The shoot controls zeatin riboside export from pea roots. Evidence from the branching mutant rms4

Authors

  • Christine A. Beveridge,

    Corresponding author
    1. Station de Génétique et d’Amélioration des Plantes, Institut National de la Recherche Agronomique (INRA), Route de Saint-Cyr, 78026 Versailles Cedex, France
    2. Phytopharmacie and Mediateurs Chimiques, INRA, Route de Saint-Cyr, 78026 Versailles Cedex, France
    3. Laboratoire de Physiologie du Développement des Plantes, URA 2135 CNRS, Université Pierre et Marie Curie, case 156, F-75252 Paris Cedex 05, France
      *For correspondence (fax +61 73 365 1699; e-mail c.beveridge@botany.uq.edu.au).
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    • Present address: Department of Botany, The University of Queensland, Brisbane, QLD 4072, Australia.

  • Ian C. Murfet,

    1. Department of Plant Science, University of Tasmania, GPO Box 252-55, Hobart, Tasmania, 7001, Australia
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  • Lucien Kerhoas,

    1. Phytopharmacie and Mediateurs Chimiques, INRA, Route de Saint-Cyr, 78026 Versailles Cedex, France
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  • Bruno Sotta,

    1. Laboratoire de Physiologie du Développement des Plantes, URA 2135 CNRS, Université Pierre et Marie Curie, case 156, F-75252 Paris Cedex 05, France
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  • Emile Miginiac,

    1. Laboratoire de Physiologie du Développement des Plantes, URA 2135 CNRS, Université Pierre et Marie Curie, case 156, F-75252 Paris Cedex 05, France
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  • Catherine Rameau

    1. Station de Génétique et d’Amélioration des Plantes, Institut National de la Recherche Agronomique (INRA), Route de Saint-Cyr, 78026 Versailles Cedex, France
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*For correspondence (fax +61 73 365 1699; e-mail c.beveridge@botany.uq.edu.au).

Abstract

The rms4 mutant of pea (Pisum sativum L.) was used in grafting studies and cytokinin analyses of the root xylem sap to provide evidence that, at least for pea, the shoot can modify the import of cytokinins from the root. The rms4 mutation, which confers a phenotype with increased branching in the shoot, causes a very substantial decrease (down to 40-fold less) in the concentration of zeatin riboside (ZR) in the xylem sap of the roots. Results from grafts between wild-type (WT) and rms4 plants indicate that the concentration of cytokinins in the xylem sap of the roots is determined almost entirely by the genotype of the shoot. WT scions normalize the cytokinin concentration in the sap of rms4 mutant roots, whereas mutant scions cause WT roots to behave like those of self-grafted mutant plants. The mechanism whereby rms4 shoots of pea cause a down-regulation in the export of cytokinins from the roots is unknown at this time. However, our data provide evidence that the shoot transmits a signal to the roots and thereby controls processes involved in the regulation of cytokinin biosynthesis in the root.

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