in the expression of genes involved in a number of biological processes, including oxidoreductase activity, amino acid metabolism, and secondary metabolite biogenesis. Taken together, our findings revealed that GATA-coding genes play diverse roles in response to environmental stress and are important regulators involved in fungal development, conidiation, ROS detoxification, as well as pathogenesis. This study, for the first time, systemically underlines the critical role of GATA transcription factors in response to environmental stress and virulence in A. alternata.
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Affiliation(s)
- Yanan Chen
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture and Rural Affairs, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Y.C.); (Y.C.); (Y.G.); (H.M.); (Z.Z.)
| | - Yingzi Cao
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture and Rural Affairs, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Y.C.); (Y.C.); (Y.G.); (H.M.); (Z.Z.)
| | - Yunpeng Gai
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture and Rural Affairs, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Y.C.); (Y.C.); (Y.G.); (H.M.); (Z.Z.)
| | - Haijie Ma
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture and Rural Affairs, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Y.C.); (Y.C.); (Y.G.); (H.M.); (Z.Z.)
- School of Agriculture and Food Sciences, Zhejiang Agriculture & Forestry University, Hangzhou 311300, China
| | - Zengrong Zhu
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture and Rural Affairs, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Y.C.); (Y.C.); (Y.G.); (H.M.); (Z.Z.)
- Hainan Institute, Zhejiang University, Sanya 572000, China
| | - Kuang-Ren Chung
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung 40227, Taiwan;
| | - Hongye Li
- The Key Laboratory of Molecular Biology of Crop Pathogens and Insects of Ministry of Agriculture and Rural Affairs, The Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China; (Y.C.); (Y.C.); (Y.G.); (H.M.); (Z.Z.)
- Correspondence: ; Tel.: +86-13634190823
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Zelmat L, Mansi JM, Aouzal S, Gaboun F, Khayi S, Ibriz M, El Guilli M, Mentag R. Genetic Diversity and Population Structure of Moroccan Isolates Belong to Alternaria spp. Causing Black Rot and Brown Spot in Citrus. Int J Genomics 2021; 2021:9976969. [PMID: 34859097 PMCID: PMC8632404 DOI: 10.1155/2021/9976969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 09/21/2021] [Accepted: 10/12/2021] [Indexed: 11/23/2022] Open
Abstract
Alternaria alternata is one of the most important fungi causing various diseases on citrus worldwide. In Morocco, Alternaria black rot (ABR) and Alternaria brown spot (ABS) are two major diseases causing serious losses in commercial cultivars of citrus. The aim of the present work was to study the genetic diversity and the population structure of isolates belonging to sect. Alternaria obtained from infected citrus fruits, collected from seven provinces at different locations in Morocco (markets, packinghouses, and orchards). Forty-five isolates were analyzed by sequence-related amplified polymorphism (SRAP) markers, and cluster analysis of DNA fragments was performed using UPGMA method and Jaccard coefficient. Cluster analysis revealed that isolates were classified in four distinct groups. AMOVA revealed also a large extent of variation within sect. Alternaria isolates (99%). The results demonstrate that no correlation was found among SRAP pattern, host, and geographical origin of these isolates. Population structure analyses showed that the Alternaria isolates from the same collection origin had almost a similar level of admixture.
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Affiliation(s)
- Lamyaa Zelmat
- Plant Pathology and Postharvest Quality laboratory, Plant Protection Research Unit, Regional Center of Agricultural Research of Kénitra, National Institue of Agricultural Research, El Menzeh Km 9, 14000, Kénitra, Morocco
- Biotechnology Research Unit, Regional Center of Agricultural Research of Rabat, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, 10090, Rabat, Morocco
- Department of Biology, Genetics and Biometrics Laboratory, Faculty of Sciences, Ibn Tofail University, Kénitra, Morocco
| | - Joseph Mbasani Mansi
- Biotechnology Research Unit, Regional Center of Agricultural Research of Rabat, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, 10090, Rabat, Morocco
- Department of Biology, Higher Institute of Medical Techniques (ISTM) Kinshasa, Democratic Republic of the Congo
| | - Sarra Aouzal
- Biotechnology Research Unit, Regional Center of Agricultural Research of Rabat, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, 10090, Rabat, Morocco
- Agro-Food and Health Laboratory, Faculty of Science and Techniques, Hassan First University of Settat, Settat, Morocco
| | - Fatima Gaboun
- Biotechnology Research Unit, Regional Center of Agricultural Research of Rabat, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, 10090, Rabat, Morocco
| | - Slimane Khayi
- Biotechnology Research Unit, Regional Center of Agricultural Research of Rabat, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, 10090, Rabat, Morocco
| | - Mohammed Ibriz
- Department of Biology, Genetics and Biometrics Laboratory, Faculty of Sciences, Ibn Tofail University, Kénitra, Morocco
| | - Mohammed El Guilli
- Plant Pathology and Postharvest Quality laboratory, Plant Protection Research Unit, Regional Center of Agricultural Research of Kénitra, National Institue of Agricultural Research, El Menzeh Km 9, 14000, Kénitra, Morocco
| | - Rachid Mentag
- Biotechnology Research Unit, Regional Center of Agricultural Research of Rabat, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, 10090, Rabat, Morocco
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10
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Witte TE, Villeneuve N, Boddy CN, Overy DP. Accessory Chromosome-Acquired Secondary Metabolism in Plant Pathogenic Fungi: The Evolution of Biotrophs Into Host-Specific Pathogens. Front Microbiol 2021; 12:664276. [PMID: 33968000 PMCID: PMC8102738 DOI: 10.3389/fmicb.2021.664276] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 03/09/2021] [Indexed: 11/25/2022] Open
Abstract
Accessory chromosomes are strain- or pathotype-specific chromosomes that exist in addition to the core chromosomes of a species and are generally not considered essential to the survival of the organism. Among pathogenic fungal species, accessory chromosomes harbor pathogenicity or virulence factor genes, several of which are known to encode for secondary metabolites that are involved in plant tissue invasion. Accessory chromosomes are of particular interest due to their capacity for horizontal transfer between strains and their dynamic "crosstalk" with core chromosomes. This review focuses exclusively on secondary metabolism (including mycotoxin biosynthesis) associated with accessory chromosomes in filamentous fungi and the role accessory chromosomes play in the evolution of secondary metabolite gene clusters. Untargeted metabolomics profiling in conjunction with genome sequencing provides an effective means of linking secondary metabolite products with their respective biosynthetic gene clusters that reside on accessory chromosomes. While the majority of literature describing accessory chromosome-associated toxin biosynthesis comes from studies of Alternaria pathotypes, the recent discovery of accessory chromosome-associated biosynthetic genes in Fusarium species offer fresh insights into the evolution of biosynthetic enzymes such as non-ribosomal peptide synthetases (NRPSs), polyketide synthases (PKSs) and regulatory mechanisms governing their expression.
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Affiliation(s)
- Thomas E. Witte
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, Canada
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, Canada
| | - Nicolas Villeneuve
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, Canada
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, Canada
| | - Christopher N. Boddy
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, Canada
| | - David P. Overy
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre, Ottawa, ON, Canada
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11
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Wu PC, Chen CW, Choo CYL, Chen YK, Yago JI, Chung KR. Proper Functions of Peroxisomes Are Vital for Pathogenesis of Citrus Brown Spot Disease Caused by Alternaria alternata. J Fungi (Basel) 2020; 6:jof6040248. [PMID: 33114679 PMCID: PMC7712655 DOI: 10.3390/jof6040248] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/14/2020] [Accepted: 10/24/2020] [Indexed: 11/27/2022] Open
Abstract
In addition to the production of a host-selective toxin, the tangerine pathotype of Alternaria alternata must conquer toxic reactive oxygen species (ROS) in order to colonize host plants. The roles of a peroxin 6-coding gene (pex6) implicated in protein import into peroxisomes was functionally characterized to gain a better understanding of molecular mechanisms in ROS resistance and fungal pathogenicity. The peroxisome is a vital organelle involved in metabolisms of fatty acids and hydrogen peroxide in eukaryotes. Targeted deletion of pex6 had no impacts on the biogenesis of peroxisomes and cellular resistance to ROS. The pex6 deficient mutant (Δpex6) reduced toxin production by 40% compared to wild type and barely induce necrotic lesions on citrus leaves. Co-inoculation of purified toxin with Δpex6 conidia on citrus leaves, however, failed to fully restore lesion formation, indicating that toxin only partially contributed to the loss of Δpex6 pathogenicity. Δpex6 conidia germinated poorly and formed fewer appressorium-like structures (nonmelanized enlargement of hyphal tips) than wild type. Δpex6 hyphae grew slowly and failed to penetrate beyond the epidermal layers. Moreover, Δpex6 had thinner cell walls and lower viability. All of these defects resulting from deletion of pex6 could also account for the loss of Δpex6 pathogenicity. Overall, our results have demonstrated that proper peroxisome functions are of vital importance to pathogenesis of the tangerine pathotype of A. alternata.
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Affiliation(s)
- Pei-Ching Wu
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung 40227, Taiwan; (C.-W.C.); (C.Y.L.C.); (Y.-K.C.)
- Correspondence: (P.-C.W.); (K.-R.C.); Tel.: +886-4-22840780 (ext. 316) (P.-C.W.); +886-4-22840780 (ext. 301) (K.-R.C.)
| | - Chia-Wen Chen
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung 40227, Taiwan; (C.-W.C.); (C.Y.L.C.); (Y.-K.C.)
| | - Celine Yen Ling Choo
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung 40227, Taiwan; (C.-W.C.); (C.Y.L.C.); (Y.-K.C.)
| | - Yu-Kun Chen
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung 40227, Taiwan; (C.-W.C.); (C.Y.L.C.); (Y.-K.C.)
| | - Jonar I. Yago
- Plant Science Department, College of Agriculture, Nueva Vizcaya State University, Bayombong, Nueva Vizcaya 3700, Philippines;
| | - Kuang-Ren Chung
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung 40227, Taiwan; (C.-W.C.); (C.Y.L.C.); (Y.-K.C.)
- Correspondence: (P.-C.W.); (K.-R.C.); Tel.: +886-4-22840780 (ext. 316) (P.-C.W.); +886-4-22840780 (ext. 301) (K.-R.C.)
