title: Clustered array of ochratoxin A biosynthetic genes in Aspergillus steynii and their expression patterns in permissive conditions.
abstract: Aspergillus steynii is probably the most relevant species of section Circumdati producing ochratoxin A (OTA). This mycotoxin contaminates a wide number of commodities and it is highly toxic for humans and animals. Little is known on the biosynthetic genes and their regulation in Aspergillus species. In this work, we identified and analysed three contiguous genes in A. steynii using 5'-RACE and genome walking approaches which predicted a cytochrome P450 monooxygenase (p450ste), a non-ribosomal peptide synthetase (nrpsste) and a polyketide synthase (pksste). These three genes were contiguous within a 20742 bp long genomic DNA fragment. Their corresponding cDNA were sequenced and their expression was analysed in three A. steynii strains using real time RT-PCR specific assays in permissive conditions in in vitro cultures. OTA was also analysed in these cultures. Comparative analyses of predicted genomic, cDNA and amino acid sequences were performed with sequences of similar gene functions. All the results obtained in these analyses were consistent and point out the involvement of these three genes in OTA biosynthesis by A. steynii and showed a co-ordinated expression pattern. This is the first time that a clustered organization OTA biosynthetic genes has been reported in Aspergillus genus. The results also suggested that this situation might be common in Aspergillus OTA-producing species and distinct to the one described for Penicillium species.
authors.affiliation: Department of Microbiology III, Faculty of Biology, Complutense University of Madrid Jose Antonio Novais 12, 28040 Madrid, Spain.
authors.forename: Jessica
authors.initials: J
authors.lastname: Gil-Serna
authors.affiliation: Department of Microbiology III, Faculty of Biology, Complutense University of Madrid Jose Antonio Novais 12, 28040 Madrid, Spain.
authors.forename: Covadonga
authors.initials: C
authors.lastname: Vázquez
authors.affiliation: Department of Genetics, Faculty of Biology, Complutense University of Madrid Jose Antonio Novais 12, 28040 Madrid, Spain.
authors.forename: María Teresa
authors.initials: MT
authors.lastname: González-Jaén
authors.affiliation: Department of Microbiology III, Faculty of Biology, Complutense University of Madrid Jose Antonio Novais 12, 28040 Madrid, Spain. Electronic address: belenp@ucm.es.
authors.forename: Belén
authors.initials: B
authors.lastname: Patiño
mesh_terms: D000595:Amino Acid Sequence; D001230:Aspergillus / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D005810:Multigene Family; D009183:Mycotoxins / Q000096:biosynthesis; D009793:Ochratoxins / Q000096:biosynthesis*; D010407:Penicillium / Q000378:metabolism; D010453:Peptide Synthases / Q000235:genetics*; D048630:Polyketide Synthases / Q000235:genetics*
chemical_list: D009183:Mycotoxins; D009793:Ochratoxins; C025589:ochratoxin A; D048630:Polyketide Synthases; D003577:Cytochrome P-450 Enzyme System; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase
keywords: Aspergillus steynii; Biosynthetic cluster; Cytochrome p450 monooxygenase; Non-ribosomal peptide synthetase; Ochratoxin A; Polyketide synthase