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Antisense inhibition of the sucrose transporter in potato: effects on amount and activity

Authors

  • R. LEMOINE,

    Corresponding author
    1. Laboratoire de Physiologie et Biochimie Végétales, URA CNRS 574, Université de Poitiers, 40, Avenue du Recteur Pineau, 86022 Poitiers Cedes. France
    2. Institut für Genbiologische Forschung. Ihnestr. 63, D-14195 Berlin, Germany
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  • C. KÜHN,

    1. Institut für Genbiologische Forschung. Ihnestr. 63, D-14195 Berlin, Germany
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  • N. THIELE,

    1. Institut für Genbiologische Forschung. Ihnestr. 63, D-14195 Berlin, Germany
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  • S. DELROT,

    1. Laboratoire de Physiologie et Biochimie Végétales, URA CNRS 574, Université de Poitiers, 40, Avenue du Recteur Pineau, 86022 Poitiers Cedes. France
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  • W.B. FROMMER

    1. Institut für Genbiologische Forschung. Ihnestr. 63, D-14195 Berlin, Germany
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    • *

      Institut für Botanik, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 1. D-72076 Tübingen, Germany.


R. Lemoine, Laboratoire de Physiologie et Biochimie Végetatés. URA CNRS 574. Université de Poitiers. Bâtiment Botanique. 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France.

ABSTRACT

The sucrose proton-cotransporter gene from potato (StSUT1) is mainly expressed in the phloem of mature, exporting leaves. To study the in vivo role of the protein, potato plants were transformed with antisense constructs of the sucrose transporter cDNA under control of the CaMV35S and the rolC promoters, respectively. Both types of transgenic plant develop symptoms characteristic of an inhibition of phloem loading. To determine the level of inhibition, immunological and transport studies were performed. Purified antibodies directed against a peptide from the central loop of SUT1 recognized a transporter with an apparent molecular mass of 47 kDa in leaf plasma membrane vesicles. Antisense repression under control of the non-specific CaMV35S promoter led to a strong reduction in SUT1 protein, whereas no such reduction could be detected when the companion cell-specific rolC promoter was used. Similarily. sucrose uptake in plasma membrane vesicles was reduced by 50–75% in CaMV35S but not in rolC plants. These data suggest that, unlike the rolC promoter, the sucrose transporter is expressed not only in the companion cells but also in other leaf cells. However, inhibition of the transporter by rolC-controlled antisense repression is sufficient to impair phloem loading.

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