Regulation of<i>aflR</i>and Its Product, AflR, Associated with Aflatoxin Biosynthesis

Liu, Biing-Hui; Chu, Fun Sun

doi:10.1128/aem.64.10.3718-3723.1998

Cited by 69 publications

(30 citation statements)

References 39 publications

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“…For example, in Aspergillus flavus, AflR, a 47-kDa specific zinc finger DNAbinding protein, regulates the expression of all the genes in the aflatoxin cluster except for aflJ, which modulates the expression of structural genes and serves as a coactivator with aflR during aflatoxin biosynthesis (39)(40)(41). In Aspergillus oryzae, AflR is affected by environmental factors, such as carbon sources and temperature, in a manner similar to that in Aspergillus parasiticus (42). In the OTA cluster, deletion of otaR1 prevents OTA production, while inactivation of otaR2 merely reduces production.…”

Section: Discussionmentioning

confidence: 99%

A Consensus Ochratoxin A Biosynthetic Pathway: Insights from the Genome Sequence of Aspergillus ochraceus and a Comparative Genomic Analysis

Wang

et al. 2018

Appl Environ Microbiol

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Ochratoxin A (OTA) is a toxic secondary metabolite produced by and species that widely contaminate food and feed. We sequenced and assembled the complete ∼37 Mb genome of fc-1, a well-known producer of OTA. Key genes of the OTA biosynthetic pathway were identified by comparative genomic analyses with five other sequenced OTA-producing fungi,, ,, , and OTA production was completely inhibited in the deletion mutants (- and ), and OTA biosynthesis was restored by feeding a post-block substrate to the corresponding mutant. The OTA biosynthetic pathway was unblocked with the addition of heterologously expressed halogenase in the mutant. OTA biosynthesis begins with PKS (), utilizing acetyl-CoA and malonyl-CoA to synthesize 7-methylmellein, which is oxidized to OTβ by cytochrome P450 monooxygenase (). OTβ and L-β-phenylalanine are combined by NRPS () to form an amide bond to synthesize OTB. Finally, OTB is chlorinated by halogenase () to OTA. The - genes were expressed at low levels in the mutant. A second regulator, otaR2, which is adjacent to the biosynthetic gene, could modulate only the expression of, and Thus, we have identified a consensus OTA biosynthetic pathway that can be used to prevent and control OTA synthesis, and to understand variation and production of the intermediate components in the biosynthetic pathway. Ochratoxin A (OTA) is a significant mycotoxin that contaminates cereal products, coffee, grapes, wine, cheese and meat. OTA is nephrotoxic, carcinogenic, teratogenic and immunotoxic. OTA contamination is a serious threat to food safety, endangers human health and can cause huge economic losses. At present, more than 20 species of the genera and are known to produce OTA. Here, we demonstrate that a consensus OTA biosynthetic pathway exists in all OTA-producing fungi and that is encoded by a gene cluster containing four highly conserved biosynthetic genes and a bZIP transcription factor.

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Section: Discussionmentioning

confidence: 99%

A Consensus Ochratoxin A Biosynthetic Pathway: Insights from the Genome Sequence of Aspergillus ochraceus and a Comparative Genomic Analysis

Wang

et al. 2018

Appl Environ Microbiol

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“…Among the 25 genes involved in aflatoxin biosynthesis (Yu et al 1995(Yu et al , 2004, we selected two genes, aflR and aflS, whose regulatory role in controlling the level of structural genes expression has been ascertained (Payne et al 1993;Woloshuk et al 1994;Flaherty and Payne 1997;Liu and Chu 1998;Meyers et al 1998;Takahashi et al 2002;Chang 2003;Ehrlich et al 2003;Chang 2004;Price et al 2006). In particular, aflR gene integrity has been considered a good candidate for diagnostic purposes in discriminating between aflatoxin producer and nonproducer strains of A. flavus .…”

Section: Discussionmentioning

confidence: 99%

“…In particular, aflR gene integrity has been considered a good candidate for diagnostic purposes in discriminating between aflatoxin producer and nonproducer strains of A. flavus . The role of aflS is less characterized than that of aflR (Liu and Chu 1998;Meyers et al 1998;Chang 2003Chang ,2004), but we did include it in our gene set in order to increase the predictability of the RT-PCR test. The other genes, aflD, aflO and aflQ, which encode for enzymes of the biosynthesis pathway, were among those that have been used by other authors; but we could not assess any preliminary advantage in their use when compared with that of other genes of the aflatoxin cluster.…”

