Production of aflatoxins by strains of the Aspergillus flavus group maintained in ATCC

Wei, Ding-Ling; Jong, S. C.

doi:10.1007/bf00437010

Cited by 50 publications

(36 citation statements)

References 15 publications

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“…Absence of the aflR gene or the presence of an abnormal aflR gene would be a strong indicator that a strain cannot produce aflatoxin. In this study, 34 strains of Aspergillus section Flavi were selected based upon diversity of source and origin, and aflatoxigenic capability (Wei & Jong, 1986); the type strain for each species was also included. The identification of each strain was confirmed by morphological observations.…”

Section: Resultsmentioning

confidence: 99%

“…All of the 23 positive strains generated the expected PCR products and all 34 strains tested produced the ITS fragment of the rDNA gene (ITS3-ITS4) as the control. (Wei & Jong, 1986).…”

Section: Resultsmentioning

confidence: 99%

“…Additionally, A. flavus BCRC 30010 has A. flavus-type aflR, but does not produce aflatoxin (Wei & Jong, 1986 59, 303, 347, 349, 441, 485, 704, 1030, 1037, 1206, 1237, 1422 and 1441 (Table 4). Some of these variations (Table 6).…”

Section: Changmentioning

confidence: 99%

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Comparison of the aflR gene sequences of strains in Aspergillus section Flavi

2006

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Aflatoxins are polyketide-derived secondary metabolites produced by Aspergillus parasiticus, Aspergillus flavus, Aspergillus nomius and a few other species. The toxic effects of aflatoxins have adverse consequences for human health and agricultural economics. The aflR gene, a regulatory gene for aflatoxin biosynthesis, encodes a protein containing a zinc-finger DNA-binding motif. Although Aspergillus oryzae and Aspergillus sojae, which are used in fermented foods and in ingredient manufacture, have no record of producing aflatoxin, they have been shown to possess an aflR gene. This study examined 34 strains of Aspergillus section Flavi. The aflR gene of 23 of these strains was successfully amplified and sequenced. No aflR PCR products were found in five A. sojae strains or six strains of A. oryzae. These PCR results suggested that the aflR gene is absent or significantly different in some A. sojae and A. oryzae strains. The sequenced aflR genes from the 23 positive strains had greater than 96·6 % similarity, which was particularly conserved in the zinc-finger DNA-binding domain. The aflR gene of A. sojae has two obvious characteristics: an extra CTCATG sequence fragment and a C to T transition that causes premature termination of AFLR protein synthesis. Differences between A. parasiticus/A. sojae and A. flavus/A. oryzae aflR genes were also identified. Some strains of A. flavus as well as A. flavus var. viridis, A. oryzae var. viridis and A. oryzae var. effuses have an A. oryzae-type aflR gene. For all strains with the A. oryzae-type aflR gene, there was no evidence of aflatoxin production. It is suggested that for safety reasons, the aflR gene could be examined to assess possible aflatoxin production by Aspergillus section Flavi strains.

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Section: Resultsmentioning

confidence: 99%

“…All of the 23 positive strains generated the expected PCR products and all 34 strains tested produced the ITS fragment of the rDNA gene (ITS3-ITS4) as the control. (Wei & Jong, 1986).…”

Section: Resultsmentioning

confidence: 99%

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Comparison of the aflR gene sequences of strains in Aspergillus section Flavi

2006

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“…Neither A. sojae nor A. oryzae is known to produce aflatoxins (28), but homologues of several aflatoxin biosynthetic genes have been found in them (1,12,17). These genes apparently are not transcribed (16,20,27).…”

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confidence: 99%

Nonfunctionality of Aspergillus sojae aflR in a Strain of Aspergillus parasiticus with a Disrupted aflR Gene

Takahashi

Chang

Matsushima

et al. 2002

Appl Environ Microbiol

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Aspergillus sojae belongs to the Aspergillus section Flavi but does not produce aflatoxins. The functionality of the A. sojae aflR gene (aflRs) was examined by transforming it into an ⌬aflR strain of A. parasiticus, derived from a nitrate-nonutilizing, versicolorin A (VERA)-accumulating strain. The A. parasiticus aflR gene (aflRp) transformants produced VERA, but the aflRs transformants did not. Even when aflRs was placed under the control of the amylase gene (amyB) promoter of Aspergillus oryzae, the amy(p)::aflRs transformants did not produce VERA. A chimeric construct containing the aflRs promoter plus the aflRs N-and aflRp C-terminal coding regions could restore VERA production, but a construct containing the aflRp promoter plus the aflRp N-and aflRs C-terminal coding regions could not. These results show that the A. sojae aflR promoter is functional in A. parasiticus and that the HAHA motif does not affect the function of the resulting hybrid AflR. We conclude that the lack of aflatoxin production by A. sojae can be attributed, at least partially, to the premature termination defect in aflRs, which deletes the C-terminal transcription activation domain that is critical for the expression of aflatoxin biosynthetic genes.

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“…For example, neither A. sojae nor A. oryzae produce aflatoxins (Wei and Jong 1986), even though homologues of aflatoxin biosynthetic genes are present in each Klich et al 1995;Yu et al 2000). Both species have been used for centuries in the food fermentation industry and are generally considered safe (Machida et al 2005;Chang et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Molecular characterization of atoxigenic strains for biological control of aflatoxins in Nigeria

Donner

Atehnkeng

Sikora

et al. 2010

Food Additives & Contaminants: Part A

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Aflatoxins are highly toxic carcinogens produced by several species in Aspergillus section Flavi. Strains of A. flavus that do not produce aflatoxins, called atoxigenic strains, have been used commercially in North America as tools for limiting aflatoxin contamination. A similar aflatoxin management strategy is being pursued in Nigeria. In the current study, loci across the 68 kb aflatoxin biosynthesis gene cluster were compared among 18 atoxigenic and two aflatoxin-producing vegetative compatibility groups (VCGs) from Nigeria and an atoxigenic VCG used commercially in North America. Five of the atoxigenic VCGs had large deletions (37-65 kb) extending from the teleomeric side of the aflatoxin biosynthesis cluster. In one VCG (AV0222) the deletion extended through the cluster to the adjacent sugar cluster. The remaining twelve atoxigenic VCGs, including the VCG used for aflatoxin management in North America, contained all the aflatoxin pathway genes, but with defects. Two observations support the long-term persistence of atoxigenicity within A. flavus: first, a comparison of pathway genes revealed more changes in atoxigenic than in aflatoxin-producing isolates relative to the aflatoxin-producing strain NRRL 3357; and second, several non-synonymous changes are unique to atoxigenics. Atoxigenic VCG diversity was assessed with phylogenetic analyses. Although some atoxigenics share relatively recent ancestry, several are more closely related to aflatoxin producers than to other atoxigenics. The current study demonstrates VCGs of A. flavus in West Africa with diverse mechanisms of atoxigenicity and potential value in aflatoxin management programmes.

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Production of aflatoxins by strains of the Aspergillus flavus group maintained in ATCC

Cited by 50 publications

References 15 publications

Comparison of the aflR gene sequences of strains in Aspergillus section Flavi

Comparison of the aflR gene sequences of strains in Aspergillus section Flavi

Nonfunctionality of Aspergillus sojae aflR in a Strain of Aspergillus parasiticus with a Disrupted aflR Gene

Molecular characterization of atoxigenic strains for biological control of aflatoxins in Nigeria

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