Restricted spatial and temporal expression of G-protein alpha subunits during Drosophila embryogenesis

Of the known signal transduction mechanisms, the most evolutionarily ancient is mediated by a family of heterotrimeric guanine nucleotide binding proteins or G proteins. In simple organisms, this form of sensory transduction is used exclusively to convey signals of developmental consequence. In metazoan organisms, however, the developmental role of G-protein-coupled sensory transduction has been more difficult to elucidate because of the wide variety of signals (peptides, small molecules, odorants, hormones, etc.) that use this form of sensory transduction. We have begun to examine the role of G-protein-coupled signaling during development by investigating the expression during Drosophila embryogenesis of a limited set of G proteins. Since these proteins are a common component of all G-protein-coupled signaling systems, their developmental pattern of expression should indicate when and where programmed changes in gene activity are initiated by, or involve the participation of, G-protein-coupled signaling events. We have focused on the spatial and temporal expression pattern of three different Drosophila G-protein alpha subunits by northern blot analysis, in situ hybridization and immunocytochemistry using antibodies directed to peptides specifically found in each alpha subunit. From the spatial and temporal restriction of the expression of each protein, our results suggest that different forms of G-protein-coupled sensory transduction may mediate developmental interactions during both early and late stages of embryogenesis and may participate in a variety of specific developmental processes such as the establishment of embryonic position, the ontogeny of the nervous system and organogenesis.