Evolutionary pattern of the gtwin retrotransposon in the Drosophila melanogaster subgroup

The gtwin retrotransposon was recently discovered in the Drosophila melanogaster genome and it is evolutionarily closer to gypsy endogenous retrovirus. This study has identified gtwin homologous sequences in the genome of D. simulans, D. sechellia, D. erecta and D. yakuba by performing homology searches against the public genome database of Drosophila species. The phylogenetic analyses of the gtwin env gene sequences of these species have shown some incongruities with the host species phylogeny, suggesting some horizontal transfer events for this retroelement. Moreover, we reported the existence of DNA sequences putatively encoding full-length Env proteins in the genomes of Drosophila species other than D. melanogaster. The results suggest that the gtwin element may be an infectious retrovirus able to invade the genome of new species, supporting the gtwin evolutionary picture shown in this work.