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Salamzade R, Tran P, Martin C, Manson AL, Gilmore MS, Earl AM, Anantharaman K, Kalan LR. zol & fai: large-scale targeted detection and evolutionary investigation of gene clusters. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.07.544063. [PMID: 37333121 PMCID: PMC10274777 DOI: 10.1101/2023.06.07.544063] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Many universally and conditionally important genes are genomically aggregated within clusters. Here, we introduce fai and zol, which together enable large-scale comparative analysis of different types of gene clusters and mobile-genetic elements (MGEs), such as biosynthetic gene clusters (BGCs) or viruses. Fundamentally, they overcome a current bottleneck to reliably perform comprehensive orthology inference at large scale across broad taxonomic contexts and thousands of genomes. First, fai allows the identification of orthologous or homologous instances of a query gene cluster of interest amongst a database of target genomes. Subsequently, zol enables reliable, context-specific inference of protein-encoding ortholog groups for individual genes across gene cluster instances. In addition, zol performs functional annotation and computes a variety of statistics for each inferred ortholog group. These programs are showcased through application to: (i) longitudinal tracking of a virus in metagenomes, (ii) discovering novel population-genetic insights of two common BGCs in a fungal species, and (iii) uncovering large-scale evolutionary trends of a virulence-associated gene cluster across thousands of genomes from a diverse bacterial genus.
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Affiliation(s)
- Rauf Salamzade
- Department of Medical Microbiology and Immunology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI, USA
| | - Patricia Tran
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
- Freshwater and Marine Science Doctoral Program, University of Wisconsin-Madison, WI, USA
| | - Cody Martin
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Abigail L. Manson
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Michael S. Gilmore
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
- Department of Ophthalmology, Harvard Medical School and Mass Eye and Ear, Boston, Massachusetts, USA
- Department of Microbiology, Harvard Medical School and Mass Eye and Ear, Boston, Massachusetts, USA
| | - Ashlee M. Earl
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | | | - Lindsay R. Kalan
- Department of Medical Microbiology and Immunology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
- Department of Medicine, Division of Infectious Disease, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
- M.G. DeGroote Institute for Infectious Disease Research, David Braley Centre for Antibiotic Discovery, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
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2
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Penagos-Tabares F, Sulyok M, Artavia JI, Flores-Quiroz SI, Garzón-Pérez C, Castillo-Lopez E, Zavala L, Orozco JD, Faas J, Krska R, Zebeli Q. Mixtures of Mycotoxins, Phytoestrogens, and Other Secondary Metabolites in Whole-Plant Corn Silages and Total Mixed Rations of Dairy Farms in Central and Northern Mexico. Toxins (Basel) 2023; 15:153. [PMID: 36828467 PMCID: PMC9965745 DOI: 10.3390/toxins15020153] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 02/08/2023] [Accepted: 02/09/2023] [Indexed: 02/16/2023] Open
Abstract
Mycotoxins and endocrine disruptors such as phytoestrogens can affect cattle health, reproduction, and productivity. Most studies of mycotoxins in dairy feeds in Mexico and worldwide have been focused on a few (regulated) mycotoxins. In contrast, less known fungal toxins, phytoestrogens, and other metabolites have been neglected and underestimated. This study analyzed a broad spectrum (>800) of mycotoxins, phytoestrogens, and fungal, plant, and unspecific secondary metabolites in whole-plant corn silages (WPCSs) and total mixed rations (TMRs) collected from 19 Mexican dairy farms. A validated multi-metabolite liquid chromatography/electrospray ionization-tandem mass spectrometric (LC/ESI-MS/MS) method was used. Our results revealed 125 of >800 tested (potentially toxic) secondary metabolites. WPCSs/TMRs in Mexico presented ubiquitous contamination with mycotoxins, phytoestrogens, and other metabolites. The average number of mycotoxins per TMR was 24, ranging from 9 to 31. Fusarium-derived secondary metabolites showed the highest frequencies, concentrations, and diversity among the detected fungal compounds. The most frequently detected mycotoxins in TMRs were zearalenone (ZEN) (100%), fumonisin B1 (FB1) (84%), and deoxynivalenol (84%). Aflatoxin B1 (AFB1) and ochratoxin A (OTA), previously reported in Mexico, were not detected. All TMR samples tested positive for phytoestrogens. Among the investigated dietary ingredients, corn stover, sorghum silage, and concentrate proportions were the most correlated with levels of total mycotoxins, fumonisins (Fs), and ergot alkaloids, respectively.
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Affiliation(s)
- Felipe Penagos-Tabares
- Unit of Nutritional Physiology, Institute of Physiology, Pathophysiology, and Biophysics, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210 Vienna, Austria
- Christian-Doppler-Laboratory for Innovative Gut Health Concepts in Livestock (CDL-LiveGUT), Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria
- FFoQSI GmbH—Austrian Competence Centre for Feed and Food Quality, Safety and Innovation, Technopark 1C, 3430 Tulln, Austria
| | - Michael Sulyok
- Department of Agrobiotechnology, IFA-Tulln, Institute of Bioanalytics and Agro-Metabolomics, University of Natural Resources and Life Sciences, Vienna, Konrad-Lorenz-Strasse 20, 3430 Tulln, Austria
| | | | - Samanta-Irais Flores-Quiroz
- Facultad de Estudios Superiores Cuautitlán, Cuautitlán, Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México (UNAM), Cuautitlán Izcalli 54714, Mexico
| | - César Garzón-Pérez
- Facultad de Estudios Superiores Cuautitlán, Cuautitlán, Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México (UNAM), Cuautitlán Izcalli 54714, Mexico
| | - Ezequías Castillo-Lopez
- Christian-Doppler-Laboratory for Innovative Gut Health Concepts in Livestock (CDL-LiveGUT), Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria
- Institute of Animal Nutrition and Functional Plant Compounds, Department of Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria
| | - Luis Zavala
- DSM-BIOMIN Research Center, Technopark 1, 3430 Tulln, Austria
| | | | - Johannes Faas
- DSM-BIOMIN Research Center, Technopark 1, 3430 Tulln, Austria
| | - Rudolf Krska
- Department of Agrobiotechnology, IFA-Tulln, Institute of Bioanalytics and Agro-Metabolomics, University of Natural Resources and Life Sciences, Vienna, Konrad-Lorenz-Strasse 20, 3430 Tulln, Austria
- Institute for Global Food Security, School of Biological Sciences, Queen’s University Belfast, 19 Chlorine Gardens, Belfast BT9 5DL, UK
| | - Qendrim Zebeli
- Christian-Doppler-Laboratory for Innovative Gut Health Concepts in Livestock (CDL-LiveGUT), Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria
- Institute of Animal Nutrition and Functional Plant Compounds, Department of Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria
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Wang J, Liang L, Wei S, Zhang S, Hu Y, Lv Y. Histone 2-Hydroxyisobutyryltransferase Encoded by Afngg1 Is Involved in Pathogenicity and Aflatoxin Biosynthesis in Aspergillus flavus. Toxins (Basel) 2022; 15:7. [PMID: 36668827 PMCID: PMC9861817 DOI: 10.3390/toxins15010007] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/07/2022] [Accepted: 12/16/2022] [Indexed: 12/24/2022] Open
Abstract
Aflatoxin, a carcinogenic secondary metabolite produced by Aspergillus flavus, is a significant threat to human health and agricultural production. Histone 2-hydroxyisobutyrylation is a novel post-translational modification that regulates various biological processes, including secondary metabolism. In this study, we identified the novel histone 2-hydroxyisobutyryltransferase Afngg1 in A. flavus, and explored its role in cell growth, development and aflatoxin biosynthesis. Afngg1 gene deletion markedly decreased lysine 2-hydroxyisobutyrylation modification of histones H4K5 and H4K8 compared with the control strain. Additionally, Afngg1 deletion inhibited mycelial growth of A. flavus, and the number of conidia and hydrophobicity were significantly decreased. Notably, aflatoxin B1 biosynthesis and sclerotia production were completely inhibited in the ΔAfngg1 strain. Furthermore, the pathogenicity of the ΔAfngg1 strain infecting peanut and corn grains was also diminished, including reduced spore production and aflatoxin biosynthesis compared with A. flavus control and Afngg1 complementation strains. Transcriptome analysis showed that, compared with control strains, differentially expressed genes in ΔAfngg1 were mainly involved in chromatin remodelling, cell development, secondary metabolism and oxidative stress. These results suggest that Afngg1 is involved in histone 2-hydroxyisobutyrylation and chromatin modification, and thus affects cell development and aflatoxin biosynthesis in A. flavus. Our results lay a foundation for in-depth research on the 2-hydroxyisobutyrylation modification in A. flavus, and may provide a novel target for aflatoxin contamination prevention.
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Affiliation(s)
- Jing Wang
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Liuke Liang
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Shan Wei
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Shuaibing Zhang
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Yuansen Hu
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Yangyong Lv
- College of Biological Engineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
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Lebar MD, Mack BM, Carter-Wientjes CH, Wei Q, Mattison CP, Cary JW. Small NRPS-like enzymes in Aspergillus sections Flavi and Circumdati selectively form substituted pyrazinone metabolites. FRONTIERS IN FUNGAL BIOLOGY 2022; 3:1029195. [PMID: 37746228 PMCID: PMC10512218 DOI: 10.3389/ffunb.2022.1029195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 10/14/2022] [Indexed: 09/26/2023]
Abstract
Aspergillus fungi produce mycotoxins that are detrimental to human and animal health. Two sections of aspergilli are of particular importance to cereal food crops such as corn and barley. Aspergillus section Flavi species like A. flavus and A. parasiticus produce aflatoxins, while section Circumdati species like A. ochraceus and A. sclerotiorum produce ochratoxin A. Mitigating these toxins in food and feed is a critical and ongoing worldwide effort. We have previously investigated biosynthetic gene clusters in Aspergillus flavus that are linked to fungal virulence in corn. We found that one such cluster, asa, is responsible for the production of aspergillic acid, an iron-binding, hydroxamic acid-containing pyrazinone metabolite. Furthermore, we found that the asa gene cluster is present in many other aflatoxin- and ochratoxin-producing aspergilli. The core gene in the asa cluster encodes the small nonribosomal peptide synthetase-like (NRPS-like) protein AsaC. We have swapped the asaC ortholog from A. sclerotiorum into A. flavus, replacing its native copy, and have also cloned both asaC orthologs into Saccharomyces cerevisiae. We show that AsaC orthologs in section Flavi and section Circumdati, while only containing adenylation-thiolation-reductase (ATR) domains, can selectively biosynthesize distinct pyrazinone natural products: deoxyaspergillic acid and flavacol, respectively. Because pyrazinone natural products and the gene clusters responsible for their production are implicated in a variety of important microbe-host interactions, uncovering the function and selectivity of the enzymes involved could lead to strategies that ultimately benefit human health.
