title: Fundamental contribution of beta-oxidation to polyketide mycotoxin production in planta.
abstract: Seed contamination with polyketide mycotoxins, including aflatoxin (AF) and sterigmatocystin (ST) produced by Aspergillus spp., is an agricultural, economic, and medical issue worldwide. Acetyl-CoA, the fundamental building block of all known fungal polyketides, is generated by a large number of biochemical pathways, including beta-oxidation of fatty acids and glycolysis of sugars. We present several lines of evidence to support a major role for seed fatty acids in formation of AF and ST in A. flavus, A. parasiticus, and A. nidulans. Aspergillus strains exhibiting canonical signs of oleic acid-induced peroxisome proliferation, including increased catalase activity, beta-oxidation gene expression, and peroxisomal clustering, also exhibited a marked increase in toxin gene expression and biosynthesis. Furthermore, microscopic observations showed that the ST and AF precursor norsolorinic acid accumulated in peroxisomes of all three Aspergilli. While a peroxisomal beta-oxidation mutation eliminated oleic acid-induced increases in ST in A. nidulans, a mitochondrial beta-oxidation mutation played a larger role in eliminating ST formation on oatmeal medium and on live corn kernels, implicating a fundamental role for both peroxisomal and mitochondrial beta-oxidation in toxin production.
authors.affiliation: Department of Plant Pathology, University of Wisconsin-Madison, 1630 Linden Drive, Madison, WI 53706, USA.
authors.forename: Lori A
authors.initials: LA
authors.lastname: Maggio-Hall
authors.forename: Richard A
authors.initials: RA
authors.lastname: Wilson
authors.forename: Nancy P
authors.initials: NP
authors.lastname: Keller
mesh_terms: D000348:Aflatoxins / Q000096:biosynthesis*; D000880:Anthraquinones / Q000378:metabolism; D001230:Aspergillus / Q000166:cytology / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism; D010944:Plants / Q000378:metabolism* / Q000382:microbiology*; D013241:Sterigmatocystin / Q000096:biosynthesis*; D014158:Transcription, Genetic
chemical_list: D000348:Aflatoxins; D000880:Anthraquinones; D005227:Fatty Acids; D013241:Sterigmatocystin; D044943:Fatty Acid Desaturases; C021904:Phosphatidylcholine desaturase; D044925:Oxidoreductases Acting on CH-CH Group Donors; C002754:norsolorinic acid