title: The Arabidopsis Rab GTPase RabA4b localizes to the tips of growing root hair cells.
abstract: Spatial and temporal control of cell wall deposition plays a unique and critical role during growth and development in plants. To characterize membrane trafficking pathways involved in these processes, we have examined the function of a plant Rab GTPase, RabA4b, during polarized expansion in developing root hair cells. Whereas a small fraction of RabA4b cofractionated with Golgi membrane marker proteins, the majority of this protein labeled a unique membrane compartment that did not cofractionate with the previously characterized trans-Golgi network syntaxin proteins SYP41 and SYP51. An enhanced yellow fluorescent protein (EYFP)-RabA4b fusion protein specifically localizes to the tips of growing root hair cells in Arabidopsis thaliana. Tip-localized EYFP-RabA4b disappears in mature root hair cells that have stopped expanding, and polar localization of the EYFP-RabA4b is disrupted by latrunculin B treatment. Loss of tip localization of EYFP-RabA4b was correlated with inhibition of expansion; upon washout of the inhibitor, root hair expansion recovered only after tip localization of the EYFP-RabA4b compartments was reestablished. Furthermore, in mutants with defective root hair morphology, EYFP-RabA4b was improperly localized or was absent from the tips of root hair cells. We propose that RabA4b regulates membrane trafficking through a compartment involved in the polarized secretion of cell wall components in plant cells.
authors.affiliation: Donald Danforth Plant Science Center, St. Louis, Missouri 63132, USA.
authors.forename: Mary L
authors.initials: ML
authors.lastname: Preuss
authors.forename: Jannie
authors.initials: J
authors.lastname: Serna
authors.forename: Tanya G
authors.initials: TG
authors.lastname: Falbel
authors.forename: Sebastian Y
authors.initials: SY
authors.lastname: Bednarek
authors.forename: Erik
authors.initials: E
authors.lastname: Nielsen
mesh_terms: D000199:Actins / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology* / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D016764:Cell Polarity; D003599:Cytoskeleton / Q000378:metabolism; D020869:Gene Expression Profiling; D007425:Intracellular Membranes / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D018517:Plant Roots / Q000166:cytology* / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D021381:Protein Transport; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D000199:Actins; D020691:rab GTP-Binding Proteins