Polyketide synthase gene responsible for citrinin biosynthesis in Monascus purpureus.
Citrinin produced by Aspergillus, Penicillium, and Monascus species is a polyketide compound that has nephrotoxic activity in mammals and is bactericidal toward gram-positive bacteria. To avoid the risk of citrinin contamination in other fermentation products produced by Monascus purpureus, knowledge of the citrinin biosynthetic genes is needed so that citrinin-nonproducing strains can be generated. We cloned a polyketide synthase (PKS) gene from M. purpureus with degenerate primers designed to amplify the conserved region of a ketosynthase domain of a fungal PKS. A 13-kb genomic DNA fragment was identified that contained a full-length PKS gene (pksCT) of 7,838 bp with a single 56-bp intron. pksCT encodes a 2,593-amino-acid protein that contains putative domains for ketosynthase, acyltransferase, acyl carrier protein (ACP), and a rare methyltransferase. There was no obvious thioesterase domain, which usually is downstream of the ACP domain in multi-aromatic-ring PKSs. pksCT transcription was correlated with citrinin production, suggesting that the pksCT gene product was involved in citrinin biosynthesis. Homologous recombination between the wild-type allele and a truncated disruption construct resulted in a pksCT-disrupted strain of M. purpureus. The disruptant did not produce citrinin, but a pksCT revertant generated by successive endogenous recombination events in the pksCT disruptant restored citrinin production, indicating that pksCT encoded the PKS responsible for citrinin biosynthesis in M. purpureus.
International Center for Biotechnology, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Takeo
T
Shimizu
Hiroshi
H
Kinoshita
Shinji
S
Ishihara
Kanae
K
Sakai
Shiro
S
Nagai
Takuya
T
Nihira
D000595:Amino Acid Sequence; D002953:Citrinin / Q000096:biosynthesis*; D003001:Cloning, Molecular; D003470:Culture Media; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D032741:Monascus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D048630:Polyketide Synthases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
D003470:Culture Media; D002953:Citrinin; D048630:Polyketide Synthases