FOX, Samuel *; VON KALM , Laurence; University of Central Florida, Orlando: Preliminary characterization of three genes with potential roles linking the RhoA signaling pathway to the ecdysone response in Drosophila epithelia

Holometabolous insects undergo metamorphosis involving the destruction of existing larval tissues and the reformation of new cell populations to create adult organs and tissues. During metamorphosis, flattened, undifferentiated epithelial cells comprising the Drosophila leg imaginal disc undergo morphogenetic cell shape changes resulting in a tubular leg structure. Morphogenesis of imaginal disc epithelia is regulated both by the steroid hormone 20-hydroxyecdysone (ecdysone) and the RhoA GTPase signaling pathway. However, the mechanism of interaction between the RhoA and ecdysone signaling hierarchies is poorly understood. We have identified mutations in three genes, 12-5, 18-5, and 31-6, with roles in the morphogenesis of leg epithelia. These mutations exhibit leg defects and interact genetically with each other, as well as mutations in RhoA pathway members including the non-muscle myosin II heavy chain. Genetic interactions are also observed with mutations in a hormone-regulated transmembrane serine protease suggesting that the 12-5, 18-5, and 31-6 loci may link hormone and RhoA signaling responses. Lethal phase analysis indicates that 12-5 and 18-5 homozygous mutants fail to complete pupal development, whereas 31-6 homozygotes are semi-viable. Our current focus is the 18-5 gene. To identify this gene we are using a mapping technique that will allow us to determine the precise molecular location of the 18-5 locus within the Drosophila genome sequence. This work is increasing our understanding of the link between intracellular signaling pathways and systemic hormone signaling during insect metamorphosis.