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Affiliation(s)
- Matthew D. Lebar
- Food and Feed Safety Research, Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA), New Orleans, LA, United States
| | - Brian M. Mack
- Food and Feed Safety Research, Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA), New Orleans, LA, United States
| | - Carol H. Carter-Wientjes
- Food and Feed Safety Research, Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA), New Orleans, LA, United States
| | - Qijian Wei
- Food and Feed Safety Research, Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA), New Orleans, LA, United States
| | - Christopher P. Mattison
- Food Processing and Sensory Quality Research, Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA), New Orleans, LA, United States
| | - Jeffrey W. Cary
- Food and Feed Safety Research, Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA), New Orleans, LA, United States
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StcU-2 Gene Mutation via CRISPR/Cas9 Leads to Misregulation of Spore-Cyst Formation in Ascosphaera apis. Microorganisms 2022; 10:microorganisms10102088. [PMID: 36296364 PMCID: PMC9607276 DOI: 10.3390/microorganisms10102088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/15/2022] [Accepted: 10/17/2022] [Indexed: 11/05/2022] Open
Abstract
Ascosphaera apis is the causative agent of honey bee chalkbrood disease, and spores are the only known source of infections. Interference with sporulation is therefore a promising way to manage A. apis. The versicolorin reductase gene (StcU-2) is a ketoreductase protein related to sporulation and melanin biosynthesis. To study the StcU-2 gene in ascospore production of A. apis, CRISPR/Cas9 was used, and eight hygromycin B antibiotic-resistant transformants incorporating enhanced green fluorescent protein (EGFP) were made and analyzed. PCR amplification, gel electrophoresis, and sequence analysis were used for target gene editing analysis and verification. The CRISPR/Cas9 editing successfully knocked out the StcU-2 gene in A. apis. StcU-2 mutants had shown albino and non-functional spore-cyst development and lost effective sporulation. In conclusion, editing of StcU-2 gene has shown direct relation with sporulation and melanin biosynthesis of A. apis; this effective sporulation reduction would reduce the spread and pathogenicity of A. apis to managed honey bee. To the best of our knowledge, this is the first time CRISPR/Cas9-mediated gene editing has been efficiently performed in A. apis, a fungal honey bee brood pathogen, which offers a comprehensive set of procedural references that contributes to A. apis gene function studies and consequent control of chalkbrood disease.
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6
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Penagos-Tabares F, Khiaosa-ard R, Schmidt M, Bartl EM, Kehrer J, Nagl V, Faas J, Sulyok M, Krska R, Zebeli Q. Cocktails of Mycotoxins, Phytoestrogens, and Other Secondary Metabolites in Diets of Dairy Cows in Austria: Inferences from Diet Composition and Geo-Climatic Factors. Toxins (Basel) 2022; 14:toxins14070493. [PMID: 35878231 PMCID: PMC9318294 DOI: 10.3390/toxins14070493] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 07/10/2022] [Accepted: 07/12/2022] [Indexed: 12/11/2022] Open
Abstract
Dairy production is a pivotal economic sector of Austrian and European agriculture. Dietary toxins and endocrine disruptors of natural origin such as mycotoxins and phytoestrogens can affect animal health, reproduction, and productivity. This study characterized the profile of a wide spectrum of fungal, plant, and unspecific secondary metabolites, including regulated, emerging, and modified mycotoxins, phytoestrogens, and cyanogenic glucosides, in complete diets of lactating cows from 100 Austrian dairy farms. To achieve this, a validated multi-metabolite liquid chromatography/electrospray ionization−tandem mass spectrometric (LC/ESI−MS/MS) method was employed, detecting 155 of >800 tested metabolites. Additionally, the most influential dietary and geo-climatic factors related to the dietary mycotoxin contamination of Austrian dairy cattle were recognized. We evidenced that the diets of Austrian dairy cows presented ubiquitous contamination with mixtures of mycotoxins and phytoestrogens. Metabolites derived from Fusarium spp. presented the highest concentrations, were the most recurrent, and had the highest diversity among the detected fungal compounds. Zearalenone, deoxynivalenol, and fumonisin B1 were the most frequently occurring mycotoxins considered in the EU legislation, with detection frequencies >70%. Among the investigated dietary factors, inclusion of maize silage (MS) and straw in the diets was the most influential factor in contamination with Fusarium-derived and other fungal toxins and metabolites, and temperature was the most influential among the geo-climatic factors.
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Affiliation(s)
- Felipe Penagos-Tabares
- Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria; (F.P.-T.); (M.S.); (E.-M.B.); (J.K.); (Q.Z.)
| | - Ratchaneewan Khiaosa-ard
- Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria; (F.P.-T.); (M.S.); (E.-M.B.); (J.K.); (Q.Z.)
- Correspondence:
| | - Marlene Schmidt
- Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria; (F.P.-T.); (M.S.); (E.-M.B.); (J.K.); (Q.Z.)
| | - Eva-Maria Bartl
- Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria; (F.P.-T.); (M.S.); (E.-M.B.); (J.K.); (Q.Z.)
| | - Johanna Kehrer
- Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria; (F.P.-T.); (M.S.); (E.-M.B.); (J.K.); (Q.Z.)
| | - Veronika Nagl
- DSM—BIOMIN Research Center, Technopark 1, 3430 Tulln, Austria; (V.N.); (J.F.)
| | - Johannes Faas
- DSM—BIOMIN Research Center, Technopark 1, 3430 Tulln, Austria; (V.N.); (J.F.)
| | - Michael Sulyok
- Department of Agrobiotechnology (IFA-Tulln), Institute of Bioanalytics and Agro-Metabolomics, University of Natural Resources and Life Sciences Vienna, Konrad Lorenz-Strasse 20, 3430 Tulln, Austria; (M.S.); (R.K.)
| | - Rudolf Krska
- Department of Agrobiotechnology (IFA-Tulln), Institute of Bioanalytics and Agro-Metabolomics, University of Natural Resources and Life Sciences Vienna, Konrad Lorenz-Strasse 20, 3430 Tulln, Austria; (M.S.); (R.K.)
- Institute for Global Food Security, School of Biological Sciences, University Road, Belfast BT7 1NN, UK
| | - Qendrim Zebeli
- Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria; (F.P.-T.); (M.S.); (E.-M.B.); (J.K.); (Q.Z.)
- Christian-Doppler-Laboratory for Innovative Gut Health Concepts in Livestock (CDL-LiveGUT), Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210 Vienna, Austria
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7
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Lv Y, Wang J, Yang H, Li N, Farzaneh M, Wei S, Zhai H, Zhang S, Hu Y. Lysine 2-hydroxyisobutyrylation orchestrates cell development and aflatoxin biosynthesis in Aspergillus flavus. Environ Microbiol 2022; 24:4356-4368. [PMID: 35621059 DOI: 10.1111/1462-2920.16077] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 05/17/2022] [Indexed: 11/30/2022]
Abstract
Lysine 2-hydroxyisobutyrylation (Khib ) is a recently identified post-translational modifications (PTM) that regulates numerous cellular metabolic processes. In pathogenic microorganism, although glycolysis and fungal virulence are regulated by Khib , its potential roles in fungi remains to be elusive. Our preliminary results showed that levels of Khib fluctuate over time in Aspergillus flavus, which frequently contaminates crops and produces carcinogenic aflatoxins. However, the perception of Khib function in A. flavus is limited, especially in mycotoxin-producing strains. Here, we performed a comprehensive analysis of Khib in A. flavus, and 7156 Khib sites were identified in 1473 proteins. Notably, we demonstrated that Khib of AflM, a key enzyme in aflatoxin biosynthesis, affected conidia production and sclerotia formation. Furthermore, aflM deletion impaired aflatoxin biosynthesis, and more importantly, strains in which Khib was mimicked by K to T mutation at K49, K179 and K180 sites showed reduced aflatoxin production compared with wild type and ΔaflM complementation strains. These results indicate that Khib at these sites of AflM negatively regulates aflatoxin biosynthesis in A. flavus. In summary, our study revealed the potential roles of Khib in A. flavus, and particularly shed light on a new way to regulate aflatoxin production via Khib . This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Yangyong Lv
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Jing Wang
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Haojie Yang
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Na Li
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Mohsen Farzaneh
- Department of Agriculture, Medicinal Plants and Drugs Research Institute, Shahid Beheshti University, 1983969411, Tehran, Iran
| | - Shan Wei
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Huanchen Zhai
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Shuaibing Zhang
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
| | - Yuansen Hu
- College of Biological Engineering, Henan University of Technology, Zhengzhou, 450001, People's Republic of China.,Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou, 450001, People's Republic of China
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8
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Reis T, Tralamazza S, Coelho E, Zorzete P, Corrêa B. Early expression of the aflatoxin gene cluster in Aspergillus nomiae isolated from Brazil nut. Toxicon 2022; 209:36-42. [DOI: 10.1016/j.toxicon.2022.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 12/30/2021] [Accepted: 01/21/2022] [Indexed: 10/19/2022]
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9
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Jia K, Yan L, Jia Y, Xu S, Yan Z, Wang S. aflN Is Involved in the Biosynthesis of Aflatoxin and Conidiation in Aspergillus flavus. Toxins (Basel) 2021; 13:toxins13110831. [PMID: 34822615 PMCID: PMC8617700 DOI: 10.3390/toxins13110831] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Revised: 11/17/2021] [Accepted: 11/20/2021] [Indexed: 01/08/2023] Open
Abstract
Aspergillus flavus poses a threat to society economy and public health due to aflatoxin production. aflN is a gene located in the aflatoxin gene cluster, but the function of AflN is undefined in Aspergillus flavus. In this study, aflN is knocked out and overexpressed to study the function of AflN. The results indicated that the loss of AflN leads to the defect of aflatoxin biosynthesis. AflN is also found to play a role in conidiation but not hyphal growth and sclerotia development. Moreover, AlfN is related to the response to environmental oxidative stress and intracellular levels of reactive oxygen species. At last, AflN is involved in the pathogenicity of Aspergillus flavus to host. These results suggested that AflN played important roles in aflatoxin biosynthesis, conidiation and reactive oxygen species generation in Aspergillus flavus, which will be helpful for the understanding of aflN function, and will be beneficial to the prevention and control of Aspergillus flavus and aflatoxins contamination.
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10
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Singh SK, Rajput A, De A, Chakraborti T, Husain SM. Promiscuity of an unrelated anthrol reductase of Talaromyces islandicus WF-38-12. Catal Sci Technol 2021. [DOI: 10.1039/d0cy02148b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new anthrol reductase from Talaromyces islandicus (ARti-2).
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Affiliation(s)
- Shailesh Kumar Singh
- Molecular Synthesis and Drug Discovery Unit
- Centre of Biomedical Research
- SGPGIMS Campus
- Lucknow-226014
- India
| | - Anshul Rajput
- Molecular Synthesis and Drug Discovery Unit
- Centre of Biomedical Research
- SGPGIMS Campus
- Lucknow-226014
- India
| | - Arijit De
- Molecular Synthesis and Drug Discovery Unit
- Centre of Biomedical Research
- SGPGIMS Campus
- Lucknow-226014
- India
| | - Tapati Chakraborti
- Department of Biochemistry and Biophysics
- University of Kalyani
- Nadia-741235
- India
| | - Syed Masood Husain
- Molecular Synthesis and Drug Discovery Unit
- Centre of Biomedical Research
- SGPGIMS Campus
- Lucknow-226014
- India
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Two New Aspergillus flavus Reference Genomes Reveal a Large Insertion Potentially Contributing to Isolate Stress Tolerance and Aflatoxin Production. G3-GENES GENOMES GENETICS 2020; 10:3515-3531. [PMID: 32817124 PMCID: PMC7534430 DOI: 10.1534/g3.120.401405] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Efforts in genome sequencing in the Aspergillus genus have led to the development of quality reference genomes for several important species including A. nidulans, A. fumigatus, and A. oryzae However, less progress has been made for A. flavus As part of the effort of the USDA-ARS Annual Aflatoxin Workshop Fungal Genome Project, the isolate NRRL3357 was sequenced and resulted in a scaffold-level genome released in 2005. Our goal has been biologically driven, focusing on two areas: isolate variation in aflatoxin production and drought stress exacerbating aflatoxin production by A. flavus Therefore, we developed two reference pseudomolecule genome assemblies derived from chromosome arms for two isolates: AF13, a MAT1-2, highly stress tolerant, and highly aflatoxigenic isolate; and NRRL3357, a MAT1-1, less stress tolerant, and moderate aflatoxin producer in comparison to AF13. Here, we report these two reference-grade assemblies for these isolates through a combination of PacBio long-read sequencing and optical mapping, and coupled them with comparative, functional, and phylogenetic analyses. This analysis resulted in the identification of 153 and 45 unique genes in AF13 and NRRL3357, respectively. We also confirmed the presence of a unique 310 Kb insertion in AF13 containing 60 genes. Analysis of this insertion revealed the presence of a bZIP transcription factor, named atfC, which may contribute to isolate pathogenicity and stress tolerance. Phylogenomic analyses comparing these and other available assemblies also suggest that the species complex of A. flavus is polyphyletic.
