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Wang W, Liang X, Li Y, Wang P, Keller NP. Genetic Regulation of Mycotoxin Biosynthesis. J Fungi (Basel) 2022; 9:jof9010021. [PMID: 36675842 PMCID: PMC9861139 DOI: 10.3390/jof9010021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 12/20/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022] Open
Abstract
Mycotoxin contamination in food poses health hazards to humans. Current methods of controlling mycotoxins still have limitations and more effective approaches are needed. During the past decades of years, variable environmental factors have been tested for their influence on mycotoxin production leading to elucidation of a complex regulatory network involved in mycotoxin biosynthesis. These regulators are putative targets for screening molecules that could inhibit mycotoxin synthesis. Here, we summarize the regulatory mechanisms of hierarchical regulators, including pathway-specific regulators, global regulators and epigenetic regulators, on the production of the most critical mycotoxins (aflatoxins, patulin, citrinin, trichothecenes and fumonisins). Future studies on regulation of mycotoxins will provide valuable knowledge for exploring novel methods to inhibit mycotoxin biosynthesis in a more efficient way.
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Affiliation(s)
- Wenjie Wang
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
- Institute of Food Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
- Correspondence: (W.W.); (N.P.K.)
| | - Xinle Liang
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
- Institute of Food Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
| | - Yudong Li
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
- Institute of Food Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China
| | - Pinmei Wang
- Ocean College, Zhejiang University, Zhoushan 316021, China
| | - Nancy P. Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
- Correspondence: (W.W.); (N.P.K.)
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Wei S, Hu C, Nie P, Zhai H, Zhang S, Li N, Lv Y, Hu Y. Insights into the Underlying Mechanism of Ochratoxin A Production in Aspergillus niger CBS 513.88 Using Different Carbon Sources. Toxins (Basel) 2022; 14:toxins14080551. [PMID: 36006213 PMCID: PMC9415321 DOI: 10.3390/toxins14080551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 07/28/2022] [Accepted: 08/08/2022] [Indexed: 11/28/2022] Open
Abstract
Aspergillus niger produces carcinogenic ochratoxin A (OTA), a serious food safety and human health concern. Here, the ability of A. niger CBS 513.88 to produce OTA using different carbon sources was investigated and the underlying regulatory mechanism was elucidated. The results indicated that 6% sucrose, glucose, and arabinose could trigger OTA biosynthesis and that 1586 differentially expressed genes (DEGs) overlapped compared to a non-inducing nutritional source, peptone. The genes that participated in OTA and its precursor phenylalanine biosynthesis, including pks, p450, nrps, hal, and bzip, were up-regulated, while the genes involved in oxidant detoxification, such as cat and pod, were down-regulated. Correspondingly, the activities of catalase and peroxidase were also decreased. Notably, the novel Gal4-like transcription factor An12g00840 (AnGal4), which is vital in regulating OTA biosynthesis, was identified. Deletion of AnGal4 elevated the OTA yields by 47.65%, 54.60%, and 309.23% using sucrose, glucose, and arabinose as carbon sources, respectively. Additionally, deletion of AnGal4 increased the superoxide anion and H2O2 contents, as well as the sensitivity to H2O2, using the three carbon sources. These results suggest that these three carbon sources repressed AnGal4, leading to the up-regulation of the OTA biosynthetic genes and alteration of cellular redox homeostasis, ultimately triggering OTA biosynthesis in A. niger.
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Affiliation(s)
- Shan Wei
- College of Bioengineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Chaojiang Hu
- College of Bioengineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Ping Nie
- College of Bioengineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Huanchen Zhai
- College of Bioengineering, 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 Bioengineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
| | - Na Li
- College of Bioengineering, 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 Bioengineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
- Correspondence: (Y.L.); (Y.H.)
| | - Yuansen Hu
- College of Bioengineering, Henan University of Technology, Zhengzhou 450001, China
- Henan Provincial Key Laboratory of Biological Processing and Nutritional Function of Wheat, Zhengzhou 450001, China
- Correspondence: (Y.L.); (Y.H.)
