title: Involvement of the mitogen-activated protein kinase SIMK in regulation of root hair tip growth.
abstract: Mitogen-activated protein kinases (MAPKs) are involved in stress signaling to the actin cytoskeleton in yeast and animals. We have analyzed the function of the stress-activated alfalfa MAP kinase SIMK in root hairs. In epidermal cells, SIMK is predominantly nuclear. During root hair formation, SIMK was activated and redistributed from the nucleus into growing tips of root hairs possessing dense F-actin meshworks. Actin depolymerization by latrunculin B resulted in SIMK relocation to the nucleus. Conversely, upon actin stabilization with jasplakinolide, SIMK co-localized with thick actin cables in the cytoplasm. Importantly, latrunculin B and jasplakinolide were both found to activate SIMK in a root-derived cell culture. Loss of tip-focused SIMK and actin was induced by the MAPK kinase inhibitor UO 126 and resulted in aberrant root hairs. UO 126 inhibited targeted vesicle trafficking and polarized growth of root hairs. In contrast, overexpression of gain-of-function SIMK induced rapid tip growth of root hairs and could bypass growth inhibition by UO 126. These data indicate that SIMK plays a crucial role in root hair tip growth.
authors.affiliation: Institute of Microbiology and Genetics, Vienna Biocenter, University of Vienna, Dr Bohrgasse 9, A-1030 Vienna, Austria.
authors.forename: Jozef
authors.initials: J
authors.lastname: Samaj
authors.forename: Miroslav
authors.initials: M
authors.lastname: Ovecka
authors.forename: Andrej
authors.initials: A
authors.lastname: Hlavacka
authors.forename: Fatma
authors.initials: F
authors.lastname: Lecourieux
authors.forename: Irute
authors.initials: I
authors.lastname: Meskiene
authors.forename: Irene
authors.initials: I
authors.lastname: Lichtscheidl
authors.forename: Peter
authors.initials: P
authors.lastname: Lenart
authors.forename: Ján
authors.initials: J
authors.lastname: Salaj
authors.forename: Dieter
authors.initials: D
authors.lastname: Volkmann
authors.forename: László
authors.initials: L
authors.lastname: Bögre
authors.forename: Frantisek
authors.initials: F
authors.lastname: Baluska
authors.forename: Heribert
authors.initials: H
authors.lastname: Hirt
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000032:analysis; D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002070:Butadienes / Q000494:pharmacology; D002467:Cell Nucleus / Q000378:metabolism; D016764:Cell Polarity; D022081:Cell Surface Extensions / Q000201:enzymology; D003593:Cytoplasm / Q000378:metabolism; D047630:Depsipeptides; D004789:Enzyme Activation / Q000187:drug effects; D020935:MAP Kinase Signaling System / Q000187:drug effects; D000455:Medicago sativa / Q000201:enzymology* / Q000254:growth & development; D018715:Microscopy, Video; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D009570:Nitriles / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010940:Plant Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development / Q000648:ultrastructure; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D014026:Nicotiana / Q000201:enzymology* / Q000254:growth & development
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002070:Butadienes; D047630:Depsipeptides; D009570:Nitriles; D010456:Peptides, Cyclic; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D013844:Thiazoles; D053778:Thiazolidines; C113580:U 0126; C057531:jasplakinolide; D020928:Mitogen-Activated Protein Kinases; C419564:salt stress-induced MAP kinase; D020929:Mitogen-Activated Protein Kinase Kinases; C037068:latrunculin B