A Polyketide Synthase Gene Required for Biosynthesis of the Aflatoxin-like Toxin, Dothistromin |
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Authors: | Rosie E Bradshaw Hongping Jin Branwen S Morgan Arne Schwelm Olivia R Teddy Carolyn A Young Shuguang Zhang |
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Institution: | (1) National Centre for Advanced Bio-Protection Technologies, Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand;(2) Noble Foundation, Ardmore, Oklahoma, USA;(3) Institute of Molecular BioSciences, Massey University, Private Bag 11222, Palmerston North, New Zealand |
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Abstract: | Dothistromin is a polyketide toxin, produced by a fungal forest pathogen, with structural similarity to the aflatoxin precursor
versicolorin B. Biochemical and genetic studies suggested that there are common steps in the biosynthetic pathways for these
metabolites and showed similarities between some of the genes. A polyketide synthase gene (pksA) was isolated from dothistromin-producing Dothistroma septosporum by hybridization with an aflatoxin ortholog from Aspergillus parasiticus. Inactivation of this gene in D. septosporum resulted in mutants that could not produce dothistromin but that could convert exogenous aflatoxin precursors, including
norsolorinic acid, into dothistromin. The mutants also had reduced asexual sporulation compared to the wild type. So far four
other genes are known to be clustered immediately alongside pksA. Three of these (cypA, moxA, avfA) are predicted to be orthologs of aflatoxin biosynthetic genes. The other gene (epoA), located between avfA and moxA, is predicted to encode an epoxide hydrolase, for which there is no homolog in either the aflatoxin or sterigmatocystin gene
clusters. The pksA gene is located on a small chromosome of ~1.3 Mb in size, along with the dothistromin ketoreductase (dotA) gene. |
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Keywords: | aflatoxin biosynthesis Dothistroma septosporum dothistromin biosynthesis epoxide hydrolase red-band needle blight sporulation |
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