A polyketide synthase gene required for biosynthesis of fumonisin mycotoxins in Gibberella fujikuroi slating population A

Fumonisins are toxins associated with several mycotoxicoses and are produce d by the maize pathogen Gibberella fujikuroi mating population A (MP-A), Bi ochemical analyses indicate that fumonisins are a product of either polyket ide or fatty acid biosynthesis. To isolate a putative polyketide synthase ( PKS) gene involved in fumonisin biosynthesis, we employed PCR with degenera te PKS primers and a cDNA template prepared from a fumonisin-producing cult ure of G. fujikuroi. Sequence analysis of the single PCR product and its fl anking DNA revealed a gene (FUM5) with a 7.8-kb coding region. The predicte d FUM5 translation product was highly similar to bacterial and fungal Type I PKSs, Transformation of a cosmid clone carrying FUM5 into G. fujikuroi en hanced production in three strains and restored wild-type production in a f umonisin nonproducing mutant. Disruption of FUM5 reduced fumonisin producti on by over 99% in G. fujikuroi MP-A. Together, these results indicate that FUM5 is a PKS gene required for fumonisin biosynthesis. (C) 1999 Academic P ress.