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12
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Zeng H, Cai J, Hatabayashi H, Nakagawa H, Nakajima H, Yabe K. verA Gene is Involved in the Step to Make the Xanthone Structure of Demethylsterigmatocystin in Aflatoxin Biosynthesis. Int J Mol Sci 2020; 21:ijms21176389. [PMID: 32887494 PMCID: PMC7503927 DOI: 10.3390/ijms21176389] [Citation(s) in RCA: 7] [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: 07/26/2020] [Revised: 08/22/2020] [Accepted: 08/26/2020] [Indexed: 11/16/2022] Open
Abstract
In the biosynthesis of aflatoxin, verA, ver-1, ordB, and hypA genes of the aflatoxin gene cluster are involved in the pathway from versicolorin A (VA) to demethylsterigmatocystin (DMST). We herein isolated each disruptant of these four genes to determine their functions in more detail. Disruptants of ver-1, ordB, and hypA genes commonly accumulated VA in their mycelia. In contrast, the verA gene disruptant accumulated a novel yellow fluorescent substance (which we named HAMA) in the mycelia as well as culture medium. Feeding HAMA to the other disruptants commonly caused the production of aflatoxins B1 (AFB1) and G1 (AFG1). These results indicate that HAMA pigment is a novel aflatoxin precursor which is involved at a certain step after those of ver-1, ordB, and hypA genes between VA and DMST. HAMA was found to be an unstable substance to easily convert to DMST and sterigmatin. A liquid chromatography-mass spectrometry (LC-MS) analysis showed that the molecular mass of HAMA was 374, and HAMA gave two close major peaks in the LC chromatogram in some LC conditions. We suggest that these peaks correspond to the two conformers of HAMA; one of them would be selectively bound on the substrate binding site of VerA enzyme and then converted to DMST. VerA enzyme may work as a key enzyme in the creation of the xanthone structure of DMST from HAMA.
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Affiliation(s)
- Hongmei Zeng
- Food Research Institute, National Agriculture and Food Research Organization (NARO), 2-1-12 Kannon-dai, Tsukuba-shi 305-8642, Ibaraki, Japan; (H.Z.); (J.C.); (H.H.); (H.N.)
- Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Jingjing Cai
- Food Research Institute, National Agriculture and Food Research Organization (NARO), 2-1-12 Kannon-dai, Tsukuba-shi 305-8642, Ibaraki, Japan; (H.Z.); (J.C.); (H.H.); (H.N.)
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Hidemi Hatabayashi
- Food Research Institute, National Agriculture and Food Research Organization (NARO), 2-1-12 Kannon-dai, Tsukuba-shi 305-8642, Ibaraki, Japan; (H.Z.); (J.C.); (H.H.); (H.N.)
| | - Hiroyuki Nakagawa
- Food Research Institute, National Agriculture and Food Research Organization (NARO), 2-1-12 Kannon-dai, Tsukuba-shi 305-8642, Ibaraki, Japan; (H.Z.); (J.C.); (H.H.); (H.N.)
| | - Hiromitsu Nakajima
- Faculty of Agriculture, Tottori University, Koyama, Tottori 680-8553, Japan;
| | - Kimiko Yabe
- Food Research Institute, National Agriculture and Food Research Organization (NARO), 2-1-12 Kannon-dai, Tsukuba-shi 305-8642, Ibaraki, Japan; (H.Z.); (J.C.); (H.H.); (H.N.)
- Department of Applied Chemistry and Food Science, Faculty of Environmental and Information Sciences, Fukui University of Technology, 3-6-1 Gakuen, Fukui-shi, Fukui 910-8505, Japan
- Correspondence: ; Tel.: +81-776-29-2408
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13
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Zheng SY, Wei ZS, Li S, Zhang SJ, Xie CF, Yao DS, Liu DL. Near-infrared reflectance spectroscopy-based fast versicolorin A detection in maize for early aflatoxin warning and safety sorting. Food Chem 2020; 332:127419. [PMID: 32622190 DOI: 10.1016/j.foodchem.2020.127419] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 05/29/2020] [Accepted: 06/23/2020] [Indexed: 10/24/2022]
Abstract
Aflatoxins (AFs) are potent carcinogens present in numerous crops. Access to accurate methods for evaluating contamination is a critical factor in aflatoxin risk assessment. Versicolorin A (Ver A), a precursor of aflatoxin B1 (AFB1), can be used as an indicator for the presence of AFB1, even when the AF is not yet detectable. Currently employed Ver A detection methods are expensive, time consuming, and difficult to apply to numerous samples. Herein, Ver A was detected via near-infrared spectroscopy. Both quantitative and two-grade sorting methods were set-up using the extreme gradient boosting algorithm coupled with a support vector machine. This two-tiered method obtained a root-mean-square error of prediction value of 3.57 μg/kg for the quantitative model, and an accuracy rate of 90.32% for the sorting approach. This novel method is rapid, accurate, solvent free, requires no sample pretreatment, and detects Ver A in maize, making it convenient for practical use.
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Affiliation(s)
- Shao-Yan Zheng
- Institute of Microbial Biotechnology, Jinan University, Guangzhou City, Guangdong Province 510632, China; National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou City, Guangdong Province 510632, China
| | - Ze-Shun Wei
- Institute of Microbial Biotechnology, Jinan University, Guangzhou City, Guangdong Province 510632, China
| | - Shuang Li
- Institute of Microbial Biotechnology, Jinan University, Guangzhou City, Guangdong Province 510632, China
| | - Shi-Jia Zhang
- Department of Bioengineering, Jinan University, Guangzhou City, Guangdong Province 510632, China
| | - Chun-Fang Xie
- Institute of Microbial Biotechnology, Jinan University, Guangzhou City, Guangdong Province 510632, China; Department of Bioengineering, Jinan University, Guangzhou City, Guangdong Province 510632, China; National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou City, Guangdong Province 510632, China
| | - Dong-Sheng Yao
- Institute of Microbial Biotechnology, Jinan University, Guangzhou City, Guangdong Province 510632, China; National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou City, Guangdong Province 510632, China.
| | - Da-Ling Liu
- Institute of Microbial Biotechnology, Jinan University, Guangzhou City, Guangdong Province 510632, China; Department of Bioengineering, Jinan University, Guangzhou City, Guangdong Province 510632, China.
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14
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Aflatoxin Biosynthesis and Genetic Regulation: A Review. Toxins (Basel) 2020; 12:toxins12030150. [PMID: 32121226 PMCID: PMC7150809 DOI: 10.3390/toxins12030150] [Citation(s) in RCA: 134] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 01/27/2020] [Accepted: 02/25/2020] [Indexed: 12/15/2022] Open
Abstract
The study of fungal species evolved radically with the development of molecular techniques and produced new evidence to understand specific fungal mechanisms such as the production of toxic secondary metabolites. Taking advantage of these technologies to improve food safety, the molecular study of toxinogenic species can help elucidate the mechanisms underlying toxin production and enable the development of new effective strategies to control fungal toxicity. Numerous studies have been made on genes involved in aflatoxin B1 (AFB1) production, one of the most hazardous carcinogenic toxins for humans and animals. The current review presents the roles of these different genes and their possible impact on AFB1 production. We focus on the toxinogenic strains Aspergillus flavus and A. parasiticus, primary contaminants and major producers of AFB1 in crops. However, genetic reports on A. nidulans are also included because of the capacity of this fungus to produce sterigmatocystin, the penultimate stable metabolite during AFB1 production. The aim of this review is to provide a general overview of the AFB1 enzymatic biosynthesis pathway and its link with the genes belonging to the AFB1 cluster. It also aims to illustrate the role of global environmental factors on aflatoxin production and the recent data that demonstrate an interconnection between genes regulated by these environmental signals and aflatoxin biosynthetic pathway.
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15
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Hua SST, Parfitt DE, Sarreal SBL, Sidhu G. Dual culture of atoxigenic and toxigenic strains of Aspergillus flavus to gain insight into repression of aflatoxin biosynthesis and fungal interaction. Mycotoxin Res 2019; 35:381-389. [PMID: 31161589 DOI: 10.1007/s12550-019-00364-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 03/27/2019] [Accepted: 05/06/2019] [Indexed: 11/24/2022]
Abstract
Application of atoxigenic strains to compete against toxigenic strains of Aspergillus flavus strains has emerged as one of the practical strategies for reducing aflatoxin contamination in corn, peanut, and tree nuts. The actual mechanism that results in aflatoxin reduction is not fully understood. Real-time RT-PCR and relative quantification of gene expression protocol were applied to elucidate the molecular mechanism. Transcriptional analyses of aflatoxin biosynthetic gene cluster in dual culture of toxigenic and atoxigenic A. flavus strains were carried out. Six targeted genes, aflR, aflJ, omtA, ordA, pksA, and vbs, were downregulated to variable levels depending on paired strains of toxigenic and atoxigenic A. flavus. Consistent with the decreased gene expression levels, the aflatoxin concentrations in dual cultures were reduced significantly in comparison with toxigenic cultures. Fluorescent images showed fungal hyphae in dual culture displayed green fluorescent, and contacts of live hyphae were seen. A coconut agar plate assay was used to show that toxigenic A. flavus colony produced blue fluorescence under long UV exposure, suggesting that aflatoxin is exported outside fungal hyphae. Furthermore, the assay was applied to demonstrate the potential role of thigmo-regulation in fungal interaction.
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Affiliation(s)
- Sui Sheng T Hua
- U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA.
| | - Dan E Parfitt
- Department of Plant Sciences, University of California, Davis, One Shields Avenue, Davis, CA, 95616, USA
| | - Siov Bouy L Sarreal
- U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA
| | - Gaganjot Sidhu
- U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA
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16
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Szwalbe AJ, Williams K, Song Z, de Mattos-Shipley K, Vincent JL, Bailey AM, Willis CL, Cox RJ, Simpson TJ. Characterisation of the biosynthetic pathway to agnestins A and B reveals the reductive route to chrysophanol in fungi. Chem Sci 2019; 10:233-238. [PMID: 30746079 PMCID: PMC6335632 DOI: 10.1039/c8sc03778g] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 11/23/2018] [Indexed: 01/08/2023] Open
Abstract
Two new dihydroxy-xanthone metabolites, agnestins A and B, were isolated from Paecilomyces variotii along with a number of related benzophenones and xanthones including monodictyphenone. The structures were elucidated by NMR analyses and X-ray crystallography. The agnestin (agn) biosynthetic gene cluster was identified and targeted gene disruptions of the PKS, Baeyer-Villiger monooxygenase, and other oxido-reductase genes revealed new details of fungal xanthone biosynthesis. In particular, identification of a reductase responsible for in vivo anthraquinone to anthrol conversion confirms a previously postulated essential step in aromatic deoxygenation of anthraquinones, e.g. emodin to chrysophanol.
