title: The elicitation of plant innate immunity by lipooligosaccharide of Xanthomonas campestris.
abstract: Lipopolysaccharides (LPSs) and lipooligosaccharides (LOSs) are major components of the cell surface of Gram-negative bacteria with diverse roles in bacterial pathogenesis of animals and plants that include elicitation of host defenses. Little is known about the mechanisms of perception of these molecules by plants and about the associated signal transduction pathways that trigger plant immunity. Here we address the issue of the molecular basis of elicitation of plant defenses through the structural determination of the LOS of the plant pathogen Xanthomonas campestris pv. campestris strain 8004 and examination of the effects of LOS and fragments obtained by chemical treatments on the immune response in Arabidopsis thaliana. The structure shows a strong accumulation of negatively charged groups in the lipid A-inner core region and has a number of novel features, including a galacturonyl phosphate attached at a 3-deoxy-D-manno-oct-2-ulosonic acid residue and a unique phosphoramide group in the inner core region. Intact LOS and the lipid A and core oligosaccharides derived from it were all able to induce the defense-related genes PR1 and PR2 in Arabidopsis and to prevent the hypersensitive response caused by avirulent bacteria. Although LOS induced defense-related gene transcription in two temporal phases, the core oligosaccharide induced only the earlier phase, and lipid A induced only the later phase. These findings suggest that plant cells can recognize lipid A and core oligosaccharide structures within LOS to trigger defensive cellular responses and that this may occur via two distinct recognition events.
authors.affiliation: Dipartimento di Chimica Organica e Biochimica, Università di Napoli Federico II, Complesso Universitario Monte Sant' Angelo, Via Cintia 4, 80126 Napoli, Italy.
authors.forename: Alba
authors.initials: A
authors.lastname: Silipo
authors.forename: Antonio
authors.initials: A
authors.lastname: Molinaro
authors.forename: Luisa
authors.initials: L
authors.lastname: Sturiale
authors.forename: J Maxwell
authors.initials: JM
authors.lastname: Dow
authors.forename: Gitte
authors.initials: G
authors.lastname: Erbs
authors.forename: Rosa
authors.initials: R
authors.lastname: Lanzetta
authors.forename: Mari-Anne
authors.initials: MA
authors.lastname: Newman
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Parrilli
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology; D017343:Genes, Plant / Q000187:drug effects* / Q000276:immunology; D006967:Hypersensitivity / Q000517:prevention & control*; D007113:Immunity, Innate / Q000187:drug effects* / Q000235:genetics; D007700:Kinetics; D008050:Lipid A / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000737:chemistry / Q000494:pharmacology*; D013058:Mass Spectrometry; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010759:Phosphorus Isotopes; D018515:Plant Leaves / Q000187:drug effects / Q000276:immunology; D011522:Protons; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014158:Transcription, Genetic / Q000187:drug effects; D016959:Xanthomonas campestris / Q000276:immunology* / Q000472:pathogenicity
chemical_list: D008050:Lipid A; D008070:Lipopolysaccharides; D010759:Phosphorus Isotopes; D011522:Protons; C023023:lipid-linked oligosaccharides