Genetic Analyses Suggesting Bacterial-Plant Signalling During Nodulation

Bacteria of the genus Rhizobium fix nitrogen in symbiotic association with leguminous plants. The establishment of symbiosis probably requires many signalling interactions between the bacteria and the plant. The bacterial nod genes are induced by plant flavones (Peters et al 1986) and are involved in synthesis of a compound which has been reported to induce plant cell division (Schmidt et al 1988). In our laboratory, we have studied three classes of Rhizobium meliloti mutants which may be involved in signalling interactions. These are mutants affected in exopolysaccharide synthesis, trpE(G) mutants, and a group of TnphoA insertion mutants.