title: Chitin-induced activation of immune signaling by the rice receptor CEBiP relies on a unique sandwich-type dimerization.
abstract: Perception of microbe-associated molecular patterns (MAMPs) through pattern recognition receptors (PRRs) triggers various defense responses in plants. This MAMP-triggered immunity plays a major role in the plant resistance against various pathogens. To clarify the molecular basis of the specific recognition of chitin oligosaccharides by the rice PRR, CEBiP (chitin-elicitor binding protein), as well as the formation and activation of the receptor complex, biochemical, NMR spectroscopic, and computational studies were performed. Deletion and domain-swapping experiments showed that the central lysine motif in the ectodomain of CEBiP is essential for the binding of chitin oligosaccharides. Epitope mapping by NMR spectroscopy indicated the preferential binding of longer-chain chitin oligosaccharides, such as heptamer-octamer, to CEBiP, and also the importance of N-acetyl groups for the binding. Molecular modeling/docking studies clarified the molecular interaction between CEBiP and chitin oligosaccharides and indicated the importance of Ile122 in the central lysine motif region for ligand binding, a notion supported by site-directed mutagenesis. Based on these results, it was indicated that two CEBiP molecules simultaneously bind to one chitin oligosaccharide from the opposite side, resulting in the dimerization of CEBiP. The model was further supported by the observations that the addition of (GlcNAc)8 induced dimerization of the ectodomain of CEBiP in vitro, and the dimerization and (GlcNAc)8-induced reactive oxygen generation were also inhibited by a unique oligosaccharide, (GlcNβ1,4GlcNAc)4, which is supposed to have N-acetyl groups only on one side of the molecule. Based on these observations, we proposed a hypothetical model for the ligand-induced activation of a receptor complex, involving both CEBiP and Oryza sativa chitin-elicitor receptor kinase-1.
authors.affiliation: Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki 214-8571, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hayafune
authors.forename: Rita
authors.initials: R
authors.lastname: Berisio
authors.forename: Roberta
authors.initials: R
authors.lastname: Marchetti
authors.forename: Alba
authors.initials: A
authors.lastname: Silipo
authors.forename: Miyu
authors.initials: M
authors.lastname: Kayama
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Desaki
authors.forename: Sakiko
authors.initials: S
authors.lastname: Arima
authors.forename: Flavia
authors.initials: F
authors.lastname: Squeglia
authors.forename: Alessia
authors.initials: A
authors.lastname: Ruggiero
authors.forename: Ken
authors.initials: K
authors.lastname: Tokuyasu
authors.forename: Antonio
authors.initials: A
authors.lastname: Molinaro
authors.forename: Hanae
authors.initials: H
authors.lastname: Kaku
authors.forename: Naoto
authors.initials: N
authors.lastname: Shibuya
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D002686:Chitin / Q000737:chemistry*; D000939:Epitopes / Q000276:immunology; D008024:Ligands; D008239:Lysine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009844:Oligosaccharides / Q000737:chemistry; D012275:Oryza / Q000276:immunology* / Q000378:metabolism; D057865:Plant Immunity; D010940:Plant Proteins / Q000378:metabolism*; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014026:Nicotiana
chemical_list: D000939:Epitopes; D008024:Ligands; D009844:Oligosaccharides; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D011956:Receptors, Cell Surface; D002686:Chitin; D008239:Lysine
keywords: LysM-receptor; MTI/PTI; chitin signaling; plant immunity; receptor–ligand interaction