Submitted to: Toxic Microorganisms Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 17, 1994
Publication Date: N/A
Technical Abstract: Trichothecenes constitute a large and structurally diverse family of sesquiterpenoid mycotoxins. The contamination of agricultural products by trichothecenes is a problem of worldwide occurrence and is primarily due to their production by Fusarium species. Studies on the biosynthesis of trichothecenes by Fusarium sporotrichioides have revealed that many of the trichothecene pathway genes are present in a gene cluster. Evidence for a gene cluster initially came from the identification of a cosmid clone (Cos9-1) carrying the trichodiene synthase gene (Tri5) that was able to complement two different trichothecene deficient mutants. Subsequently, six pathway genes (Tri3, Tri4, Tri6, Tri7, Tri8, and Tri9) have been identified on Cos9-1 within a 17 Kb region that includes Tri5. The involvement of Tri3, Tri4, Tri6, Tri7, and Tri8 in trichothecene biosynthesis has been confirmed by gene disruption experiments. Based on biochemical and genetic studies the functions of three genes (Tri3, Tri4, and Tri6) have been determined. One of these, Tri6, encodes a transcriptional factor that serves as a positive regulator of pathway gene expression. The levels of pathway gene mRNAs are greatly reduced in mutants lacking a functional Tri6 gene. These results indicate that trichothecene pathway genes are closely linked and that their expression is coordinately regulated. Efforts to identify other possible pathway genes which may be closely linked to Tri5 are in progress.