A DROSOPHILA G-PROTEIN ALPHA-SUBUNIT, GF-ALPHA, EXPRESSED IN A SPATIALLY AND TEMPORALLY RESTRICTED PATTERN DURING DROSOPHILA DEVELOPMENT

Heterotrimeric guanine nucleotide binding proteins (G proteins) couple receptors for extracellular signals to intracellular second messenger-generating systems. Previous studies have shown that G-protein alpha subunits (Galpha) are expressed in a spatially and temporally restricted manner during Drosophila embryogenesis and, thus, may be responsible for mediating developmental interactions. We have used the polymerase chain reaction to search for specific Galpha subunits that function primarily during development and not in the adult fly. Using poly(A)+ RNA isolated from early pupae (day 1), we have isolated a cDNA coding for a fly Galpha subunit, designated Gfalpha. This subunit is 30-38% identical to previously described vertebrate and Drosophila Galpha subunits and appears to define an additional family of Galpha proteins. Gfalpha transcripts are expressed primarily during embryonic, larval, and early pupal stages and only at low levels in adult flies. In situ hybridization studies indicate that Gfalpha transcripts are expressed maternally and later during embryogenesis primarily in the developing midgut and transiently in the amnioserosa. The Gfalpha gene has been characterized and mapped to position 73B of the Drosophila genome.