First published online May 5, 2006; 10.1104/pp.106.079202
Plant Physiology 141:887-897 (2006)
© 2006 American Society of Plant Biologists
CELL BIOLOGY AND SIGNAL TRANSDUCTION
Differential Roles of Arabidopsis Heterotrimeric G-Protein Subunits in Modulating Cell Division in Roots1,[W]
Jin-Gui Chen,
Yajun Gao and
Alan M. Jones*
Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada (J.-G.C., Y.G.); College of Resources and Environment, Northwest Agricultural and Forestry University, Yangling, Shaanxi 712100, China (Y.G.); and Departments of Biology and Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599–3280 (J.-G.C., A.M.J.)
Signaling through heterotrimeric G proteins is conserved in diverse eukaryotes. Compared to vertebrates, the simpler repertoire of G-protein complex and accessory components in Arabidopsis (Arabidopsis thaliana) offers a unique advantage over all other multicellular, genetic-model systems for dissecting the mechanism of G-protein signal transduction. One of several biological processes that the G-protein complex regulates in Arabidopsis is cell division. We determined cell production rate in the primary root and the formation of lateral roots in Arabidopsis to define individually the types of modulatory roles of the respective G-protein  - and  -subunits, as well as the heterotrimer in cell division. The growth rate of the root is in part a consequence of cell cycle maintenance in the root apical meristem (RAM), while lateral root production requires meristem formation by founder pericycle cells. Thus, a comparison of these two parameters in various genetic backgrounds enabled dissection of the role of the G-protein subunits in modulation of cell division, both in maintenance and initiation. Cell production rates were determined for the RAM and lateral root formation in gpa1 (Arabidopsis G-protein -subunit) and agb1 (Arabidopsis G-protein -subunit) single and double mutants, and in transgenic lines overexpressing GPA1 or AGB1 in agb1 or gpa1 mutant backgrounds, respectively. We found in the RAM that the heterotrimeric complex acts as an attenuator of cell proliferation, whereas the GTP-bound form of the G-subunit's role is a positive modulator. In contrast, for the formation of lateral roots, the G -dimer acts largely independently of the G-subunit to attenuate cell division. These results suggest that Arabidopsis heterotrimeric G-protein subunits have differential and opposing roles in the modulation of cell division in roots.
1 This work was supported by grants from the National Institutes of Health (grant no. GM65989–01) and the National Science Foundation (grant no. MCB–0209711) to A.M.J. Work in J.-G.C.'s lab is supported by the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the British Columbia Ministry of Advanced Education, and the University of British Columbia. Y.G. is supported by a scholarship from the China Scholarship Council.
The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Alan M. Jones (alan_jones{at}unc.edu).
[W] The online version of this article contains Web-only data.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.106.079202.
* Corresponding author; e-mail alan_jones{at}unc.edu; fax 919–962–1625.
Received February 13, 2006;
returned for revision May 1, 2006;
accepted May 1, 2006.
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