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Sharma S, Choudhary B, Yadav S, Mishra A, Mishra VK, Chand R, Chen C, Pandey SP. Metabolite profiling identified pipecolic acid as an important component of peanut seed resistance against Aspergillus flavus infection. JOURNAL OF HAZARDOUS MATERIALS 2021; 404:124155. [PMID: 33049626 DOI: 10.1016/j.jhazmat.2020.124155] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 09/03/2020] [Accepted: 09/28/2020] [Indexed: 06/11/2023]
Abstract
In a previous study, we identified a halotolerant rhizobacterium belonging to the genus Klebsiella (MBE02) that protected peanut seeds from Aspergillus flavus infection. Here, we investigated the mechanisms underlying the effect of MBE02 against A. flavus via untargeted metabolite profiling of peanut seeds treated with MBE02, A. flavus, or MBE02+A. flavus. Thirty-five metabolites were differentially accumulated across the three treatments (compared to the control), and the levels of pipecolic acid (Pip) were reduced upon A. flavus treatment only. We validated the function of Pip against A. flavus using multiple resistant and susceptible peanut cultivars. Pip accumulation was strongly associated with the resistant genotypes that also accumulated several mRNAs of the ALD1-like gene in the Pip biosynthesis pathway. Furthermore, exogenous treatment of a susceptible peanut cultivar with Pip reduced A. flavus infection in the seeds. Our findings indicate that Pip is a key component of peanut resistance to A. flavus.
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Affiliation(s)
- Sandeep Sharma
- Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India.
| | - Babita Choudhary
- CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, India.
| | - Sonam Yadav
- CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, India.
| | - Avinash Mishra
- CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, India.
| | - Vinod K Mishra
- Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India.
| | - Ramesh Chand
- Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India.
| | - Chen Chen
- Jiangsu Key Laboratory of Crop Genetics and Physiology, Co-Innovation Center for Modern Production Technology of Grain Crops, Key Laboratory of Plant Functional Genomics of the Ministry of Education, Yangzhou University, Yangzhou, China.
| | - Shree P Pandey
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Jena, Germany.
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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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Metabolites Identified during Varied Doses of Aspergillus Species in Zea mays Grains, and Their Correlation with Aflatoxin Levels. Toxins (Basel) 2018; 10:toxins10050187. [PMID: 29735944 PMCID: PMC5983243 DOI: 10.3390/toxins10050187] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 04/30/2018] [Accepted: 05/04/2018] [Indexed: 11/16/2022] Open
Abstract
Aflatoxin contamination is associated with the development of aflatoxigenic fungi such as Aspergillus flavus and A. parasiticus on food grains. This study was aimed at investigating metabolites produced during fungal development on maize and their correlation with aflatoxin levels. Maize cobs were harvested at R3 (milk), R4 (dough), and R5 (dent) stages of maturity. Individual kernels were inoculated in petri dishes with four doses of fungal spores. Fungal colonisation, metabolite profile, and aflatoxin levels were examined. Grain colonisation decreased with kernel maturity: milk-, dough-, and dent-stage kernels by approximately 100%, 60%, and 30% respectively. Aflatoxin levels increased with dose at dough and dent stages. Polar metabolites including alanine, proline, serine, valine, inositol, iso-leucine, sucrose, fructose, trehalose, turanose, mannitol, glycerol, arabitol, inositol, myo-inositol, and some intermediates of the tricarboxylic acid cycle (TCA—also known as citric acid or Krebs cycle) were important for dose classification. Important non-polar metabolites included arachidic, palmitic, stearic, 3,4-xylylic, and margaric acids. Aflatoxin levels correlated with levels of several polar metabolites. The strongest positive and negative correlations were with arabitol (R = 0.48) and turanose and (R = −0.53), respectively. Several metabolites were interconnected with the TCA; interconnections of the metabolites with the TCA cycle varied depending upon the grain maturity.
