Developmental expression of Drosophila melanogaster retrovirus-like transposable elements.

We have determined the pattern of temporal expression of several Drosophila retrovirus-like transposable elements. Some of these elements can be grouped into classes whose members show a similar profile of developmental transcription. The members of the 412 class, which includes 412, mdg1, 17.6 and 3S18, are transcribed mainly in the early larval and pupal stages of development, with small differences among the various members. HMS Beagle and Springer constitute another class where RNA accumulation in the larval stages is higher than in pupae and the adult flies accumulate more RNA than any other stage of development. Finally, the transcription of other elements such as copia, 297 and B104 follows a specific and individual pattern distinct from those described above. These results suggest the existence of evolutionary relationships among different transposable elements in Drosophila and the involvement of different cellular genes in the control of their expression.