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12
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Fu H, Chung K, Gai Y, Mao L, Li H. The basal transcription factor II H subunit Tfb5 is required for stress response and pathogenicity in the tangerine pathotype of Alternaria alternata. MOLECULAR PLANT PATHOLOGY 2020; 21:1337-1352. [PMID: 32776683 PMCID: PMC7488464 DOI: 10.1111/mpp.12982] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/25/2020] [Accepted: 07/20/2020] [Indexed: 05/16/2023]
Abstract
The basal transcription factor II H (TFIIH) is a multicomponent complex. In the present study, we characterized a TFIIH subunit Tfb5 by analysing loss- and gain-of-function mutants to gain a better understanding of the molecular mechanisms underlying stress resistance and pathogenicity in the citrus fungal pathogen Alternaria alternata. Tfb5 deficiency mutants (ΔAatfb5) decreased sporulation and pigmentation, and were impaired in the maintenance of colony surface hydrophobicity and cell wall integrity. ΔAatfb5 increased sensitivity to ultraviolet light, DNA-damaging agents, and oxidants. The expression of Aatfb5 was up-regulated in the wild type upon infection in citrus leaves, implicating the requirement of Aatfb5 in fungal pathogenesis. Biochemical and virulence assays revealed that ΔAatfb5 was defective in toxin production and cellwall-degrading enzymes, and failed to induce necrotic lesions on detached citrus leaves. Aatfb5 fused with green fluorescent protein (GFP) was localized in the cytoplasm and nucleus and physically interacted with another subunit, Tfb2, based on yeast two-hybrid and co-immunoprecipitation analyses. Transcriptome and Antibiotics & Secondary Metabolite Analysis Shell (antiSMASH) analyses revealed the positive and negative roles of Aatfb5 in the production of various secondary metabolites and in the regulation of many metabolic and biosynthetic processes in A. alternata. Aatfb5 may play a negative role in oxidative phosphorylation and a positive role in peroxisome biosynthesis. Two cutinase-coding genes (AaCut2 and AaCut15) required for full virulence were down-regulated in ΔAatfb5. Overall, this study expands our understanding of how A. alternata uses the basal transcription factor to deal with stress and achieve successful infection in the plant host.
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Affiliation(s)
- Huilan Fu
- Key Laboratory of Molecular Biology of Crop Pathogens and InsectsInstitute of BiotechnologyZhejiang UniversityHangzhouChina
| | - Kuang‐Ren Chung
- Department of Plant PathologyCollege of Agriculture and Natural ResourcesNational Chung‐Hsing UniversityTaichungTaiwan
| | - Yunpeng Gai
- Key Laboratory of Molecular Biology of Crop Pathogens and InsectsInstitute of BiotechnologyZhejiang UniversityHangzhouChina
| | - Lijuan Mao
- Analysis Center of Agrobiology and Environmental SciencesFaculty of Agriculture, Life and Environment SciencesZhejiang UniversityHangzhouChina
| | - Hongye Li
- Key Laboratory of Molecular Biology of Crop Pathogens and InsectsInstitute of BiotechnologyZhejiang UniversityHangzhouChina
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13
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Wu PC, Chen CW, Choo CYL, Chen YK, Yago JI, Chung KR. Biotin biosynthesis affected by the NADPH oxidase and lipid metabolism is required for growth, sporulation and infectivity in the citrus fungal pathogen Alternaria alternata. Microbiol Res 2020; 241:126566. [PMID: 33032167 DOI: 10.1016/j.micres.2020.126566] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/30/2020] [Accepted: 07/23/2020] [Indexed: 02/06/2023]
Abstract
The tangerine pathotype of Alternaria alternata affects many citrus cultivars, resulting in yield losses. The capability to produce the host-selective toxin and cell-wall-degrading enzymes and to mitigate toxic reactive oxygen species is crucial for A. alternata pathogenesis to citrus. Little is known about nutrient availability within citrus tissues to the fungal pathogen. In the present study, we assess the infectivity of a biotin deficiency mutant (ΔbioB) and a complementation strain (CP36) on citrus leaves to determine how biotin impacts A. alternata pathogenesis. Growth and sporulation of ΔbioB are highly dependent on biotin. ΔbioB retains its ability to acquire and transport biotin from the surrounding environment. Growth deficiency of ΔbioB can also be partially restored by the presence of oleic acid or Tween 20, suggesting the requirement of biotin in lipid metabolism. Experimental evidence indicates that de novo biotin biosynthesis is regulated by the NADPH oxidase, implicating in the production of H2O2, and is affected by the function of peroxisomes. Three genes involved in the biosynthesis of biotin are clustered and co-regulated by biotin indicating a transcriptional feedback loop activation. Infectivity assays using fungal mycelium reveal that ΔbioB cultured on medium without biotin fails to infect citrus leaves; co-inoculation with biotin fully restores infectivity. The CP36 strain re-expressing a functional copy of bioB displays wild-type growth, sporulation and virulence. Taken together, we conclude that the attainability or accessibility of biotin is extremely restricted in citrus cells. A. alternata must be able to synthesize biotin in order to utilize nutrients for growth, colonization and development within the host.
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Affiliation(s)
- Pei-Ching Wu
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Chia-Wen Chen
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Celine Yen Ling Choo
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Yu-Kun Chen
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Jonar I Yago
- Plant Science Department, College of Agriculture, Nueva Vizcaya State University, Bayombong, Nueva Vizcaya, 3700, Philippines
| | - Kuang-Ren Chung
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung Hsing University, Taichung, 40227, Taiwan.
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Fu H, Chung KR, Liu X, Li H. Aaprb1, a subtilsin-like protease, required for autophagy and virulence of the tangerine pathotype of Alternaria alternata. Microbiol Res 2020; 240:126537. [PMID: 32739584 DOI: 10.1016/j.micres.2020.126537] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 06/20/2020] [Accepted: 06/24/2020] [Indexed: 02/06/2023]
Abstract
Subtilisin-like serine protease secreted by pathogenic fungi can facilitate the infection and acquisition of nutrients. Functions of subtilisin-like serine proteases in the phytopathogenic fungus Alternaria alternata remains unknown. In the current study, 15 subtilisin-like serine proteases were individually deleted in the citrus fungal pathogen A. alternata. Only one, designated AaPrb1, was found to be required for A. alternata pathogenesis. The AaPrb1 deficiency strain (ΔAaprb1) reduced growth, conidiation, the formation of aerial hyphae, protease production, and virulence on citrus leaves. However, biochemical analyses and bioassays revealed that ΔAaprb1 plays no role in the production of ACT toxin. Through Y2H assays, Aaprb1 was found to interact with Aapep4, a vacuole-localized proteinase A in A. alternata. Furthermore, silencing AaPep4 in A. alternata resulted in phenotypes similar with those of ΔAaprb1. Expression of AaPrb1 was found to be regulated by AaPep4. TEM showed that AaPrb1and AaPep4 were involved in the suppression of the degradation of autophagosomes. Deletion of the autophagy gene AaAtg8 in A. alternata decreased conidiation, the formation of aerial hyphae and pathogenicity similar to ΔAaprb1, implying that some phenotypes of ΔAaprb1 were due to the impairment of autophagy. Overall, this study expands our understanding of how A. alternata utilizes the subtilisin-like serine protease to achieve successful infection in the plant host.
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Affiliation(s)
- Huilan Fu
- Key Lab of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Kuang-Ren Chung
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Xiaohong Liu
- Key Lab of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - Hongye Li
- Key Lab of Molecular Biology of Crop Pathogens and Insects, Institute of Biotechnology, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
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15
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Ferreira FV, Herrmann-Andrade AM, Calabrese CD, Bello F, Vázquez D, Musumeci MA. Effectiveness of Trichoderma strains isolated from the rhizosphere of citrus tree to control Alternaria alternata, Colletotrichum gloeosporioides and Penicillium digitatum A21 resistant to pyrimethanil in post-harvest oranges (Citrus sinensis L. (Osbeck)). J Appl Microbiol 2020; 129:712-727. [PMID: 32249987 DOI: 10.1111/jam.14657] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/26/2020] [Accepted: 03/27/2020] [Indexed: 12/16/2022]
Abstract
AIMS Penicillium digitatum, Alternaria alternata and Colletotrichum gloeosporioides are pathogens responsible for large decays and production losses of citrus. They are commonly controlled by fungicides, whose excessive applications have led to the emergence of resistant P. digitatum strains. Alternative approaches are imperative for sustainable and environmental harmless citrus production, being biological control a promising strategy. The objective was to evaluate the potential of Trichoderma strains native from the rhizosphere of citrus trees to control these pathogens. METHODS AND RESULTS Seven strains were isolated and identified as Trichoderma harzianum, T. guizhouense, T. atroviride and T. koningiopsis through morphological and molecular analyses. Five of them showed effective antagonist performance in vitro against the pathogens. The strain T. harzianum IC-30 was the best biological control agent in vivo, obtaining a reduction of rot percentage around 80% after 3 weeks of infection of oranges with P. digitatum A21 (resistant to pyrimethanil). This strain also showed the highest chitinase and glucanase activities. CONCLUSIONS Trichoderma harzianum IC-30 is an optimal antagonist for the control of green mould spreading and other pathogens in post-harvest citrus fruits. SIGNIFICANCE AND IMPACT OF THE STUDY The strain combined with supplementary practices could lead to sustainable management of citrus fungal diseases, dispensing with synthetic fungicides.
