|Hohn, Thomas - NOVARTIS SEEDS, RTP, NC|
Submitted to: Fungal Genetics Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 28, 1999
Publication Date: N/A
Technical Abstract: Fumonisins are toxins produced by the maize pathogen Gibberella fujikuroi mating population A (MP-A) and are associated with mycotoxicoses in both humans and animals. Structural and precursor feeding studies indicate fumonisins are products of either polyketide or fatty acid metabolism. We attempted to isolate a polyketide synthase (PKS) gene involved in fumonisin biosynthesis via PCR with degenerate PKS primers and a cDNA template prepared from a fumonisin-producing culture of G. fujikuroi. Nucleotide sequence analysis of the single PCR product and flanking DNA from a cosmid clone revealed a gene (FUM5) with a 7.8 kb coding region interrupted by 5 introns. The predicted FUM5 translation product had conserved amino acid sequences indicative of the ketoacyl synthase, acyl transferase, ketoreductase, dehydratase, enoyl reductase, and acyl carrier protein domains present in Type I bacterial and fungal PKSs. Transformation of a cosmid clone that included FUM5 into G. fujikuroi increased the levels of production in three strains and restored wild-type production in a fumonisin-nonproducing strain. Disruption of FUM5 reduced fumonisin production by over 99% in G. fujikuroi MP-A. These results indicate that FUM5 is a PKS gene required for fumonisin biosynthesis and, further, that fumonisins are products of polyketide rather than fatty acid metabolism.