Dev Genes Evol (2008) 218:141–152 DOI 10.1007/s00427-008-0212-5 ORIGINAL ARTICLE Do teashirt family genes specify trunk identity? Insights from the single tiptop/teashirt homolog of Tribolium castaneum Teresa D. Shippy & Yoshinori Tomoyasu & Wensheng Nie & Susan J. Brown & Robin E. Denell Received: 3 January 2008 / Accepted: 12 February 2008 # The Author(s) 2008 Abstract The Drosophila teashirt gene acts in concert with the homeotic selector (Hox) genes to specify trunk (thorax and abdomen) identity. There has been speculation that this trunk-specifying function might be very ancient, dating back to the common ancestor of insects and vertebrates. However, other evidence suggests that the role of teashirt in trunk identity is not well conserved even within the Insecta. To address this issue, we have analyzed the function of Tc-tiotsh, the lone teashirt family member in the red flour beetle, Tribolium castaneum. Although Tc-tiotsh is impor- tant for aspects of both embryonic and imaginal develop- ment including some trunk features, we find no evidence that it acts as a trunk identity gene. We discuss this finding in the context of recent insights into the evolution and function of the Drosophila teashirt family genes. Keywords Tribolium . Teashirt . Tiptop . Trunk . Homeotic Electronic supplementary material The online version of this article (doi:10.1007/s00427-008-0212-5) contains supplementary material, which is available to authorized users. Communicated by S. Roth T. D. Shippy (*) : Y. Tomoyasu : W. Nie : S. J. Brown : R. E. Denell Division of Biology, Kansas State University, Manhattan, KS 66506, USA e-mail: tshippy@ksu.edu Present address: W. Nie Fibrogen, 225 Gateway Boulevard, South San Francisco, CA 94080, USA Introduction Homeotic genes are responsible for defining regional identity, and mutations in these genes often transform one body part into another. The best characterized homeotic genes are the Hox genes, which have been identified in representatives of most animal phyla (reviewed by Martindale 2005) and have been extensively studied in several organisms. However, some non-Hox genes have also been classified as homeotic genes based on their mutant phenotypes. One such gene encodes the zinc finger transcription factor Teashirt (Fasano et al. 1991). Loss-of-function (LOF) teashirt (tsh) mutations are reported to cause partial transformation of the larval prothorax to a labial identity due to ectopic expression of the Hox gene Sex combs reduced (Fasano et al. 1991; Roder et al. 1992). The trunk (thoracic and abdominal) segments of tsh− larvae are shorter than normal and the denticle belts (a trunk-specific feature) are severely disorganized. Moreover, patches of sclerotic cuticle, which have been interpreted as head structures, form between the remaining denticle belts (Fasano et al. 1991). Conversely, ectopic expression of tsh results in the development of denticle belts in the head (de Zulueta et al. 1994). On the basis of these phenotypes, tsh has been suggested to function as a specifier of trunk vs head identity (Roder et al. 1992). tsh is believed to act in parallel with the trunk Hox genes (Scr, Antennapedia (Antp), Ultrabithorax (Ubx), abdomi- nal-A (abd-A), and Abdominal-B (Abd-B)) to determine segmental identity (de Zulueta et al. 1994; Roder et al. 1992). When all of these Hox genes are inactivated, trunk segments develop with what has been interpreted as a mixed head/trunk identity. That is, sclerotized tissue develops in the posterior compartment of each trunk segment, whereas denticle belts (a trunk-specific feature) still develop in the anterior compartment (Sato et al. 1985;