The gooseberry-zipper region of Drosophila: five genes encode different spatially restricted transcripts in the embryo.

Genetic analysis of the Drosophila chromosome region 60 E9-F1 identified two functions affecting embryonic development; gooseberry (gsb), a segment polarity gene, and zipper (zip), an unclassified gene which affects cuticle formation severely. By contrast, molecular analysis revealed five genes with different temporal and spatial patterns of expression in the embryo. Candidate genes for gsb and zip functions were identified. Two adjacent genes are eventually expressed in regular stripes within the posterior region of each segment. One of them is expressed initially in a pair-rule mode; the second gene expresses reduced levels of transcripts in a mutant which leaves the transcribed region and the sequences up to the second gene intact. This observation, the patterns of transcripts in the embryo and the genetic data suggest that both genes are involved in gooseberry segmentation function. zip is expressed in neural tissue and not in epidermal anlagen. Embryos lacking zip activity also develop abnormal neural tissue consistent with the argument that the zip cuticle phenotype is a secondary effect. Additional newly identified genes are expressed in specific domains of the embryo, covering mesoderm anlagen and the dorsal region of embryos at blastoderm stage, respectively.