Localized expression of a novel micropia-like element in the blastoderm of Drosophila melanogaster is dependent on the anterior morphogen bicoid.

We have identified a novel transposon-like element of Drosophila melanogaster that is present in approximately 20 copies in the genome. It codes for a polyprotein containing the diagnostic sequence motifs for a nucleic acid binding CCHC protein, a proteinase, a reverse transcriptase and an integrase as typically found in retroviruses. Owing to its early expression in the blastoderm embryo, and its close relationship to micropia, a previously identified Drosophila retrotransposon, we termed the novel element "blastopia". The spatially restricted expression of blastopia transcripts in head anlagen of the blastoderm embryo is under the direct or indirect control of the Drosophila morphogen bicoid, which is normally required to establish the anterior pattern elements in the embryo. Our results suggest that a blastopia element acts as an "enhancer trap", and thereby participates in the control of an as yet unidentified gene normally expressed in the head anlagen of the embryo.