Molecular characterization of Cephalothorax, the Tribolium ortholog of sexcombs reduced

Sex combs reduced (Scr), a Hox gene located in the Antennapedia complex of Drosophila melanogaster, is required for the proper development of the labi al and first thoracic segments. The Tribolium castaneum genetically defined locus Cephalothorax (Cx) is a candidate Scr ortholog based on the location of Cx in the beetle Homeotic complex and mutant effects on the labial and first thoracic segments. To address this hypothesis, we have cloned and cha racterized the Tribolium ortholog of Scr (TcScr). The transcription unit is less complex and encodes a smaller protein than Scr, The predicted amino a cid sequence of the Tribolium protein shares motifs with orthologous protei ns from multiple species, In addition, we have analyzed the TcScr expressio n pattern during embryonic development, TcScr is expressed in parts of the maxillary, labial, and first thoracic segments in a pattern similar to but not identical to Scr. Furthermore, TcScr RNA interference results in a phen ocopy of the Cephalothorax (Cx) mutant phenotype in which the labial palps are transformed into antennae and the head and first thoracic segment are f used. All of the available results indicate that ox is the Tribolium orthol og of Scr. genesis 30:12-20, 2001. (C) 2001 Wiley-Liss, Inc.