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IN BRIEF

G Protein Subunits Provide Functional Selectivity

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Heterotrimeric G protein signaling mediated by transmembrane G protein–coupled receptors (GPCRs) is ubiquitous among eukaryotes. The G protein heterotrimer consists of , ß, and subunits bound to specific GPCRs. Ligand binding to the GPCR induces a change in G and the exchange of bound GDP for GTP, which turns the G subunit and the Gß dimer into two functional signaling units. Intrinsic GTPase activity of G returns the heterotrimer back to the inactive form. Diversity and selectivity in G protein signaling in mammals is provided by the existence of gene families for each of the G protein subunits. Humans contain at least 23 G subunits, 6 Gß subunits, and 12 G subunits, which show selectivity in their interactions and differences in tissue specificity. By contrast, Arabidopsis and a number of other plants contain one G subunit, one Gß subunit, and two G subunits (some legumes have two G subunits). Evidence is emerging that G and Gß are involved in signaling in specific and independent pathways in plants. Trusov et al. (pages 1235–1250) show that the two G subunits in Arabidopsis provide functional selectivity to Gß signaling. Genetic analyses reveal that the two G subunits provide specificity to the Gß dimer action in at least three different signaling pathways: fungal resistance, glucose sensing, and auxin-mediated lateral root development.

View larger version (48K): [in this window] [in a new window] [as a PowerPoint slide]   Distinct patterns of expression of the two G genes, AGG1 and AGG2, in root tissue, relative to expression of AGB1, which encodes the Gß subunit.

www.plantcell.org/cgi/doi/10.1105/tpc.107.190411

Related articles in Plant Cell:

Heterotrimeric G Protein Subunits Provide Functional Selectivity in Gß Dimer Signaling in Arabidopsis

Yuri Trusov, James Edward Rookes, Kimberley Tilbrook, David Chakravorty, Michael Glenn Mason, David Anderson, Jin-Gui Chen, Alan M. Jones, and José Ramón Botella
Plant Cell 2007 19: 1235-1250. [Abstract] [Full Text]  

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