Transcript of a homolog of aflR, a regulatory gene for aflatoxin synthesis in Aspergillus parasiticus, was not detected in Aspergillus oryzae strains

Kusumoto, K

doi:10.1016/s0378-1097(98)00503-5

Cited by 6 publications

(9 citation statements)

References 12 publications

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“…Our inability to amplify aflR implies that the aflR gene is missing or highly abnormal in some strains of these two species. Kusumoto et al (1998b) also noted that A. oryzae IFO 30104 lacks the aflR gene. Some filamentous fungi traits can be unexpectedly lost, especially in cultures maintained in the laboratory for long periods (Bennett et al, 1997).…”

Section: Resultsmentioning

confidence: 93%

“…Earlier studies did not identify an aflR transcript in A. oryzae or A. sojae (Klich et al, 1997;Kusumoto et al, 1998b;Matsushima et al, 2001a). Our inability to amplify aflR implies that the aflR gene is missing or highly abnormal in some strains of these two species.…”

Section: Resultsmentioning

confidence: 94%

“…Further, based on our results, we postulate that when A. flavus strains have the A. oryzae-type aflR, they are non-toxigenic. Kusumoto et al (1998b) have shown that some strains of A. oryzae have an aflR gene but do not produce detectable transcript. Since it is known that the AFLR protein possesses an autoregulation function (Chang et al, 1995b), it is an appealing hypothesis to suggest that the changed amino acid residues of the A. oryzae-type aflR affect the autoregulation function and are responsible for the fact that aflR expression is non-detectable in these strains.…”

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: 93%

Section: Resultsmentioning

confidence: 94%

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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“…However, A. oryzae and A. sojae, used in the fermentation industry, does not produce aflatoxin, since the aflR gene is not expressed and/or AflR is nonfunctional in these strains. [62][63][64][65] 2. C2H2 transcription factors C2H2 transcription factors are found in both prokaryotic and eukaryotic organisms, and they constitute the second-largest family in the filamentous fungus N. crassa.…”

Section: Proteolytic Enzymesmentioning

confidence: 99%

Genomics ofAspergillus oryzae

Kobayashi

Abe

Asai

et al. 2007

Bioscience, Biotechnology, and Biochemistry

171

118

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“…These genes apparently are not transcribed (16,20,27). The molecular mechanisms that prevent production of aflatoxins by A. oryzae isolates have been examined only recently.…”

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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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Transcript of a homolog of aflR, a regulatory gene for aflatoxin synthesis in Aspergillus parasiticus, was not detected in Aspergillus oryzae strains

Cited by 6 publications

References 12 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

Genomics ofAspergillus oryzae

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

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