Molecular cloning and characterization of cDNAs encoding heterotrimeric G protein alpha and beta subunits from potato (Solanum tuberosum L.).

Two cDNAs, STGA2 and STGB2, that encode heterotrimeric G protein alpha and beta subunit proteins, respectively, were cloned from an early tuber cDNA library of potato (Solanum tuberosum cv. Superior). The cDNA of STGA2 encoded 384 amino acids, which showed 75-98% identities to plant Ga-subunits; STGB2 encoded 377 amino acids, which showed 83-92% identities to plant Gbeta-subunits. The transcript levels of the two genes were abundant in leaves, shoots, axially buds, unopened flowers, and active growing sprouts. However, the transcripts were barely detectable in roots. The expressions of STGA2 and STGB2 were up-regulated by light. Interestingly, the STGA2 and STGB2 gene expression showed synchronous patterns in the examined organs. During the early tuber development, the transcripts of STGA2 and STGB2 were abundant in unswollen stolons, swollen stolons, and new tubers, but were undetected in matured tubers. This indicates that potato Galpha- and beta-subunit genes are developmentally regulated. Based on these observations, we propose that heterotrimeric G proteins may be involved in the signaling pathway during potato tuber development.