Hvmar1, a mariner-like element from the tobacco budworm Heliothis virescens, can transpose in Drosophila melanogaster

Transposable elements of the mariner family are widespread and have been found in the genome of plants, animals and insects. However, most of these elements contain multiple inactivating mutations and so far, only three naturally occurring mariner elements are known to be functional. In a previous study, a mariner-like element called Hvmar1 was discovered in the genome of the tobacco budworm Heliothis virescens. Further analysis of the Hvmar1 nucleotide sequence revealed the presence of 30-bp imperfect inverted terminal repeats and an intact open reading frame, which is considered to encode a functional transposase. In the present study, we show that the Hvmar1 element is active using interplasmid transposition assays in Drosophila melanogaster embryos. When injected into Drosophila embryos, the helper plasmid produced a transposase that was able to mediate transposition of the Hvmar1 element from a donor to a target plasmid. The transposition efficiency of Hvmar1 in D. melanogaster is approximately 11-fold lower than that of the well-known Mos1 mariner transposon. However, this efficiency is comparable to those observed previously with Mos1 in non-Drosophila insects. We identified 10 independent interplasmid transposition events, albeit the recovery of these events was rare. In each case the Hvmar1 element transposed in a precise manner, with the characteristic TA dinucleotides being duplicated on insertion. Furthermore, two of the target sites identified have been used previously by Mos1 for insertion. The active transposition of Hvmar1 in D. melanogaster provides a basis for examining the mobility of this element in its natural host as well as a starting point for comparative studies with Mos1 and other functional mariner transposons.