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Affiliation(s)
- Agnieszka J Szwalbe
- School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK .
| | - Katherine Williams
- School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK .
| | - Zhongshu Song
- School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK .
| | - Kate de Mattos-Shipley
- School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK .
| | - Jason L Vincent
- Syngenta , Jealott's Hill International Research Centre , Bracknell , RG42 6EY , UK
| | - Andrew M Bailey
- School of Biological Sciences , 24 Tyndall Avenue , Bristol , BS8 1TQ , UK
| | - Christine L Willis
- School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK .
| | - Russell J Cox
- School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK .
- Institute for Organic Chemistry , Leibniz University of Hannover , 30167 , Germany
- BMWZ , Leibniz University of Hannover , 30167 , Germany
| | - Thomas J Simpson
- School of Chemistry , University of Bristol , Cantock's Close , Bristol , BS8 1TS , UK .
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17
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Yuan J, Chen Z, Guo Z, Li D, Zhang F, Shen J, Zhang Y, Wang S, Zhuang Z. PbsB Regulates Morphogenesis, Aflatoxin B1 Biosynthesis, and Pathogenicity of Aspergillus flavus. Front Cell Infect Microbiol 2018; 8:162. [PMID: 29868518 PMCID: PMC5966551 DOI: 10.3389/fcimb.2018.00162] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 04/27/2018] [Indexed: 12/15/2022] Open
Abstract
As an opportunistic pathogen, Aspergillus flavus is one of the major causes of food contamination around the world. In this study, pbsB gene knockout mutant (ΔpbsB) and pbsB overexpression strain (OE) of A. flavus were constructed by homologous recombination. The results showed that the mycelia growth, conidiation, and the formation of sclerotia in ΔpbsB mutant were significantly suppressed, and up-regulated in OE strian compared to wild-type strain (WT). Q-PCR analysis showed that PbsB regulated the sclerotia formation through sclerotia related gene nsdC. With TLC and qRT-PCR analysis, it was found that PbsB up-regulated the bio-synthesis of aflatoxin B1 (AFB1) through regulatory gene aflR and structural gene aflC, aflD, aflK, and aflQ in the aflatoxin gene cluster. In osmotic stress response analysis, ΔpbsB mutant was significantly more sensitive to osmotic pressure with 1.2 mol/L sorbitol, compared to WT and OE strains. In virulence analysis, the infection capacity of ΔpbsB strain to peanut and maize kernels decreased dramatically, and significantly fewer spores and lesser mycelia were produced in ΔpbsB strain on the surface of peanut and maize kernels, and the infection capacity of OE strain to kernels increased significantly compared with WT strain. The AFB1 bio-synthesis ability of A. flavus in crop invasion models was also found to be coincide with the expression level of pbsB. All the results of the study shows that, as a MAPKK, PbsB is critical for growth and virulence in A. flavus, and lay a theoretical foundation for the prevention and control of A. flavus contamination.
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Affiliation(s)
- Jun Yuan
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhong Chen
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhiqiang Guo
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Ding Li
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Feng Zhang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jiaojiao Shen
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yi Zhang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhenhong Zhuang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
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18
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Lebar MD, Cary JW, Majumdar R, Carter-Wientjes CH, Mack BM, Wei Q, Uka V, De Saeger S, Diana Di Mavungu J. Identification and functional analysis of the aspergillic acid gene cluster in Aspergillus flavus. Fungal Genet Biol 2018; 116:14-23. [PMID: 29674152 DOI: 10.1016/j.fgb.2018.04.009] [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: 09/29/2017] [Revised: 04/04/2018] [Accepted: 04/12/2018] [Indexed: 10/17/2022]
Abstract
Aspergillus flavus can colonize important food staples and produce aflatoxins, a group of toxic and carcinogenic secondary metabolites. Previous in silico analysis of the A. flavus genome revealed 56 gene clusters predicted to be involved in the biosynthesis of secondary metabolites. A. flavus secondary metabolites produced during infection of maize seed are of particular interest, especially with respect to their roles in the biology of the fungus. A predicted nonribosomal peptide synthetase-like (NRPS-like) gene, designated asaC (AFLA_023020), present in the uncharacterized A. flavus secondary metabolite gene cluster 11 was previously shown to be expressed during the earliest stages of maize kernel infection. Cluster 11 is composed of six additional genes encoding a number of putative decorating enzymes as well as a transporter and transcription factor. We generated knock-out mutants of the seven predicted cluster 11 genes. LC-MS analysis of extracts from knockout mutants of these genes showed that they were responsible for the synthesis of the previously characterized antimicrobial mycotoxin aspergillic acid. Extracts of the asaC mutant showed no production of aspergillic acid or its precursors. Knockout of the cluster 11 P450 oxidoreductase afforded a pyrazinone metabolite, the aspergillic acid precursor deoxyaspergillic acid. The formation of hydroxyaspergillic acid was abolished in a desaturase/hydroxylase mutant. The hydroxamic acid functional group in aspergillic acid allows the molecule to bind to iron resulting in the production of a red pigment in A. flavus identified previously as ferriaspergillin. A reduction of aflatoxin B1 and cyclopiazonic acid that correlated with reduced fungal growth was observed in maize kernel infection assays when aspergillic acid biosynthesis in A. flavus is halted.
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Affiliation(s)
- Matthew D Lebar
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA.
| | - Jeffrey W Cary
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | | | | | - Brian M Mack
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | - Qijian Wei
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | - Valdet Uka
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Sarah De Saeger
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - José Diana Di Mavungu
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
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19
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The 14-3-3 Protein Homolog ArtA Regulates Development and Secondary Metabolism in the Opportunistic Plant Pathogen Aspergillus flavus. Appl Environ Microbiol 2018; 84:AEM.02241-17. [PMID: 29247055 PMCID: PMC5812931 DOI: 10.1128/aem.02241-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 12/06/2017] [Indexed: 01/07/2023] Open
Abstract
The opportunistic plant-pathogenic fungus Aspergillus flavus produces carcinogenic mycotoxins termed aflatoxins (AF). Aflatoxin contamination of agriculturally important crops, such as maize, peanut, sorghum, and tree nuts, is responsible for serious adverse health and economic impacts worldwide. In order to identify possible genetic targets to reduce AF contamination, we have characterized the artA gene, encoding a putative 14-3-3 homolog in A. flavus The artA deletion mutant presents a slight decrease in vegetative growth and alterations in morphological development and secondary metabolism. Specifically, artA affects conidiation, and this effect is influenced by the type of substrate and culture condition. In addition, normal levels of artA are required for sclerotial development. Importantly, artA negatively regulates AF production as well as the concomitant expression of genes in the AF gene cluster. An increase in AF is also observed in seeds infected with the A. flavus strain lacking artA Furthermore, the expression of other secondary metabolite genes is also artA dependent, including genes in the cyclopiazonic acid (CPA) and ustiloxin gene clusters, in this agriculturally important fungus.IMPORTANCE In the current study, artA, which encodes a 14-3-3 homolog, was characterized in the agriculturally and medically important fungus Aspergillus flavus, specifically, its possible role governing sporulation, formation of resistant structures, and secondary metabolism. The highly conserved artA is necessary for normal fungal morphogenesis in an environment-dependent manner, affecting the balance between production of conidiophores and the formation of resistant structures that are necessary for the dissemination and survival of this opportunistic pathogen. This study reports a 14-3-3 protein affecting secondary metabolism in filamentous fungi. Importantly, artA regulates the biosynthesis of the potent carcinogenic compound aflatoxin B1 (AFB1) as well as the production of other secondary metabolites.
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20
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Majumdar R, Lebar M, Mack B, Minocha R, Minocha S, Carter-Wientjes C, Sickler C, Rajasekaran K, Cary JW. The Aspergillus flavus Spermidine Synthase ( spds) Gene, Is Required for Normal Development, Aflatoxin Production, and Pathogenesis During Infection of Maize Kernels. FRONTIERS IN PLANT SCIENCE 2018; 9:317. [PMID: 29616053 PMCID: PMC5870473 DOI: 10.3389/fpls.2018.00317] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 02/27/2018] [Indexed: 05/10/2023]
Abstract
Aspergillus flavus is a soil-borne saprophyte and an opportunistic pathogen of both humans and plants. This fungus not only causes disease in important food and feed crops such as maize, peanut, cottonseed, and tree nuts but also produces the toxic and carcinogenic secondary metabolites (SMs) known as aflatoxins. Polyamines (PAs) are ubiquitous polycations that influence normal growth, development, and stress responses in living organisms and have been shown to play a significant role in fungal pathogenesis. Biosynthesis of spermidine (Spd) is critical for cell growth as it is required for hypusination-mediated activation of eukaryotic translation initiation factor 5A (eIF5A), and other biochemical functions. The tri-amine Spd is synthesized from the diamine putrescine (Put) by the enzyme spermidine synthase (Spds). Inactivation of spds resulted in a total loss of growth and sporulation in vitro which could be partially restored by addition of exogenous Spd. Complementation of the Δspds mutant with a wild type (WT) A. flavus spds gene restored the WT phenotype. In WT A. flavus, exogenous supply of Spd (in vitro) significantly increased the production of sclerotia and SMs. Infection of maize kernels with the Δspds mutant resulted in a significant reduction in fungal growth, sporulation, and aflatoxin production compared to controls. Quantitative PCR of Δspds mutant infected seeds showed down-regulation of aflatoxin biosynthetic genes in the mutant compared to WT A. flavus infected seeds. Expression analyses of PA metabolism/transport genes during A. flavus-maize interaction showed significant increase in the expression of arginine decarboxylase (Adc) and S-adenosylmethionine decarboxylase (Samdc) genes in the maize host and PA uptake transporters in the fungus. The results presented here demonstrate that Spd biosynthesis is critical for normal development and pathogenesis of A. flavus and pre-treatment of a Δspds mutant with Spd or Spd uptake from the host plant, are insufficient to restore WT levels of pathogenesis and aflatoxin production during seed infection. The data presented here suggest that future studies targeting spermidine biosynthesis in A. flavus, using RNA interference-based host-induced gene silencing approaches, may be an effective strategy to reduce aflatoxin contamination in maize and possibly in other susceptible crops.
