Cross-Regulatory Interactions Among Pair-Rule Genes in Drosophila

The pair-rule genes of Drosophila are required for the subdivision of the developing embryo into a repeating series of homologous body segments. One of the pair-rule genes, even-skipped ( eve ), appears to be particularly important for the overall segmentation pattern since eve - embryos lack all segmental subdivisions in the middle body region. On the basis of homeo box cross-homology we have isolated a gene, S72, which probably corresponds to eve . In embryo tissue sections S72 transcripts show a periodic distribution pattern. The eve - phenotype appears to involve altered patterns of fushi tarazu and engrailed expression. These and other findings suggest that pair-rule gene expression might involve hierarchical cross-regulatory interactions.