SummaryThis paper describes the characteristics of a binding site for the major, lipo-oligossccharide 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 mmo1-1 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 (K d) 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 (~acotyl and the suIphyl group and did not depend on the uncaturation of the fatty acid. However, both moieties of the lipooligossccharide are required for high-affinity binding since tetra-N-acatyl-chitotetraose and palmitate were found to be poor competitors of Iigand 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.

No abstract

No abstract

No abstract