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Published online June 30, 2008
doi:10.1083/jcb.200801086
The Journal of Cell Biology, Vol. 181, No. 7, 1155-1168
The Rockefeller University Press, 0021-9525 $30.00
© 2008 Lee et al.
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Article

 Rho-GTPase–dependent filamentous actin dynamics coordinate vesicle targeting and exocytosis during tip growth

Yong Jik Lee1,2, Amy Szumlanski3, Erik Nielsen3, and Zhenbiao Yang1,2

1 Department of Botany and Plant Sciences and 2 Center for Plant Cell Biology, Institute for Integrative Genome Biology, University of California, Riverside, Riverside, CA 92521
3 Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109

Correspondence to Zhenbiao Yang: yang{at}ucr.edu

The dynamic activity of tip-localized filamentous actin (F-actin) in pollen tubes is controlled by counteracting RIC4 and RIC3 pathways downstream of the ROP1 guanosine triphosphatase promoting actin assembly and disassembly, respectively. We show here that ROP1 activation is required for both the polar accumulation and the exocytosis of vesicles at the plasma membrane apex. The apical accumulation of exocytic vesicles oscillated in phase with, but slightly behind, apical actin assembly and was enhanced by overexpression of RIC4. However, RIC4 overexpression inhibited exocytosis, and this inhibition could be suppressed by latrunculin B treatment or RIC3 overexpression. We conclude that RIC4-dependent actin assembly is required for polar vesicle accumulation, whereas RIC3-mediated actin disassembly is required for exocytosis. Thus ROP1-dependent F-actin dynamics control tip growth through spatiotemporal coordination of vesicle targeting and exocytosis.

Abbreviations used in this paper: BFA, brefeldin A; CA, constitutively active; DN, dominant-negative; LatB, latrunculin B; MT, microtubule; PM, plasma membrane; RLK, receptor-like kinase.

© 2008 Lee et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jcb.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).


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