Molecular characterization of Tclabial and the 3' end of the Tribolium homeotic complex.

The homeotic selector gene labial is located at the 3' end of the Antennapedia complex (ANTC) and is required for proper head development in Drosophila. We have cloned and characterized the Tribolium ortholog of labial, Tclabial (Tclab). Similar to Drosophila labial, Tclab contains a single large intron upstream of the homeobox. In contrast, Tclab lacks an intron within the homeobox. The Tribolium ortholog of chaoptic, Tcchaoptic, transcribed from the opposite strand, is located immediately downstream of the homeotic complex, and its 3'UTR overlaps that of Tclab by 50 nucleotides. We have also sequenced the 13.5 kb interval between Tclab and maxillopedia (the Tribolium ortholog of Drosophila proboscipedia). In contrast to Drosophila, there is not a cluster of cuticle genes in this region. Finally, we have examined the expression of Tclab transcripts in Tribolium embryos. As previously described for Drosophila and other insects, the expression of Tclab is specific to the intercalary segment.