Rapid spread of a P element/Adh gene construct through experimental populations of Drosophila melanogaster

Transposable elements may be potential tools for the dispersal of engineered DNA through target insect populations. The utility of this hypothesis is predicated on the ability of transposable elements carrying a large DNA insert to rapidly disperse through a population. In addition, the inserted DNA must be replicated with a high degree of fidelity during this dispersal. We have monitored the ability of a transposable element with an inserted gene to spread through experimental populations and tested whether the passenger gene retains its ability to encode an active protein. Several Drosophila melanogaster laboratory populations were initiated with female flies that were null for alcohol dehydrogenase activity and contained no P elements. Most of the females were mated to males of the same strain; however, 1 or 10% of the females were mated to males from a strain that had previously been transformed with a helper P element and a P element/Adh gene construct. The dispersal of P elements to new genomes was monitored at each generation by randomly selecting females and performing DNA hybridization assays on dissected ovarian tissue. In addition, each female was tested for alcohol dehydrogenase activity using a simple histochemical assay. We find that, despite an approximate threefold increase in size, the P element constructs containing a functioning gene are still capable of rapid dispersal through the experimental populations. We also show that many of the inserted Adh genes still encode an active product.Key words: P element, transformation, Adh, transposable element.