Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2004
Publication Date: April 20, 2004
Citation: Alexander, N.J., Mc Cormick, S.P., Proctor, R. 2004. Heterologous expression provides method for proving the multifunctionality of the tri4 oxygenase in trichothecene biosynthesis in fusarium. Meeting Abstract. Technical Abstract: The biosynthesis of Fusarium trichothecenes involves a complex pathway that begins with the cyclization of farnesyl pyrophosphate to form the sesquiterpene hydrocarbon trichodiene followed by multiple oxygenation, cyclization and esterification steps. Mutant strains of Fusarium sporotrichioides NRRL3299 and F. graminearum Z3639 produced by disruption of Tri4 are unable to make T-2 toxin and 15-acetyldeoxynivalenol, respectively, and accumulate trichodiene. Tri4 encodes a P450 enzyme which must therefore act on trichodiene. To identify the actions of TRI4, we chose a heterologous expression system using F. verticillioides M3125, a strain that produces fumonisins rather than trichothecenes. Transgenic F. verticillioides M3125 expressing FgTri4 under the control of a FUM8 promoter converted added trichodiene to isotrichodermin. Conversion of trichodiene to isotrichodermin requires seven steps, two of which are non-enzymatic. Feeding studies showed that wild-type F. verticillioides M3125 could convert isotrichodermol to isotrichodermin, indicating that trichothecene C-3 acetyltransferase activity is present in this organism. These experiments indicate that FgTri4 encodes a multifunctional P450 oxygenase that catalyzes the four oxygenation steps required for the conversion of trichodiene to isotrichotriol.