A polyketide synthase gene required for ochratoxin A biosynthesis in Aspergillus ochraceus

Abstract

Ochratoxin A is an important nephrotoxic and nephrocarcinogenic mycotoxin, produced by Aspergillus ochraceus as a polyketide-derived secondary metabolite. A portion of a putative polyketide synthase gene ( pks) involved in the biosynthesis of this mycotoxin was cloned by using a suppression subtractive hybridization PCR-based approach. The predicted amino acid sequence of the 1?4 kb clone shared 28-35 % identity to acyl transferase regions from fungal polyketide synthases found in the databases. Based on reverse transcription PCR studies, the pks gene is expressed only under ochratoxin A permissive conditions and only during the early stages of the mycotoxin synthesis. A mutant in which the pks gene has been interrupted cannot synthesize ochratoxin A. This report is the first of the cloning and characterization of a gene involved in ochratoxin A biosynthesis.

Genome sequencing and analysis of the versatile cell factory Aspergillus niger CBS 513.88

“…This cluster is absent from the genomes of other sequenced aspergilli such as A. fumigatus, A. oryzae and A. nidulans [8][9][10] . A putative ochratoxin cluster was identified on the basis of a PKS fragment of A. ochraceus involved in ochratoxin biosynthesis 41 . Some A. niger strains have been reported to synthesize this toxin but little is known about the biosynthetic pathway 42 .…”

Identification of Genes Differentially Expressed Between Ochratoxin-Producing and Non-Producing Strains of Aspergillus westerdijkiae

“…The strains UEL91 and ITAL163 were selected for the purpose of this research because they showed expressive level of genetic similarity as revealed by RAPD profiles, but contrasted for their ability to produce OTA. This tactic was chosen as an alternative to that adopted by other authors [5,13], who have made comparisons of gene expression in a single strain growing in two different media (permissive and restrictive medium for OTA production) in order to minimize the detection of transcripts not related to OTA biosynthesis.…”

“…Despite of its importance, only a small number of genes were designed to be involved in the biosynthetic pathway of OTA in Aspergillus species. These include P450 monoxygenase, nonribosomal peptide synthetase, chloroperoxidase and polyketide synthase genes [3][4][5][6].…”

Ochratoxin A and Brewing Technology: A Review

“…Recent data has shown that this step requires the activity of a polyketide synthase 26 . Furthermore, the gene encoding polyketide synthase appears to be very different between Penicillium and Aspergillus species 26,46 .…”

“…Recent data has shown that this step requires the activity of a polyketide synthase 26 . Furthermore, the gene encoding polyketide synthase appears to be very different between Penicillium and Aspergillus species 26,46 . In A. ochraceus, the gene of polyketide synthase is expressed only under OTA permissive conditions and only during the early stages of mycotoxin synthesis 26 .…”