THE TRANSPOSABLE ELEMENT MARINER MEDIATES GERMLINE TRANSFORMATION IN DROSOPHILA-MELANOGASTER

A vector for germline transformation in Drosophila melanogaster was co nstructed using the transposable element mariner. The vector, denoted pMlwB, contains a mariner element disrupted by an insertion containing the wild-type white gene from D. melanogaster, the beta-galactosidase gene from Escherichia coli and sequences that enable plasmid replicat ion and selection in E. coli. The white gene is controlled by the prom oter of the D. melanogaster gene for heat-shock protein 70, and the be ta-galactosidase gene is flanked upstream by the promoter of the trans posable element P as well as that of mariner. The MlwB element was int roduced into the germline of D. melanogaster by co-injection into embr yos with an active mariner element, Mos1, which codes for a functional transposase and serves as a helper. Two independent germline insertio ns were isolated and characterized. The results show that the MlwB ele ment inserted into the genome in a mariner-dependent manner with the t ermini of the inverted repeats inserted at a TA dinucleotide. Both ins ertions exhibit an unexpected degree of germline and somatic stability , even in the presence of an active mariner element in the genetic bac kground. These results demonstrate that the mariner transposable eleme nt, which is small (1286 bp) and relatively homogeneous in size among different copies, is nevertheless capable of promoting the insertion o f the large (13.2 kb) MlwB element. Because of the widespread phylogen etic distribution of mariner among insects, these results suggest that mariner might provide a wide host-range transformation vector for ins ects.