DAX, A LOCUST HOX GENE-RELATED TO FUSHI-TARAZU BUT SHOWING NO PAIR-RULE EXPRESSION

We describe an unusual Antennapedia class homeobox gene from the grass hopper Schistocerca gregaria (Orthoptera, African Plague Locust). Its sequence is not sufficiently similar to that of any other insect Hem-H ox gene to identify it unambiguously, but short conserved elements sug gest a relationship to the segmentation gene fushi-tarazu, (ftz). We t erm it Sg Dax (divergent Antennapedia class homeobox gene). Antibodies raised against the protein encoded by this gene reveal two phases of expression during embryogenesis. In the early embryo, it is a marker f or the posterior part of the forming embryonic primordium, and subsequ ently for the posterior part of the growing germ band. In older embryo s, it labels a subset of neural precursor cells in each trunk segment, very similar to that defined by the expression of fushi tarazu (ftz) in Drosophila. We suggest that Schistocerca Dax and Drosophila ftz are homologous members of a gene family whose members are diverging relat ively rapidly, both in terms of sequence and role in early development .