title: Gain-of-Function Mutants of the Cytokinin Receptors AHK2 and AHK3 Regulate Plant Organ Size, Flowering Time and Plant Longevity.
abstract: The phytohormone cytokinin is a regulator of numerous processes in plants. In Arabidopsis (Arabidopsis thaliana), the cytokinin signal is perceived by three membrane-located receptors named ARABIDOPSIS HISTIDINE KINASE2 (AHK2), AHK3, and AHK4/CRE1. How the signal is transmitted across the membrane is an entirely unknown process. The three receptors have been shown to operate mostly in a redundant fashion, and very few specific roles have been attributed to single receptors. Using a forward genetic approach, we isolated constitutively active gain-of-function variants of theAHK2andAHK3genes, namedrepressor of cytokinin deficiency2(rock2) androck3, respectively. It is hypothesized that the structural changes caused by these mutations in the sensory and adjacent transmembrane domains emulate the structural changes caused by cytokinin binding, resulting in domain motion propagating the signal across the membrane. Detailed analysis of lines carryingrock2androck3alleles revealed how plants respond to locally enhanced cytokinin signaling. Early flowering time, a prolonged reproductive growth phase, and, thereby, increased seed yield suggest that cytokinin regulates various aspects of reproductive growth. In particular, it counteracts the global proliferative arrest, a correlative inhibition of maternal growth by seeds, an as yet unknown activity of the hormone.
authors.affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany (I.B., H.J., T.W., T.S.).|Laboratory of Growth Regulators, Palacký University, and Institute of Experimental Botany, ASCR, CZ-78371 Olomouc, Slechtitelu 11, Czech Republic (O.N., M.S.); and.|Institute of Plant Sciences, Department of Plant Physiology, University of Graz, 8010 Graz, Austria (T.W.).
authors.forename: Isabel
authors.initials: I
authors.lastname: Bartrina
authors.affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany (I.B., H.J., T.W., T.S.).|Laboratory of Growth Regulators, Palacký University, and Institute of Experimental Botany, ASCR, CZ-78371 Olomouc, Slechtitelu 11, Czech Republic (O.N., M.S.); and.|Institute of Plant Sciences, Department of Plant Physiology, University of Graz, 8010 Graz, Austria (T.W.).
authors.forename: Helen
authors.identifier: 0000-0003-3452-0154
authors.initials: H
authors.lastname: Jensen
authors.affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany (I.B., H.J., T.W., T.S.).|Laboratory of Growth Regulators, Palacký University, and Institute of Experimental Botany, ASCR, CZ-78371 Olomouc, Slechtitelu 11, Czech Republic (O.N., M.S.); and.|Institute of Plant Sciences, Department of Plant Physiology, University of Graz, 8010 Graz, Austria (T.W.).
authors.forename: Ondřej
authors.initials: O
authors.lastname: Novák
authors.affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany (I.B., H.J., T.W., T.S.).|Laboratory of Growth Regulators, Palacký University, and Institute of Experimental Botany, ASCR, CZ-78371 Olomouc, Slechtitelu 11, Czech Republic (O.N., M.S.); and.|Institute of Plant Sciences, Department of Plant Physiology, University of Graz, 8010 Graz, Austria (T.W.).
authors.forename: Miroslav
authors.identifier: 0000-0002-2806-794X
authors.initials: M
authors.lastname: Strnad
authors.affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany (I.B., H.J., T.W., T.S.); tower@zedat.fu-berlin.de thomas.schmuelling@fu-berlin.de.|Laboratory of Growth Regulators, Palacký University, and Institute of Experimental Botany, ASCR, CZ-78371 Olomouc, Slechtitelu 11, Czech Republic (O.N., M.S.); and tower@zedat.fu-berlin.de thomas.schmuelling@fu-berlin.de.|Institute of Plant Sciences, Department of Plant Physiology, University of Graz, 8010 Graz, Austria (T.W.) tower@zedat.fu-berlin.de thomas.schmuelling@fu-berlin.de.
authors.forename: Tomáš
authors.identifier: 0000-0001-5179-0581
authors.initials: T
authors.lastname: Werner
authors.affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany (I.B., H.J., T.W., T.S.); tower@zedat.fu-berlin.de thomas.schmuelling@fu-berlin.de.|Laboratory of Growth Regulators, Palacký University, and Institute of Experimental Botany, ASCR, CZ-78371 Olomouc, Slechtitelu 11, Czech Republic (O.N., M.S.); and tower@zedat.fu-berlin.de thomas.schmuelling@fu-berlin.de.|Institute of Plant Sciences, Department of Plant Physiology, University of Graz, 8010 Graz, Austria (T.W.) tower@zedat.fu-berlin.de thomas.schmuelling@fu-berlin.de.
authors.forename: Thomas
authors.identifier: 0000-0001-5532-9645
authors.initials: T
authors.lastname: Schmülling
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics*; D003583:Cytokinins / Q000378:metabolism / Q000494:pharmacology; D035264:Flowers / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D000071677:Histidine Kinase / Q000235:genetics*; D018519:Meristem / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D030821:Plants, Genetically Modified; D012098:Reproduction / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D010937:Plant Growth Regulators; D000071677:Histidine Kinase; C000605492:AHK2 protein, Arabidopsis; C000605493:AHK3 protein, Arabidopsis