title: Bacteria-derived peptidoglycans constitute pathogen-associated molecular patterns triggering innate immunity in Arabidopsis.
abstract: Pathogen-associated molecular pattern (PAMP)-triggered immunity constitutes the primary plant immune response that has evolved to recognize invariant structures of microbial surfaces. Here we show that Gram-positive bacteria-derived peptidoglycan (PGN) constitutes a novel PAMP of immune responses in Arabidopsis thaliana. Treatment with PGN from Staphylococcus aureus results in the activation of plant responses, such as medium alkalinization, elevation of cytoplasmic calcium concentrations, nitric oxide, and camalexin production and the post-translational induction of MAPK activities. Microarray analysis performed with RNA prepared from PGN-treated Arabidopsis leaves revealed enhanced transcript levels for 236 genes, many of which are also altered upon administration of flagellin. Comparison of cellular responses after treatment with bacteria-derived PGN and structurally related fungal chitin indicated that both PAMPs are perceived via different perception systems. PGN-mediated immune stimulation in Arabidopsis is based upon recognition of the PGN sugar backbone, while muramyl dipeptide, which is inactive in this plant, triggers immunity-associated responses in animals. PGN adds to the list of PAMPs that induce innate immune programs in both plants and animals. However, we propose that PGN perception systems arose independently in both lineages and are the result of convergent evolution.
authors.affiliation: Center for Plant Molecular Biology, Plant Biochemistry, and Microbial Genetics, University of Tübingen, 72076 Tübingen, Germany. andrea.gust@zmbp.uni-tuebingen.de
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Gust
authors.forename: Raja
authors.initials: R
authors.lastname: Biswas
authors.forename: Heike D
authors.initials: HD
authors.lastname: Lenz
authors.forename: Thomas
authors.initials: T
authors.lastname: Rauhut
authors.forename: Stefanie
authors.initials: S
authors.lastname: Ranf
authors.forename: Birgit
authors.initials: B
authors.lastname: Kemmerling
authors.forename: Friedrich
authors.initials: F
authors.lastname: Götz
authors.forename: Erich
authors.initials: E
authors.lastname: Glawischnig
authors.forename: Justin
authors.initials: J
authors.lastname: Lee
authors.forename: Georg
authors.initials: G
authors.lastname: Felix
authors.forename: Thorsten
authors.initials: T
authors.lastname: Nürnberger
mesh_terms: D017360:Arabidopsis / Q000276:immunology* / Q000382:microbiology*; D002240:Carbohydrate Sequence; D002686:Chitin / Q000276:immunology; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D010457:Peptidoglycan / Q000276:immunology*; D013211:Staphylococcus aureus / Q000276:immunology*
chemical_list: D010457:Peptidoglycan; D002686:Chitin