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Affiliation(s)
- F V Ferreira
- Centro de Investigaciones y Transferencia de Entre Ríos, CONICET, Concordia, Entre Ríos, Argentina
| | - A M Herrmann-Andrade
- Facultad de Ciencias de la Alimentación, Universidad Nacional de Entre Ríos, Concordia, Entre Ríos, Argentina
| | - C D Calabrese
- Facultad de Ciencias de la Alimentación, Universidad Nacional de Entre Ríos, Concordia, Entre Ríos, Argentina
| | - F Bello
- Instituto Nacional de Tecnología Agropecuaria (INTA), Estación Experimental Agropecuaria Concordia, Concordia, Entre Ríos, Argentina
| | - D Vázquez
- Instituto Nacional de Tecnología Agropecuaria (INTA), Estación Experimental Agropecuaria Concordia, Concordia, Entre Ríos, Argentina
| | - M A Musumeci
- Centro de Investigaciones y Transferencia de Entre Ríos, CONICET, Concordia, Entre Ríos, Argentina.,Facultad de Ciencias de la Alimentación, Universidad Nacional de Entre Ríos, Concordia, Entre Ríos, Argentina
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16
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The siderophore repressor SreA maintains growth, hydrogen peroxide resistance, and cell wall integrity in the phytopathogenic fungus Alternaria alternata. Fungal Genet Biol 2020; 139:103384. [PMID: 32278718 DOI: 10.1016/j.fgb.2020.103384] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 03/25/2020] [Accepted: 03/31/2020] [Indexed: 01/18/2023]
Abstract
The siderophore-mediated iron uptake machinery is required by the tangerine pathotype of Alternaria alternata to colonize host plants. The present study reports the functions of the GATA-type transcription regulator SreA by analyzing loss- and gain-of-function mutants. The expression of sreA is transiently upregulated by excess iron. The sreA deficiency mutant (ΔsreA) shows severe growth defect but produces ACT toxin and incites necrotic lesions on citrus leaves as efficiently as wild type. SreA suppresses the expression of genes encoding polypeptides required for siderophore biosynthesis and transport under iron-replete conditions. Under iron-replete conditions, SreA impacts the expression of the genes encoding the NADPH oxidase complex involved in H2O2 production. SreA negatively impacts H2O2 resistance as ΔsreA increases resistance to H2O2. However, sreA deficiency has no effects on the expression of genes encoding several key factors (Yap1, Hog1, and Skn7) involved in oxidative stress resistance. ΔsreA increases resistance to calcofluor white and Congo red, which may suggest a role of SreA in the maintenance of cell wall integrity. Those are novel phenotypes associated with fungal sreA. Overall, our results indicate that SreA is required to protect fungal cells from cytotoxicity caused by excess iron. The results also highlight the regulatory functions of SreA and provide insights into the critical role of siderophore-mediated iron homeostasis in resistance to oxidative stress in A. alternata.
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17
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Santos Dória M, Silva Guedes M, de Andrade Silva EM, Magalhães de Oliveira T, Pirovani CP, Kupper KC, Bastianel M, Micheli F. Comparative proteomics of two citrus varieties in response to infection by the fungus Alternaria alternata. Int J Biol Macromol 2019; 136:410-423. [PMID: 31199975 DOI: 10.1016/j.ijbiomac.2019.06.069] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 06/10/2019] [Accepted: 06/11/2019] [Indexed: 01/04/2023]
Abstract
Alternaria brown spot (ABS) is a disease caused by the necrotrophic fungus Alternaria alternata, which induces necrotic lesions on fruits and young leaves due to the production of the host-specific ACT toxin by the fungus. To better understand the citrus-A. alternata interaction and to identify putative resistance proteins, as well as the receptor of the ACT toxin, citrus plants susceptible ('Minneola' mandarin) and resistant ('Clemenules' tangor) to A. alternata, infected or not (control) with the pathogen were analyzed by proteomics. Protein changes were observed between citrus genotypes after infection, and 150 candidate proteins were obtained. A general scheme of the metabolic processes involved in susceptible and resistant citrus-A. alternata interactions was designed. Susceptible plants presented a high level of proteins involved in stress response at the final stages of the infection, whereas resistant plants presented high level of ROS proteins, metabolic proteins, and proteins involved in the immune system process. Proteins like ferredoxin and cyclophilin are specific to the susceptible variety and may be good candidates as fungal effector-interacting proteins. This is the first citrus-A. alternata proteomics analysis, which has allowed a better understanding of the molecular bases of the citrus response to ABS disease.
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Affiliation(s)
- Milena Santos Dória
- Centro de Biotecnologia e Genética (CBG), Universidade Estadual de Santa Cruz (UESC), BA, Brazil
| | - Meg Silva Guedes
- Centro de Biotecnologia e Genética (CBG), Universidade Estadual de Santa Cruz (UESC), BA, Brazil
| | | | | | - Carlos Priminho Pirovani
- Centro de Biotecnologia e Genética (CBG), Universidade Estadual de Santa Cruz (UESC), BA, Brazil
| | - Katia Cristina Kupper
- Centro de Citricultura "Sylvio Moreira", Instituto Agronômico de Campinas (IAC), SP, Brazil
| | - Marinês Bastianel
- Centro de Citricultura "Sylvio Moreira", Instituto Agronômico de Campinas (IAC), SP, Brazil
| | - Fabienne Micheli
- Centro de Biotecnologia e Genética (CBG), Universidade Estadual de Santa Cruz (UESC), BA, Brazil; CIRAD, UMR AGAP, F-34398 Montpellier, France.
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18
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Dietzel K, Valle D, Fierer N, U'Ren JM, Barberán A. Geographical Distribution of Fungal Plant Pathogens in Dust Across the United States. Front Ecol Evol 2019. [DOI: 10.3389/fevo.2019.00304] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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19
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Choudhary P, Chakdar H, Singh A, Kumar S, Singh SK, Aarthy M, Goswami SK, Srivastava AK, Saxena AK. Computational identification and antifungal bioassay reveals phytosterols as potential inhibitor of Alternaria arborescens. J Biomol Struct Dyn 2019; 38:1143-1157. [PMID: 30898083 DOI: 10.1080/07391102.2019.1597767] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Alternaria arborescens is a major pathogen for crops like tomato, tangerine and so on and its control is mostly dependent on the application of chemical agents. Plants as the sources of natural products are very attractive option for developing eco-friendly and natural antifungal agents. In this study, we modeled three-dimensional structure of chorismate synthase (CS) enzyme from A. arborescens. Docking studies of phytosterols, namely, γ-sitosterol and β-sitosterol, with CS showed them to be potential inhibitor of CS. To explore the stability and conformational flexibility of all the AaCS complex systems, molecular dynamics simulations were performed. None of the putative inhibitors as well as β- and γ-sitosterol showed interaction with the FMNH2 binding pocket of the tomato CS (major host of A. arborescens) indicating their suitability as antifungal compounds inhibiting the shikimate pathway without causing any harm to the host. An in vivo antifungal bioassay showed a significant reduction in fungal growth in the presence of β-sitosterol (500 ppm) which resulted in ∼23% and ∼17% reduction in fungal fresh and dry weight, respectively, at 8 days after inoculation. This study provides experimental evidence establishing natural sterols like β-sitosterol can be useful in curbing A. arborescens damage in an eco-friendly manner.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Prassan Choudhary
- Microbial Technology Unit, ICAR-National Bureau of Agriculturally Important Microorganisms, Mau, Uttar Pradesh, India
| | - Hillol Chakdar
- Microbial Technology Unit, ICAR-National Bureau of Agriculturally Important Microorganisms, Mau, Uttar Pradesh, India
| | - Arjun Singh
- Microbial Technology Unit, ICAR-National Bureau of Agriculturally Important Microorganisms, Mau, Uttar Pradesh, India
| | - Sunil Kumar
- Microbial Technology Unit, ICAR-National Bureau of Agriculturally Important Microorganisms, Mau, Uttar Pradesh, India
| | - Sanjeev Kumar Singh
- Department of Bioinformatics, Algappa University, Karaikudi, Tamil Nadu, India
| | - Murali Aarthy
- Department of Bioinformatics, Algappa University, Karaikudi, Tamil Nadu, India
| | - Sanjay Kumar Goswami
- Microbial Technology Unit, ICAR-National Bureau of Agriculturally Important Microorganisms, Mau, Uttar Pradesh, India
| | - Alok Kumar Srivastava
- Microbial Technology Unit, ICAR-National Bureau of Agriculturally Important Microorganisms, Mau, Uttar Pradesh, India
| | - Anil Kumar Saxena
- Microbial Technology Unit, ICAR-National Bureau of Agriculturally Important Microorganisms, Mau, Uttar Pradesh, India
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Abstract
Alternaria brown spot, caused by Alternaria alternata (Fr.) Keissl, is an important disease in tangerines and their hybrids, affecting leaves, twigs, and immature fruit. Differences in susceptibility to this pathogenic fungus have been described for different Citrus species. In this paper, the expression of the mycotoxins alternariol and alternariol monomethyl ether in different A. alternata isolates was analyzed by HPLC-MS. A correlation was observed between the mycotoxins content and the pathogenicity of each isolated of A. alternata used, suggesting that the mycotoxins may be involved in the evolution of brown spot in ‘Fortune’ fruits caused by this fungus. The increased expression of the above mycotoxins was associated with the end of mycelia growth, high sporulation, and an increase in hyphal melanization in the fungus. On the other hand, the presence of laccase activity in the xylem of ‘Fortune’ fruits inoculated with A. alternata suggests that this is the way the fungus propagates in the plant. These results add to our knowledge of the pathogenesis of A. alternata in Citrus.
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Dong M, Wen G, Tang H, Wang T, Zhao Z, Song W, Wang W, Zhao L. Dissipation and safety evaluation of novaluron, pyriproxyfen, thiacloprid and tolfenpyrad residues in the citrus-field ecosystem. Food Chem 2018; 269:136-141. [DOI: 10.1016/j.foodchem.2018.07.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 06/14/2018] [Accepted: 07/01/2018] [Indexed: 12/13/2022]
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The methionine biosynthesis regulator AaMetR contributes to oxidative stress tolerance and virulence in Alternaria alternata. Microbiol Res 2018; 219:94-109. [PMID: 30642471 DOI: 10.1016/j.micres.2018.11.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 11/12/2018] [Accepted: 11/23/2018] [Indexed: 12/29/2022]
Abstract
The tangerine pathotype of A. alternata, which produces a unique host-selective ACT toxin causes brown spots on citrus leaves and fruits. In this study, we report a methionine biosynthesis regulator (MetR), which belong to bZIP transcription factor, is required for methionine metabolism, oxidative stress tolerance and pathogenicity. We generated two ΔAaMetR mutants in the tangerine pathotype of Alternaria alternata and investigated the resulting mutant phenotypes. The ΔAaMetR disruption mutant grew poorly in the absence of methionine and unable to produce conidia. Furthermore, pathogenicity tests have shown that ΔAaMetR mutant on their tangerine host can neither penetrate nor cause disease. These ΔAaMetR mutants exhibit an increased sensitivity to exogenous H2O2 and many ROS generating oxidants. To elucidate the transcription network of AaMetR, we performed RNA-Seq experiments on wild-type and ΔAaMetR mutant and identified genes that were differentially expressed between the two genotypes. Transcriptome data demonstrated that AaMetR contributes in many other biological processes including ROS detoxification, sulfur transfer, and amino acid metabolism. Comparative transcriptome analysis indicated that the ΔAaMetR mutant up-regulated several genes involved in cysteine and methionine metabolism. In conclusion, our results highlight the global regulatory role of AaMetR in cysteine and methionine metabolism and provide new insights into the crucial role of ROS detoxification, sporulation and pathogenicity in the tangerine pathotype of A. alternata.