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6
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Detection of Transcriptionally Active Mycotoxin Gene Clusters: DNA Microarray. Methods Mol Biol 2016. [PMID: 27924550 DOI: 10.1007/978-1-4939-6707-0_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Various bioanalytical tools including DNA microarrays are frequently used to map global transcriptional changes in mycotoxin producer filamentous fungi. This effective hybridization-based transcriptomics technology helps researchers to identify genes of secondary metabolite gene clusters and record concomitant gene expression changes in these clusters initiated by versatile environmental conditions and/or gene deletions. Such transcriptional data are of great value when future mycotoxin control technologies are considered and elaborated. Giving the readers insights into RNA extraction and DNA microarray hybridization steps routinely used in our laboratories and also into the normalization and evaluation of primary gene expression data, we would like to contribute to the interlaboratory standardization of DNA microarray based transcriptomics studies being carried out in many laboratories worldwide in this important field of fungal biology.
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Verheecke C, Liboz T, Anson P, Zhu Y, Mathieu F. Streptomyces-Aspergillus flavus interactions: impact on aflatoxin B accumulation. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2015; 32:572-6. [PMID: 25632796 DOI: 10.1080/19440049.2014.1003336] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The aim of this work was to investigate the potential of Streptomyces sp. as biocontrol agents against aflatoxins in maize. As such, we assumed that Streptomyces sp. could provide a complementary approach to current biocontrol systems such as Afla-guard(®) and we focused on biocontrol that was able to have an antagonistic contact with A. flavus. A previous study showed that 27 (out of 38) Streptomyces sp. had mutual antagonism in contact with A. flavus. Among these, 16 Streptomyces sp. were able to reduce aflatoxin content to below 17% of the residual concentration. We selected six strains to understand the mechanisms involved in the prevention of aflatoxin accumulation. Thus, in interaction with A. flavus, we monitored by RT-qPCR the gene expression of aflD, aflM, aflP, aflR and aflS. All the Streptomyces sp. were able to reduce aflatoxin concentration (24.0-0.2% residual aflatoxin B1). They all impacted on gene expression, but only S35 and S38 were able to repress expression significantly. Indeed, S35 significantly repressed aflM expression and S38 significantly repressed aflR, aflM and aflP. S6 reduced aflatoxin concentrations (2.3% residual aflatoxin B1) and repressed aflS, aflM and enhanced aflR expression. In addition, the S6 strain (previously identified as the most reducing pure aflatoxin B1) was further tested to determine a potential adsorption mechanism. We did not observe any adsorption phenomenon. In conclusion, this study showed that Streptomyces sp. prevent the production of (aflatoxin gene expression) and decontamination of (aflatoxin B1 reduction) aflatoxins in vitro.
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Affiliation(s)
- C Verheecke
- a Laboratoire de Génie Chimique , Université de Toulouse , Castanet-Tolosan , France
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Woloshuk CP, Shim WB. Aflatoxins, fumonisins, and trichothecenes: a convergence of knowledge. FEMS Microbiol Rev 2012; 37:94-109. [PMID: 23078349 DOI: 10.1111/1574-6976.12009] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 09/27/2012] [Accepted: 10/15/2012] [Indexed: 01/03/2023] Open
Abstract
Plant pathogenic fungi Aspergillus flavus, Fusarium verticillioides, and Fusarium graminearum infect seeds of the most important food and feed crops, including maize, wheat, and barley. More importantly, these fungi produce aflatoxins, fumonisins, and trichothecenes, respectively, which threaten health and food security worldwide. In this review, we examine the molecular mechanisms and environmental factors that regulate mycotoxin biosynthesis in each fungus, and discuss the similarities and differences in the collective body of knowledge. Whole-genome sequences are available for these fungi, providing reference databases for genomic, transcriptomic, and proteomic analyses. It is well recognized that genes responsible for mycotoxin biosynthesis are organized in clusters. However, recent research has documented the intricate transcriptional and epigenetic regulation that affects these gene clusters. Significantly, molecular networks that respond to environmental factors, namely nitrogen, carbon, and pH, are connected to components regulating mycotoxin production. Furthermore, the developmental status of seeds and specific tissue types exert conditional influences during fungal colonization. A comparison of the three distinct mycotoxin groups provides insight into new areas for research collaborations that will lead to innovative strategies to control mycotoxin contamination of grain.
