GERMLINE TRANSFORMATION OF DROSOPHILA-VIRILIS WITH THE TRANSPOSABLE ELEMENT MARINER

An important goal in molecular genetics has been to identify a transpo sable element that might serve as an efficient transformation vector i n diverse species of insects. The transposable element mariner occurs naturally in a wide variety of insects, Although virtually all mariner elements are nonfunctional, the Mos1 element isolated from Drosophila mauritiana is functional. Mos1 was injected into the pole-cell region of embryos of D. virilis, which last shared a common ancestor with D. mauritiana 40 million years ago. Mos1 PCR fragments were detected in several pools of DNA from progeny of injected animals, and backcross l ines were established. Because Go lines were pooled, possibly only one transformation event was actually obtained, yielding a minimum freque ncy of 4%. Mos1 segregated in a Mendelian fashion, demonstrating chrom osomal integration. The copy number increased by spontaneous mobilizat ion. In situ hybridization confirmed multiple polymorphic locations of Mos1. Integration results in a characteristic 2-bp TA duplication. On e Mos1 element integrated into a tandem array of 370-bp repeats. Some copies may have integrated into heterochromatin, as evidenced by their ability to support PCR amplification despite absence of a signal in S outhern and in situ hybridizations.