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Analysis of the xylem sap proteome of Brassica oleracea reveals a high content in secreted proteins

Authors

  • Laetitia Ligat,

    1. Université de Toulouse, UPS, UMR, Surfaces Cellulaires et Signalisation chez les Végétaux, Castanet-Tolosan, France
    2. CNRS, UMR, Castanet-Tolosan, France
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    • These authors contributed equally to this work.

  • Emmanuelle Lauber,

    1. Laboratoire des Interactions Plantes Microorganismes (LIPM), UMR CNRS-INRA, Castanet-Tolosan, France
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    • These authors contributed equally to this work.

  • Cécile Albenne,

    1. Université de Toulouse, UPS, UMR, Surfaces Cellulaires et Signalisation chez les Végétaux, Castanet-Tolosan, France
    2. CNRS, UMR, Castanet-Tolosan, France
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  • Hélène San Clemente,

    1. Université de Toulouse, UPS, UMR, Surfaces Cellulaires et Signalisation chez les Végétaux, Castanet-Tolosan, France
    2. CNRS, UMR, Castanet-Tolosan, France
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  • Benoît Valot,

    1. CNRS, PAPPSO, UMR/UMR Génétique Végétale, France
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  • Michel Zivy,

    1. INRA, PAPPSO, UMR/UMR Génétique Végétale, France
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  • Rafael Pont-Lezica,

    1. Université de Toulouse, UPS, UMR, Surfaces Cellulaires et Signalisation chez les Végétaux, Castanet-Tolosan, France
    2. CNRS, UMR, Castanet-Tolosan, France
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  • Matthieu Arlat,

    1. Laboratoire des Interactions Plantes Microorganismes (LIPM), UMR CNRS-INRA, Castanet-Tolosan, France
    2. Université de Toulouse, UPS, Toulouse, France
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  • Elisabeth Jamet

    Corresponding author
    1. Université de Toulouse, UPS, UMR, Surfaces Cellulaires et Signalisation chez les Végétaux, Castanet-Tolosan, France
    2. CNRS, UMR, Castanet-Tolosan, France
    • UMR 5546 UPS/CNRS, Surfaces Cellulaires et Signalisation chez les Végétaux; BP 42617, F-31326 Castanet-Tolosan, France Fax: +33-534-32-38-02
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  • Colour online: See the article online to view Fig. 1 in colour.

Abstract

Xylem plays a major role in plant development and is considered part of the apoplast. Here, we studied the proteome of Brassica oleracea cv Bartolo and compared it to the plant cell wall proteome of another Brassicaceae, the model plant Arabidopsis thaliana. B. oleracea was chosen because it is technically difficult to harvest enough A. thaliana xylem sap for proteomic analysis. We studied the whole proteome and an N-glycoproteome obtained after Concanavalin A affinity chromatography. Altogether, 189 proteins were identified by LC-MS/MS using Brassica EST and cDNA sequences. A predicted signal peptide was found in 164 proteins suggesting that most proteins of the xylem sap are secreted. Eighty-one proteins were identified in the N-glycoproteome, with 25 of them specific of this fraction, suggesting that they were concentrated during the chromatography step. All the protein families identified in this study were found in the cell wall proteomes. However, proteases and oxido-reductases were more numerous in the xylem sap proteome, whereas enzyme inhibitors were rare. The origin of xylem sap proteins is discussed. All the experimental data including the MS/MS data were made available in the WallProtDB cell wall proteomic database.

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