The Hox gene fushi tarazu (ftz) functions as a pair-rule segmentation gene in Drosophila. In contrast, Ftz protein from a beetle (Tc-Ftz) retains homeotic potential, indicated by its ability to transform antenna (upper left) to leg (lower right) and to repress Homothorax expression (red) when expressed in Drosophila, observed as loss of overlap between GFP, which marks Tc-Ftz expression, and Homothorax expression (upper right). Heffer et al. review the evidence that ftz evolved from a traditional Hox gene with homeotic potential to a gene with exclusive pair-rule segmentation function in Drosophila. The authors correlate Ftz functional evolution with the presence and absence of distinct co-factor interaction domains, necessary for either homeotic or segmentation function.
Backcover by A. Heffer, U. Löhr and L. Pick