Molecular characterization and embryonic expression of the even-skipped ortholog of Tribolium castaneum.

In short germ insects, the procephalon and presumptive anterior segments comprise most of the embryonic rudiment which lengthens as posterior segments are added during development (Sander, K. (1976) Adv. Insect Physiol. 12, 125-238). The expression pattern of a grasshopper ortholog of the primary pair-rule gene even-skipped (eve) suggests that it is not relevant to segmentation in this short germ insect (Patel, N.H., Ball, E.E. and Goodman, C.S. (1992) Nature 357, 339-342). However in Drosophila, a long germ insect that forms all segments simultaneously, eve plays a vital role in segment formation (Nüsslein-Volhard, C., Wieschaus, E. and Klüding, H. (1984) Roux's Arch. Dev. Biol. 193, 267-282). We have characterized the eve ortholog of the beetle Tribolium castaneum. The homeodomain sequence is highly conserved between beetle, fly, and grasshopper eve orthologs. Tc eve is expressed in stripes during segmentation, but in a pattern differing in some details from that of the fly gene. This pattern is coincident with that detected with a cross-reacting antibody (Patel, N.H., Condron, B.G. and Zinn, K. (1994) Nature 367, 429-434). Thus, an ancestral even-skipped gene appears to have evolved a role in segmentation in a common ancestor of flies and beetles. Unlike vertebrate orthologs but similar to eve, Tc eve is not linked to the homeotic complex.