GABA receptor minigene rescues insecticide resistance phenotypes in Drosophila

A single point mutation within the GABA receptor gene Resistance to dieldrin (Rdl) confers a high level of resistance to cyclodiene insecticides in a wide range of insects. Previous studies have shown partial rescue of the susceptible phenotype via germline transformation of a 36 kb cosmid coding (or all four alternative Rdl splice forms. Here, we describe the construction of two Rdl promoter/cDNA minigenes, each coding for one of the splice forms alone. Single splice forms rescued both the insecticide susceptible and resistant phenotypes associated with the locus as effectively as the complete cosmid. The minigenes also rescue the lethality associated with homozygous re-arrangements disrupting the Rdl gene, and the level of rescue observed is not increased by the addition of more than one splice form. This demonstrates that only a single Rdl splice form is necessary both to confer insecticide sensitivity and also to rescue lethality. Methods by which phenotype rescue could be enhanced and the potential advantages of using Rdl as a selectable marker are discussed.