DROSOPHILA HORMONE-RECEPTOR-38 FUNCTIONS IN METAMORPHOSIS - A ROLE INADULT CUTICLE FORMATION

DHR38 is a member of the steroid receptor superfamily in Drosophila ho mologous to the vertebrate NGFI-B-type orphan receptors. In addition t o binding to specific response elements as a monomer, DHR38 interacts with the USP component of the ecdysone receptor complex in vitro, in y east and in a cell line, suggesting that DHR38 might modulate ecdysone -triggered signals in the fly.We characterized the molecular structure and expression of the Dhr38 gene and initiated an in vivo analysis of its function(s) in development. The Dhr38 transcription unit spans mo re than 40 kb in length, includes four introns, and produces at least four mRNA isoforms differentially expressed in development; two of the se are greatly enriched in the pupal stage and encode nested polypepti des. We characterized four alleles of Dhr38: a P-element enchancer tra p line, l(2)02306, which shows exclusively epidermal staining in the l ate larval, pre-pupal and pupal stages, and three EMS-induced alleles. Dhr38 alleles cause localized fragility and rupturing of the adult cu ticle, demonstrating that Dhr38 plays an important role in late stages of epidermal metamorphosis.