P-element-induced male recombination can be produced in Drosophila melanogaster by combining end-deficient elements in trans.

Male recombination, not normally present in Drosophila melanogaster, can be produced at high rates when target P elements at homologous sites are combined in the presence of transposase protein. We have produced a set of elements by in situ deletion of a particular insertion and have found elements that have deletions stretching into either end. Elements were tested in pairs to see whether they complement each other in their ability to induce recombination. The combination of elements that are deficient for the same end produces very little recombination, but the combination of a right-end and a left-end element can generate recombination values higher than given by two complete P[CaSpeR] elements at homologous sites. This strongly suggests that "hybrid" P elements, containing ends from two different elements, can be recognized by transposase protein. We have also examined genotypes containing a normal and an end-deficient element and found that they yield reasonably high levels of recombination. We interpret the resultant gametes from such genotypes as showing that the majority of events in this genotype derive from the association of complementary ends from the same element, whereas the complementary ends from elements in trans associate in only a minority of cases.