Characterization of a binding site for chemically synthesized lipo-oligosaccharidic NodRm factors in particulate fractions prepared from roots.
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.
Bono
J J
JJ
Centre de Recherches en Biologie et Physiologie Végétale, URA CNRS, Université Paul Sabatier, Toulouse, France.
Riond
J
J
Nicolaou
K C
KC
Bockovich
N J
NJ
Estevez
V A
VA
Cullimore
J V
JV
Ranjeva
R
R
D001665:Binding Sites; D002240:Carbohydrate Sequence; D008070:Lipopolysaccharides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D000455:Medicago sativa / Q000382:microbiology; D008969:Molecular Sequence Data; D016962:Sinorhizobium meliloti / Q000378:metabolism; D013559:Symbiosis
D008070:Lipopolysaccharides; C092082:Nod factor IV, Rhizobium meliloti