title: Rho-GTPase-dependent filamentous actin dynamics coordinate vesicle targeting and exocytosis during tip growth.
abstract: 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.
authors.affiliation: Department of Botany and Plant Sciences, Institute for Integrative Genome Biology, University of California, Riverside, Riverside, CA 92521, USA.
authors.forename: Yong Jik
authors.initials: YJ
authors.lastname: Lee
authors.forename: Amy
authors.initials: A
authors.lastname: Szumlanski
authors.forename: Erik
authors.initials: E
authors.lastname: Nielsen
authors.forename: Zhenbiao
authors.initials: Z
authors.lastname: Yang
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism; D002352:Carrier Proteins; D004789:Enzyme Activation; D005089:Exocytosis; D036681:Fluorescence Recovery After Photobleaching; D019204:GTP-Binding Proteins / Q000378:metabolism; D008954:Models, Biological; D053205:Pollen Tube / Q000166:cytology* / Q000201:enzymology* / Q000254:growth & development; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology / Q000201:enzymology / Q000254:growth & development*; D022161:Transport Vesicles / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C499716:RIC4 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D019204:GTP-Binding Proteins; C501663:ROP1 protein, Arabidopsis; D020741:rho GTP-Binding Proteins