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Affiliation(s)
- Rajtilak Majumdar
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Matt Lebar
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Brian Mack
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Rakesh Minocha
- United States Department of Agriculture Forest Service, Northern Research Station, Durham, NH, United States
| | - Subhash Minocha
- Department of Biological Sciences, University of New Hampshire, Durham, NH, United States
| | - Carol Carter-Wientjes
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Christine Sickler
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Kanniah Rajasekaran
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
| | - Jeffrey W. Cary
- Food and Feed Safety Research Unit, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, United States
- *Correspondence: Jeffrey W. Cary,
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21
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Ren S, Yue Y, Li Y, Guo X, Wang S. Functional analyses of the versicolorin B synthase gene in Aspergillus flavus. Microbiologyopen 2017; 6. [PMID: 28612469 PMCID: PMC5552937 DOI: 10.1002/mbo3.471] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Revised: 01/26/2017] [Accepted: 02/08/2017] [Indexed: 02/06/2023] Open
Abstract
Aflatoxin is a toxic, carcinogenic mycotoxin primarily produced by Aspergillus parasiticus and Aspergillus flavus. Previous studies have predicted the existence of more than 20 genes in the gene cluster involved in aflatoxin biosynthesis. Among these genes, aflK encodes versicolorin B synthase, which converts versiconal to versicolorin B. Past research has investigated aflK in A. parasiticus, but few studies have characterized aflK in the animal, plant, and human pathogen A. flavus. To understand the potential role of aflK in A. flavus, its function was investigated here for the first time using gene replacement and gene complementation strategies. The aflK deletion-mutant ΔaflK exhibited a significant decrease in sclerotial production and aflatoxin biosynthesis compared with wild-type and the complementation strain ΔaflK::aflK. ΔaflK did not affect the ability of A. flavus to infect seeds, but downregulated aflatoxin production after seed infection. This is the first report of a relationship between aflK and sclerotial production in A. flavus, and our findings indicate that aflK regulates aflatoxin formation.
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Affiliation(s)
- Silin Ren
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yuewei Yue
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yu Li
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaodong Guo
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
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Yang K, Liu Y, Liang L, Li Z, Qin Q, Nie X, Wang S. The high-affinity phosphodiesterase PdeH regulates development and aflatoxin biosynthesis in Aspergillus flavus. Fungal Genet Biol 2017; 101:7-19. [PMID: 28212851 DOI: 10.1016/j.fgb.2017.02.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 02/08/2017] [Indexed: 01/25/2023]
Abstract
Cyclic AMP signaling controls a range of physiological processes in response to extracellular stimuli in organisms. Among the signaling cascades, cAMP, as a second messenger, is orchestrated by adenylate cyclase (biosynthesis) and cAMP phosphodiesterases (PDEs) (hydrolysis). In this study, we investigated the function of the high-affinity (PdeH) and low-affinity (PdeL) cAMP phosphodiesterase from the carcinogenic aflatoxin producing fungus Aspergillus flavus, and found that instead of PdeL, inactivation of PdeH exhibited a reduction in conidiation and sclerotia formation. However, the ΔpdeL/ΔpdeH mutant exhibited an enhanced phenotype defects, a similar phenotype defects to wild-type strain treated with exogenous cAMP. The activation of PKA activity was inhibited in the ΔpdeH or ΔpdeL/ΔpdeH mutant, both of whom exhibited increasing AF production. Further analysis by qRT-PCR revealed that pdeH had a high transcriptional level compared to pdeL in wild-type strain, and affected pdeL transcription. Green fluorescent protein tagging at the C-terminus of PDEs showed that PdeH-GFP is broadly compartmentalized in the cytosol, while PdeL-GFP localized mainly to the nucleus. Overall, our results indicated that PdeH plays a major role, but has overlapping function with PdeL, in vegetative growth, development and AF biosynthesis in A. flavus.
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Affiliation(s)
- Kunlong Yang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yinghang Liu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Linlin Liang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Zhenguo Li
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Qiuping Qin
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Xinyi Nie
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Shihua Wang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Yang K, Qin Q, Liu Y, Zhang L, Liang L, Lan H, Chen C, You Y, Zhang F, Wang S. Adenylate Cyclase AcyA Regulates Development, Aflatoxin Biosynthesis and Fungal Virulence in Aspergillus flavus. Front Cell Infect Microbiol 2016; 6:190. [PMID: 28066725 PMCID: PMC5175447 DOI: 10.3389/fcimb.2016.00190] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 12/05/2016] [Indexed: 01/27/2023] Open
Abstract
Aspergillus flavus is one of the most important opportunistic pathogens of crops and animals. The carcinogenic mycotoxin, aflatoxins produced by this pathogen cause a health problem to human and animals. Since cyclic AMP signaling controls a range of physiological processes, like fungal development and infection when responding to extracellular stimuli in fungal pathogens, in this study, we investigated the function of adenylate cyclase, a core component of cAMP signaling, in aflatoxins biosynthesis and virulence on plant seeds in A. flavus. A gene replacement strategy was used to generate the deletion mutant of acyA that encodes the adenylate cyclase. Severe defects in fungal growth, sporulation and sclerotia formation were observed in the acyA deletion mutant. The defect in radical growth could be partially rescued by exogenous cAMP analog. The acyA mutant was also significantly reduced in aflatoxins production and virulence. Similar to the former studies in other fungi, The acyA mutant showed enhancing tolerance to oxidative stress, but more sensitive to heat stress. Overall, the pleiotropic defects of the acyA deletion mutant indicates that the cAMP-PKA pathway is involved in fungal development, aflatoxins biosynthesis and plant seed invasion in A. flavus.
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Affiliation(s)
- Kunlong Yang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Qiuping Qin
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Yinghang Liu
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Limei Zhang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Linlin Liang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Huahui Lan
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Chihao Chen
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Yunchao You
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Feng Zhang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
| | - Shihua Wang
- Fujian Key Laboratory of Pathogenic Fungi and Mycotoxins, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University Fuzhou, China
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Hemmerling F, Hahn F. Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides. Beilstein J Org Chem 2016; 12:1512-50. [PMID: 27559404 PMCID: PMC4979870 DOI: 10.3762/bjoc.12.148] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 06/22/2016] [Indexed: 01/01/2023] Open
Abstract
This review highlights the biosynthesis of heterocycles in polyketide natural products with a focus on oxygen and nitrogen-containing heterocycles with ring sizes between 3 and 6 atoms. Heterocycles are abundant structural elements of natural products from all classes and they often contribute significantly to their biological activity. Progress in recent years has led to a much better understanding of their biosynthesis. In this context, plenty of novel enzymology has been discovered, suggesting that these pathways are an attractive target for future studies.
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Affiliation(s)
- Franziska Hemmerling
- Institut für Organische Chemie and Zentrum für Biomolekulare Wirkstoffe, Gottfried Wilhelm Leibniz Universität Hannover, Schneiderberg 38, 30167 Hannover, Germany; Fakultät für Biologie, Chemie und Geowissenschaften, Universität Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
| | - Frank Hahn
- Institut für Organische Chemie and Zentrum für Biomolekulare Wirkstoffe, Gottfried Wilhelm Leibniz Universität Hannover, Schneiderberg 38, 30167 Hannover, Germany; Fakultät für Biologie, Chemie und Geowissenschaften, Universität Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany
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Satterlee T, Cary JW, Calvo AM. RmtA, a Putative Arginine Methyltransferase, Regulates Secondary Metabolism and Development in Aspergillus flavus. PLoS One 2016; 11:e0155575. [PMID: 27213959 PMCID: PMC4877107 DOI: 10.1371/journal.pone.0155575] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 05/01/2016] [Indexed: 12/31/2022] Open
Abstract
Aspergillus flavus colonizes numerous oil seed crops such as corn, peanuts, treenuts and cotton worldwide, contaminating them with aflatoxin and other harmful potent toxins. In the phylogenetically related model fungus Aspergillus nidulans, the methyltransferase, RmtA, has been described to be involved in epigenetics regulation through histone modification. Epigenetics regulation affects a variety of cellular processes, including morphogenesis and secondary metabolism. Our study shows that deletion of rmtA in A. flavus results in hyperconidiating colonies, indicating that rmtA is a repressor of asexual development in this fungus. The increase in conidiation in the absence of rmtA coincides with greater expression of brlA, abaA, and wetA compared to that in the wild type. Additionally, the rmtA deletion mutant presents a drastic reduction or loss of sclerotial production, while forced expression of this gene increased the ability of this fungus to generate these resistant structures, revealing rmtA as a positive regulator of sclerotial formation. Importantly, rmtA is also required for the production of aflatoxin B1 in A. flavus, affecting the expression of aflJ. Furthermore, biosynthesis of additional metabolites is also controlled by rmtA, indicating a broad regulatory output in the control of secondary metabolism. This study also revealed that rmtA positively regulates the expression of the global regulatory gene veA, which could contribute to mediate the effects of rmtA on development and secondary metabolism in this relevant opportunistic plant pathogen.
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Affiliation(s)
- Timothy Satterlee
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, United States of America
| | - Jeffrey W. Cary
- USDA, ARS, Southern Regional Research Center, New Orleans, LA, 70124, United States of America
| | - Ana M. Calvo
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, United States of America
- * E-mail:
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rtfA, a putative RNA-Pol II transcription elongation factor gene, is necessary for normal morphological and chemical development in Aspergillus flavus. Appl Microbiol Biotechnol 2016; 100:5029-41. [PMID: 27020290 DOI: 10.1007/s00253-016-7418-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 02/22/2016] [Accepted: 02/24/2016] [Indexed: 01/05/2023]
Abstract
The filamentous fungus Aspergillus flavus is an agriculturally important opportunistic plant pathogen that produces potent carcinogenic compounds called aflatoxins. We identified the A. flavus rtfA gene, the ortholog of rtf1 in Saccharomyces cerevisiae and rtfA in Aspergillus nidulans. Interestingly, rtfA has multiple cellular roles in this mycotoxin-producing fungus. In this study, we show that rtfA regulates conidiation. The rtfA deletion mutant presented smaller conidiophores with significantly reduced conidial production compared to the wild-type strain. The absence of rtfA also resulted in a significant decrease or lack of sclerotial production under conditions that allowed abundant production of these resistance structures in the wild type. Importantly, the deletion of rtfA notably reduced the production of aflatoxin B1, indicating that rtfA is a regulator of mycotoxin biosynthesis in A. flavus. In addition, the deletion rtfA also altered the production of several unknown secondary metabolites indicating a broader regulatory scope. Furthermore, our study revealed that rtfA controls the expression of the global regulators veA and laeA, which further influence morphogenesis and secondary metabolism in A. flavus.
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27
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Zhuang Z, Lohmar JM, Satterlee T, Cary JW, Calvo AM. The Master Transcription Factor mtfA Governs Aflatoxin Production, Morphological Development and Pathogenicity in the Fungus Aspergillus flavus. Toxins (Basel) 2016; 8:toxins8010029. [PMID: 26805883 PMCID: PMC4728551 DOI: 10.3390/toxins8010029] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 12/23/2015] [Accepted: 01/06/2016] [Indexed: 11/30/2022] Open
Abstract
Aspergillus flavus produces a variety of toxic secondary metabolites; among them, the aflatoxins (AFs) are the most well known. These compounds are highly mutagenic and carcinogenic, particularly AFB1. A. flavus is capable of colonizing a number of economically-important crops, such as corn, cotton, peanut and tree nuts, and contaminating them with AFs. Molecular genetic studies in A. flavus could identify novel gene targets for use in strategies to reduce AF contamination and its adverse impact on food and feed supplies worldwide. In the current study, we investigated the role of the master transcription factor gene mtfA in A. flavus. Our results revealed that forced overexpression of mtfA results in a drastic decrease or elimination of several secondary metabolites, among them AFB1. The reduction in AFB1 was accompanied by a decrease in aflR expression. Furthermore, mtfA also regulates development; conidiation was influenced differently by this gene depending on the type of colonized substrate. In addition to its effect on conidiation, mtfA is necessary for the normal maturation of sclerotia. Importantly, mtfA positively affects the pathogenicity of A. flavus when colonizing peanut seeds. AF production in colonized seeds was decreased in the deletion mtfA strain and particularly in the overexpression strain, where only trace amounts were detected. Interestingly, a more rapid colonization of the seed tissue occurred when mtfA was overexpressed, coinciding with an increase in lipase activity and faster maceration of the oily part of the seed.
