title: Plasma membrane H+-ATPase is involved in auxin-mediated cell elongation during wheat embryo development.
abstract: Previous investigations suggested that specific auxin spatial distribution due to auxin movements to particular embryonic regions was important for normal embryonic pattern formation. To gain information on the molecular mechanism(s) by which auxin acts to direct pattern formation in specific embryonic regions, the role of a plasma membrane (PM) ATPase was evaluated as downstream target of auxin in the present study. Western-blot analysis revealed that the PM H(+)-ATPase expression level was significantly increased by auxin in wheat (Triticum aestivum) embryos (two-three times increase). In bilaterally symmetrical embryos, the spatial expression pattern of the PM H(+)-ATPase correlates with the distribution pattern of the auxin analog, tritiated 5-azidoindole-3-acetic acid. A strong immunosignal was observed in the abaxial epidermis of the scutellum and in the epidermal cells at the distal tip of this organ. Pseudoratiometric analysis using a fluorescent pH indicator showed that the pH in the apoplast of the cells expressing the PM H(+)-ATPase was in average more acidic than the apoplastic pH of nonexpressing cells. Cellulose staining of living embryos revealed that cells of the scutellum abaxial epidermis expressing the ATPase were longer than the scutellum adaxial epidermal cells, where the protein was not expressed. Our data indicate that auxin activates the proton pump resulting in apoplastic acidification, a process contributing to cell wall loosening and elongation of the scutellum. Therefore, we suggest that the PM H(+)-ATPase is a component of the auxin-signaling cascade that may direct pattern formation in embryos.
authors.affiliation: Institute for Biology II, Department of Cell Biology, Albert-Ludwigs-University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Rober-Kleber
authors.forename: Jolana T P
authors.initials: JT
authors.lastname: Albrechtová
authors.forename: Sonja
authors.initials: S
authors.lastname: Fleig
authors.forename: Norbert
authors.initials: N
authors.lastname: Huck
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Michalke
authors.forename: Edgar
authors.initials: E
authors.lastname: Wagner
authors.forename: Volker
authors.initials: V
authors.lastname: Speth
authors.forename: Gunther
authors.initials: G
authors.lastname: Neuhaus
authors.forename: Christiane
authors.initials: C
authors.lastname: Fischer-Iglesias
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000201:enzymology / Q000648:ultrastructure; D048429:Cell Size / Q000187:drug effects; D002473:Cell Wall / Q000201:enzymology / Q000648:ultrastructure; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D007210:Indoleacetic Acids / Q000494:pharmacology*; D016253:Microscopy, Immunoelectron; D010937:Plant Growth Regulators / Q000494:pharmacology*; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D012639:Seeds / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D014908:Triticum / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development
chemical_list: D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D006180:Proton-Translocating ATPases