SERB, J.M.*; OMILIAN, A.; OAKLEY, T.H.; Univ. of California, Santa Barbara; Indiana Univ., Bloomington; Univ. of California, Santa Barbara: Ancient duplication of Pax-6 homologs eyeless (ey) and twin of eyeless (toy)

Two Pax-6 homologs, eyeless (ey) and twin of eyeless (toy), play important and non-redundant roles in controlling Drosophila eye and nervous system development. Strong mutants of either toy or ey result in lethal headless phenotypes, suggesting that both genes are required for normal development. Nevertheless, toy has only been found in holometabolous insects, hypothesized to be the result of a recent gene duplication event during insect evolution. We present evidence that refutes a holometabolous duplication of ey and toy. New sequence data from Euphilomedes (Crustacea: Ostracoda) and Daphnia (Crustacea: Branchiopoda), coupled with phylogenetic analyses of Pax-6 genes, identify the presence of both paralogs in Crustacea. These results indicate that the duplication of ey and toy is ancient, probably occurring before the ancestor of the Pancrustacea (Crustacea + Insecta). Interestingly, the ostracod Euphilomedes appears to possess only a single Pax-6 gene, toy.