title: Bacterial cyclic beta-(1,2)-glucan acts in systemic suppression of plant immune responses.
abstract: Although cyclic glucans have been shown to be important for a number of symbiotic and pathogenic bacterium-plant interactions, their precise roles are unclear. Here, we examined the role of cyclic beta-(1,2)-glucan in the virulence of the black rot pathogen Xanthomonas campestris pv campestris (Xcc). Disruption of the Xcc nodule development B (ndvB) gene, which encodes a glycosyltransferase required for cyclic glucan synthesis, generated a mutant that failed to synthesize extracellular cyclic beta-(1,2)-glucan and was compromised in virulence in the model plants Arabidopsis thaliana and Nicotiana benthamiana. Infection of the mutant bacterium in N. benthamiana was associated with enhanced callose deposition and earlier expression of the PATHOGENESIS-RELATED1 (PR-1) gene. Application of purified cyclic beta-(1,2)-glucan prior to inoculation of the ndvB mutant suppressed the accumulation of callose deposition and the expression of PR-1 in N. benthamiana and restored virulence in both N. benthamiana and Arabidopsis plants. These effects were seen when cyclic glucan and bacteria were applied either to the same or to different leaves. Cyclic beta-(1,2)-glucan-induced systemic suppression was associated with the transport of the molecule throughout the plant. Systemic suppression is a novel counterdefensive strategy that may facilitate pathogen spread in plants and may have important implications for the understanding of plant-pathogen coevolution and for the development of phytoprotection measures.
authors.affiliation: Fundación Pablo Cassará, Centro de Ciencia y Tecnología Dr. Cesar Milstein, Consejo Nacional de Investigaciones Científicas y Técnicas, Saladillo 2468 C1440FFX, Ciudad de Buenos Aires, Argentina.
authors.forename: Luciano Ariel
authors.initials: LA
authors.lastname: Rigano
authors.forename: Caroline
authors.initials: C
authors.lastname: Payette
authors.forename: Geneviève
authors.initials: G
authors.lastname: Brouillard
authors.forename: Maria Rosa
authors.initials: MR
authors.lastname: Marano
authors.forename: Laura
authors.initials: L
authors.lastname: Abramowicz
authors.forename: Pablo Sebastián
authors.initials: PS
authors.lastname: Torres
authors.forename: Maximina
authors.initials: M
authors.lastname: Yun
authors.forename: Atilio Pedro
authors.initials: AP
authors.lastname: Castagnaro
authors.forename: Mohamed El
authors.initials: ME
authors.lastname: Oirdi
authors.forename: Vanessa
authors.initials: V
authors.lastname: Dufour
authors.forename: Florencia
authors.initials: F
authors.lastname: Malamud
authors.forename: John Maxwell
authors.initials: JM
authors.lastname: Dow
authors.forename: Kamal
authors.initials: K
authors.lastname: Bouarab
authors.forename: Adrian Alberto
authors.initials: AA
authors.lastname: Vojnov
mesh_terms: D017360:Arabidopsis / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D004305:Dose-Response Relationship, Drug; D007113:Immunity, Innate; D010935:Plant Diseases / Q000276:immunology; D018515:Plant Leaves / Q000382:microbiology; D015398:Signal Transduction; D013997:Time Factors; D014026:Nicotiana / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D037521:Virulence Factors; D016959:Xanthomonas campestris / Q000472:pathogenicity; D047071:beta-Glucans / Q000378:metabolism*
chemical_list: D037521:Virulence Factors; D047071:beta-Glucans