9632005 Williamson Dr. Williamson and Dr. Ullman have recently discovered a gene, Meu1, that confers resistance to the potato aphid, Macrosiphum euphorbiae, in tomato. Meul is tighly linked to Mi, a single, dominant locus that mediates resistance to root-knot nematodes. The Mi-mediated resistance response to nematodes has been well characterized and shown to be associated with a rapid, hypersensitive response localized at the feeding site. The means by which Meu1 mediates resistance to the aphid is unknown, though preliminary data indicate that Meu1-mediated resistance profoundly alters aphid development and affects feeding behavior. It is hypothesized that the Meu1 gene product recognizes the aphid and triggers an active defense response. Preliminary data are consistent with a rapidly induced hypersensitive similar to that widely described for plant pathogens and for Mi-mediated resistance to nemotodes. The possiblity that a similar mechanism exists for insect resistance has been suggested, but not documented experimentally. The major goal of this research is to characterize Meu1 and elucidate the mechanism of Meu1-mediated resistance. If the hypotheses regarding Meu1-mediated resistance are correct, the research will elucidate a rarely reported mechanism of insect resistance in plants.
