Abstract
Using antibodies directed against the protein produced from the homeotic selector locus Deformed (Dfd), we have determined its spatial distribution both in wild-type embryos and in embryos mutant for a variety of segmentation genes. The Dfd protein is first detectable in a single circumferential stripe of about six cells at the cellular blastoderm stage. During gastrulation and at later stages its principal domain of epidermal expression is in the mandibular and maxillary segments of the embryonic head. Though not strongly altered by mutations in most of the zygotic gap genes and other selector genes, the pattern of Dfd expression is dramatically altered in mutants for eight of the nine pair-rule segmentation genes. The precise delimitation of Dfd expression can be largely accounted for by hierarchical and combinatorial effects of segmentation gene activities. In addition, the control of Dfd expression is also regulated by at least two other factors that are differentially active on both the anterior-posterior and dorsal-ventral axes. Our results support the idea that a hierarchy of homeobox regulatory genes plays a key role in dividing and determining the Drosophila body pattern.
