The specific overexpression of a cyclin-dependent kinase inhibitor in tomato fruit mesocarp cells uncouples endoreduplication and cell growth

Authors

  • Mehdi Nafati,

    1. Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche 619 sur la Biologie du Fruit, BP 81, F-33883 Villenave d’Ornon Cedex, France
    2. Université de Bordeaux 2, Unité Mixte de Recherche 619 sur la Biologie du Fruit, BP 81, F-33883 Villenave d’Ornon Cedex, France
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  • Catherine Cheniclet,

    1. Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche 619 sur la Biologie du Fruit, BP 81, F-33883 Villenave d’Ornon Cedex, France
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  • Michel Hernould,

    1. Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche 619 sur la Biologie du Fruit, BP 81, F-33883 Villenave d’Ornon Cedex, France
    2. Université de Bordeaux 2, Unité Mixte de Recherche 619 sur la Biologie du Fruit, BP 81, F-33883 Villenave d’Ornon Cedex, France
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  • Phuc T. Do,

    1. Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14467 Potsdam-Golm, Germany
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  • Alisdair R. Fernie,

    1. Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14467 Potsdam-Golm, Germany
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  • Christian Chevalier,

    Corresponding author
    1. Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche 619 sur la Biologie du Fruit, BP 81, F-33883 Villenave d’Ornon Cedex, France
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  • Frédéric Gévaudant

    1. Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche 619 sur la Biologie du Fruit, BP 81, F-33883 Villenave d’Ornon Cedex, France
    2. Université de Bordeaux 2, Unité Mixte de Recherche 619 sur la Biologie du Fruit, BP 81, F-33883 Villenave d’Ornon Cedex, France
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(fax +33 557122541; e-mail chevalie@bordeaux.inra.fr).

Summary

The size of tomato fruit results from the combination of cell number and cell size, which are respectively determined by the cell division and cell expansion processes. As fruit growth is mainly sustained by cell expansion, the development of fleshy pericarp tissue is characterized by numerous rounds of endoreduplication inducing a spectacular increase in DNA ploidy and mean cell size. Although a clear relationship exists between endoreduplication and cell growth in plants, the exact role of endoreduplication has not been clearly elucidated. To decipher the molecular basis of endoreduplication-associated cell growth in fruit, we investigated the putative involvement of the tomato cyclin-dependent kinase inhibitor SlKRP1. We studied the kinetics of pericarp development in tomato fruit at the morphological and cytological levels, and demonstrated that endoreduplication is directly proportional to cell and fruit diameter. We established a mathematical model for tissue growth according to the number of divisions and endocycles. This model was tested in fruits where we managed to decrease the extent of endoreduplication by over-expressing SlKRP1 under the control of a fruit-specific promoter expressed during early development. Despite the fact that endoreduplication was affected, we could not observe any morphological, cytological or metabolic phenotypes, indicating that determination of cell and fruit size can be, at least conditionally, uncoupled from endoreduplication.

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