Section: Discussionmentioning

confidence: 99%

A multiplex RT-PCR approach to detect aflatoxigenic strains of Aspergillus flavus

et al. 2007

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Aims: To develop a multiplex reverse transciption‐polymerase chain reaction (RT‐PCR) protocol to discriminate aflatoxin‐producing from aflatoxin‐nonproducing strains of Aspergillus flavus. Methods and Results: The protocol was first optimized on a set of strains obtained from laboratory collections and then validated on A. flavus strains isolated from corn grains collected in the fields of the Po Valley (Italy). Five genes of the aflatoxin gene cluster of A. flavus, two regulatory (aflR and aflS) and three structural (aflD, aflO and aflQ), were targeted with specific primers to highlight their expression in mycelia cultivated under inducing conditions for aflatoxins production. 48‐h‐old cultures expressed the complete set of the genes analysed here whereas 24‐h‐old ones did not. Genomic PCR (quadruplex PCR) was also performed in parallel using chromosomal DNA extracted from the same set of strains to correlate the integrity of the genes with their expression. Conclusions: We show that a good correlation exists between gene expression of the aflatoxin genes, here analysed by multipex RT‐PCR, and aflatoxin production, except for one strain that apparently transcribed all the relevant genes but did not produce aflatoxin in the medium. Significance and Impact of the Study: This is the first example of the application of a combination of multiplex PCR and RT‐PCR approaches to screen a population of A. flavus for the presence of aflatoxigenic and nonaflatoxigenic strains. The proposed protocol will be helpful in evaluating the risk posed by A. flavus in natural environments and might also be a useful tool to monitor its presence during the processing steps of food and feed commodities.

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“…4); indicating for the first time that regulation of patulin biosynthesis in P. expansum is mediated at the level of gene transcription. Transcriptional regulation of mycotoxin biosynthetic genes under different physiological conditions is quite common in mycotoxigenic fungi, for example for aflatoxin and sterigmatocystin production in Aspergillus parasiticus and Aspergillus nidulans (Liu & Chu, 1998;Bhatnagar et al, 2003). This suggested to us that other genes involved in patulin (1) idh gene, (2) msas gene, (3) peab1 gene, (4) p450-1, (5) p450-2 and (6) glyceraldehyde-3-phosphate dehydrogenase gene as a control in patulin permissive (1) potato dextrose medium (PDB) and restrictive ( À ) Czapek-Dox yeast medium (CYB).…”

Section: Discussionmentioning

confidence: 99%

Cloning and molecular characterization ofPenicillium expansumgenes upregulated under conditions permissive for patulin biosynthesis

White

O’Callaghan

Dobson

2006

FEMS Microbiology Letters

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Penicillium expansum is commonly associated with patulin production in pomaceous fruits. Both the full-length isoepoxydon dehydrogenase (idh) gene and a 470 bp fragment of the 6-methylsalicylic acid synthase (6-msas) gene have been cloned from P. expansum. In addition, we cloned a 715 bp fragment of a putative ATP-binding cassette transporter gene peab1, together with part of two putative cytochrome P450 monooxygenase genes P-450 1 and P-450 2. Increased expression of all five genes was observed under patulin-permissive conditions, indicating not only their likely involvement in patulin biosynthesis but indicating for the first time that regulation of patulin biosynthesis in P. expansum is mediated at the level of gene transcription.

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Regulation ofaflRand Its Product, AflR, Associated with Aflatoxin Biosynthesis

Cited by 69 publications

References 39 publications

A Consensus Ochratoxin A Biosynthetic Pathway: Insights from the Genome Sequence of Aspergillus ochraceus and a Comparative Genomic Analysis

A Consensus Ochratoxin A Biosynthetic Pathway: Insights from the Genome Sequence of Aspergillus ochraceus and a Comparative Genomic Analysis

A multiplex RT-PCR approach to detect aflatoxigenic strains of Aspergillus flavus

Cloning and molecular characterization ofPenicillium expansumgenes upregulated under conditions permissive for patulin biosynthesis

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