title: Analysis of the xylem sap proteome of Brassica oleracea reveals a high content in secreted proteins.
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.
authors.affiliation: Université de Toulouse, UPS, UMR, Surfaces Cellulaires et Signalisation chez les Végétaux, Castanet-Tolosan, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Ligat
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Lauber
authors.forename: Cécile
authors.initials: C
authors.lastname: Albenne
authors.forename: Hélène
authors.initials: H
authors.lastname: San Clemente
authors.forename: Benoît
authors.initials: B
authors.lastname: Valot
authors.forename: Michel
authors.initials: M
authors.lastname: Zivy
authors.forename: Rafael
authors.initials: R
authors.lastname: Pont-Lezica
authors.forename: Matthieu
authors.initials: M
authors.lastname: Arlat
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Jamet
mesh_terms: D017360:Arabidopsis / Q000378:metabolism; D001937:Brassica / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D002846:Chromatography, Affinity / Q000379:methods; D002853:Chromatography, Liquid; D003208:Concanavalin A; D030562:Databases, Protein; D006023:Glycoproteins / Q000032:analysis; D013058:Mass Spectrometry; D010940:Plant Proteins / Q000032:analysis* / Q000378:metabolism; D020543:Proteome / Q000032:analysis*; D040901:Proteomics / Q000379:methods; D052584:Xylem / Q000378:metabolism*
chemical_list: D006023:Glycoproteins; D010940:Plant Proteins; D020543:Proteome; D003208:Concanavalin A