title: Structure-dependent modulation of a pathogen response in plants by synthetic O-antigen polysaccharides.
abstract: Many phytopathogenic bacteria display lipopolysaccharides (LPS) with the O-chain repeating unit [alpha-l-Rha-(1-->3)-alpha-l-Rha-(1-->3)-alpha-l-Rha-(1-->2)](n)(). This trisaccharide unit was synthesized and oligomerized to obtain hexa- and nonasaccharides. The deprotected rhamnans were effective in suppressing the hypersensitive response (HR) and in inducing PR-1 gene expression in Arabidopsis thaliana. Conformational analysis of the oligorhamnans by NMR spectroscopy and molecular dynamics calculations revealed that a coiled structure develops with increasing chain length of the oligosaccharide. This is associated with increasing efficacy in HR suppression and PR-1 gene expression. We therefore infer that the coiled structure of phytopathogenic bacteria is a plant-recognizable pathogen-associated molecular pattern (PAMP).
authors.affiliation: Dipartimento di Chimica Organica e Biochimica Complesso, Universitario Monte Sant'Angelo, Via Cintia 4, 80126, Napoli, Italy.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Bedini
authors.forename: Cristina
authors.initials: C
authors.lastname: De Castro
authors.forename: Gitte
authors.initials: G
authors.lastname: Erbs
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Mangoni
authors.forename: J Maxwell
authors.initials: JM
authors.lastname: Dow
authors.forename: Mari-Anne
authors.initials: MA
authors.lastname: Newman
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Parrilli
authors.forename: Carlo
authors.initials: C
authors.lastname: Unverzagt
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000235:genetics; D002240:Carbohydrate Sequence; D003837:Deoxy Sugars / Q000737:chemistry / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D008351:Mannans / Q000737:chemistry / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D019081:O Antigens / Q000737:chemistry* / Q000494:pharmacology*; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D044224:Pseudomonas syringae / Q000276:immunology / Q000472:pathogenicity*; D013329:Structure-Activity Relationship
chemical_list: D029681:Arabidopsis Proteins; D003837:Deoxy Sugars; D008351:Mannans; D019081:O Antigens; C065836:rhamnan; C077262:PR-1 protein, Arabidopsis