Characterization of a binding site for chemically synthesized lipo‐oligosaccharidic NodRm factors in particulate fractions prepared from roots

• Published in: The Plant journal : for cell and molecular biology 1995-02, Vol.7 (2), p.253-260
• Main Authors: Bono, Jean‐Jacques, Riond, Joëlle, Nicolaou, K.C., Bockovich, Nicholas J., Estevez, Virginia A., Cullimore, Julie V., Ranjeva, Raoul
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Binding Sites; Biological and medical sciences; Carbohydrate Sequence; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Genetics; Life Sciences; Lipopolysaccharides - chemical synthesis; Lipopolysaccharides - chemistry; Lipopolysaccharides - metabolism; Medicago sativa - microbiology; Medicago truncatula; Molecular Sequence Data; Parasitism and symbiosis; Plant physiology and development; Plants genetics; Rhizobium meliloti; Sinorhizobium meliloti - metabolism; Symbiosis; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...)
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1995.7020253.x

Summary This paper describes the characteristics of a binding site for the major, lipo‐oligosaccharide Nod factor of Rhizobium meliloti in roots of the symbiotic host plant, Medicago truncatula. Chemically synthesized NodRm‐IV(Ac, S, C16:2) was labelled by tritiation to a specific activity of 56 Ci mmol−1 and this ligand was shown to be biologically active in the root hair deformation assay at 10−11 M. Binding of the ligand to a particulate fraction from roots of M. truncatula was found to be saturable and reversible with an affinity (Kd) of 86 nM and the binding characteristics were consistent with a single class of binding sites. Competition with modified Nod factors showed that the binding was independent of both the O‐acetyl and the sulphyl group and did not depend on the unsaturation of the fatty acid. However, both moieties of the lipo‐oligosaccharide are required for high‐affinity binding since tetra‐N‐acetyl‐chitotetraose and palmitate were found to be poor competitors of ligand binding. A binding site with analogous characteristics was also found in a similarly prepared particulate fraction of tomato roots. This binding site for Nod factors, termed NFBS1, which is present in both a leguminous and a non‐leguminous plant, may have a more general role than symbiosis.