MOLECULAR CHARACTERIZATION OF THE ZERKNULLT REGION OF THE ANTENNAPEDIA COMPLEX OF D-SUBOBSCURA

We have characterized at the molecular level the zerknullt (zen) regio n of the Drosophila subobscura Antennapedia complex. The sequence comp arison be tween D. subobscura and D. melanogaster shows an irregular d istribution of the conserved and diverged regions, with the homeobox a nd a putative activating domain completely conserved. Comparisons of t he promoter sequence and pattern of expression of the gene during deve lopment suggest that the regulation of zen has been conserved during e volution. The conservation of zen expression in a subpopulation of the polar cells indicates the existence of an important role in such cell s. We describe a transitory segmented pattern of expression of zen in both species, suggesting the existence of interactions with a pair rul e gene. Some indirect clues indicate that the z2 gene might be absent from the D. subobscura genome. A chromosome walk initiated to reach th e proboscipedia gene of D. subobscura reveals that the distance betwee n pb and ten is at least four times the one described for D. melanogas ter and for D. pseudoobscura. Finally, we present cytolog ical evidenc e showing that the ANT-C is inverted in D. subobscura as compared to D . melanogaster.