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Affiliation(s)
- Charles P Woloshuk
- Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.
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Yu J. Current understanding on aflatoxin biosynthesis and future perspective in reducing aflatoxin contamination. Toxins (Basel) 2012; 4:1024-57. [PMID: 23202305 PMCID: PMC3509697 DOI: 10.3390/toxins4111024] [Citation(s) in RCA: 197] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 10/08/2012] [Accepted: 10/09/2012] [Indexed: 01/20/2023] Open
Abstract
Traditional molecular techniques have been used in research in discovering the genes and enzymes that are involved in aflatoxin formation and genetic regulation. We cloned most, if not all, of the aflatoxin pathway genes. A consensus gene cluster for aflatoxin biosynthesis was discovered in 2005. The factors that affect aflatoxin formation have been studied. In this report, the author summarized the current status of research progress and future possibilities that may be used for solving aflatoxin contamination.
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Affiliation(s)
- Jiujiang Yu
- Southern Regional Research Center, Agricultural Research Service, United States Department of Agriculture (USDA/ARS), New Orleans, LA 70112, USA.
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10
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Yan S, Liang Y, Zhang J, Liu CM. Aspergillus flavus grown in peptone as the carbon source exhibits spore density- and peptone concentration-dependent aflatoxin biosynthesis. BMC Microbiol 2012; 12:106. [PMID: 22694821 PMCID: PMC3412747 DOI: 10.1186/1471-2180-12-106] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 06/13/2012] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Aflatoxins (AFs) are highly carcinogenic compounds produced by Aspergillus species in seeds with high lipid and protein contents. It has been known for over 30 years that peptone is not conducive for AF productions, although reasons for this remain unknown. RESULTS In this study, we showed that when Aspergillus flavus was grown in peptone-containing media, higher initial spore densities inhibited AF biosynthesis, but promoted mycelial growth; while in glucose-containing media, more AFs were produced when initial spore densities were increased. This phenomenon was also observed in other AF-producing strains including A. parasiticus and A. nomius. Higher peptone concentrations led to inhibited AF production, even in culture with a low spore density. High peptone concentrations did however promote mycelial growth. Spent medium experiments showed that the inhibited AF production in peptone media was regulated in a cell-autonomous manner. mRNA expression analyses showed that both regulatory and AF biosynthesis genes were repressed in mycelia cultured with high initial spore densities. Metabolomic studies revealed that, in addition to inhibited AF biosynthesis, mycelia grown in peptone media with a high initial spore density showed suppressed fatty acid biosynthesis, reduced tricarboxylic acid (TCA) cycle intermediates, and increased pentose phosphate pathway products. Additions of TCA cycle intermediates had no effect on AF biosynthesis, suggesting the inhibited AF biosynthesis was not caused by depleted TCA cycle intermediates. CONCLUSIONS We here demonstrate that Aspergillus species grown in media with peptone as the sole carbon source are able to sense their own population densities and peptone concentrations to switch between rapid growth and AF production. This switching ability may offer Aspergillus species a competition advantage in natural ecosystems, producing AFs only when self-population is low and food is scarce.
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Affiliation(s)
- Shijuan Yan
- Practaculture College, Gansu Agricultural University, Lanzhou, 730070, China
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Fragrant Hill, Beijing,, 100093, China
| | - Yating Liang
- Practaculture College, Gansu Agricultural University, Lanzhou, 730070, China
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215000, China
| | - Jindan Zhang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Fragrant Hill, Beijing,, 100093, China
| | - Chun-Ming Liu
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 20 Nanxincun, Fragrant Hill, Beijing,, 100093, China
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Wilkinson JR, Kale SP, Bhatnagar D, Yu J, Ehrlich KC. Expression profiling of non-aflatoxigenic Aspergillus parasiticus mutants obtained by 5-azacytosine treatment or serial mycelial transfer. Toxins (Basel) 2011; 3:932-48. [PMID: 22069749 PMCID: PMC3202869 DOI: 10.3390/toxins3080932] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 07/19/2011] [Accepted: 07/26/2011] [Indexed: 11/17/2022] Open
Abstract
Aflatoxins are carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. Previous studies found that repeated serial mycelial transfer or treatment of A. parasiticus with 5-azacytidine produced colonies with a fluffy phenotype and inability to produce aflatoxins. To understand how these treatments affect expression of genes involved in aflatoxin production and development, we carried out expressed sequence tag (EST)-based microarray assays to identify genes in treated clones that are differentially expressed compared to the wild-type. Expression of 183 genes was significantly dysregulated. Of these, 38 had at least two-fold or lower expression compared to the untreated control and only two had two-fold or higher expression. The most frequent change was downregulation of genes predicted to encode membrane-bound proteins. Based on this result we hypothesize that the treatments cause changes in the structure of cellular and organelle membranes that prevent normal development and aflatoxin biosynthesis.
