Isolation, structure, and expression of even-skipped: a second pair-rule gene of Drosophila containing a homeo box.

We report the isolation, sequence, and transcriptional behavior of the Drosophila even-skipped (eve) gene, a member of the pair-rule class of segmentation genes. We show that the eve gene contains a homeo box and hence is related structurally to the pair-rule gene fushi tarazu and to homeotic selector genes. However, the eve homeo box differs significantly from those previously described and encodes a putative DNA recognition helix that would probably recognize different sequences. The eve gene resembles other pair-rule genes in showing a transient seven stripe zebra pattern during the blastoderm stage, but seven additional stripes arise soon thereafter. Together, these 14 stripes are required for the activation of coincident stripes of engrailed transcripts, leading to the subdivision of the embryo into compartmental and segmental units.