Interplasmid transposition of the mariner transposable element in non-drosophilid insects.

Plasmid-based transposition assays were performed in developing embryos of the Australian sheep blowfly Lucilia cuprina and the Queensland fruit fly Bactrocera tryoni, using the mariner transposable element from Drosophila mauritiana. Transposition products were recovered that were identical in structure to those recovered from D. melanogaster. Only sequences delimited by the mariner terminal repeats were transposed and all insertions occurred at TA residues, and duplicated these. These are the hallmarks of mariner transpositions observed in the chromosomes of D. melanogaster and D. mauritiana, indicating that the plasmid-based assays are accurate indicators of mariner transposition activity. The recovery of precise transposition products from L. cuprina and B. tryoni demonstrates that mariner should be capable of producing germline transformants in these species. The results obtained from these assays suggests that they will be extremely useful in determining if mariner can transpose in other non-drosophilid insects and for investigating factors that might affect mariner transposition frequency.

The transposable element mariner can excise in non-drosophilid insects.

Plasmid-based excision assays performed in embryos of two non-drosophilid species using the mariner transposable element from Drosophila mauritiana resulted in empty excision sites identical to those observed after the excision of mariner from D. mauritiana chromosomes. In the presence of the autonomous mariner element Mos1, excision products were recovered from D. melanogaster, D. mauritiana and the blowfly Lucilia cuprina. When a hsp82 heat shock promoter-Mos1 construct was used to supply mariner transposase, excision products were also recovered from the Queensland fruitfly Bactrocera tryoni. Analysis of DNA sequences at empty excision sites led us to hypothesise that the mariner excision/repair process involves the formation of a heteroduplex at the excision breakpoint. The success of these assays suggests that they will provide a valuable tool for assessing the ability of mariner and mariner-like elements to function in non-drosophilid insects and for investigating the basic mechanisms of mariner excision and repair.