Do plants have rhodopsin after all? A mystery of plant G protein-coupled signalling

Considerable physiological and biochemical evidence suggests that plants, like animals, widely use intracellular signalling coupled to heterotrimeric G proteins. Yet, the molecular components of this machinery remained elusive until recently. We overview the work carried out during the last two decades, aimed at identification of the plant proteins involved in G protein-coupled signalling. The completion of the sequencing of the Arabidopsis genome now permits to assess whether plants possess signalling and regulatory components of this machinery corresponding to those known from animals.