[G-protein-coupled receptors, heterotrimeric G-proteins and protein effectors in plants]

The superfamily of G-protein-coupled receptors (GPCRs) is one of the largest and most diverse family of proteins in mammals. Plants, in contrast to animals, have a greatly simplified repertoire of GPCRs. To date, only AtGCR1 and AtRGS1 have been shown to physically interacts with a plant G-protein. Also, the number of G-protein complex components in plants is dramatically less than in other Eukaryotes. Only one prototypical Ga subunit, one Gbeta and two Ggamma subunits have been identified in A. thaliana and rice. Similarly, there are few known downstream effectors that physicaly interact with either the plant Ga subunit or the Gbetagamma dimer. The best-characterized effector is phospholipase D (PLDalpha1). Besides, the potential Galpha effectors are: cupin-domain protein designated as Atpirin1, prephenate dehydratase--a cytosolic enzyme involved in regulation of the shikimate pathway, and THF1 protein located in plastid membranes. Indirect evidences suggest that Galpha may interact with ion channels and phospholipases A2 and C, whereas Gbetagamma dimer supposedly interacts with a Golgi-localized hexose transporter.