Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/2004
Publication Date: 4/20/2004
Citation: Alexander, N.J., Mc Cormick, S.P., Proctor, R. 2004. Heterologous expression of the fusarium graminearum tri4 gene in f. verticillioides provides evidence for a multifunctional oxygenase in trichothecene biosynthesis. Meeting Abstract. Interpretive Summary:
Technical Abstract: The biosynthesis of trichothecene mycotoxins by Fusarium sporotrichioides and F. graminearum involves a complex biochemical pathway that begins with the cyclization of farnesyl pyrophosphate to the sesquiterpene hydrocarbon trichodiene and continues with multiple oxygenation, cyclization and esterification reactions. In previous studies using F. sporotrichioides, disruption of the P450 monooxygenase-encoding gene Tri4 blocked trichothecene production and lead to the accumulation of trichodiene. Therefore, the TRI4 protein must act on trichodiene. To further elucidate the function of the TRI4 protein, we heterologously expressed the F. graminearum Tri4 (FgTri4) in F. verticillioides, which does not produce trichothecenes. Transgenic F. verticillioides carrying FgTri4 under the control of a fumonisin biosynthetic gene (FUM8) promoter converted exogenous trichodiene to isotrichodermin. Conversion of trichodiene to isotrichodermin requires seven biochemical reactions (trichodiene to 2-hydroxytrichodiene to 12,13-Epoxy-9,10-trichoene-2-ol to isotrichodiol to isotrichotriol to trichotriol to isotrichodermol to isotrichodermin). Previous studies indicate that two of these reactions (isotrichotriol to trichotriol to isotrichodermol) are non-enzymatic, and feeding studies done here indicate that wild-type F. verticillioides can convert isotrichodermol to isotrichodermin. Together, these results indicate that the FgTri4 protein is a multifunctional monooxygenase that catalyzes the four oxygenation reactions required for the conversion of trichodiene to isotrichotriol during trichothecene biosynthesis.