9317586 Robertson The transposon, mariner, was initially found in Drosophila melanogaster. It was isolated and characterized. Five major subfamilies of these elements were found in insects and closely related arthropods using a PCR assay with primers designed to regions of amino acid conservation in their putative transposases. Other workers have discovered additional mariners in more diverse organisms including a nematode and a planarian. We have recently discovered mariners in other platyhelminthes, hydra and most recently in humans. A homologous relationship of the mariner family with the Tc-related family of transposons in nematodes, insects, and fish has also been recently recognized. On this basis, we postulate that the evolution of these transposons involves horizontal transfer into new hosts followed by a amplification of copy number, after which neutral evolution usually results in extinction of the element. The work proposed here will examine two aspects of the diversity, evolution, and interactions of these mariners.The PCR survey will be continued and selected interesting elements, particularly those indicating recent horizontal transfers across phyla will be cloned and sequenced. Related species will be examined to test the hypothesis of recent horizontal transfer. Rates of evolution will also be examined directly by comparison with mariner elements isolated from amber fossil insects. The interaction of the different mariners and Tc-like found in some genomes will be investigated by genetically combining active and marked representatives of the different families and subfamiles into the genome of Drosophila melanogaster and assaying their ability to mobilize and/or repress each other. Similar mix-and-match experiments will be done in a comparative study of the different transposases. %%% The discovery that a specific transposon, first detected in Drosophila melanogaster, is also present in many different species and phyla suggests that the horizontal transfer of DNA has occurr ed. This hypothesis will be tested in various ways and the search for mariner elements in insects, other arthropods and other animals will be continued. The proposed work will develop mariners as the best understood example of molecular evolution of the short inverted terminal repeat class of transposons in eukaryotes. It will also provide information on horizontal transfer of transposons necessary for regulatory evaluation of risks of release of genetically engineered arthropods. ***