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Affiliation(s)
- Jeffrey R. Wilkinson
- Southern Regional Research Center, ARS/USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA; (J.R.W.); (D.B.); (J.Y)
| | - Shubha P. Kale
- Department of Biology, 1 Drexel Dr., Box 85B, Xavier University of Louisiana, New Orleans, LA 70125, USA;
| | - Deepak Bhatnagar
- Southern Regional Research Center, ARS/USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA; (J.R.W.); (D.B.); (J.Y)
| | - Jiujiang Yu
- Southern Regional Research Center, ARS/USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA; (J.R.W.); (D.B.); (J.Y)
| | - Kenneth C. Ehrlich
- Southern Regional Research Center, ARS/USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA; (J.R.W.); (D.B.); (J.Y)
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Yu J, Fedorova ND, Montalbano BG, Bhatnagar D, Cleveland TE, Bennett JW, Nierman WC. Tight control of mycotoxin biosynthesis gene expression in Aspergillus flavus by temperature as revealed by RNA-Seq. FEMS Microbiol Lett 2011; 322:145-9. [PMID: 21707733 DOI: 10.1111/j.1574-6968.2011.02345.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
To better understand the effect of temperature on mycotoxin biosynthesis, RNA-Seq technology was used to profile the Aspergillus flavus transcriptome under different temperature conditions. This approach allowed us to quantify transcript abundance for over 80% of fungal genes including 1153 genes that were differentially expressed at 30 and 37 °C. Eleven of the 55 secondary metabolite clusters were upregulated at the lower temperature, including aflatoxin biosynthesis genes, which were among the most highly upexpressed genes. On average, transcript abundance for the 30 aflatoxin biosynthesis genes was 3300 times greater at 30 °C as compared with 37 °C. The results are consistent with the view that high temperature negatively affects aflatoxin production by turning down transcription of the two key transcriptional regulators, aflR and aflS. Subtle changes in the expression levels of aflS to aflR appear to control transcription activation of the aflatoxin cluster.
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Affiliation(s)
- Jiujiang Yu
- Southern Regional Research Center, Agricultural Research Service-ARS, US Department of Agriculture-USDA, New Orleans, LA 70124, USA.
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Gene expression profiling and identification of resistance genes to Aspergillus flavus infection in peanut through EST and microarray strategies. Toxins (Basel) 2011; 3:737-53. [PMID: 22069737 PMCID: PMC3202856 DOI: 10.3390/toxins3070737] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 06/09/2011] [Accepted: 06/14/2011] [Indexed: 11/16/2022] Open
Abstract
Aspergillus flavus and A. parasiticus infect peanut seeds and produce aflatoxins, which are associated with various diseases in domestic animals and humans throughout the world. The most cost-effective strategy to minimize aflatoxin contamination involves the development of peanut cultivars that are resistant to fungal infection and/or aflatoxin production. To identify peanut Aspergillus-interactive and peanut Aspergillus-resistance genes, we carried out a large scale peanut Expressed Sequence Tag (EST) project which we used to construct a peanut glass slide oligonucleotide microarray. The fabricated microarray represents over 40% of the protein coding genes in the peanut genome. For expression profiling, resistant and susceptible peanut cultivars were infected with a mixture of Aspergillusflavus and parasiticus spores. The subsequent microarray analysis identified 62 genes in resistant cultivars that were up-expressed in response to Aspergillus infection. In addition, we identified 22 putative Aspergillus-resistance genes that were constitutively up-expressed in the resistant cultivar in comparison to the susceptible cultivar. Some of these genes were homologous to peanut, corn, and soybean genes that were previously shown to confer resistance to fungal infection. This study is a first step towards a comprehensive genome-scale platform for developing Aspergillus-resistant peanut cultivars through targeted marker-assisted breeding and genetic engineering.