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Affiliation(s)
- Zhenhong Zhuang
- Department of Biological Sciences, Northern Illinois University, 155 Castle Dr., Dekalb, IL 60115, USA.
| | - Jessica M Lohmar
- Department of Biological Sciences, Northern Illinois University, 155 Castle Dr., Dekalb, IL 60115, USA.
| | - Timothy Satterlee
- Department of Biological Sciences, Northern Illinois University, 155 Castle Dr., Dekalb, IL 60115, USA.
| | - Jeffrey W Cary
- Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA.
| | - Ana M Calvo
- Department of Biological Sciences, Northern Illinois University, 155 Castle Dr., Dekalb, IL 60115, USA.
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Throckmorton K, Wiemann P, Keller NP. Evolution of Chemical Diversity in a Group of Non-Reduced Polyketide Gene Clusters: Using Phylogenetics to Inform the Search for Novel Fungal Natural Products. Toxins (Basel) 2015; 7:3572-607. [PMID: 26378577 PMCID: PMC4591646 DOI: 10.3390/toxins7093572] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 08/21/2015] [Accepted: 08/26/2015] [Indexed: 12/11/2022] Open
Abstract
Fungal polyketides are a diverse class of natural products, or secondary metabolites (SMs), with a wide range of bioactivities often associated with toxicity. Here, we focus on a group of non-reducing polyketide synthases (NR-PKSs) in the fungal phylum Ascomycota that lack a thioesterase domain for product release, group V. Although widespread in ascomycete taxa, this group of NR-PKSs is notably absent in the mycotoxigenic genus Fusarium and, surprisingly, found in genera not known for their secondary metabolite production (e.g., the mycorrhizal genus Oidiodendron, the powdery mildew genus Blumeria, and the causative agent of white-nose syndrome in bats, Pseudogymnoascus destructans). This group of NR-PKSs, in association with the other enzymes encoded by their gene clusters, produces a variety of different chemical classes including naphthacenediones, anthraquinones, benzophenones, grisandienes, and diphenyl ethers. We discuss the modification of and transitions between these chemical classes, the requisite enzymes, and the evolution of the SM gene clusters that encode them. Integrating this information, we predict the likely products of related but uncharacterized SM clusters, and we speculate upon the utility of these classes of SMs as virulence factors or chemical defenses to various plant, animal, and insect pathogens, as well as mutualistic fungi.
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Affiliation(s)
- Kurt Throckmorton
- Department of Genetics, University of Wisconsin-Madison, 425 Henry Mall, Madison, WI 53706-1580, USA.
| | - Philipp Wiemann
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706-1521, USA.
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706-1521, USA.
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Gilbert MK, Mack BM, Wei Q, Bland JM, Bhatnagar D, Cary JW. RNA sequencing of an nsdC mutant reveals global regulation of secondary metabolic gene clusters in Aspergillus flavus. Microbiol Res 2015; 182:150-61. [PMID: 26686623 DOI: 10.1016/j.micres.2015.08.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 08/21/2015] [Accepted: 08/31/2015] [Indexed: 01/16/2023]
Abstract
The filamentous fungus, Aspergillus flavus (A. flavus) is an opportunistic pathogen capable of invading a number of crops and contaminating them with toxic secondary metabolites such as aflatoxins. Characterizing the molecular mechanisms governing growth and development of this organism is vital for developing safe and effective strategies for reducing crop contamination. The transcription factor nsdC has been identified as being required for normal asexual development and aflatoxin production in A. flavus. Building on a previous study using a large (L)-sclerotial morphotype A. flavus nsdC mutant we observed alterations in conidiophore development and loss of sclerotial and aflatoxin production using a nsdC mutant of a small (S)-sclerotial morphotype, that normally produces aflatoxin and sclerotia in quantities much higher than the L-morphotype. RNA sequencing analysis of the nsdC knockout mutant and isogenic control strain identified a number of differentially expressed genes related to development and production of secondary metabolites, including aflatoxin, penicillin and aflatrem. Further, RNA-seq data indicating down regulation of aflatrem biosynthetic gene expression in the nsdC mutant correlated with HPLC analyses showing a decrease in aflatrem levels. The current study expands the role of nsdC as a globally acting transcription factor that is a critical regulator of both asexual reproduction and secondary metabolism in A. flavus.
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Affiliation(s)
- Matthew K Gilbert
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - Brian M Mack
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - Qijian Wei
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - John M Bland
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - Deepak Bhatnagar
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA
| | - Jeffrey W Cary
- USDA, ARS, Southern Regional Research Center 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA.
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Conradt D, Schätzle MA, Haas J, Townsend CA, Müller M. New Insights into the Conversion of Versicolorin A in the Biosynthesis of Aflatoxin B1. J Am Chem Soc 2015; 137:10867-9. [PMID: 26266881 DOI: 10.1021/jacs.5b06770] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A crucial and enigmatic step in the complex biosynthesis of aflatoxin B1 is the oxidative rearrangement of versicolorin A to demethylsterigmatocystin. This step is thought to proceed by an oxidation-reduction-oxidation sequence, in which the NADPH-dependent oxidoreductase AflM catalyzes the enclosed reduction step. AflM from Aspergillus parasiticus, after heterologous production in E. coli and purification, however, catalyzed the reduction of the hydroquinoid form of the starting compound versicolorin A (25% conversion) to a so far unknown product of aflatoxin biosynthesis. The asymmetric reduction of emodin hydroquinone to (R)-3,8,9,10-tetrahydroxy-6-methyl-3,4-dihydroanthracen-1(2H)-one (up to 82% for AflM) has also been observed in previous studies using MdpC from Aspergillus nidulans (monodictyphenone biosynthetic gene cluster). The first (nonenzymatic) reduction of emodin to emodin hydroquinone, for example with sodium dithionite, is obligatory for the enzymatic reduction by AflM or MdpC. These results imply an unprecedented role of AflM in the complex enzymatic network of aflatoxin biosynthesis.
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Affiliation(s)
- David Conradt
- Institut für Pharmazeutische Wissenschaften, Albert-Ludwigs-Universität Freiburg , Albertstr. 25, 79104 Freiburg, Germany
| | - Michael A Schätzle
- Institut für Pharmazeutische Wissenschaften, Albert-Ludwigs-Universität Freiburg , Albertstr. 25, 79104 Freiburg, Germany
| | - Julian Haas
- Institut für Pharmazeutische Wissenschaften, Albert-Ludwigs-Universität Freiburg , Albertstr. 25, 79104 Freiburg, Germany
| | - Craig A Townsend
- Department of Chemistry, The Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Michael Müller
- Institut für Pharmazeutische Wissenschaften, Albert-Ludwigs-Universität Freiburg , Albertstr. 25, 79104 Freiburg, Germany
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Arroyo-Manzanares N, Diana Di Mavungu J, Uka V, Malysheva SV, Cary JW, Ehrlich KC, Vanhaecke L, Bhatnagar D, De Saeger S. Use of UHPLC high-resolution Orbitrap mass spectrometry to investigate the genes involved in the production of secondary metabolites inAspergillus flavus. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2015; 32:1656-73. [DOI: 10.1080/19440049.2015.1071499] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Cary JW, Uka V, Han Z, Buyst D, Harris-Coward PY, Ehrlich KC, Wei Q, Bhatnagar D, Dowd PF, Martens SL, Calvo AM, Martins JC, Vanhaecke L, Coenye T, De Saeger S, Di Mavungu JD. An Aspergillus flavus secondary metabolic gene cluster containing a hybrid PKS–NRPS is necessary for synthesis of the 2-pyridones, leporins. Fungal Genet Biol 2015; 81:88-97. [DOI: 10.1016/j.fgb.2015.05.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/22/2015] [Accepted: 05/26/2015] [Indexed: 01/04/2023]
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Transcriptome Analysis of Aspergillus flavus Reveals veA-Dependent Regulation of Secondary Metabolite Gene Clusters, Including the Novel Aflavarin Cluster. EUKARYOTIC CELL 2015. [PMID: 26209694 DOI: 10.1128/ec.00092-15] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The global regulatory veA gene governs development and secondary metabolism in numerous fungal species, including Aspergillus flavus. This is especially relevant since A. flavus infects crops of agricultural importance worldwide, contaminating them with potent mycotoxins. The most well-known are aflatoxins, which are cytotoxic and carcinogenic polyketide compounds. The production of aflatoxins and the expression of genes implicated in the production of these mycotoxins are veA dependent. The genes responsible for the synthesis of aflatoxins are clustered, a signature common for genes involved in fungal secondary metabolism. Studies of the A. flavus genome revealed many gene clusters possibly connected to the synthesis of secondary metabolites. Many of these metabolites are still unknown, or the association between a known metabolite and a particular gene cluster has not yet been established. In the present transcriptome study, we show that veA is necessary for the expression of a large number of genes. Twenty-eight out of the predicted 56 secondary metabolite gene clusters include at least one gene that is differentially expressed depending on presence or absence of veA. One of the clusters under the influence of veA is cluster 39. The absence of veA results in a downregulation of the five genes found within this cluster. Interestingly, our results indicate that the cluster is expressed mainly in sclerotia. Chemical analysis of sclerotial extracts revealed that cluster 39 is responsible for the production of aflavarin.
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Baidya S, Duran RM, Lohmar JM, Harris-Coward PY, Cary JW, Hong SY, Roze LV, Linz JE, Calvo AM. VeA is associated with the response to oxidative stress in the aflatoxin producer Aspergillus flavus. EUKARYOTIC CELL 2014; 13:1095-103. [PMID: 24951443 PMCID: PMC4135802 DOI: 10.1128/ec.00099-14] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 06/14/2014] [Indexed: 12/20/2022]
Abstract
Survival of fungal species depends on the ability of these organisms to respond to environmental stresses. Osmotic stress or high levels of reactive oxygen species (ROS) can cause stress in fungi resulting in growth inhibition. Both eukaryotic and prokaryotic cells have developed numerous mechanisms to counteract and survive the stress in the presence of ROS. In many fungi, the HOG signaling pathway is crucial for the oxidative stress response as well as for osmotic stress response. This study revealed that while the osmotic stress response is only slightly affected by the master regulator veA, this gene, also known to control morphological development and secondary metabolism in numerous fungal species, has a profound effect on the oxidative stress response in the aflatoxin-producing fungus Aspergillus flavus. We found that the expression of A. flavus homolog genes involved in the HOG signaling pathway is regulated by veA. Deletion of veA resulted in a reduction in transcription levels of oxidative stress response genes after exposure to hydrogen peroxide. Furthermore, analyses of the effect of VeA on the promoters of cat1 and trxB indicate that the presence of VeA alters DNA-protein complex formation. This is particularly notable in the cat1 promoter, where the absence of VeA results in abnormally stronger complex formation with reduced cat1 expression and more sensitivity to ROS in a veA deletion mutant, suggesting that VeA might prevent binding of negative transcription regulators to the cat1 promoter. Our study also revealed that veA positively influences the expression of the transcription factor gene atfB and that normal formation of DNA-protein complexes in the cat1 promoter is dependent on AtfB.
