title: Xanthan Pyruvilation Is Essential for the Virulence of Xanthomonas campestris pv. campestris.
abstract: Xanthan, the main exopolysaccharide (EPS) synthesized by Xanthomonas spp., contributes to bacterial stress tolerance and enhances attachment to plant surfaces by helping in biofilm formation. Therefore, xanthan is essential for successful colonization and growth in planta and has also been proposed to be involved in the promotion of pathogenesis by calcium ion chelation and, hence, in the suppression of the plant defense responses in which this cation acts as a signal. The aim of this work was to study the relationship between xanthan structure and its role as a virulence factor. We analyzed four Xanthomonas campestris pv. campestris mutants that synthesize structural variants of xanthan. We found that the lack of acetyl groups that decorate the internal mannose residues, ketal-pyruvate groups, and external mannose residues affects bacterial adhesion and biofilm architecture. In addition, the mutants that synthesized EPS without pyruvilation or without the external mannose residues did not develop disease symptoms in Arabidopsis thaliana. We also observed that the presence of the external mannose residues and, hence, pyruvilation is required for xanthan to suppress callose deposition as well as to interfere with stomatal defense. In conclusion, pyruvilation of xanthan seems to be essential for Xanthomonas campestris pv. campestris virulence.
authors.affiliation: 1 Instituto de Ciencia y Tecnología Dr. César Milstein, Fundación Pablo Cassará, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Saladillo 2468 (C1440FFX), Ciudad de Buenos Aires, Argentina.
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Bianco
authors.affiliation: 1 Instituto de Ciencia y Tecnología Dr. César Milstein, Fundación Pablo Cassará, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Saladillo 2468 (C1440FFX), Ciudad de Buenos Aires, Argentina.
authors.forename: Laila
authors.initials: L
authors.lastname: Toum
authors.affiliation: 2 Centro de Investigaciones y Transferencia (CIT Villa María), CONICET-Instituto de Ciencias Básicas y Aplicadas, Universidad Nacional de Villa María. Av. Arturo Jauretche 1555, (5900), Villa María, Córdoba, Argentina.
authors.forename: Pablo Marcelo
authors.initials: PM
authors.lastname: Yaryura
authors.affiliation: 1 Instituto de Ciencia y Tecnología Dr. César Milstein, Fundación Pablo Cassará, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Saladillo 2468 (C1440FFX), Ciudad de Buenos Aires, Argentina.
authors.forename: Natalia
authors.initials: N
authors.lastname: Mielnichuk
authors.affiliation: 1 Instituto de Ciencia y Tecnología Dr. César Milstein, Fundación Pablo Cassará, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Saladillo 2468 (C1440FFX), Ciudad de Buenos Aires, Argentina.|3 Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Departamento de Biodiversidad y Biología Experimental (DBBE), CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Buenos Aires (C1428EGA), Argentina.
authors.forename: Gustavo Eduardo
authors.initials: GE
authors.lastname: Gudesblat
authors.affiliation: 4 Instituto de Biología Molecular y Celular de Rosario (IBR)-CONICET, Área Virología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Ocampo y Esmeralda s/n, (S2000FHN) Rosario, Argentina; and.
authors.forename: Roxana
authors.initials: R
authors.lastname: Roeschlin
authors.affiliation: 4 Instituto de Biología Molecular y Celular de Rosario (IBR)-CONICET, Área Virología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Ocampo y Esmeralda s/n, (S2000FHN) Rosario, Argentina; and.
authors.forename: María Rosa
authors.initials: MR
authors.lastname: Marano
authors.affiliation: 5 Laboratorio de Genética Bacteriana, Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA)-CONICET, Patricias Argentinas 435 (C1405BWE), Ciudad de Buenos Aires, Argentina.
authors.forename: Luis
authors.initials: L
authors.lastname: Ielpi
authors.affiliation: 1 Instituto de Ciencia y Tecnología Dr. César Milstein, Fundación Pablo Cassará, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Saladillo 2468 (C1440FFX), Ciudad de Buenos Aires, Argentina.
authors.forename: Adrián A
authors.initials: AA
authors.lastname: Vojnov
mesh_terms: D017360:Arabidopsis / Q000382:microbiology*; D018441:Biofilms / Q000254:growth & development*; D005936:Glucans / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D009154:Mutation; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D054046:Plant Stomata / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019289:Pyruvic Acid / Q000737:chemistry; D014774:Virulence; D037521:Virulence Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016959:Xanthomonas campestris / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity* / Q000502:physiology
chemical_list: D005936:Glucans; D011135:Polysaccharides, Bacterial; D037521:Virulence Factors; D019289:Pyruvic Acid; C048306:callose; C002563:xanthan gum