A Seven-Transmembrane RGS Protein That Modulates Plant Cell Proliferation
Jin-Gui Chen,1 Francis S. Willard,2 Jirong Huang,1 Jiansheng Liang,1* Scott A. Chasse,3 Alan M. Jones,1 David P. Siderovski2

G protein–coupled receptors (GPCRs) at the cell surface activate heterotrimeric G proteins by inducing the G protein alpha (G) subunit to exchange guanosine diphosphate for guanosine triphosphate. Regulators of G protein signaling (RGS) proteins accelerate the deactivation of G subunits to reduce GPCR signaling. Here we identified an RGS protein (AtRGS1) in Arabidopsis that has a predicted structure similar to a GPCR as well as an RGS box with GTPase accelerating activity. Expression of AtRGS1 complemented the pheromone supersensitivity phenotype of a yeast RGS mutant, sst2. Loss of AtRGS1 increased the activity of the Arabidopsis G subunit, resulting in increased cell elongation in hypocotyls in darkness and increased cell production in roots grown in light. These findings suggest that AtRGS1 is a critical modulator of plant cell proliferation.

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