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Yang K, Shadkchan Y, Tannous J, Landero Figueroa JA, Wiemann P, Osherov N, Wang S, Keller NP. Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus. Virulence 2019; 9:1273-1286. [PMID: 30027796 PMCID: PMC6177249 DOI: 10.1080/21505594.2018.1496774] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The ubiquitous fungus Aspergillus flavus is notorious for contaminating many important crops and food-stuffs with the carcinogenic mycotoxin, aflatoxin. This fungus is also the second most frequent Aspergillus pathogen after A. fumigatus infecting immunosuppressed patients. In many human fungal pathogens including A. fumigatus, the ability to defend from toxic levels of copper (Cu) is essential in pathogenesis. In A. fumigatus, the Cu-fist DNA binding protein, AceA, and the Cu ATPase transporter, CrpA, play critical roles in Cu defense. Here, we show that A. flavus tolerates higher concentrations of Cu than A. fumigatus and other Aspergillus spp. associated with the presence of two homologs of A. fumigatus CrpA termed CrpA and CrpB. Both crpA and crpB are transcriptionally induced by increasing Cu concentrations via AceA activity. Deletion of crpA or crpB alone did not alter high Cu tolerance, suggesting they are redundant. Deletion of both genes resulted in extreme Cu sensitivity that was greater than that following deletion of the regulatory transcription factor aceA. The ΔcrpAΔcrpB and ΔaceA strains were also sensitive to ROI stress. Compared to wild type, these mutants were impaired in the ability to colonize maize seed treated with Cu fungicide but showed no difference in virulence on non-treated seed. A mouse model of invasive aspergillosis showed ΔcrpAΔcrpB and to a lesser degree ΔaceA to be significantly reduced in virulence, following the greater sensitivity of ΔcrpAΔcrpB to Cu than ΔaceA.
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Affiliation(s)
- Kunlong Yang
- a 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.,b Department of Medical Microbiology and Immunology , University of Wisconsin , Madison , WI , USA
| | - Yana Shadkchan
- c Aspergillus and Antifungal Research Laboratory, Department of Clinical Microbiology and Immunology, Sackler School of Medicine , Tel Aviv University , Tel Aviv , Israel
| | - Joanna Tannous
- b Department of Medical Microbiology and Immunology , University of Wisconsin , Madison , WI , USA
| | - Julio A Landero Figueroa
- d Agilent Metallomics Center, College of Arts & Science, Chemistry Department , University of Cincinnati , Cincinnati , OH , USA
| | - Philipp Wiemann
- b Department of Medical Microbiology and Immunology , University of Wisconsin , Madison , WI , USA
| | - Nir Osherov
- c Aspergillus and Antifungal Research Laboratory, Department of Clinical Microbiology and Immunology, Sackler School of Medicine , Tel Aviv University , Tel Aviv , Israel
| | - Shihua Wang
- a 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
| | - Nancy P Keller
- b Department of Medical Microbiology and Immunology , University of Wisconsin , Madison , WI , USA
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Sandosskumar R, Karthikeyan M, Mathiyazhagan S, Mohankumar M, Chandrasekar G, Velazhahan R. Inhibition of Aspergillus flavus growth and detoxification of aflatoxin B1 by the medicinal plant zimmu (Allium sativum L. × Allium cepa L.). World J Microbiol Biotechnol 2006. [DOI: 10.1007/s11274-006-9327-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Lisker N, Michaeli R, Frank ZR. Aspergillus flavus and other mycoflora of groundnut kernels in Israel and the absence of aflatoxin. Mycotoxin Res 1994; 10:47-55. [PMID: 23605921 DOI: 10.1007/bf03192250] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/1993] [Accepted: 01/06/1994] [Indexed: 11/26/2022]
Abstract
More than 300 groundnut (peanut) samples collected from different regions of Israel were examined by ELISA for aflatoxin contamination. Samples were designated for export, local consumption or for sowing. None of the samples were contaminated with the toxin. However, when kernels were kept at high humidity (RH≊99%), aflatoxin could be frequently detected seven days after incubation and the toxin was not uniformly distributed among kernels.Aspergillus niger, A flavus, Penicillium citrinum andP pinophilum were the dominant fungi and no differences were observed among cultivars. Almost half of the commercial samples examined were devoid ofA flavus. Other fungi identified wereA tamaril, A amstelodami, P rubrum, Rhizoctonia solani, Macrophomina phaseolina, Rhizopus spp., Sclerotium rolfsll, Fusarium andAlternaria spp; the two last ones comprising a group of low incidence.Although groundnut samples that containA flavus-infected kernels are moderately common, the local climate and agrotechniques In use in Israel are not conducive to aflatoxin accumulation. Nevertheless infected kernels may become a threat to health if stored under inadequate conditions.