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Lin HC, Yu PL, Chen LH, Tsai HC, Chung KR. A Major Facilitator Superfamily Transporter Regulated by the Stress-Responsive Transcription Factor Yap1 Is Required for Resistance to Fungicides, Xenobiotics, and Oxidants and Full Virulence in Alternaria alternata. Front Microbiol 2018; 9:2229. [PMID: 30279684 PMCID: PMC6153361 DOI: 10.3389/fmicb.2018.02229] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 08/31/2018] [Indexed: 11/29/2022] Open
Abstract
Alternaria alternata relies on the ability to produce a host-selective toxin and to detoxify reactive oxygen species to successfully colonize the host. An A. alternata major facilitator superfamily transporter designated AaMFS54 was functionally characterized by analysis of loss- and gain-of-function mutations to better understand the factors required for fungal pathogenesis. AaMFS54 was originally identified from a wild-type expression library after being subtracted with that of a mutant impaired for the oxidative stress-responsive transcription regulator Yap1. AaMFS54 contains 14 transmembrane helixes. Fungal mutant lacking AaMFS54 produced fewer conidia and increased sensitivity to many potent oxidants (potassium superoxide and singlet-oxygen generating compounds), xenobiotics (2,3,5-triiodobenzoic acid and 2-chloro-5-hydroxypyridine), and fungicides (clotrimazole, fludioxonil, vinclozolin, and iprodione). AaMFS54 mutant induced necrotic lesion sizes similar to those induced by wild-type on leaves of susceptible citrus cultivars after point inoculation with spore suspensions. However, the mutant produced smaller colonies and less fluffy hyphae on the affected leaves. Virulence assays on citrus leaves inoculated by spraying with spores revealed that AaMFS54 mutant induced less severe lesions than wild-type, indicating the requirement of AaMFS54 in pathogenesis. All defective phenotypes were restored in a strain re-acquiring a functional copy of AaMFS54. Northern blotting analysis revealed that the expression of AaMFS54 was suppressed by xenobiotics. The current studies indicate that the Yap1-mediated transporter plays a role in resistance to toxic oxidants and fungicides in A. alternata. The relationships of MFS transporters with other regulatory components conferring stress resistance and A. alternata pathogenesis are also discussed.
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Affiliation(s)
- Hsien-Che Lin
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Pei-Ling Yu
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Li-Hung Chen
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Hsieh-Chin Tsai
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Kuang-Ren Chung
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
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Phospholipases play multiple cellular roles including growth, stress tolerance, sexual development, and virulence in fungi. Microbiol Res 2018; 209:55-69. [DOI: 10.1016/j.micres.2017.12.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 12/21/2017] [Accepted: 12/31/2017] [Indexed: 12/16/2022]
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25
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Rotondo F, Hong SG, Peever T, Pryor BM. Molecular diversity and allergenic profiles of Alternaria spp. from desert environments in Arizona. Fungal Biol 2017; 122:74-85. [PMID: 29248116 DOI: 10.1016/j.funbio.2017.10.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Revised: 10/12/2017] [Accepted: 10/23/2017] [Indexed: 12/13/2022]
Abstract
This study examined the genetic diversity of small-spored Alternaria species in the southwest desert of the USA by sampling 552 isolates from different habitats (soil and plant debris) in different locations (urban and an undisturbed desert). To estimate the genetic diversity, Amplified Fragment Length Polymorphism (AFLP) fingerprinting analysis was performed for all isolates. Strains representative of the sampled genotypic diversity (n = 125) were further characterized according their sporulation pattern and the capability to produce allergens. Morphological characterization assigned the majority of the strains to the Alternaria alternata and Alternaria tenuissima morpho-groups with only two isolates assigned to the Alternaria arborescens morpho-group. AFLP fingerprinting differentiated the A. arborescens morpho-groups, but could not distinguish between the A. alternata and A. tenuissima morpho-groups. Western blot analysis showed that a large number of allergenic proteins were produced by strains. These proteins were not specific for any morpho-group nor source of isolation. A hierarchical analysis of molecular variance was performed on the AFLP data to quantify molecular variation and partition this variation among sampled locations and habitat. No statistically significant differentiation among locations and habitat was detected indicating a lack of population structure across environments.
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Affiliation(s)
- Francesca Rotondo
- Department of Plant Pathology, The Ohio State University - OARDC, Wooster, OH 44691, USA; School of Plant Sciences, College of Agriculture, University of Arizona, Tucson, AZ 85721, USA
| | - Soon Gyu Hong
- Korea Polar Research Institute, Korea Polar Research Institute, Incheon 406-840, Republic of Korea; School of Plant Sciences, College of Agriculture, University of Arizona, Tucson, AZ 85721, USA
| | - Tobin Peever
- Department of Plant Pathology, Washington State University, Pullman, WA 99164, USA
| | - Barry M Pryor
- School of Plant Sciences, College of Agriculture, University of Arizona, Tucson, AZ 85721, USA.
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Dalio RJD, Magalhães DM, Rodrigues CM, Arena GD, Oliveira TS, Souza-Neto RR, Picchi SC, Martins PMM, Santos PJC, Maximo HJ, Pacheco IS, De Souza AA, Machado MA. PAMPs, PRRs, effectors and R-genes associated with citrus-pathogen interactions. ANNALS OF BOTANY 2017; 119:749-774. [PMID: 28065920 PMCID: PMC5571375 DOI: 10.1093/aob/mcw238] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 07/08/2016] [Accepted: 10/22/2016] [Indexed: 05/08/2023]
Abstract
BACKGROUND Recent application of molecular-based technologies has considerably advanced our understanding of complex processes in plant-pathogen interactions and their key components such as PAMPs, PRRs, effectors and R-genes. To develop novel control strategies for disease prevention in citrus, it is essential to expand and consolidate our knowledge of the molecular interaction of citrus plants with their pathogens. SCOPE This review provides an overview of our understanding of citrus plant immunity, focusing on the molecular mechanisms involved in the interactions with viruses, bacteria, fungi, oomycetes and vectors related to the following diseases: tristeza, psorosis, citrus variegated chlorosis, citrus canker, huanglongbing, brown spot, post-bloom, anthracnose, gummosis and citrus root rot.
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Affiliation(s)
- Ronaldo J. D. Dalio
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Diogo M. Magalhães
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Carolina M. Rodrigues
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Gabriella D. Arena
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Tiago S. Oliveira
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Reinaldo R. Souza-Neto
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Simone C. Picchi
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Paula M. M. Martins
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Paulo J. C. Santos
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Heros J. Maximo
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Inaiara S. Pacheco
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Alessandra A. De Souza
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
| | - Marcos A. Machado
- Citrus Biotechnology Lab, Centro de Citricultura Sylvio Moreira, IAC, Cordeirópolis-SP, Brazil
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Chen LH, Tsai HC, Yu PL, Chung KR. A Major Facilitator Superfamily Transporter-Mediated Resistance to Oxidative Stress and Fungicides Requires Yap1, Skn7, and MAP Kinases in the Citrus Fungal Pathogen Alternaria alternata. PLoS One 2017; 12:e0169103. [PMID: 28060864 PMCID: PMC5218470 DOI: 10.1371/journal.pone.0169103] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Accepted: 12/12/2016] [Indexed: 12/19/2022] Open
Abstract
Major Facilitator Superfamily (MFS) transporters play an important role in multidrug resistance in fungi. We report an AaMFS19 gene encoding a MFS transporter required for cellular resistance to oxidative stress and fungicides in the phytopathogenic fungus Alternaria alternata. AaMFS19, containing 12 transmembrane domains, displays activity toward a broad range of substrates. Fungal mutants lacking AaMFS19 display profound hypersensitivities to cumyl hydroperoxide, potassium superoxide, many singlet oxygen-generating compounds (eosin Y, rose Bengal, hematoporphyrin, methylene blue, and cercosporin), and the cell wall biosynthesis inhibitor, Congo red. AaMFS19 mutants also increase sensitivity to copper ions, clotrimazole, fludioxonil, and kocide fungicides, 2-chloro-5-hydroxypyridine (CHP), and 2,3,5-triiodobenzoic acid (TIBA). AaMFS19 mutants induce smaller necrotic lesions on leaves of a susceptible citrus cultivar. All observed phenotypes in the mutant are restored by introducing and expressing a wild-type copy of AaMFS19. The wild-type strain of A. alternata treated with either CHP or TIBA reduces radial growth and formation and germination of conidia, increases hyphal branching, and results in decreased expression of the AaMFS19 gene. The expression of AaMFS19 is regulated by the Yap1 transcription activator, the Hog1 and Fus3 mitogen-activated protein (MAP) kinases, the ‘two component’ histidine kinase, and the Skn7 response regulator. Our results demonstrate that A. alternata confers resistance to different chemicals via a membrane-bound MFS transporter.
