Research Notes Expression of a Modified Dutch Elm Disease Toxin in Escherichia coli. Mark G. Bolyard. Department of Crop and Soil Sciences and Department of Entomology, Pesticide Research Center, Michigan State University, East Lansing, MI 48824-1311 U.S.A. Mariam B. Sticklen. Department of Crop and Soil Sciences and Department of Entomology, Pesticide Research Center, Michigan State University, East Lansing, MI 48824-1311 U.S.A. MPMI 5:520-524. Accepted 21 August 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1992.

The fungal toxin associated with Dutch elm disease, ceratoulmin, has been produced in the bacterium Escherichia coli by the assembly of oligonucleotides according to the unpublished amino acid sequence of the toxin. This toxin was produced at approximately 80 μg/L of cell culture as a fusion to glutathione S-transferase. We synthesized the toxin as a fusion protein to improve purification and stability. Recombinant cerato-ulmin was analyzed by immunoblot analysis and then separated from its fusion partner by thrombin. We incorporated this molecule into an appropriate medium to test the activity of the toxin on the growth of American elm callus cultures.