A novel highly unsaturated fatty acid moiety of lipo-oligosaccharide signals determines host specificity of Rhizobium

In Rhizobium leguminosarum biovar viciae , the nodABC and nodFEL operons are involved in the production of lipo-oligosaccharide signals which mediate host specificity. The structure of these metabolites and those produced in nod mutants links the nodE and nodi genes to specific chemical features of the signal molecules. A nodE -determined, highly unsaturated fatty acid and a nod-determined O -acetyl substituent are essential for the ability of the signals to induce nodule meristems on the host plant Vicia sativa .