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Affiliation(s)
- Li-Hung Chen
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Hsieh-Chin Tsai
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Pei-Ling Yu
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Kuang-Ren Chung
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
- Biotechnology Center, NCHU, Taichung, Taiwan
- NCHU-UCD Plant and Food Biotechnology Center, NCHU, Taichung, Taiwan
- * E-mail:
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Cuenca J, Aleza P, Garcia-Lor A, Ollitrault P, Navarro L. Fine Mapping for Identification of Citrus Alternaria Brown Spot Candidate Resistance Genes and Development of New SNP Markers for Marker-Assisted Selection. FRONTIERS IN PLANT SCIENCE 2016; 7:1948. [PMID: 28066498 PMCID: PMC5179576 DOI: 10.3389/fpls.2016.01948] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 12/07/2016] [Indexed: 05/20/2023]
Abstract
Alternaria brown spot (ABS) is a serious disease affecting susceptible citrus genotypes, which is a strong concern regarding citrus breeding programs. Resistance is conferred by a recessive locus (ABSr) previously located by our group within a 3.3 Mb genome region near the centromere in chromosome III. This work addresses fine-linkage mapping of this region for identifying candidate resistance genes and develops new molecular markers for ABS-resistance effective marker-assisted selection (MAS). Markers closely linked to ABSr locus were used for fine mapping using a 268-segregating diploid progeny derived from a heterozygous susceptible × resistant cross. Fine mapping limited the genomic region containing the ABSr resistance gene to 366 kb, flanked by markers at 0.4 and 0.7 cM. This region contains nine genes related to pathogen resistance. Among them, eight are resistance (R) gene homologs, with two of them harboring a serine/threonine protein kinase domain. These two genes along with a gene encoding a S-adenosyl-L-methionine-dependent-methyltransferase protein, should be considered as strong candidates for ABS-resistance. Moreover, the closest SNP was genotyped in 40 citrus varieties, revealing very high association with the resistant/susceptible phenotype. This new marker is currently used in our citrus breeding program for ABS-resistant parent and cultivar selection, at diploid, triploid and tetraploid level.
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Affiliation(s)
- Jose Cuenca
- Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones AgrariasValencia, Spain
| | - Pablo Aleza
- Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones AgrariasValencia, Spain
| | - Andres Garcia-Lor
- Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones AgrariasValencia, Spain
| | | | - Luis Navarro
- Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones AgrariasValencia, Spain
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Xu W, Han X, Li F, Zhang L. Natural Occurrence of Alternaria Toxins in the 2015 Wheat from Anhui Province, China. Toxins (Basel) 2016; 8:E308. [PMID: 27792182 PMCID: PMC5127105 DOI: 10.3390/toxins8110308] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/08/2016] [Accepted: 10/19/2016] [Indexed: 12/11/2022] Open
Abstract
The exposure to Alternaria toxins from grain and grain-based products has been reported to be related to human esophageal cancer in China. In this study, a total of 370 freshly harvested wheat kernel samples collected from Anhui province of China in 2015 were analyzed for the four Alternaria toxins tenuazonic acid (TeA), tentoxin (TEN), alternariol (AOH) and alternariol monomethyl ether (AME) by high performance liquid chromatography-tandem mass spectrometry method (HPLC-MS/MS). TeA was the predominant toxin detected followed by TEN, AOH and AME. The concentrations of the four Alternaria toxins varied geographically. The samples from Fuyang district showed higher TEN concentration levels than the other regions studied (p < 0.05). Furthermore, 95% (352/370) of the wheat samples were positive for more than one type of Alternaria toxins. Positive correlation was observed between concentration levels of TeA and TEN, AOH and AME, TeA and AOH, and the total dibenzopyrone derivatives (AOH + AME) and TeA. Results indicate that there is a need to set the tolerance limit for Alternaria toxins in China, and more data on the contamination of these toxins in agro-products is required.
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Affiliation(s)
- Wenjing Xu
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing 100021, China.
- Institute of Nutrition and Food Hygiene, West China College of Public Health, Sichuan University, Chengdu 610041, China.
| | - Xiaomin Han
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing 100021, China.
| | - Fengqin Li
- Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment, Beijing 100021, China.
| | - Lishi Zhang
- Institute of Nutrition and Food Hygiene, West China College of Public Health, Sichuan University, Chengdu 610041, China.
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Garganese F, Schena L, Siciliano I, Prigigallo MI, Spadaro D, De Grassi A, Ippolito A, Sanzani SM. Characterization of Citrus-Associated Alternaria Species in Mediterranean Areas. PLoS One 2016; 11:e0163255. [PMID: 27636202 PMCID: PMC5026349 DOI: 10.1371/journal.pone.0163255] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 09/05/2016] [Indexed: 01/05/2023] Open
Abstract
Alternaria brown spot is one of the most important diseases of tangerines and their hybrids worldwide. Recently, outbreaks in Mediterranean areas related to susceptible cultivars, refocused attention on the disease. Twenty representatives were selected from a collection of 180 isolates of Alternaria spp. from citrus leaves and fruit. They were characterized along with reference strains of Alternaria spp. Micro- and macroscopic characteristics separated most Alternaria isolates into six morphotypes referable to A. alternata (5) and A. arborescens (1). Phylogenetic analyses, based on endopolygalacturonase (endopg) and internal transcribed spacer (ITS), confirmed this finding. Moreover, a five-gene phylogeny including two anonymous genomics regions (OPA 1-3 and OPA 2-1), and the beta-tubulin gene (ß-tub), produced a further clustering of A. alternata into three clades. This analysis suggested the existence of intra-species molecular variability. Investigated isolates showed different levels of virulence on leaves and fruit. In particular, the pathogenicity on fruit seemed to be correlated with the tissue of isolation and the clade. The toxigenic behavior of Alternaria isolates was also investigated, with tenuazonic acid (TeA) being the most abundant mycotoxin (0.2-20 mg/L). Isolates also synthesized the mycotoxins alternariol (AOH), its derivate alternariol monomethyl ether (AME), and altenuene (ALT), although to a lesser extent. AME production significantly varied among the six morphotypes. The expression of pksJ/pksH, biosynthetic genes of AOH/AME, was not correlated with actual toxin production, but it was significantly different between the two genotypes and among the four clades. Finally, ten isolates proved to express the biosynthetic genes of ACTT1 phytotoxin, and thus to be included in the Alternaria pathotype tangerine. A significant correlation between pathogenicity on leaves and ACTT1 gene expression was recorded. The latter was significantly dependent on geographical origin. The widespread occurrence of Alternaria spp. on citrus fruit and their ability to produce mycotoxins might represent a serious concern for producers and consumers.
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Affiliation(s)
- Francesca Garganese
- Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi Aldo Moro, Bari, Italy
| | - Leonardo Schena
- Dipartimento di Agraria, Università Mediterranea, Reggio Calabria, Italy
| | - Ilenia Siciliano
- Centro di Competenza per l'Innovazione in campo agro-ambientale-AGROINNOVA, Università degli Studi di Torino, Grugliasco (TO), Italy
| | | | - Davide Spadaro
- Centro di Competenza per l'Innovazione in campo agro-ambientale-AGROINNOVA, Università degli Studi di Torino, Grugliasco (TO), Italy
- Dipartimento di Scienze Agrarie, Forestali e Alimentari, Università degli Studi di Torino, Grugliasco (TO), Italy
| | - Anna De Grassi
- Dipartimento di Bioscienze, Biotecnologie e Biofarmaceutica, Università degli Studi Aldo Moro, Bari, Italy
| | - Antonio Ippolito
- Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi Aldo Moro, Bari, Italy
| | - Simona Marianna Sanzani
- Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi Aldo Moro, Bari, Italy
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Yang SL, Yu PL, Chung KR. The glutathione peroxidase-mediated reactive oxygen species resistance, fungicide sensitivity and cell wall construction in the citrus fungal pathogen Alternaria alternata. Environ Microbiol 2016; 18:923-35. [PMID: 26567914 DOI: 10.1111/1462-2920.13125] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/04/2015] [Accepted: 11/05/2015] [Indexed: 12/18/2022]
Abstract
The ability to detoxify reactive oxygen species (ROS) is critical for pathogenicity in the necrotrophic fungus Alternaria alternata. We report a glutathione peroxidase 3 (AaGPx3) involved in the complex signalling network that is essential for the detoxification of cellular stresses induced by ROS and for A. alternata pathogenesis in citrus. AaGPx3 deletion mutants displayed increased sensitivity to H2 O2 and many ROS-generating compounds. AaGPx3 is required for correct fungal development as the AaGPx3 mutant strains showed a severe reduction in conidiation. AaGPx3 mutants accumulated higher chitin content than the wild-type and were less sensitive to the cell wall-targeting compounds calcofluor white and Congo red, as well as the fungicides fludioxonil and vinclozolin, suggesting a role of the glutathione systems in fungal cell wall construction. Virulence assays revealed that AaGPx3 is required for full virulence. The expression of AaGPx3 was downregulated in fungal strains carrying defective NADPH oxidase (Nox) or the oxidative stress responsive regulators YAP1 and HOG1, all implicated in ROS resistance. These results further support the important role of ROS detoxification during A. alternata pathogenesis in citrus. Overall, our study provides genetic evidence to define the central role of AaGPx3 in the biological and pathological functions of A. alternata.
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Affiliation(s)
- Siwy Ling Yang
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA
| | - Pei-Ling Yu
- Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
| | - Kuang-Ren Chung
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA.,Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan
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Nagrale DT, Sharma L, Kumar S, Gawande SP. Recent Diagnostics and Detection Tools: Implications for Plant Pathogenic Alternaria and Their Disease Management. Fungal Biol 2016. [DOI: 10.1007/978-3-319-27312-9_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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33
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Armitage AD, Barbara DJ, Harrison RJ, Lane CR, Sreenivasaprasad S, Woodhall JW, Clarkson JP. Discrete lineages within Alternaria alternata species group: Identification using new highly variable loci and support from morphological characters. Fungal Biol 2015; 119:994-1006. [DOI: 10.1016/j.funbio.2015.06.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 06/29/2015] [Accepted: 06/30/2015] [Indexed: 01/24/2023]
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Perina FJ, Amaral DC, Fernandes RS, Labory CR, Teixeira GA, Alves E. Thymus vulgaris essential oil and thymol against Alternaria alternata (Fr.) Keissler: effects on growth, viability, early infection and cellular mode of action. PEST MANAGEMENT SCIENCE 2015; 71:1371-1378. [PMID: 25354766 DOI: 10.1002/ps.3933] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 10/22/2014] [Accepted: 10/24/2014] [Indexed: 06/04/2023]
Abstract
BACKGROUND In initial assays, Thymus vulgaris essential oil (TEO) has demonstrated activity against several plant-pathogenic fungi and has reduced the fungal diseases to levels comparable with commercial fungicides. Thus, the goal of this work was to identify the mode of action in fungi of TEO and its major compound thymol (TOH) at the cellular level using an ultrastructure approach. RESULTS TEO from leaves and TOH had minimum inhibitory concentrations (MICs) of 500 and 250 µg mL(-1) respectively against A. alternata; under the same conditions, MIC for a commercial fungicide was 1250 µg mL(-1) . Ultrastructure analysis showed that TOH phenolic substance prevented fungal growth, reduced fungal viability and prevented the penetration in fruits by a cell wall/plasma membrane interference mode of action with organelles targeted for destruction in the cytoplasm. Such mode of action differs from protective and preventive-curative commercial fungicides used as pattern control. CONCLUSION These findings suggest that TOH was responsible for the antifungal activity of TEO. Therefore, both the essential oil and its major substance have potential for use in the development of new phenolic structures and analogues to control Alternaria brown spot disease caused by Alternaria alternata.
