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Title: BIOSYNTHESIS OF TRICHOTHECENES, GENETIC AND MOLECULAR ASPECTS

Author
item Hohn, Thomas
item Desjardins, Anne
item McCormick, Susan
item Proctor, Robert

Submitted to: Toxic Microorganisms Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/21/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: The mold Fusarium is a common contaminant of grain and other livestock feeds. Several species of Fusarium are known to produce trichothecene toxins which cause adverse effects on human and animal health. We identified several genes in Fusarium sporotrichioides that control the production of trichothecene toxins. Our investigations have shown that these genes are closely linked to each other. This knowledge will be useful in the development of new strategies for controlling the contamination of food and feed products by fungal toxins.

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 additional pathway genes (Tri3, Tri4, Tri6, Tri7, Tri8, and Tri9) were 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. Biochemical and genetic studies have determined the functions of three genes (Tri3, Tri4, and Tri6). 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.