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14
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Rank C, Nielsen KF, Larsen TO, Varga J, Samson RA, Frisvad JC. Distribution of sterigmatocystin in filamentous fungi. Fungal Biol 2011; 115:406-20. [PMID: 21530923 DOI: 10.1016/j.funbio.2011.02.013] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 01/28/2011] [Accepted: 02/16/2011] [Indexed: 10/18/2022]
Abstract
During the last 50y, the carcinogenic mycotoxin sterigmatocystin (ST) has been reported in several phylogenetically and phenotypically different genera: Aschersonia, Aspergillus, Bipolaris, Botryotrichum, Chaetomium, Emericella, Eurotium, Farrowia, Fusarium, Humicola, Moelleriella, Monocillium and Podospora. We have reexamined all available strains of the original producers, in addition to ex type and further strains of each species reported to produce ST and the biosynthetically derived aflatoxins. We also screened strains of all available species in Penicillium and Aspergillus for ST and aflatoxin. Six new ST producing fungi were discovered: Aspergillus asperescens, Aspergillus aureolatus, Aspergillus eburneocremeus, Aspergillus protuberus, Aspergillus tardus, and Penicillium inflatum and one new aflatoxin producer: Aspergillus togoensis (=Stilbothamnium togoense). ST was confirmed in 23 Emericella, four Aspergillus, five Chaetomium, one Botryotrichum and one Humicola species grown on a selection of secondary metabolite inducing media, and using multiple detection methods: HPLC-UV/Vis DAD, - HRMS and - MS/MS. The immediate precursor for aflatoxin, O-methylsterigmatocystin was found in Chaetomium cellulolyticum, Chaetomium longicolleum, Chaetomium malaysiense and Chaetomium virescens, but aflatoxin was not detected from any Chaetomium species. In all 55 species, representing more than 11 clades throughout the Pezizomycotina, can be reliably claimed to be ST producers and 13 of these can also produce aflatoxins. It is not known yet whether the ST/aflatoxin pathway has been developed independently 11 times, or is the result of partial horizontal gene transfer.
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Affiliation(s)
- Christian Rank
- Technical University of Denmark, Department of Systems Biology, Center for Microbial Biotechnology, Søltofts Plads Building 221, DK-2800 Kongens Lyngby, Denmark
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15
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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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16
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Cary J, Rajasekaran K, Yu J, Brown R, Bhatnagar D, Cleveland T. Transgenic approaches for pre-harvest control of mycotoxin contamination in crop plants. WORLD MYCOTOXIN J 2009. [DOI: 10.3920/wmj2009.1138] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mycotoxins are fungal metabolites that can contaminate food and feed crops worldwide and are responsible for toxic effects in animals and humans that consume contaminated commodities. Regulatory guidelines and limits for mycotoxins have been set by the US Food and Drug Administration (FDA) and food safety agencies of other countries for both import and export of affected commodities. Mycotoxin contamination of foods and feeds can also cause serious economic hardships to producers, processors, and the consumer. Therefore, there has been a concerted effort by researchers worldwide to develop strategies for the effective control of mycotoxin contamination of crops, particularly at the pre-harvest stage. Strategies currently being utilised to combat pre-harvest mycotoxin contamination include: (1) use of non-toxigenic biocontrol strains; (2) improved agricultural practices; (3) application of agrochemicals; (4) plant breeding for resistance; and (5) genetic engineering of resistance genes into crop plants. This article highlights research on the genetic engineering of plants for resistance to invasion by mycotoxigenic fungi as well as detoxification of mycotoxins. Emphasis is placed on the most economically relevant fungi and the mycotoxins they produce. These include aflatoxins produced mainly by Aspergillus flavus and A. parasiticus, trichothecenes produced mainly by Fusarium graminearum, and to a lesser extent, fumonisins produced by F. verticillioides. Information is also presented on the use of genomics and proteomics technologies as a means of identifying genes and proteins that can be utilised in transgenic approaches to control the growth of mycotoxigenic fungi and the mycotoxins that they produce in food and feed crops.