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Affiliation(s)
- Fabiano J Perina
- Embrapa - Empresa Brasileira de Pesquisa Agropecuária, Embrapa Algodão, Campina Grande, PB, Brazil
| | - Douglas C Amaral
- Department of Soil Sciences, Universidade Federal de Lavras, Lavras, MG, Brazil
| | - Rafael S Fernandes
- Department of Plant Pathology, Universidade Federal de Lavras, Lavras, MG, Brazil
| | - Claudia Rg Labory
- Department of Soil Sciences, Universidade Federal de Lavras, Lavras, MG, Brazil
| | - Glauco A Teixeira
- Department of Plant Pathology, Universidade Federal de Lavras, Lavras, MG, Brazil
| | - Eduardo Alves
- Department of Plant Pathology, Universidade Federal de Lavras, Lavras, MG, Brazil
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Hickert S, Bergmann M, Ersen S, Cramer B, Humpf HU. Survey of Alternaria toxin contamination in food from the German market, using a rapid HPLC-MS/MS approach. Mycotoxin Res 2015; 32:7-18. [PMID: 26408172 DOI: 10.1007/s12550-015-0233-7] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 09/17/2015] [Accepted: 09/18/2015] [Indexed: 11/25/2022]
Abstract
A HPLC-MS/MS-based method for the quantification of nine mycotoxins produced by fungi of the genus Alternaria in various food matrices was developed. The method relies on a single-step extraction, followed by dilution of the raw extract and direct analysis. In combination with an analysis time per sample of 12 min, the sample preparation is cost-effective and easy to handle. The method covers alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TeA), altenuene (ALT), iso-altenuene (isoALT), tentoxin (TEN), altertoxin-I (ATX-I), and the AAL toxins TA1 and TA2. Some Alternaria toxins which are either not commercially available or very expensive, namely AOH, AME, ALT, isoALT, and ATX-I, were isolated as reference compounds from fungal cultures. The method was extensively validated for tomato products, bakery products, sunflower seeds, fruit juices, and vegetable oils. AOH, AME, TeA, and TEN were found in quantifiable amounts and 92.1% of all analyzed samples (n = 96) showed low level contamination with one or more Alternaria toxins. Based on the obtained results, the average daily exposure to Alternaria toxins in Germany was calculated.
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Affiliation(s)
- Sebastian Hickert
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 45, 48149, Münster, Germany
- NRW Graduate School of Chemistry, Wilhelm-Klemm-Str. 10, 48149, Münster, Germany
| | - Marian Bergmann
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 45, 48149, Münster, Germany
| | - Seyma Ersen
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 45, 48149, Münster, Germany
| | - Benedikt Cramer
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 45, 48149, Münster, Germany
| | - Hans-Ulrich Humpf
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 45, 48149, Münster, Germany.
- NRW Graduate School of Chemistry, Wilhelm-Klemm-Str. 10, 48149, Münster, Germany.
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Vega B, Dewdney MM. Sensitivity of Alternaria alternata from Citrus to Boscalid and Polymorphism in Iron-Sulfur and in Anchored Membrane Subunits of Succinate Dehydrogenase. PLANT DISEASE 2015; 99:231-239. [PMID: 30699560 DOI: 10.1094/pdis-04-14-0374-re] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Boscalid, a succinate dehydrogenase inhibitor (SDHI), was registered in 2011 to control Alternaria brown spot (ABS) of citrus, caused by Alternaria alternata. In this study, the effect of boscalid on mycelial growth, conidial germination, and resazurin reduction was established in a subset of 16 sensitive isolates using three different media. Conidial germination and mycelial growth inhibition were not suppressed even at higher concentrations of boscalid, although effective concentration to inhibit 50% growth (EC50) values were established with each method. Resazurin reduction produced the lowest EC50 values and was selected for further sensitivity tests. In total, 419 isolates, never exposed to boscalid and collected from Florida tangerine orchards between 1996 to 2012, were tested for boscalid sensitivity. The sensitivity distribution was a unimodal curve with a mean EC50 value of 0.60 μg/ml and a range of 0.07 to 5.84 μg/ml. The molecular characterization of the succinate dehydrogenase (SDH) genes were also determined in a subset of 15 isolates, exhibiting great variability in boscalid sensitivity, by cloning and sequencing the sdhB, sdhC, and sdhD genes. Sequence comparisons of the SDH complex revealed the presence of mutations in 14 of 15 isolates. In total, 21 mutations were identified. Double and multiple mutations were observed in SDHC and SDHD, respectively. In SDHB, 4 mutations were observed while, in SDHC and SDHD, 5 and 12 mutations were detected, respectively. No mutations were found in the highly conserved histidine residues at positions 277 in SDHB, 134 in SDHC, and 133 in SDHD, typically observed in SDHI-resistant isolates. Our findings suggest that A. alternata populations from Florida are sensitive to boscalid and it could be used in ABS spray programs. Boscalid resistance is currently not a problem, although further monitoring for resistance is advisable.
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Affiliation(s)
- Byron Vega
- Citrus Research and Education Center, University of Florida, Lake Alfred 33850
| | - Megan M Dewdney
- Citrus Research and Education Center, University of Florida, Lake Alfred 33850
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Campos VA, Perina FJ, Alves E, Sartorelli J, Moura AM, Oliveira DF. Anadenanthera colubrina (Vell.) Brenan produces steroidal substances that are active against Alternaria alternata (Fr.) Keissler and that may bind to oxysterol-binding proteins. PEST MANAGEMENT SCIENCE 2014; 70:1815-1822. [PMID: 24408227 DOI: 10.1002/ps.3722] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 12/18/2013] [Accepted: 12/26/2013] [Indexed: 06/03/2023]
Abstract
BACKGROUND In previous studies, the extract from Anadenanthera colubrina was active against Alternaria alternata in vitro and reduced the disease caused by this fungus on Murcott tangor fruits to levels that have been obtained using commercial fungicides. Therefore, the goal of the present work was to isolate and identify the active substances in this extract and identify in silico their protein target in the fungus. RESULTS The bioguided fractionation of the methanol extract from the fruits of A. colubrina resulted in the isolation of β-sitosterol and β-sitosteryl linoleate, which had minimal inhibitory concentrations (MICs) of 250 and 500 µg mL(-1) , respectively, against A. alternata. Under the same conditions, the MICs for two commercial fungicides were 1250 and 19 µg mL(-1) . In silico studies showed that these steroidal substances bind well to oxysterol-binding proteins from Saccharomyces cerevisiae. CONCLUSION β-Sitosterol and β-sitosteryl linoleate, produced by A. colubrina, are active against A. alternata. In silico studies suggest that these substances may act by binding to oxysterol-binding proteins. Therefore, both substances and these proteins have potential use in the development of new steroidal structures and analogues to control the disease caused by A. alternata.
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Affiliation(s)
- Viviane Ac Campos
- Departamento de Química, Universidade Federal de Lavras, Lavras, MG, Brasil
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Huang F, Fu Y, Nie D, Stewart JE, Peever TL, Li H. Identification of a novel phylogenetic lineage of Alternaria alternata causing citrus brown spot in China. Fungal Biol 2014; 119:320-30. [PMID: 25937061 DOI: 10.1016/j.funbio.2014.09.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 09/13/2014] [Accepted: 09/21/2014] [Indexed: 01/11/2023]
Abstract
Alternaria alternata sensu lato, casual agent of citrus brown spot, first identified in Yunnan province in 2010 and subsequently found in Zhejiang, Hunan, Guangdong provinces, Chongqing municipality andGuangxi autonomous region in China. During 2010-2012, 86 isolates were collected from diseased citrus, of which 85 % isolates were pathogenic to Ponkan tangerine. Phylogenetic analyses of Chinese and worldwide isolates using partial sequences of an endopolygalacturonase gene (endoPG) and combined dataset ofendoPG and two anonymous loci (OPA1-3, OPA2-1) found that Chinese isolates fell into two of three previously described clades. One clade ('clade 3') contained isolates from Turkey and Israel, and the other clade ('clade 1') contained isolates from Florida, USA. None of the isolates from China fell into the last previously described clade ('clade 2'). However, 24 isolates from Hunan, Guangdong and Guangxi fell into a fourth clade ('clade 4') not previously reported to be associated with citrus brown spot. This clade included multilocus haplotypes known to infect Japanese pear and strawberry. The observation that Chinese brown spot isolates fell into only two of three known worldwide lineages suggests that this fungus may not have co-evolved with its host in China but elsewhere in Southeast Asia and introduced to China.
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Affiliation(s)
- Feng Huang
- Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Yushi Fu
- Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Danni Nie
- Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Jane E Stewart
- Department of Plant Pathology, University of Georgia, Athens, GA 30602, USA
| | - Tobin L Peever
- Department of Plant Pathology, Washington State University, Pullman 99164, USA
| | - Hongye Li
- Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China.
