Submitted to: ARS Workshop on Fusarium Toxins Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 26, 1995
Publication Date: N/A
Technical Abstract: The pathway for trichothecene toxin biosynthesis in Fusarium is being characterized by biochemical and molecular genetic methods. The ordered sequence of oxygenations, isomerizations, cyclizations and esterifications leading from the sesquiterpene hydrocarbon trichodiene to more complex trichothecene toxins such as vomitoxin and T-2 toxin has been established through experiments with Fusarium sporotrichioides, F. sambucinum, and F. graminearum. For T-2 toxin biosynthesis: - trichodiene - 2-hydroxytrichodiene - 12,13- epoxytrichoene-2-ol - isotrichodiol - isotrichotriol - trichotriol - isotrichodermol - isotrichodermin - 15-decalonectrin - calonectrin - 3,15-diacetoxyscirpenol - 3,4,15-triacetoxyscirpenol - 3- acetylneosolaniol - 3-acetyl T-2 toxin - T-2 toxin. Trichothecene biosynthesis of vomitoxin shares the initial steps of this pathway branching after 15-decalonectrin. Trichothecene biosynthetic genes are clustered. At least eight genes involved in F. sporotrichioides trichothecene biosynthesis have been shown to be present on a single cosmid clone. The functions of these genes have been determined through biochemical analysis of mutants generated by molecular gene disruption. These include a sesquiterpene cyclase, cytochrome P450 monooxygenases, transacetylases and regulatory genes. By using molecular disruption of the gene encoding the sesquiterpene cyclase, mutants of F. sporotrichioides, F. sambucinum, and F. graminearum have been generated. Transformants carrying the disrupted allele produce no trichothecenes.