Genetic localization of a Drosophila melanogaster resistance gene to a parasitoid wasp and physical mapping of the region

Drosophila melanogaster larvae usually react against eggs of the parasitoid wasp Leptopilina boulardi by surrounding them with a multicellular melanot ic capsule. The genetic determinism of this response has been studied previ ously using susceptible (non-capsule-forming) and resistant (capsule-formin g) strains. The results suggest that differences in their encapsulation res ponse involve a single gene, resistance to Leptopilina boulardi (Rlb), with two alleles, the resistant one being dominant. Rlb confers specific protec tion against Leptopilina boulardi and is thus probably involved in parasito id recognition. Recent studies have localized this gene on the right arm of the second chromosome and our aint was to precisely determine its genetic and molecular location. Using strains bearing deletions, we demonstrated th at resistance to Leptopilina boulardi is conferred by the 55C; 55F3 region and that the 55E2-E6; F3 region is particularly involved. A physical map of the 55C; 56A region was then constructed, based on a set of overlapping co smid and PI phage clones. Using single and double digests, cross hybridizat ion of restriction fragments, and location of genetically mapped genes and STSs, a complete, five-enzyme restriction map of this 830-kb region was obt ained.