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Vega B, Dewdney MM. QoI-Resistance Stability in Relation to Pathogenic and Saprophytic Fitness Components of Alternaria alternata from Citrus. PLANT DISEASE 2014; 98:1371-1378. [PMID: 30703928 DOI: 10.1094/pdis-01-14-0078-re] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The phenotypic stability, fitness components, and ability to cause disease of isolates of the Alternaria alternata tangerine pathotype resistant to quinone-outside inhibitors (QoIs) were studied. Stability of resistance to azoxystrobin (AZ) and pyraclostrobin (PYR) was determined after consecutive transfers on potato dextrose agar (PDA). The sensitivity to QoIs did not change significantly after 10 transfers on PDA compared with the initial sensitivity of all isolates tested. Fitness components evaluated in vitro were mycelial growth, conidial germination, and conidial production. Incubation period, number of lesions per leaf area, and virulence were determined with detached leaf assays using four cultivars: Dancy, Minneola, Murcott, and Sunburst. Variability in fitness components was observed among isolates within the same sensitivity group. As a group, no significant differences in the mean values of these fitness components were observed between resistant and sensitive phenotypes, except for virulence. Resistant isolates were significantly (P < 0.05) more virulent than the sensitive isolates on Dancy, Minneola, and Sunburst but not on Murcott (P = 0.3506). There was no significant correlation between individual fitness components and the level of sensitivity to AZ and PYR. Preventive applications of Abound (commercial formulation of AZ) at full field rates failed to control disease caused by QoI-resistant isolates under greenhouse conditions. Our results suggest that QoI resistance in A. alternata tangerine pathotype is stable in the absence of QoI selection pressure and that resistance development did not affect the fitness of resistant isolates.
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Affiliation(s)
- Byron Vega
- Citrus Research and Education Center, University of Florida, Lake Alfred
| | - Megan M Dewdney
- Citrus Research and Education Center, University of Florida, Lake Alfred
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Tsai HC, Chung KR. Calcineurin phosphatase and phospholipase C are required for developmental and pathological functions in the citrus fungal pathogen Alternaria alternata. MICROBIOLOGY-SGM 2014; 160:1453-1465. [PMID: 24763426 DOI: 10.1099/mic.0.077818-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Excessive Ca(2+) or compounds interfering with phosphoinositide cycling have been found to inhibit the growth of the tangerine pathotype of Alternaria alternata, suggesting a crucial role of Ca(2+) homeostasis in this pathotype. The roles of PLC1, a phospholipase C-coding gene and CAL1, a calcineurin phosphatase-coding gene were investigated. Targeted gene disruption showed that both PLC1 and CAL1 were required for vegetative growth, conidial formation and pathogenesis in citrus. Fungal strains lacking PLC1 or CAL1 exhibited extremely slow growth and induced small lesions on calamondin leaves. Δplc1 mutants produced fewer conidia, which germinated at slower rates than wild-type. Δcal1 mutants produced abnormal hyphae and failed to produce any mature conidia, but instead produced highly melanized bulbous hyphae with distinct septae. Fluorescence microscopy using Fluo-3 dye as a Ca(2+) indicator revealed that the Δplc1 mutant hyphae emitted stronger cytosolic fluorescence, and the Δcal1 mutant hyphae emitted less cytosolic fluorescence, than those of wild-type. Infection assessed on detached calamondin leaves revealed that application of CaCl2 or neomycin 24 h prior to inoculation provided protection against Alt. alternata. These data indicate that a dynamic equilibrium of cellular Ca(2+) is critical for developmental and pathological processes of Alt. alternata.
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Affiliation(s)
- Hsieh-Chin Tsai
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
| | - Kuang-Ren Chung
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL 32611, USA.,Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
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Chen LH, Yang SL, Chung KR. Resistance to oxidative stress via regulating siderophore-mediated iron acquisition by the citrus fungal pathogen Alternaria alternata. MICROBIOLOGY-SGM 2014; 160:970-979. [PMID: 24586035 DOI: 10.1099/mic.0.076182-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The ability of the necrotrophic fungus Alternaria alternata to detoxify reactive oxygen species (ROS) is crucial for pathogenesis to citrus. We report regulation of siderophore-mediated iron acquisition and ROS resistance by the NADPH oxidase (NOX), the redox activating yes-associated protein 1 (YAP1) regulator, and the high-osmolarity glycerol 1 (HOG1) mitogen-activated protein kinase (MAPK). The A. alternata nonribosomal peptide synthetase (NPS6) is essential for the biosynthesis of siderophores, contributing to iron uptake under low-iron conditions. Fungal strains impaired for NOX, YAP1, HOG1 or NPS6 all display increased sensitivity to ROS. Exogenous addition of iron at least partially rescues ROS sensitivity seen for NPS6, YAP1, HOG1, and NOX mutants. Importantly, expression of the NPS6 gene and biosynthesis of siderophores are regulated by NOX, YAP1 and HOG1, supporting a functional link among these regulatory pathways. Although iron fully rescues H2O2 sensitivity seen in mutants impaired for the response regulator SKN7, neither expression of NPS6 nor biosynthesis of siderophores is controlled by SKN7. Our results indicate that the acquisition of environmental iron has profound effects on ROS detoxification.
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Affiliation(s)
- Li-Hung Chen
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
| | - Siwy Ling Yang
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL 32611, USA.,Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
| | - Kuang-Ren Chung
- Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL 32611, USA.,Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
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Vega B, Dewdney MM. Distribution of QoI Resistance in Populations of Tangerine-Infecting Alternaria alternata in Florida. PLANT DISEASE 2014; 98:67-76. [PMID: 30708574 DOI: 10.1094/pdis-04-13-0449-re] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Chemical control, based on copper and quinone outside inhibitor (QoI) fungicides, has been essential for the management of brown spot of citrus, caused by Alternaria alternata. However, QoI control failures were detected recently in Florida. From 2008 to 2012, 817 monoconidial isolates of A. alternata from 46 citrus orchards were examined for sensitivity to azoxystrobin (AZ) and pyraclostrobin (PYR). Of the isolates, 57.6% were resistant to both fungicides, with effective concentration to inhibit 50% growth (EC50) values greater than 5 μg/ml for AZ and 1 μg/ml for PYR. The mean EC50 values for sensitive isolates were 0.139 and 0.020 μg/ml for AZ and PYR, respectively. The EC50 values of both fungicides were highly correlated (P < 0.0001), indicating cross resistance. The proportion of resistant isolates differed significantly (P < 0.0001) among cultivars and with QoI application frequency (P < 0.0001). However, resistance was not significantly related (P = 0.364) to disease severity in the field (low, moderate, and high) or isolate virulence (P = 0.397). The molecular basis for QoI resistance was determined for a subset of 235 isolates using polymerase chain reaction restriction fragment length polymorphism of the cytochrome b gene. All resistant isolates showed the point mutation G143A. Based on the presence of one or two introns, isolates were classified as profile I and profile II, respectively. The resistance frequency was significantly higher (P < 0.0001) in isolate profile II, suggesting a higher selection pressure for resistant population profile II.
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Affiliation(s)
- Byron Vega
- Citrus Research and Education Center, University of Florida, Lake Alfred
| | - Megan M Dewdney
- Citrus Research and Education Center, University of Florida, Lake Alfred
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Mikula H, Skrinjar P, Sohr B, Ellmer D, Hametner C, Fröhlich J. Total synthesis of masked Alternaria mycotoxins—sulfates and glucosides of alternariol (AOH) and alternariol-9-methyl ether (AME). Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.10.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Cuenca J, Aleza P, Vicent A, Brunel D, Ollitrault P, Navarro L. Genetically based location from triploid populations and gene ontology of a 3.3-mb genome region linked to Alternaria brown spot resistance in citrus reveal clusters of resistance genes. PLoS One 2013; 8:e76755. [PMID: 24116149 PMCID: PMC3792864 DOI: 10.1371/journal.pone.0076755] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 08/23/2013] [Indexed: 12/17/2022] Open
Abstract
Genetic analysis of phenotypical traits and marker-trait association in polyploid species is generally considered as a challenge. In the present work, different approaches were combined taking advantage of the particular genetic structures of 2n gametes resulting from second division restitution (SDR) to map a genome region linked to Alternaria brown spot (ABS) resistance in triploid citrus progeny. ABS in citrus is a serious disease caused by the tangerine pathotype of the fungus Alternaria alternata. This pathogen produces ACT-toxin, which induces necrotic lesions on fruit and young leaves, defoliation and fruit drop in susceptible genotypes. It is a strong concern for triploid breeding programs aiming to produce seedless mandarin cultivars. The monolocus dominant inheritance of susceptibility, proposed on the basis of diploid population studies, was corroborated in triploid progeny. Bulk segregant analysis coupled with genome scan using a large set of genetically mapped SNP markers and targeted genetic mapping by half tetrad analysis, using SSR and SNP markers, allowed locating a 3.3 Mb genomic region linked to ABS resistance near the centromere of chromosome III. Clusters of resistance genes were identified by gene ontology analysis of this genomic region. Some of these genes are good candidates to control the dominant susceptibility to the ACT-toxin. SSR and SNP markers were developed for efficient early marker-assisted selection of ABS resistant hybrids.