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Affiliation(s)
- Sachin Baidya
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Rocio M Duran
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Jessica M Lohmar
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
| | - Pamela Y Harris-Coward
- Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana, USA
| | - Jeffrey W Cary
- Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana, USA
| | - Sung-Yong Hong
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Ludmila V Roze
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - John E Linz
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Ana M Calvo
- Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA
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Cary JW, Harris-Coward PY, Ehrlich KC, Di Mavungu JD, Malysheva SV, De Saeger S, Dowd PF, Shantappa S, Martens SL, Calvo AM. Functional characterization of a veA-dependent polyketide synthase gene in Aspergillus flavus necessary for the synthesis of asparasone, a sclerotium-specific pigment. Fungal Genet Biol 2014; 64:25-35. [DOI: 10.1016/j.fgb.2014.01.001] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 12/03/2013] [Accepted: 01/02/2014] [Indexed: 11/28/2022]
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Hua SST, Beck JJ, Sarreal SBL, Gee W. The major volatile compound 2-phenylethanol from the biocontrol yeast, Pichia anomala, inhibits growth and expression of aflatoxin biosynthetic genes of Aspergillus flavus. Mycotoxin Res 2014; 30:71-8. [PMID: 24504634 DOI: 10.1007/s12550-014-0189-z] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 01/13/2014] [Accepted: 01/16/2014] [Indexed: 11/28/2022]
Abstract
Aspergillus flavus is a ubiquitous saprophyte that is able to produce the most potent natural carcinogenic compound known as aflatoxin B1 (AFB1). This toxin frequently contaminates crops including corn, cotton, peanuts, and tree nuts causing substantial economic loss worldwide. Consequently, more than 100 countries have strict regulations limiting AFB1 in foodstuffs and feedstuffs. Plants and microbes are able to produce volatile compounds that act as a defense mechanism against other organisms. Pichia anomala strain WRL-076 is a biocontrol yeast currently being tested to reduce AF contamination of tree nuts in California. We used the SPME-GC/MS analysis and identified the major volatile compound produced by this strain to be 2-phenylethanol (2-PE). It inhibited spore germination and AF production of A. flavus. Inhibition of AF formation by 2-PE was correlated with significant down regulation of clustering AF biosynthesis genes as evidenced by several to greater than 10,000-fold decrease in gene expression. In a time-course analysis we found that 2-PE also altered the expression patterns of chromatin modifying genes, MYST1, MYST2, MYST3, gcn5, hdaA and rpdA. The biocontrol capacity of P. anomala can be attributed to the production of 2-PE, which affects spore germination, growth, toxin production, and gene expression in A. flavus.
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Affiliation(s)
- Sui Sheng T Hua
- U. S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA,
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Xu X, Liu L, Zhang F, Wang W, Li J, Guo L, Che Y, Liu G. Identification of the First Diphenyl Ether Gene Cluster for Pestheic Acid Biosynthesis in Plant EndophytePestalotiopsis fici. Chembiochem 2013; 15:284-92. [DOI: 10.1002/cbic.201300626] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Indexed: 11/10/2022]
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NsdC and NsdD affect Aspergillus flavus morphogenesis and aflatoxin production. EUKARYOTIC CELL 2012; 11:1104-11. [PMID: 22798394 DOI: 10.1128/ec.00069-12] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The transcription factors NsdC and NsdD are required for sexual development in Aspergillus nidulans. We now show these proteins also play a role in asexual development in the agriculturally important aflatoxin (AF)-producing fungus Aspergillus flavus. We found that both NsdC and NsdD are required for production of asexual sclerotia, normal aflatoxin biosynthesis, and conidiophore development. Conidiophores in nsdC and nsdD deletion mutants had shortened stipes and altered conidial heads compared to those of wild-type A. flavus. Our results suggest that NsdC and NsdD regulate transcription of genes required for early processes in conidiophore development preceding conidium formation. As the cultures aged, the ΔnsdC and ΔnsdD mutants produced a dark pigment that was not observed in the wild type. Gene expression data showed that although AflR is expressed at normal levels, a number of aflatoxin biosynthesis genes are expressed at reduced levels in both nsd mutants. Expression of aflD, aflM, and aflP was greatly reduced in nsdC mutants, and neither aflatoxin nor the proteins for these genes could be detected. Our results support previous studies showing that there is a strong association between conidiophore and sclerotium development and aflatoxin production in A. flavus.
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Klejnstrup ML, Frandsen RJN, Holm DK, Nielsen MT, Mortensen UH, Larsen TO, Nielsen JB. Genetics of Polyketide Metabolism in Aspergillus nidulans. Metabolites 2012; 2:100-33. [PMID: 24957370 PMCID: PMC3901194 DOI: 10.3390/metabo2010100] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 12/23/2011] [Accepted: 01/17/2012] [Indexed: 12/12/2022] Open
Abstract
Secondary metabolites are small molecules that show large structural diversity and a broad range of bioactivities. Some metabolites are attractive as drugs or pigments while others act as harmful mycotoxins. Filamentous fungi have the capacity to produce a wide array of secondary metabolites including polyketides. The majority of genes required for production of these metabolites are mostly organized in gene clusters, which often are silent or barely expressed under laboratory conditions, making discovery and analysis difficult. Fortunately, the genome sequences of several filamentous fungi are publicly available, greatly facilitating the establishment of links between genes and metabolites. This review covers the attempts being made to trigger the activation of polyketide metabolism in the fungal model organism Aspergillus nidulans. Moreover, it will provide an overview of the pathways where ten polyketide synthase genes have been coupled to polyketide products. Therefore, the proposed biosynthesis of the following metabolites will be presented; naphthopyrone, sterigmatocystin, aspyridones, emericellamides, asperthecin, asperfuranone, monodictyphenone/emodin, orsellinic acid, and the austinols.
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Affiliation(s)
- Marie L Klejnstrup
- Department of Systems Biology, Center for Microbial Biotechnology, Technical University of Denmark, Søltofts Plads B221, DK-2800 Kgs. Lyngby, Denmark.
| | - Rasmus J N Frandsen
- Department of Systems Biology, Center for Microbial Biotechnology, Technical University of Denmark, Søltofts Plads B223, DK-2800 Kgs. Lyngby, Denmark.
| | - Dorte K Holm
- Department of Systems Biology, Center for Microbial Biotechnology, Technical University of Denmark, Søltofts Plads B223, DK-2800 Kgs. Lyngby, Denmark.
| | - Morten T Nielsen
- Department of Systems Biology, Center for Microbial Biotechnology, Technical University of Denmark, Søltofts Plads B223, DK-2800 Kgs. Lyngby, Denmark.
| | - Uffe H Mortensen
- Department of Systems Biology, Center for Microbial Biotechnology, Technical University of Denmark, Søltofts Plads B223, DK-2800 Kgs. Lyngby, Denmark.
| | - Thomas O Larsen
- Department of Systems Biology, Center for Microbial Biotechnology, Technical University of Denmark, Søltofts Plads B221, DK-2800 Kgs. Lyngby, Denmark.
| | - Jakob B Nielsen
- Department of Systems Biology, Center for Microbial Biotechnology, Technical University of Denmark, Søltofts Plads B223, DK-2800 Kgs. Lyngby, Denmark.
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YABE K, NAKAJIMA H. Aflatoxin Biosynthesis. Food Hygiene and Safety Science (Shokuhin Eiseigaku Zasshi) 2011; 52:135-47. [DOI: 10.3358/shokueishi.52.135] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Roze LV, Chanda A, Laivenieks M, Beaudry RM, Artymovich KA, Koptina AV, Awad DW, Valeeva D, Jones AD, Linz JE. Volatile profiling reveals intracellular metabolic changes in Aspergillus parasiticus: veA regulates branched chain amino acid and ethanol metabolism. BMC BIOCHEMISTRY 2010; 11:33. [PMID: 20735852 PMCID: PMC2939540 DOI: 10.1186/1471-2091-11-33] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 08/24/2010] [Indexed: 01/17/2023]
Abstract
Background Filamentous fungi in the genus Aspergillus produce a variety of natural products, including aflatoxin, the most potent naturally occurring carcinogen known. Aflatoxin biosynthesis, one of the most highly characterized secondary metabolic pathways, offers a model system to study secondary metabolism in eukaryotes. To control or customize biosynthesis of natural products we must understand how secondary metabolism integrates into the overall cellular metabolic network. By applying a metabolomics approach we analyzed volatile compounds synthesized by Aspergillus parasiticus in an attempt to define the association of secondary metabolism with other metabolic and cellular processes. Results Volatile compounds were examined using solid phase microextraction - gas chromatography/mass spectrometry. In the wild type strain Aspergillus parasiticus SU-1, the largest group of volatiles included compounds derived from catabolism of branched chain amino acids (leucine, isoleucine, and valine); we also identified alcohols, esters, aldehydes, and lipid-derived volatiles. The number and quantity of the volatiles produced depended on media composition, time of incubation, and light-dark status. A block in aflatoxin biosynthesis or disruption of the global regulator veA affected the volatile profile. In addition to its multiple functions in secondary metabolism and development, VeA negatively regulated catabolism of branched chain amino acids and synthesis of ethanol at the transcriptional level thus playing a role in controlling carbon flow within the cell. Finally, we demonstrated that volatiles generated by a veA disruption mutant are part of the complex regulatory machinery that mediates the effects of VeA on asexual conidiation and sclerotia formation. Conclusions 1) Volatile profiling provides a rapid, effective, and powerful approach to identify changes in intracellular metabolic networks in filamentous fungi. 2) VeA coordinates the biosynthesis of secondary metabolites with catabolism of branched chain amino acids, alcohol biosynthesis, and β-oxidation of fatty acids. 3) Intracellular chemical development in A. parasiticus is linked to morphological development. 4) Understanding carbon flow through secondary metabolic pathways and catabolism of branched chain amino acids is essential for controlling and customizing production of natural products.
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Affiliation(s)
- Ludmila V Roze
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI, USA.
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Roze LV, Chanda A, Linz JE. Compartmentalization and molecular traffic in secondary metabolism: a new understanding of established cellular processes. Fungal Genet Biol 2010; 48:35-48. [PMID: 20519149 DOI: 10.1016/j.fgb.2010.05.006] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 05/11/2010] [Accepted: 05/12/2010] [Indexed: 01/15/2023]
Abstract
Great progress has been made in understanding the regulation of expression of genes involved in secondary metabolism. Less is known about the mechanisms that govern the spatial distribution of the enzymes, cofactors, and substrates that mediate catalysis of secondary metabolites within the cell. Filamentous fungi in the genus Aspergillus synthesize an array of secondary metabolites and provide useful systems to analyze the mechanisms that mediate the temporal and spatial regulation of secondary metabolism in eukaryotes. For example, aflatoxin biosynthesis in Aspergillus parasiticus has been studied intensively because this mycotoxin is highly toxic, mutagenic, and carcinogenic in humans and animals. Using aflatoxin synthesis to illustrate key concepts, this review focuses on the mechanisms by which sub-cellular compartmentalization and intra-cellular molecular traffic contribute to the initiation and completion of secondary metabolism within the cell. We discuss the recent discovery of aflatoxisomes, specialized trafficking vesicles that participate in the compartmentalization of aflatoxin synthesis and export of the toxin to the cell exterior; this work provides a new and clearer understanding of how cells integrate secondary metabolism into basic cellular metabolism via the intra-cellular trafficking machinery.
