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| The EMBO Journal
(2001) 20, 2779–2788, doi:10.1093/emboj/20.11.2779 |
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| Arabidopsis thaliana Rop GTPases are localized to tips of root hairs and control polar growth |
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Arthur J Molendijk1, 2, Friedrich Bischoff1, Chadalavada S V Rajendrakumar1, Ji í Friml1, Markus Braun3, Simon Gilroy4 and Klaus Palme1, 2
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1 Max-Delbrück-Laboratorium in der Max-Planck-Gesellschaft, D-53115 Bonn, Germany 2 Max-Planck Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, D-50829 Köln, Germany 3 Botanisches Institut, Zellbiologie der Pflanzen, Universität Bonn, Venusbergweg 22, D-53115 Bonn, Germany 4 Department of Biology, The Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802, USA To whom correspondence should be addressed Klaus Palme, palme@mpiz-koeln.mpg.de Received 8 February 2001; Revised 3 April 2001; Accepted 3 April 2001. |
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| Abstract |
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| Plants contain a novel unique subfamily of Rho GTPases, vital components of cellular signalling networks. Here we report a general role for some members of this family in polarized plant growth processes. We show that Arabidopsis AtRop4 and AtRop6 encode functional GTPases with similar intrinsic GTP hydrolysis rates. We localized AtRop proteins in root meristem cells to the cross-wall and cell plate membranes. Polar localization of AtRops in trichoblasts specifies the growth sites for emerging root hairs. These sites were visible before budding and elongation of the Arabidopsis root hair when AtRops accumulated at their tips. Expression of constitutively active AtRop4 and AtRop6 mutant proteins in root hairs of transgenic Arabidopsis plants abolished polarized growth and delocalized the tip-focused Ca2+ gradient. Polar localization of AtRops was inhibited by brefeldin A, but not by other drugs such as latrunculin B, cytochalasin D or caffeine. Our results demonstrate a general function of AtRop GTPases in tip growth and in polar diffuse growth. |
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| Keywords: Arabidopsis thaliana, polarity, Rho GTPase, root development, root hair |
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