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Affiliation(s)
- José Cuenca
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias. Moncada, Valencia, Spain
| | - Pablo Aleza
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias. Moncada, Valencia, Spain
| | - Antonio Vicent
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias. Moncada, Valencia, Spain
| | - Dominique Brunel
- Etude du Polymorphisme des Genomes Vegetaux, Institut National de la Recherche Agronomique, Évry, France
| | - Patrick Ollitrault
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias. Moncada, Valencia, Spain
- Etude du Polymorphisme des Genomes Vegetaux, Institut National de la Recherche Agronomique, Évry, France
- BIOS Department, Amélioration Génétique des Espèces à Multiplication Végétative. Centre de Coopeération Internationale en Recherche Agronomique pour le Développement, Montpellier, France
| | - Luis Navarro
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias. Moncada, Valencia, Spain
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Yang SL, Chung KR. Similar and distinct roles of NADPH oxidase components in the tangerine pathotype of Alternaria alternata. MOLECULAR PLANT PATHOLOGY 2013; 14:543-556. [PMID: 23527595 PMCID: PMC6638896 DOI: 10.1111/mpp.12026] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The fungal nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) complex, which has been implicated in the production of low-level reactive oxygen species (ROS), contains mainly NoxA, NoxB (gp91(phox) homologues) and NoxR (p67(phox) homologue). Here, we report the developmental and pathological functions of NoxB and NoxR in the tangerine pathotype of Alternaria alternata. Loss-of-function genetics revealed that all three Nox components are required for the accumulation of cellular hydrogen peroxide (H₂O₂). Alternaria alternata strains lacking NoxA, NoxB or NoxR also displayed an increased sensitivity to H₂O₂ and many ROS-generating oxidants. These phenotypes are highly similar to those previously seen for the Δyap1 mutant lacking a YAP1 transcriptional regulator and for the Δhog1 mutant lacking a HOG1 mitogen-activated protein (MAP) kinase, implicating a possible link among them. A fungal strain carrying a NoxA NoxB or NoxA NoxR double mutation was more sensitive to the test compounds than the strain mutated at a single gene, implicating a synergistic function among Nox components. The ΔnoxB mutant strain failed to produce any conidia; both ΔnoxA and ΔnoxR mutant strains showed a severe reduction in sporulation. Mutant strains carrying defective NoxB had higher chitin content than the wild-type and were insensitive to calcofluor white, Congo red and the fungicides vinclozolin and fludioxonil. Virulence assays revealed that all three Nox components are required for the elaboration of the penetration process. The inability to penetrate the citrus host, observed for Δnox mutants, could be overcome by wounding and by reacquiring a dominant Nox gene. The A. alternata NoxR did not influence the expression of NoxB, but negatively regulated NoxA. Importantly, the expression of both YAP1 and HOG1 genes, whose products are involved in resistance to ROS, was down-regulated in fungi carrying defective NoxA, NoxB or NoxR. Our results highlight the requirement of Nox in ROS resistance and provide insights into its critical role in regulating both YAP1 and HOG1 in A. alternata.
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Affiliation(s)
- Siwy Ling Yang
- Citrus Research and Education Center, Institute of Food and Agricultural Sciences-IFAS, University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
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de Souza GD, Mithöfer A, Daolio C, Schneider B, Rodrigues-Filho E. Identification of Alternaria alternata mycotoxins by LC-SPE-NMR and their cytotoxic effects to soybean (Glycine max) cell suspension culture. Molecules 2013; 18:2528-38. [PMID: 23442929 PMCID: PMC6270395 DOI: 10.3390/molecules18032528] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 01/29/2013] [Accepted: 02/16/2013] [Indexed: 11/16/2022] Open
Abstract
This present work describes the application of liquid chromatography-solid phase extraction-nuclear magnetic resonance spectroscopy to analyse Alternaria alternata crude extracts. Altenusin (1), alternariol (2), 3'-hydroxyalternariol monomethyl ether (3), and alternariol monomethyl ether (4), were separated and identified. High-resolution mass spectrometry confirmed the proposed structures. The cytotoxic effects of these compounds towards plants were determined using soybean (Glycine max) cell cultures as a model. EC(50) values which range from 0.11 (± 0.02) to 4.69 (± 0.47) μM showed the high cytotoxicity of these compounds.
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Affiliation(s)
- Gezimar D. de Souza
- Laboratório de Bioquímica Micromolecular de Micro-organismos, Departamento de Química, Universidade Federal de São Carlos—UFSCar, Rodovia Washington Luiz, Km 235, 676 São Carlos-SP, Brazil; E-Mail:
- Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology; Hans-Knöll-Straße 8, Jena D-07745, Germany; E-Mail:
- Accert Chemistry and Biotechnology Inc., Rua Alfredo Lopes 1717, São Carlos-SP, Brazil
| | - Axel Mithöfer
- Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology; Hans-Knöll-Straße 8, Jena D-07745, Germany; E-Mail:
| | - Cristina Daolio
- Biosynthesis/NMR Research Group, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, Jena D-07745, Germany; E-Mails: (C.D.); (B.S.)
- NMR Applications Group, Bruker Biospin GmbH, Silberstreifen 4, Rheinstetten 76287, Germany
| | - Bernd Schneider
- Biosynthesis/NMR Research Group, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, Jena D-07745, Germany; E-Mails: (C.D.); (B.S.)
| | - Edson Rodrigues-Filho
- Laboratório de Bioquímica Micromolecular de Micro-organismos, Departamento de Química, Universidade Federal de São Carlos—UFSCar, Rodovia Washington Luiz, Km 235, 676 São Carlos-SP, Brazil; E-Mail:
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Tsuge T, Harimoto Y, Akimitsu K, Ohtani K, Kodama M, Akagi Y, Egusa M, Yamamoto M, Otani H. Host-selective toxins produced by the plant pathogenic fungusAlternaria alternata. FEMS Microbiol Rev 2013; 37:44-66. [DOI: 10.1111/j.1574-6976.2012.00350.x] [Citation(s) in RCA: 247] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 06/14/2012] [Accepted: 07/19/2012] [Indexed: 12/19/2022] Open
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Nishimura S, Tatano S, Miyamoto Y, Ohtani K, Fukumoto T, Gomi K, Tada Y, Ichimura K, Akimitsu K. A zinc-binding citrus protein metallothionein can act as a plant defense factor by controlling host-selective ACR-toxin production. PLANT MOLECULAR BIOLOGY 2013; 81:1-11. [PMID: 23086497 DOI: 10.1007/s11103-012-9976-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 10/04/2012] [Indexed: 06/01/2023]
Abstract
Metallothionein is a small cysteine-rich protein known to have a metal-binding function. We isolated three different lengths of rough lemon cDNAs encoding a metallothionein (RlemMT1, RlemMT2 and RlemMT3), and only RlemMT1-recombinant protein had zinc-binding activity. Appropriate concentration of zinc is an essential micronutrient for living organisms, while excess zinc is toxic. Zinc also stimulates the production of host-selective ACR-toxin for citrus leaf spot pathogen of Alternaria alternata rough lemon pathotype. Trapping of zinc by RlemMT1-recombinant protein or by a zinc-scavenging agent in the culture medium caused suppression of ACR-toxin production by the fungus. Since ACR-toxin is the disease determinant for A. alternata rough lemon pathotype, addition of RlemMT1 to the inoculum suspension led to a significant decrease in symptoms on rough lemon leaves as a result of reduced ACR-toxin production from the zinc trap around infection sites. RlemMT1-overexpression mutant of A. alternata rough lemon pathotype also produced less ACR-toxin and reduced virulence on rough lemon. This suppression was caused by an interruption of zinc absorption by cells from the trapping of the mineral by RlemMT1 and an excess supplement of ZnSO(4) restored toxin production and pathogenicity. Based on these results, we propose that zinc adsorbents including metallothionein likely can act as a plant defense factor by controlling toxin biosynthesis via inhibition of zinc absorption by the pathogen.
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Izumi Y, Ohtani K, Miyamoto Y, Masunaka A, Fukumoto T, Gomi K, Tada Y, Ichimura K, Peever TL, Akimitsu K. A polyketide synthase gene, ACRTS2, is responsible for biosynthesis of host-selective ACR-toxin in the rough lemon pathotype of Alternaria alternata. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:1419-1429. [PMID: 22835272 DOI: 10.1094/mpmi-06-12-0155-r] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The rough lemon pathotype of Alternaria alternata produces host-selective ACR-toxin and causes Alternaria leaf spot disease of rough lemon (Citrus jambhiri). The structure of ACR-toxin I (MW = 496) consists of a polyketide with an α-dihydropyrone ring in a 19-carbon polyalcohol. Genes responsible for toxin production were localized to a 1.5-Mb chromosome in the genome of the rough lemon pathotype. Sequence analysis of this chromosome revealed an 8,338-bp open reading frame, ACRTS2, that was present only in the genomes of ACR-toxin-producing isolates. ACRTS2 is predicted to encode a putative polyketide synthase of 2,513 amino acids and belongs to the fungal reducing type I polyketide synthases. Typical polyketide functional domains were identified in the predicted amino acid sequence, including β-ketoacyl synthase, acyl transferase, methyl transferase, dehydratase, β-ketoreductase, and phosphopantetheine attachment site domains. Combined use of homologous recombination-mediated gene disruption and RNA silencing allowed examination of the functional role of multiple paralogs in ACR-toxin production. ACRTS2 was found to be essential for ACR-toxin production and pathogenicity of the rough lemon pathotype of A. alternata.
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Affiliation(s)
- Y Izumi
- Kagawa University, Kagawa, Japan
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Vega B, Liberti D, Harmon PF, Dewdney MM. A Rapid Resazurin-Based Microtiter Assay to Evaluate QoI Sensitivity for Alternaria alternata Isolates and Their Molecular Characterization. PLANT DISEASE 2012; 96:1262-1270. [PMID: 30727145 DOI: 10.1094/pdis-12-11-1037-re] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Chemical management of Alternaria brown spot of citrus is based upon the timely application of site-specific fungicides, many of which are vulnerable to the development of fungicide resistance. A rapid microtiter bioassay based on the colorimetric changes of resazurin (RZ) dye was developed to evaluate the sensitivity of Alternaria alternata to quinone outside inhibitor (QoI) fungicides. Four liquid media (complete medium, minimal medium, potato dextrose broth, and yeast peptone dextrose broth), five conidia concentrations (from 101 to 105 conidia/ ml), and five RZ concentrations (10, 20, 30, 40, and 50 μM) were evaluated. Complete medium at 105 conidia/ml and 40 μM RZ were identified as optimal for measuring RZ reduction. The effective concentration of two QoI fungicides (azoxystrobin and pyraclostrobin) needed to reduce RZ by 50% (EC50) was calculated and compared with those obtained from conidia germination tests on fungicide-amended media. Concordant EC50 values were observed (R2 = 0.923; P < 0.0001) from both methods. Resistant phenotypes were further characterized by the partial sequencing of the cytochrome b gene. Genetic variability associated with the presence or absence of two introns was observed among isolates. The identified resistant isolates had the amino acid substitution G143A, typical of QoI resistance in other fungi.
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Affiliation(s)
- Byron Vega
- Citrus Research and Education Center, University of Florida, Lake Alfred
| | - Daniele Liberti
- Department of Plant Pathology, University of Florida, Gainesville
| | - Philip F Harmon
- Department of Plant Pathology, University of Florida, Gainesville
| | - Megan M Dewdney
- Citrus Research and Education Center, University of Florida, Lake Alfred
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