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Affiliation(s)
- Ludmila V Roze
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI-48824, USA
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Characterization of the Aspergillus nidulans monodictyphenone gene cluster. Appl Environ Microbiol 2010; 76:2067-74. [PMID: 20139316 DOI: 10.1128/aem.02187-09] [Citation(s) in RCA: 147] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Deletion of cclA, a component of the COMPASS complex of Aspergillus nidulans, results in the production of monodictyphenone and emodin derivatives. Through a set of targeted deletions in a cclA deletion strain, we have identified the genes required for monodictyphenone and emodin analog biosynthesis. Identification of an intermediate, endocrocin, from an mdpHDelta strain suggests that mdpH might encode a decarboxylase. Furthermore, by replacing the promoter of mdpA (a putative aflJ homolog) and mdpE (a putative aflR homolog) with the inducible alcA promoter, we have confirmed that MdpA functions as a coactivator. We propose a biosynthetic pathway for monodictyphenone and emodin derivatives based on bioinformatic analysis and characterization of biosynthetic intermediates.
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45
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Moore GG, Singh R, Horn BW, Carbone I. Recombination and lineage-specific gene loss in the aflatoxin gene cluster of Aspergillus flavus. Mol Ecol 2009; 18:4870-87. [PMID: 19895419 DOI: 10.1111/j.1365-294x.2009.04414.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Aflatoxins produced by Aspergillus flavus are potent carcinogens that contaminate agricultural crops. Recent efforts to reduce aflatoxin concentrations in crops have focused on biological control using nonaflatoxigenic A. flavus strains AF36 (=NRRL 18543) and NRRL 21882 (the active component of afla-guard. However, the evolutionary potential of these strains to remain nonaflatoxigenic in nature is unknown. To elucidate the underlying population processes that influence aflatoxigenicity, we examined patterns of linkage disequilibrium (LD) spanning 21 regions in the aflatoxin gene cluster of A. flavus. We show that recombination events are unevenly distributed across the cluster in A. flavus. Six distinct LD blocks separate late pathway genes aflE, aflM, aflN, aflG, aflL, aflI and aflO, and there is no discernable evidence of recombination among early pathway genes aflA, aflB, aflC, aflD, aflR and aflS. The discordance in phylogenies inferred for the aflW/aflX intergenic region and two noncluster regions, tryptophan synthase and acetamidase, is indicative of trans-species evolution in the cluster. Additionally, polymorphisms in aflW/aflX divide A. flavus strains into two distinct clades, each harbouring only one of the two approved biocontrol strains. The clade with AF36 includes both aflatoxigenic and nonaflatoxigenic strains, whereas the clade with NRRL 21882 comprises only nonaflatoxigenic strains and includes all strains of A. flavus missing the entire gene cluster or with partial gene clusters. Our detection of LD blocks in partial clusters indicates that recombination may have played an important role in cluster disassembly, and multilocus coalescent analyses of cluster and noncluster regions indicate lineage-specific gene loss in A. flavus. These results have important implications in assessing the stability of biocontrol strains in nature.
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Affiliation(s)
- Geromy G Moore
- Center for Integrated Fungal Research, Department of Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA
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Ehrlich KC. Predicted roles of the uncharacterized clustered genes in aflatoxin biosynthesis. Toxins (Basel) 2009; 1:37-58. [PMID: 22069531 PMCID: PMC3202775 DOI: 10.3390/toxins1010037] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 09/22/2009] [Accepted: 09/24/2009] [Indexed: 11/21/2022] Open
Abstract
Biosynthesis of the toxic and carcinogenic aflatoxins (AFs) requires the activity of more than 27 enzymes. The roles in biosynthesis of newly described enzymes are discussed in this review. We suggest that HypC catalyzes the oxidation of norsolorinic acid anthrone; AvfA (AflI), the ring-closure step in formation of hydroxyversicolorone; HypB, the second oxidation step in conversion of O-methylsterigmatocystin to AF; and HypE and NorA (AflE), the final two steps in AFB(1) formation. HypD, an integral membrane protein, affects fungal development and lowers AF production while AflJ (AflS), has a partial methyltransferase domain that may be important in its function as a transcriptional co-activator.
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Affiliation(s)
- Kenneth C Ehrlich
- Southern Regional Research Center, ARS, USDA/1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA.
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The effect of temperature on Natural Antisense Transcript (NAT) expression in Aspergillus flavus. Curr Genet 2008; 54:241-69. [PMID: 18813928 DOI: 10.1007/s00294-008-0215-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2008] [Revised: 09/02/2008] [Accepted: 09/03/2008] [Indexed: 12/25/2022]
Abstract
Naturally occurring Antisense Transcripts (NATs) compose an emerging group of regulatory RNAs. These regulatory elements appear in all organisms examined, but little is known about global expression of NATs in fungi. Analysis of currently available EST sequences suggests that 352 cis NATs are present in Aspergillus flavus. An Affymetrix GeneChip microarray containing probes for these cis NATs, as well as all predicted genes in A. flavus, allowed a whole genome expression analysis of these elements in response to two ecologically important temperatures for the fungus. RNA expression analysis showed that 32 NATs and 2,709 genes were differentially expressed between 37 degrees C, the optimum temperature for growth, and 28 degrees C, the conducive temperature for the biosynthesis of aflatoxin (AF) and many other secondary metabolites. These NATs correspond to sense genes with diverse functions including transcription initiation, carbohydrate processing and binding, temperature sensitive morphogenesis, and secondary metabolism. This is the first report of a whole genome transcriptional analysis of NAT expression in a fungus.
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Chang PK, Matsushima K, Takahashi T, Yu J, Abe K, Bhatnagar D, Yuan GF, Koyama Y, Cleveland TE. Understanding nonaflatoxigenicity of Aspergillus sojae: a windfall of aflatoxin biosynthesis research. Appl Microbiol Biotechnol 2007; 76:977-84. [PMID: 17665189 DOI: 10.1007/s00253-007-1116-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Accepted: 07/07/2007] [Indexed: 10/23/2022]
Abstract
Aspergillus section Flavi includes aflatoxin-producing and nonproducing fungi. Aspergillus sojae is unable to produce aflatoxins and is generally recognized as safe for food fermentation. However, because of its taxonomical relatedness to aflatoxin-producing Aspergillus parasiticus and A. flavus, it is necessary to decipher the underlying mechanisms for its inability to produce aflatoxins. This review addresses the relationship between A. sojae and A. parasiticus and the advances that have been made in aflatoxin biosynthesis research, especially with regard to gene structure, genome organization, and gene regulation in A. parasiticus and A. flavus and how this has been used to assure the safety of A. sojae as an organism for food fermentation. The lack of aflatoxin-producing ability of A. sojae results primarily from an early termination point mutation in the pathway-specific aflR regulatory gene, which causes the truncation of the transcriptional activation domain of AflR and the abolishment of interaction between AflR and the AflJ co-activator. Both are required for gene expression. In addition, a defect in the polyketide synthase gene also contributes to its nonaflatoxigenicity.
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Affiliation(s)
- Perng-Kuang Chang
- Food and Feed Safety Research Unit, Southern Regional Research Center, Agricultural Research Service, US Department of Agriculture, 1100 Robert E. Lee Boulevard, New Orleans, LA 70124, USA.
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Carbone I, Ramirez-Prado JH, Jakobek JL, Horn BW. Gene duplication, modularity and adaptation in the evolution of the aflatoxin gene cluster. BMC Evol Biol 2007; 7:111. [PMID: 17620135 PMCID: PMC1949824 DOI: 10.1186/1471-2148-7-111] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2007] [Accepted: 07/09/2007] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND The biosynthesis of aflatoxin (AF) involves over 20 enzymatic reactions in a complex polyketide pathway that converts acetate and malonate to the intermediates sterigmatocystin (ST) and O-methylsterigmatocystin (OMST), the respective penultimate and ultimate precursors of AF. Although these precursors are chemically and structurally very similar, their accumulation differs at the species level for Aspergilli. Notable examples are A. nidulans that synthesizes only ST, A. flavus that makes predominantly AF, and A. parasiticus that generally produces either AF or OMST. Whether these differences are important in the evolutionary/ecological processes of species adaptation and diversification is unknown. Equally unknown are the specific genomic mechanisms responsible for ordering and clustering of genes in the AF pathway of Aspergillus. RESULTS To elucidate the mechanisms that have driven formation of these clusters, we performed systematic searches of aflatoxin cluster homologs across five Aspergillus genomes. We found a high level of gene duplication and identified seven modules consisting of highly correlated gene pairs (aflA/aflB, aflR/aflS, aflX/aflY, aflF/aflE, aflT/aflQ, aflC/aflW, and aflG/aflL). With the exception of A. nomius, contrasts of mean Ka/Ks values across all cluster genes showed significant differences in selective pressure between section Flavi and non-section Flavi species. A. nomius mean Ka/Ks values were more similar to partial clusters in A. fumigatus and A. terreus. Overall, mean Ka/Ks values were significantly higher for section Flavi than for non-section Flavi species. CONCLUSION Our results implicate several genomic mechanisms in the evolution of ST, OMST and AF cluster genes. Gene modules may arise from duplications of a single gene, whereby the function of the pre-duplication gene is retained in the copy (aflF/aflE) or the copies may partition the ancestral function (aflA/aflB). In some gene modules, the duplicated copy may simply augment/supplement a specific pathway function (aflR/aflS and aflX/aflY) or the duplicated copy may evolve a completely new function (aflT/aflQ and aflC/aflW). Gene modules that are contiguous in one species and noncontiguous in others point to possible rearrangements of cluster genes in the evolution of these species. Significantly higher mean Ka/Ks values in section Flavi compared to non-section Flavi species indicate increased positive selection acting in the evolution of genes in OMST and AF gene clusters.
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Affiliation(s)
- Ignazio Carbone
- Center for Integrated Fungal Research, Department of Plant Pathology, North Carolina State University, Raleigh, NC 27695 USA
| | - Jorge H Ramirez-Prado
- Center for Integrated Fungal Research, Department of Plant Pathology, North Carolina State University, Raleigh, NC 27695 USA
| | - Judy L Jakobek
- Center for Integrated Fungal Research, Department of Plant Pathology, North Carolina State University, Raleigh, NC 27695 USA
| | - Bruce W Horn
- National Peanut Research Laboratory, USDA, ARS, Dawson, GA 39842, USA
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Frisvad JC, Larsen TO, de Vries R, Meijer M, Houbraken J, Cabañes FJ, Ehrlich K, Samson RA. Secondary metabolite profiling, growth profiles and other tools for species recognition and important Aspergillus mycotoxins. Stud Mycol 2007; 59:31-7. [PMID: 18490955 PMCID: PMC2275202 DOI: 10.3114/sim.2007.59.04] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Species in the genus Aspergillus have been classified primarily based on morphological features. Sequencing of house-hold genes has also been used in Aspergillus taxonomy and phylogeny, while extrolites and physiological features have been used less frequently. Three independent ways of classifying and identifying aspergilli appear to be applicable: Morphology combined with physiology and nutritional features, secondary metabolite profiling and DNA sequencing. These three ways of identifying Aspergillus species often point to the same species. This consensus approach can be used initially, but if consensus is achieved it is recommended to combine at least two of these independent ways of characterising aspergilli in a polyphasic taxonomy. The chemical combination of secondary metabolites and DNA sequence features has not been explored in taxonomy yet, however. Examples of these different taxonomic approaches will be given for Aspergillus section Nigri.
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Affiliation(s)
- J C Frisvad
- Center for Microbial Biotechnology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
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