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Magnesium deficiency in sugar beets alters sugar partitioning and phloem loading in young mature leaves

Hermans, Christian ; Bourgis, Fabienne ; Faucher, Mireille ; Strasser, Reto ; Delrot, Serge ; Verbruggen, Nathalie

In: Planta, 2005, vol. 220, no. 4, p. 541-549

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    Titre
    • Magnesium deficiency in sugar beets alters sugar partitioning and phloem loading in young mature leaves
    Auteur
    • Hermans, Christian. Laboratoire de Physiologie et de Génétique Moléculaire des Plantes, Université Libre de Bruxelles, 1050, Brussels, Belgium
    • Bourgis, Fabienne. Laboratoire de Physiologie et de Génétique Moléculaire des Plantes, Université Libre de Bruxelles, 1050, Brussels, Belgium
    • Faucher, Mireille. Laboratoire de Physiologie, Biochimie et Biologie Moléculaire Végétales, Unité Mixte de Recherches Centre National de la Recherche Scientifique 6161, Université de Poitiers, 86022, Poitiers Cedex, France
    • Strasser, Reto. Bioenergetics Laboratory, University of Geneva, 1254, Geneva, Switzerland
    • Delrot, Serge. Laboratoire de Physiologie, Biochimie et Biologie Moléculaire Végétales, Unité Mixte de Recherches Centre National de la Recherche Scientifique 6161, Université de Poitiers, 86022, Poitiers Cedex, France
    • Verbruggen, Nathalie. Laboratoire de Physiologie et de Génétique Moléculaire des Plantes, Université Libre de Bruxelles, 1050, Brussels, Belgium
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:311503
    Summary
    Magnesium deficiency has been reported to affect plant growth and biomass partitioning between root and shoot. The present work aims to identify how Mg deficiency alters carbon partitioning in sugar beet (Beta vulgaris L.) plants. Fresh biomass, Mg and sugar contents were followed in diverse organs over 20days under Mg-sufficient and Mg-deficient conditions. At the end of the treatment, the aerial biomass, but not the root biomass, of Mg-deficient plants was lower compared to control plants. A clear inverse relationship between Mg and sugar contents in leaves was found. Mg deficiency promoted a marked increase in sucrose and starch accumulation in the uppermost expanded leaves, which also had the lowest content of Mg among all the leaves of the rosette. The oldest leaves maintained a higher Mg content. [14C]Sucrose labelling showed that sucrose export from the uppermost expanded leaves was inhibited. In contrast, sucrose export from the oldest leaves, which are close to, and export mainly to, the roots, was not restricted. In response to Mg deficiency, the BvSUT1 gene encoding a companion cell sucrose/H+ symporter was induced in the uppermost expanded leaves, but without further enhancement of sucrose loading into the phloem. The observed increase in BvSUT1 gene expression supports the idea that sucrose loading into the phloem is defective, resulting in its accumulation in the leaf