Binding Site for Chitin Oligosaccharides in the Soybean Plasma Membrane

• Published in: Plant physiology (Bethesda) Vol. 126; no. 3; pp. 1162 - 1173
• Main Authors: Day, R. Bradley, Mitsuo Okada, Ito, Yuki, Koji Tsukada, Zaghouani, Habib, Shibuya, Naoto, Stacey, Gary
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.07.2001; American Society of Plant Physiologists
• Subjects: Agronomy. Soil science and plant productions; Binding Sites; Binding, Competitive; Biological and medical sciences; Carbohydrate Sequence; Cell Membrane - metabolism; Cell membranes; Cell physiology; Cells, Cultured; Chemical suspensions; Chitin; Chitin - metabolism; Cultured cells; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Glycine max - metabolism; Ligands; Lipopolysaccharides - metabolism; Membrane Proteins - metabolism; Molecular and cellular biology; Molecular Sequence Data; Oligomers; Oligosaccharides; Parasitism and symbiosis; Plant physiology and development; Plants; Plants Interacting with Other Organisms; Signal Transduction; Soybeans; Symbiosis; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Symbiosis; Symbionte; Oligosaccharide; Bradyrhizobium japonicum; Nodulation; Chitin; Identification; Plant nodule; Binding site; Glycine max; Characterization; Grain legume; Binding protein; Signal transduction; Leguminosae; Dicotyledones; Substrate specificity; Angiospermae; Plasma membrane; Bacteria; Perception; Spermatophyta; Interspecific recognition; Rhizobiaceae
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.126.3.1162

Affinity cross-linking of the plasma membrane fraction to an 125I-labeled chitin oligosaccharide led to the identification and characterization of an 85-kD, chitin binding protein in plasma membrane-enriched fractions from both suspension-cultured soybean cells and root tissue. Inhibition analysis indicated a binding preference for larger (i.e. degrees of polymerization = 8) N-acetylated chitin molecules with a 50% inhibition of initial activity value of approximately 50 nM. N-Acetyl-glucosamine and chitobiose showed no inhibitory effects at concentrations as high as 250 μM. It is noteworthy that the major lipo-chitin oligosaccharide Nod signal produced by Bradyrhizobium japonicum was also shown to be a competitive inhibitor of ligand binding. However, the binding site appeared to recognize the chitin portion of the Nod signal, and it is unlikely that this binding activity represents a specific Nod signal receptor. Chitooligosaccharide specificity for induction of medium alkalinization and the generation of reactive oxygen in suspension-cultured cells paralleled the binding activity. Taken together, the presence of the chitin binding protein in the plasma membrane fraction and the specificity and induction of a biological response upon ligand binding suggest a role for the protein as an initial response mechanism for chitin perception in soybean (Glycine max).