|Hohn, Thomas - NOVARTIS SEEDS, RTP, NC|
Submitted to: Fungal Genetics and Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 16, 1999
Publication Date: N/A
Interpretive Summary: Fumonisins are toxins associated with a number of serious health problems in humans and animals. These toxins are produced by the fungus Gibberella fujikuroi, which causes disease on corn. When the fungus grows within corn ears, it can produce fumonisins which make their way into human food and animal feed that contain corn. We have identified, isolated, and characterized a gene that is required for fumonisin production in G. fujikuroi. This gene is the blueprint for an enzyme that catalyzes the first unique chemical reaction in fumonisin production. In addition, it is the first gene involved in the formation of fumonisin to be isolated and analyzed at the DNA level. The isolation and characterization of this and other fumonisin genes in G. fujikuroi should help to determine how and why these important toxins are produced and lead to strategies that minimize or eliminate fumonisin contamination in corn.
Technical Abstract: Fumonisins are toxins associated with several mycotoxicoses and are produced by the maize pathogen Gibberella fujikuroi mating population A (MP-A). Chemical analyses indicate fumonisins are a product of polyketide or fatty acid biosynthesis. To isolate a polyketide synthase (PKS) gene involved in fumonisin biosynthesis, we employed PCR with degenerate PKS primers and a cDNA template prepared from a fumonisin-producing culture of G. fujikuroi. Sequence analysis of the single PCR product and its flanking DNA revealed a gene (FUM5) with a 7.8 kb coding region. The predicted FUM5 translation product was highly similar to bacterial and fungal Type I PKSs. Transformation of a cosmid clone carrying FUM5 into G. fujikuroi enhanced production in three strains and restored wild-type production in a fumonisin nonproducing mutant. Disruption of FUM5 reduced fumonisin production by over 99% in G. fujikuroi MP-A. Together, these results indicate that FUM5 is a PKS gene required for fumonisin biosynthesis.