title: Evidence for the localization of the Arabidopsis cytokinin receptors AHK3 and AHK4 in the endoplasmic reticulum.
abstract: Cytokinins are hormones that are involved in various processes of plant growth and development. The model of cytokinin signalling starts with hormone perception through membrane-localized histidine kinase receptors. Although the biochemical properties and functions of these receptors have been extensively studied, there is no solid proof of their subcellular localization. Here, cell biological and biochemical evidence for the localization of functional fluorophor-tagged fusions of Arabidopsis histidine kinase 3 (AHK3) and 4 (AHK4), members of the cytokinin receptor family, in the endoplasmic reticulum (ER) is provided. Furthermore, membrane-bound AHK3 interacts with AHK4 in vivo. The ER localization and putative function of cytokinin receptors from the ER have major impacts on the concept of cytokinin perception and signalling, and hormonal cross-talk in plants.
authors.affiliation: Center for Plant Molecular Biology, Department of Plant Physiology, University of Tübingen, Auf der Morgenstelle 1, D-72076 Tübingen, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Caesar
authors.forename: Antje M K
authors.initials: AM
authors.lastname: Thamm
authors.forename: Janika
authors.initials: J
authors.lastname: Witthöft
authors.forename: Kirstin
authors.initials: K
authors.lastname: Elgass
authors.forename: Peter
authors.initials: P
authors.lastname: Huppenberger
authors.forename: Christopher
authors.initials: C
authors.lastname: Grefen
authors.forename: Jakub
authors.initials: J
authors.lastname: Horak
authors.forename: Klaus
authors.initials: K
authors.lastname: Harter
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D000071677:Histidine Kinase; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D011956:Receptors, Cell Surface; D011494:Protein Kinases; D000071677:Histidine Kinase; C000605493:AHK3 protein, Arabidopsis; C421783:WOL protein, Arabidopsis