Pair-rule genes cooperate to activate en stripe 15 and refine its margins during germ band elongation in the D-melanogaster embryo

Patterns of gene expression have been well documented during embryogenesis for the Drosophila melanogaster trunk segments. The same is not the case fo r the terminal segments. Here, gene expression patterns are followed during embryogenesis in the caudal segments (A8-A10 and the anal plate), with spe cial attention paid to the novel regulation of engrailed (en). Chosen for t his study are the pair-rule genes even-skipped (eve), Sushi tarazu (ftz), r unt (run), hairy (h), paired (prd) and odd-skipped (odd), and the segment p olarity gene (en). The results demonstrate a progressive and coupled transl ocation of gene expression distally for all genes studied, suggesting that the most posterior segments are determined later than trunk segments. (C) 2 000 Elsevier Science Ireland Ltd. All rights reserved.