Characterization of the Tribolium Deformed ortholog and its ability to directly regulate Deformed target genes in the rescue of a Drosophila Deformednull mutant

We have analyzed the Tribolium castaneum ortholog of the Drosophila homeoti c gene Deformed (Dfd) and determined its expression pattern during embryoge nesis in this beetle. Tc Deformed (Te Dfd) is expressed in the blastoderm a nd the condensing germ rudiment in a region that gives rise to gnathal segm ents. During germ band extension Te Dfd is expressed in the mandibular and maxillary segments, their appendages, and the dorsal ridge. Comparison of i nsect Dfd protein sequences reveals several highly conserved regions. To de termine whether common molecular features reflect conserved regulatory func tions we used the Ga14 system to express the Tribolium protein in Drosophil a embryos. When Tc Dfd is expressed throughout embryonic ectoderm under the control of P69B, the beetle protein autoregulates the endogenous Dfd gene. In addition, the Drosophila proboscipedia gene (a normal target of Dfd) is ectopically activated in the antennal and thoracic segments. We also compa red the ability of the beetle and fly proteins to rescue defects in Dfd(-) mutants by expressing each throughout the embryonic during embryogenesis. B oth proteins rescued Dfd(-) defects to the same extent in that they each re store the development of mouth hooks and cirri, as well as cause gain-of-fu nction abnormalities of posterior mouth parts. As before, pb was ectopicall y activated in the antennal segment. This is the first demonstration of the ability of a heterologous homeotic selector protein to directly regulate a target gene independent of an endogenous Drosophila autoregulatory loop.