The Rg-1 encoded regeneration capacity of tomato is not related to an altered cytokinin homeostasis

Authors

  • Hilde Boiten,

    1. Laboratory of Plant Biochemistry and Physiology, Department of Biology, University of Antwerp (UA), B−2610 Antwerp, Belgium;
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  • Abdelkrim Azmi,

    1. Laboratory of Plant Biochemistry and Physiology, Department of Biology, University of Antwerp (UA), B−2610 Antwerp, Belgium;
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  • Willy Dillen,

    1. Department of Plant Systems Biology, University of Ghent (RUG), B−9000 Ghent, Belgium;
    2. Present address: Crop Design, Technologiepark 3, B−9052 Zwijnaarde, Belgium;
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  • Sandra De Schepper,

    1. Laboratory of Horticulture and Plant Biotechnology, Department of Plant Production, University of Ghent (RUG), B−9000 Ghent, Belgium;
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  • Pierre Debergh,

    1. Laboratory of Horticulture and Plant Biotechnology, Department of Plant Production, University of Ghent (RUG), B−9000 Ghent, Belgium;
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  • Tom Gerats,

    1. Department of Plant Systems Biology, University of Ghent (RUG), B−9000 Ghent, Belgium;
    2. Present address: Laboratory of Plant Genetics, Department of Experimental Botany, University of Nijmegen (KUN), Toernooiveld 1, NL−6525 ED Nijmegen, The Netherlands
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  • Harry Van Onckelen,

    1. Laboratory of Plant Biochemistry and Physiology, Department of Biology, University of Antwerp (UA), B−2610 Antwerp, Belgium;
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  • Els Prinsen

    Corresponding author
    1. Laboratory of Plant Biochemistry and Physiology, Department of Biology, University of Antwerp (UA), B−2610 Antwerp, Belgium;
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Author for correspondence: Els Prinsen Tel: +32 3 8202266 Fax: +32 3 8202271 Email: els.prinsen@ua.ac.be

Summary

  • • Cytokinin (CK) metabolism was analyzed in tomato (Lycopersicon esculentum) Rg-1 hybrids during in vitro shoot organogenesis from root explants.
  • • Data were obtained by combining physicochemical analysis with quantification and in situ detection methods.
  • • Although exogenous zeatin is added in all classical regeneration protocols, we show here that regenerating (Rg+) tomato explants did not require an exogenous CK source for regeneration. Irrespective of the presence or absence of exogenous zeatin, the endogenous CK levels were not affected by Rg-1 in the initial explants or in the early callus phase. In a later stage, and related to the presence of numerous shoots, the Rg+ explants showed much lower endogenous CK concentrations than the nonregenerating (rg) explants. Cells of rg explants were not able to differentiate, despite their high endogenous CK content, and did not respond to exogenously applied CKs.
  • • We show that the insensitivity of rg explants to a hormonal signal, normally initiating regeneration, is not related to an altered endogenous CK metabolism. We therefore postulate that Rg-1 action involves a regeneration-specific CK receptor or a regeneration-specific CK signal transduction pathway.

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