title: A Rho family GTPase controls actin dynamics and tip growth via two counteracting downstream pathways in pollen tubes.
abstract: Tip growth in neuronal cells, plant cells, and fungal hyphae is known to require tip-localized Rho GTPase, calcium, and filamentous actin (F-actin), but how they interact with each other is unclear. The pollen tube is an exciting model to study spatiotemporal regulation of tip growth and F-actin dynamics. An Arabidopsis thaliana Rho family GTPase, ROP1, controls pollen tube growth by regulating apical F-actin dynamics. This paper shows that ROP1 activates two counteracting pathways involving the direct targets of tip-localized ROP1: RIC3 and RIC4. RIC4 promotes F-actin assembly, whereas RIC3 activates Ca(2+) signaling that leads to F-actin disassembly. Overproduction or depletion of either RIC4 or RIC3 causes tip growth defects that are rescued by overproduction or depletion of RIC3 or RIC4, respectively. Thus, ROP1 controls actin dynamics and tip growth through a check and balance between the two pathways. The dual and antagonistic roles of this GTPase may provide a unifying mechanism by which Rho modulates various processes dependent on actin dynamics in eukaryotic cells.
authors.affiliation: Center for Plant Cell Biology, Institute for Integrative Genome Biology, Department of Botany and Plant Sciences, University of California, Riverside 92521, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Gu
authors.forename: Ying
authors.initials: Y
authors.lastname: Fu
authors.forename: Peter
authors.initials: P
authors.lastname: Dowd
authors.forename: Shundai
authors.initials: S
authors.lastname: Li
authors.forename: Vanessa
authors.initials: V
authors.lastname: Vernoud
authors.forename: Simon
authors.initials: S
authors.lastname: Gilroy
authors.forename: Zhenbiao
authors.initials: Z
authors.lastname: Yang
mesh_terms: D000199:Actins / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins; D032306:Petunia / Q000201:enzymology / Q000254:growth & development; D011058:Pollen / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D015398:Signal Transduction / Q000502:physiology*; D014026:Nicotiana / Q000201:enzymology / Q000254:growth & development
chemical_list: D000199:Actins; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C499716:RIC4 protein, Arabidopsis; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C501663:ROP1 protein, Arabidopsis