title: The acylation and phosphorylation pattern of lipid A from Xanthomonas campestris strongly influence its ability to trigger the innate immune response in Arabidopsis.
abstract: Lipopolysaccharides (LPSs) are major components of the cell surface of Gram-negative bacteria. LPSs comprise a hydrophilic heteropolysaccharide (formed by the core oligosaccharide and the O-specific polysaccharide) that is covalently linked to the glycolipid moiety lipid A, which anchors these macromolecules to the external membrane. LPSs are one of a group of molecules called pathogen-associated molecular patterns (PAMPs) that are indispensable for bacterial growth and viability, and act to trigger innate defense responses in eukaryotes. We have previously shown that LPS from the plant pathogen Xanthomonas campestris pv. campestris (Xcc) can elicit defense responses in the model plant Arabidopsis thaliana. Here we have extended these studies by analysis of the structure and biological activity of LPS from a nonpathogenic Xcc mutant, strain 8530. We show that this Xcc strain is defective in core completion and introduces significant modification in the lipid A region, which involves the degree of acylation and nonstoichiometric substitution of the phosphate groups with phosphoethanolamine. Lipid A that was isolated from Xcc strain 8530 did not have the ability to induce the defense-related gene PR1 in Arabidopsis, or to prevent the hypersensitive response (HR) that is caused by avirulent bacteria as the lipid A from the wild-type could. This suggests that Xcc has the capacity to modify the structure of the lipid A to reduce its activity as a PAMP. We speculate that such effects might occur in wild-type bacteria that are exposed to stresses such as those that might be encountered during plant colonization and disease.
authors: Dipartimento di Chimica Organica e Biochimica, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, Via Cintia 4, 80126 Napoli, Italy. silipo@unina.it
authors: Alba
authors: A
authors: Silipo
authors: Luisa
authors: L
authors: Sturiale
authors: Domenico
authors: D
authors: Garozzo
authors: Gitte
authors: G
authors: Erbs
authors: Tina Tandrup
authors: TT
authors: Jensen
authors: Rosa
authors: R
authors: Lanzetta
authors: J Maxwell
authors: JM
authors: Dow
authors: Michelangelo
authors: M
authors: Parrilli
authors: Mari-Anne
authors: MA
authors: Newman
authors: Antonio
authors: A
authors: Molinaro
mesh_terms: D000215:Acylation; D017360:Arabidopsis / Q000276:immunology*; D018506:Gene Expression Regulation, Plant; D007113:Immunity, Innate; D008050:Lipid A / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation; D009844:Oligosaccharides / Q000032:analysis / Q000737:chemistry; D010766:Phosphorylation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D016959:Xanthomonas campestris
chemical_list: D008050:Lipid A; D009844:Oligosaccharides