Abstract
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 (G alpha) 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 G alpha 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 G alpha subunit, designated Gf alpha. This subunit is 30-38% identical to previously described vertebrate and Drosophila G alpha subunits and appears to define an additional family of G alpha proteins. Gf alpha 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 Gf alpha transcripts are expressed maternally and later during embryogenesis primarily in the developing midgut and transiently in the amnioserosa. The Gf alpha gene has been characterized and mapped to position 73B of the Drosophila genome.
