maxillopedia is the Tribolium ortholog of proboscipedia

Null mutations in the Drosophila melanogaster homeotic gene proboscipedia ( pb) cause transformation of the adult labial palps to legs. The similar phe notype produced by mutations in the Tribolium castaneum homeotic complex (H OMC) gene maxillopedia (mxp) has led to suggestions that the two genes may be orthologous. We have cloned the Tribolium ortholog of pb, which predicts a protein with a homeodomain identical to that of Drosophila Pb. The two p roteins also share several additional regions of identity, including an N-b ox, a motif unique to Pb orthologs. We have identified a frameshift mutatio n within Tribolium pb associated with an mxp null mutation, demonstrating t hat Tribolium pb corresponds to the mxp genetic locus. Thus, we will refer to the cloned gene as mxp. In addition, we have begun to construct a molecu lar map of the Tribolium HOMC. Two overlapping BAC clones which span the mx p locus also include the Tribolium labial ortholog (Tclabial) and part of T czerknullt, indicating that the order of these genes in the HOMC is conserv ed between Drosophila and Tribolium.