title: The N-Glycan cluster from Xanthomonas campestris pv. campestris: a toolbox for sequential plant N-glycan processing.
abstract: N-Glycans are widely distributed in living organisms but represent only a small fraction of the carbohydrates found in plants. This probably explains why they have not previously been considered as substrates exploited by phytopathogenic bacteria during plant infection. Xanthomonas campestris pv. campestris, the causal agent of black rot disease of Brassica plants, possesses a specific system for GlcNAc utilization expressed during host plant infection. This system encompasses a cluster of eight genes (nixE to nixL) encoding glycoside hydrolases (GHs). In this paper, we have characterized the enzymatic activities of these GHs and demonstrated their involvement in sequential degradation of a plant N-glycan using a N-glycopeptide containing two GlcNAcs, three mannoses, one fucose, and one xylose (N2M3FX) as a substrate. The removal of the α-1,3-mannose by the α-mannosidase NixK (GH92) is a prerequisite for the subsequent action of the β-xylosidase NixI (GH3), which is involved in the cleavage of the β-1,2-xylose, followed by the α-mannosidase NixJ (GH125), which removes the α-1,6-mannose. These data, combined to the subcellular localization of the enzymes, allowed us to propose a model of N-glycopeptide processing by X. campestris pv. campestris. This study constitutes the first evidence suggesting N-glycan degradation by a plant pathogen, a feature shared with human pathogenic bacteria. Plant N-glycans should therefore be included in the repertoire of molecules putatively metabolized by phytopathogenic bacteria during their life cycle.
authors.affiliation: From the Université de Toulouse and CNRS, Laboratoire de Recherches en Sciences Végétales, UMR 5546, BP 42617, F-31326 Castanet-Tolosan, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Dupoiron
authors.affiliation: INRA and CNRS, Laboratoire des Interactions Plantes-Microorganismes, UMR 2594, F-31326 Castanet-Tolosan, France, and.
authors.forename: Claudine
authors.initials: C
authors.lastname: Zischek
authors.affiliation: From the Université de Toulouse and CNRS, Laboratoire de Recherches en Sciences Végétales, UMR 5546, BP 42617, F-31326 Castanet-Tolosan, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Ligat
authors.affiliation: From the Université de Toulouse and CNRS, Laboratoire de Recherches en Sciences Végétales, UMR 5546, BP 42617, F-31326 Castanet-Tolosan, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Carbonne
authors.affiliation: INRA and CNRS, Laboratoire des Interactions Plantes-Microorganismes, UMR 2594, F-31326 Castanet-Tolosan, France, and.
authors.forename: Alice
authors.initials: A
authors.lastname: Boulanger
authors.affiliation: INRA and CNRS, Laboratoire des Interactions Plantes-Microorganismes, UMR 2594, F-31326 Castanet-Tolosan, France, and.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dugé de Bernonville
authors.affiliation: INRA and CNRS, Laboratoire des Interactions Plantes-Microorganismes, UMR 2594, F-31326 Castanet-Tolosan, France, and the Université de Toulouse, UPS, F-31062 Toulouse, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Lautier
authors.affiliation: From the Université de Toulouse and CNRS, Laboratoire de Recherches en Sciences Végétales, UMR 5546, BP 42617, F-31326 Castanet-Tolosan, France, INRA and CNRS, Laboratoire des Interactions Plantes-Microorganismes, UMR 2594, F-31326 Castanet-Tolosan, France, and.
authors.forename: Pauline
authors.initials: P
authors.lastname: Rival
authors.affiliation: INRA and CNRS, Laboratoire des Interactions Plantes-Microorganismes, UMR 2594, F-31326 Castanet-Tolosan, France, and the Université de Toulouse, UPS, F-31062 Toulouse, France.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Arlat
authors.affiliation: From the Université de Toulouse and CNRS, Laboratoire de Recherches en Sciences Végétales, UMR 5546, BP 42617, F-31326 Castanet-Tolosan, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Jamet
authors.affiliation: INRA and CNRS, Laboratoire des Interactions Plantes-Microorganismes, UMR 2594, F-31326 Castanet-Tolosan, France, and emmanuelle.lauber@toulouse.inra.fr.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Lauber
authors.affiliation: From the Université de Toulouse and CNRS, Laboratoire de Recherches en Sciences Végétales, UMR 5546, BP 42617, F-31326 Castanet-Tolosan, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Albenne
mesh_terms: D001937:Brassica / Q000201:enzymology / Q000235:genetics*; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D011134:Polysaccharides / Q000235:genetics* / Q000378:metabolism; D016959:Xanthomonas campestris / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D014995:Xylosidases / Q000235:genetics / Q000378:metabolism; D043323:alpha-Mannosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D011134:Polysaccharides; D006026:Glycoside Hydrolases; D014995:Xylosidases; D043323:alpha-Mannosidase; C026579:exo-1,4-beta-D-xylosidase
keywords: Bacteria; Carbohydrate Processing; Enzyme Kinetics; Glycoside Hydrolase; N-Linked Glycosylation; Phytopathogen; Plant; Xanthomonas