We have isolated cDNAs for a gene coding for a G protein alpha subunit from tomato (Lycopersicon esculentum, cv. VF36). This gene, named TGA1, was isolated using a cDNA of the Arabidopsis thaliana G protein alpha subunit-encoding gene, GPA1, as a DNA probe. The sequences of four cDNA clones indicate that the deduced amino acid (aa) sequence of the gene product (TG alpha 1) has 384 aa (44906 Da). The predicted TG alpha 1 protein exhibits similarity to all known G protein alpha subunits. The aa are 84.6% identical and 93% similar (identical and conservative changes) to A. thaliana GP alpha 1, and 34% identical and 59% similar to mammalian transducins. Furthermore, it has all of the consensus regions for a GTP-binding protein. Finally, hybridizations of tomato genomic DNA indicate that TGA1 is a single-copy gene.