Poster: Intracellular Signaling

Abs # 820: A new class of regulator of G-protein signalling modulates cell proliferation in Arabidopsis

Presenter:	Chen, Jin-Gui , jgchen@email.unc.edu
Authors	Chen, Jin-Gui  (A)   Willard, Francis S. (B)   Huang, Jirong  (A)   Liang, Jiansheng  (A) (D)  Chasse, Scott A. (C)   Jones, Alan M. (A)   Siderovski, David P. (B)
Affiliations:	(A): The University of North Carolina at Chapel Hill, Department of Biology (B): The University of North Carolina at Chapel Hill, Department of Pharmacology (C): The University of North Carolina at Chapel Hill, Department of Biochemistry and Biophysics (D): Yangzhou University, College of Bioscience and Biotechnology

Conventional heterotrimeric GTP-binding protein complexes are activated by seven-transmembrane (7TM) cell-surface receptors that induce exchange of GTP for GDP by the Ga subunit. Regulators of G-protein signalling (RGS) proteins accelerate the intrinsic GTPase activity of the alpha subunit, thus returning the complex to its basal GDP-bound state. Here we show the first RGS protein identified in Arabidopsis, designated AtRGS1. This protein is predicted to have the structural features of a 7TM receptor as well as a C-terminal RGS-box. The RGS-box of AtRGS1 binds and accelerates the GTPase activity of the Arabidopsis Ga subunit AtGPA1 and complements the pheromone supersensitivity phenotype of the yeast RGS mutant, sst2D. AtRGS1 co-localizes with AtGPA1 in the plasma membrane and accumulates at the nascent cell plate in dividing cells. This polarized localization is maintained in elongated cells. Increase in the activity of AtGPA1, either by loss of AtRGS1 function or by expression of constitutively active, GTPase-deficient AtGPA1, results in increased cell elongation in hypocotyls grown in darkness and increased cell production in roots grown in light. Collectively, these findings suggest that AtRGS1 is a critical modulator of G-protein-coupled plant cell proliferation, where it has been shown that G proteins are directly involved.