title: Exclusion of a proton ATPase from the apical membrane is associated with cell polarity and tip growth in Nicotiana tabacum pollen tubes.
abstract: Polarized growth in pollen tubes results from exocytosis at the tip and is associated with conspicuous polarization of Ca(2+), H(+), K(+), and Cl(-) -fluxes. Here, we show that cell polarity in Nicotiana tabacum pollen is associated with the exclusion of a novel pollen-specific H(+)-ATPase, Nt AHA, from the growing apex. Nt AHA colocalizes with extracellular H(+) effluxes, which revert to influxes where Nt AHA is absent. Fluorescence recovery after photobleaching analysis showed that Nt AHA moves toward the apex of growing pollen tubes, suggesting that the major mechanism of insertion is not through apical exocytosis. Nt AHA mRNA is also excluded from the tip, suggesting a mechanism of polarization acting at the level of translation. Localized applications of the cation ionophore gramicidin A had no effect where Nt AHA was present but acidified the cytosol and induced reorientation of the pollen tube where Nt AHA was absent. Transgenic pollen overexpressing Nt AHA-GFP developed abnormal callose plugs accompanied by abnormal H(+) flux profiles. Furthermore, there is no net flux of H(+) in defined patches of membrane where callose plugs are to be formed. Taken together, our results suggest that proton dynamics may underlie basic mechanisms of polarity and spatial regulation in growing pollen tubes.
authors: Instituto Gulbenkian de Ciência, Centro de Biologia do Desenvolvimento, 2780-156 Oeiras, Portugal.
authors: Ana C
authors: AC
authors: Certal
authors: Ricardo B
authors: RB
authors: Almeida
authors: Lara M
authors: LM
authors: Carvalho
authors: Eric
authors: E
authors: Wong
authors: Nuno
authors: N
authors: Moreno
authors: Erwan
authors: E
authors: Michard
authors: Jorge
authors: J
authors: Carneiro
authors: Joaquín
authors: J
authors: Rodriguéz-Léon
authors: Hen-Ming
authors: HM
authors: Wu
authors: Alice Y
authors: AY
authors: Cheung
authors: José A
authors: JA
authors: Feijó
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology* / Q000378:metabolism; D016764:Cell Polarity; D036681:Fluorescence Recovery After Photobleaching; D018506:Gene Expression Regulation, Plant; D017403:In Situ Hybridization; D030821:Plants, Genetically Modified; D053205:Pollen Tube / Q000166:cytology / Q000201:enzymology / Q000254:growth & development*; D011522:Protons; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics
chemical_list: D011522:Protons; D000251:Adenosine Triphosphatases