Three neighboring genes interact with the Broad-Complex and the Stubble-stubbloid locus to affect imaginal disc morphogenesis in Drosophila.

The Broad-Complex (BR-C) is a complex regulatory locus at 2B-5 on the X chromosome of Drosophila melanogaster. The wild-type BR-C products are apparent transcription factors necessary for imaginal disc morphogenesis. Alleles of the Stubble-stubbloid (Sb-sbd) locus at 89B9-10 act as dominant enhancers of broad alleles of the BR-C. Sb-sbd wild-type products are necessary for appendage elongation. We report, here, on three new loci implicated in imaginal disc morphogenesis based on their genetic interactions with both BR-C and/or Sb-sbd mutants. Enhancer of broad (E(br)) was identified as a dominant enhancer of the br1 allele of the BR-C and is a recessive lethal. Mapping of E(br) has led to the identification of two loci, blistered and l(2)B485, mutants of which interact with E(br) and the Sb-sbd locus. Blistered, but not l(2)B485, interacts strongly with the BR-C. Alleles of the blistered locus are viable and disrupt proper wing disc morphogenesis independent of genetic interactions. All three loci map within the 0.6-map unit interval between the genetic markers speck and Irregular facets and to the cytological region 60C5-6; 60E9-10 at the tip of chromosome 2R. Genetic evidence is consistent with the view that the BR-C regulates blistered.