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Affiliation(s)
- N Lisker
- Department of Agronomy and Natural Resources, The Volcani Center, Agricultural Research Organization, 50250, Bet Dagan, Israel
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Wotton HR, Strange RN. Increased susceptibility and reduced phytoalexin accumulation in drought-stressed peanut kernels challenged with Aspergillus flavus. Appl Environ Microbiol 1987; 53:270-3. [PMID: 3105455 PMCID: PMC203650 DOI: 10.1128/aem.53.2.270-273.1987] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Three genotypes of peanut (Arachis hypogaea L.), with ICG numbers 221, 1104, and 1326, were grown in three replicate plots and drought stressed during the last 58 days before harvest by withholding irrigation water. Within each plot there were eight levels of stress ranging from 1.1 to 25.9 cm of water. Kernels harvested from the plots were hydrated to 20% moisture and challenged with Aspergillus flavus. Fungal colonization, aflatoxin content, and phytoalexin accumulation were measured. Fungal colonization of non-drought-stressed kernels virtually ceased by 3 days after inoculation, when the phytoalexin concentration exceeded 50 micrograms/g (fresh weight) of kernels, but the aflatoxin concentration continued to rise exponentially for an additional day. When fungal colonization, aflatoxin production, and phytoalexin accumulation were measured 3 days after drought-stressed material was challenged, the following relationships were apparent. Fungal colonization was inversely related to water supply (r varied from -0.848 to -0.904, according to genotype), as was aflatoxin production (r varied from -0.876 to -0.912, according to genotype); the phytoalexin concentration was correlated with water supply when this exceeded 11 cm (r varied from 0.696 to 0.917, according to genotype). The results are discussed in terms of the critical role played by drought stress in predisposing peanuts to infection by A. flavus and the role of the impaired phytoalexin response in mediating this increased susceptibility.
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Cole RJ, Sanders TH, Hill RA, Blankenship PD. Mean geocarposphere temperatures that induce preharvest aflatoxin contamination of peanuts under drought stress. Mycopathologia 1985; 91:41-6. [PMID: 3930968 DOI: 10.1007/bf00437286] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Apparently undamaged peanuts grown under environmental stress in the form of drought and heat become contaminated with Aspergillus flavus and aflatoxin in the soil prior to harvest. The upper mean temperature limit for aflatoxin contamination in undamaged peanut kernels grown under drought stress the latter 4-6 weeks of the growing season was between 29.6-31.3 degrees C. The lower limit was between 25.7-26.3 degrees C. That is, peanuts grown under drought stress with a mean geocarposphere temperature of 29.6 degrees C were highly contaminated while those at 31.3 degrees C were not contaminated. Likewise, those grown under drought stress with a mean geocarposphere temperature of 25.7 degrees C were not contaminated while those subjected to a mean geocarposphere temperature of 26.0 degrees C resulted in some categories becoming contaminated. Increasing the mean temperature up to 29.6 degrees C caused increasing amounts of contamination.
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Lillehoj EB, McMillian WW, Widstrom NW, Guthrie WD, Jarvis JL, Barry D, Kwolek WF. Aflatoxin contamination of maize kernels before harvest. Interaction of Aspergillus flavus spores, corn earworm larvae and fungicide applications. Mycopathologia 1984; 86:77-81. [PMID: 6738673 DOI: 10.1007/bf00436490] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Two maize (Zea mays L.) hybrids with varying degrees of resistance to damage by corn earworm (CEW) (Heliothis zea Boddie) were grown in Iowa, Georgia, and Missouri. Treatments included: introduction of Aspergillus flavus Link ex. Fr. spores onto newly-emerged silks, application of a fungicide as an aqueous spray onto test ears during the first three weeks after flowering, infestation of ears with CEW eggs, and combinations of these variables. CEW larvae were collected from developing ears and examined for the presence of internal A. flavus group propagules. Aflatoxin levels were determined in mature kernels. Toxin concentrations exhibited a distinct regional variation with relatively high levels in Georgia samples, intermediate concentrations in Missouri kernels and low levels in Iowa samples. No treatment effects were noted in Georgia samples but introduction of A. flavus and CEW increased toxin accumulation in Missouri kernels. Although the CEW-susceptible hybrid exhibited a trend towards increased damage by the insect, no treatment-related differences were observed in the presence of the fungus in larvae or in aflatoxin contamination. Fungicide applications did not significantly reduce aflatoxin levels in mature kernels.
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Hill RA, Blankenship PD, Cole RJ, Sanders TH. Effects of soil moisture and temperature on preharvest invasion of peanuts by the Aspergillus flavus group and subsequent aflatoxin development. Appl Environ Microbiol 1983; 45:628-33. [PMID: 6402980 PMCID: PMC242335 DOI: 10.1128/aem.45.2.628-633.1983] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Four soil temperature and moisture treatment regimens were imposed on Florunner peanuts 94 days after planting in experimental plots in 1980. At harvest (145 days after planting), the incidence of the Aspergillus flavus group and the aflatoxin concentration were greatest in damaged kernels. Extensive colonization of sound mature kernels (SMK) by the A. flavus group occurred with the drought stress treatment (56% kernels colonized); colonization was less in the irrigated plot (7%) and the drought stress plot with cooled soil (11%) and was intermediate in the irrigated plot with heated soil (26%). Aflatoxin was virtually absent from SMK with the last three treatments, but it was found at an average concentration of 244 ppb (ng/g) in drought-stressed SMK. Colonization of SMK by the A. flavus group and aflatoxin production were greater with hot dry conditions. Neither elevated temperature alone nor drought stress alone caused aflatoxin contamination in SMK. When the ratio of SMK colonized by A. flavus compared with A. niger was greater than 19:1, there was aflatoxin contamination, but there was none if this ratio was less than 9:1. Irrigation caused a higher incidence of A. niger than drought did. This may have prevented the aflatoxin contamination of undamaged peanuts.
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