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Affiliation(s)
- J. Cary
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
| | - K. Rajasekaran
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
| | - J. Yu
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
| | - R. Brown
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
| | - D. Bhatnagar
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
| | - T. Cleveland
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA
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17
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Cleveland TE, Yu J, Fedorova N, Bhatnagar D, Payne GA, Nierman WC, Bennett JW. Potential of Aspergillus flavus genomics for applications in biotechnology. Trends Biotechnol 2009; 27:151-7. [PMID: 19195728 DOI: 10.1016/j.tibtech.2008.11.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Revised: 11/18/2008] [Accepted: 11/19/2008] [Indexed: 10/21/2022]
Abstract
Aspergillus flavus is a common saprophyte and opportunistic pathogen that produces numerous secondary metabolites. The primary objectives of the A. flavus genomics program are to reduce and eliminate aflatoxin contamination in food and feed and to discover genetic factors that contribute to plant and animal pathogenicity. A. flavus expressed sequence tags (ESTs) and whole-genome sequencing have been completed. Annotation of the A. flavus genome has revealed numerous genes and gene clusters that are potentially involved in the formation of aflatoxin and other secondary metabolites, as well as in the degradation of complex carbohydrate polymers. Analysis of putative secondary metabolism pathways might facilitate the discovery of new compounds with pharmaceutical properties, as well as new enzymes for biomass degradation.
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Affiliation(s)
- Thomas E Cleveland
- United States Department of Agriculture, Agricultural Research Service (USDA/ARS), Southern Regional Research Center, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA.
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18
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Wilkinson JR, Abbas HK. AFLATOXIN,ASPERGILLUS, MAIZE, AND THE RELEVANCE TO ALTERNATIVE FUELS (OR AFLATOXIN: WHAT IS IT, CAN WE GET RID OF IT, AND SHOULD THE ETHANOL INDUSTRY CARE?). TOXIN REV 2008. [DOI: 10.1080/15569540802439667] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Georgianna DR, Payne GA. Genetic regulation of aflatoxin biosynthesis: from gene to genome. Fungal Genet Biol 2008; 46:113-25. [PMID: 19010433 DOI: 10.1016/j.fgb.2008.10.011] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 10/10/2008] [Accepted: 10/10/2008] [Indexed: 01/12/2023]
Abstract
Aflatoxins are notorious toxic secondary metabolites known for their impacts on human and animal health, and their effects on the marketability of key grain and nut crops. Understanding aflatoxin biosynthesis is the focus of a large and diverse research community. Concerted efforts by this community have led not only to a well-characterized biosynthetic pathway, but also to the discovery of novel regulatory mechanisms. Common to secondary metabolism is the clustering of biosynthetic genes and their regulation by pathway specific as well as global regulators. Recent data show that arrangement of secondary metabolite genes in clusters may allow for an important global regulation of secondary metabolism based on physical location along the chromosome. Available genomic and proteomic tools are now allowing us to examine aflatoxin biosynthesis more broadly and to put its regulation in context with fungal development and fungal ecology. This review covers our current understanding of the biosynthesis and regulation of aflatoxin and highlights new and emerging information garnered from structural and functional genomics. The focus of this review will be on studies in Aspergillus flavus and Aspergillus parasiticus, the two agronomically important species that produce aflatoxin. Also covered will be the important contributions gained by studies on production of the aflatoxin precursor sterigmatocystin in Aspergillus nidulans.
