G protein-coupled receptor activity is controlled by a number of factors including phosphorylation by the family of G protein-coupled receptor kinases. This phosphorylation is an important first step in desensitization of the receptor. The role of G protein-coupled receptor kinases in cellular physiology has been extensively studied, but less is known about their role in development. A Drosophila G protein-coupled receptor kinase mutant (gprk2(6936)) has developmental defects throughout the life cycle of the fly. This allows the opportunity to address G protein-coupled receptor kinase's function in vivo. Using a series of transgenic flies in which the wild type Gprk2 gene is expressed under the control of the hsp70 or germline-specific promoter, in combination with germline mosaic analysis, we have made a detailed analysis of the developmental stages in which Gprk2 expression is required and the tissues that must express Gprk2 for rescue of the gprk2(6936) mutant. These studies have shown that Gprk2 expression is required in the germline for proper formation of the anterior egg structures and for early embryogenesis. In the absence of maternal Gprk2 activity, zygotic expression affords partial rescue of egg hatching, suggesting that Gprk2 also plays an important role in late embryogenesis. (C) 2002 Elsevier Science (USA). All rights reserved.