Epithelial morphogenesis is contingent upon cell shape changes. Cell shape changes are the driving force for the metamorphosis of the adult Drosophila leg from the leg imaginal disc precursor. Genetic analysis has identified several Drosophila genes involved in regulating cell shape changes during leg disc morphogenesis. These include members of the RhoA signaling pathway and the product of the Stubble-stubbloid (Sb-sbd) locus, a transmembrane serine protease. Mutations in the Sb-sbd gene interact genetically with the members of the RhoA signaling pathway, however the nature of the relationship between Sb-sbd serine protease activity and RhoA signaling is not understood. To identify additional components of the RhoA signaling pathway that may help us to understand the role of the Sb-sbd protease in RhoA signaling the Drosophila genome was systematically scanned for genes that interact with Sb-sbd and RhoA mutations using deletions/deficiencies of specified regions of each chromosome. A total of 201 deficiencies uncovering approximately 84.9-91% of the euchromatic genome and spanning the X, second, and third chromosoms were tested. Of the 201 deficiencies tested, five putative interacting genetic regions and one gene within these deficiencies were identified. The candidate gene Eip78C encodes a nuclear steroid hormone receptor previously identified as having an important role in metamorphosis.