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Affiliation(s)
- D Ryan Georgianna
- Department of Plant Pathology, North Carolina State University, 851 Main Campus, Dr. Partners III Suite 267, Raleigh, NC 27606, Campus Box 7244, USA
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Aspergillus parasiticus crzA, which encodes calcineurin response zinc-finger protein, is required for aflatoxin production under calcium stress. Int J Mol Sci 2008; 9:2027-2043. [PMID: 19325734 PMCID: PMC2635607 DOI: 10.3390/ijms9102027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Revised: 10/27/2008] [Accepted: 10/28/2008] [Indexed: 11/17/2022] Open
Abstract
Two morphologically different Aspergillus parasiticus strains, one producing aflatoxins, abundant conidia but few sclerotia (BN9) and the other producing O-methyl-sterimatocystin (OMST), copious sclerotia but a low number of conidia (RH), were used to assess the role of crzA which encodes a putative calcium-signaling pathway regulatory protein. Under standard culture conditions, BN9ΔcrzA mutants conidiated normally but decreased slightly in radial growth, regardless of illumination conditions. RHΔcrzA mutants produced only conidia under light and showed decreased conidiation and delayed sclerotial formation in the dark. Regulation of conidiation of both A. parasiticus strains by light was independent of crzA. Increased concentrations of lithium, sodium, and potassium impaired conidiation and sclerotial formation of the RHΔcrzA mutants but they did not affect conidiation of the BN9ΔcrzA mutants. Vegetative growth and asexual development of both ΔcrzA mutants were hypersensitive to increased calcium concentrations. Calcium supplementation (10 mM) resulted in 3-fold and 2-fold decreases in the relative expression of the endoplasmic reticulum calcium ATPase 2 gene in the BN9 and RH parental strains, respectively, but changes in both ΔcrzA mutants were less significant. Compared to the parental strains, the ΔcrzA mutants barely produced aflatoxins or OMST after the calcium supplementation. The relative expression levels of aflatoxin biosynthesis genes, nor1, ver1, and omtA, in both ΔcrzA mutants were decreased significantly, but the decreases in the parental strains were at much lower extents. CrzA is required for growth and development and for aflatoxin biosynthesis under calcium stress conditions.
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Genes differentially expressed by Aspergillus flavus strains after loss of aflatoxin production by serial transfers. Appl Microbiol Biotechnol 2007; 77:917-25. [PMID: 17955191 DOI: 10.1007/s00253-007-1224-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 09/21/2007] [Accepted: 09/24/2007] [Indexed: 01/02/2023]
Abstract
Aflatoxins are carcinogenic fungal secondary metabolites produced by Aspergillus flavus and other closely related species. Levels of aflatoxins in agricultural commodities are stringently regulated by many countries because of the health hazard, and thus, aflatoxins are of major concern to both producers and consumers. A cluster of genes responsible for aflatoxin biosynthesis has been identified; however, expression of these genes is a complex and poorly understood phenomenon. To better understand the molecular events that are associated with aflatoxin production, three separate nonaflatoxigenic A. flavus strains were produced through serial transfers of aflatoxigenic parental strains. The three independent aflatoxigenic/nonaflatoxigenic pairs were compared via transcription profiling by microarray analyses. Cross comparisons identified 22 features in common between the aflatoxigenic/nonaflatoxigenic pairs. Physical mapping of the 22 features using the Aspergillus oryzae genome sequence for reference identified 16 unique genes. Aflatoxin biosynthetic and regulatory gene expression levels were not significantly different between the aflatoxigenic/nonaflatoxigenic pairs, which suggests that the inability to produce aflatoxins is not due to decreased expression of known biosynthetic or regulatory genes. Of the 16 in common genes, only one gene homologous to glutathione S-transferase genes showed higher expression in the nonaflatoxigenic progeny relative to the parental strains. This gene, named hcc, was selected for over-expression in an aflatoxigenic A. flavus strain to determine if it was directly responsible for loss of aflatoxin production. Although hcc transformants showed six- to ninefold increase in expression, no discernible changes in colony morphology or aflatoxin production were detected. Possible roles of hcc and other identified genes are discussed in relation to regulation of aflatoxin biosynthesis.
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