| American elms were a nearly ubiquitous part of both urban and rural life in the United States until Dutch-elm disease, caused by the introduced fungus Ophiostoma novo-ulmi, killed almost all mature trees in the mid-twentieth century. In this project, Agrobacterium was used to transform American elm with a vascular-expressed gene encoding the synthetic antimicrobial peptide ESF39A. At least three unique, single-copy transgenic lines were produced and regenerated into whole plants, which showed significantly less wilting and sapwood staining than non-transformed controls after O. novo-ulmi inoculation. Copy number was determined by Southern hybridization, expression was confirmed by RT-PCR, and peptide activity against O. novo-ulmi was tested with an in vitro 'minimum inhibitory concentration' assay. Preliminary observations indicated that mycorrhizal colonization was not significantly different between transgenic and wild-type trees. These results indicate that transgenes encoding antimicrobial peptides hold promise for enhancing pathogen resistance in American elm. |
