Werner, Dietrich; Ahlborn, Bettina; Antoun, Hani; Bernhard, Simone; Bolanos, Christina; Cooper, James E.; Görge, Elisabeth; Jacobi, Andreas; Kalliopi, Papadopoulou; Kape, Rüdiger; Katinakis, Panagiotis; Kosch, Kerstin; Müller, Peter; Schmidt, Petra; Streit, Wolfgang; Wetzel, Astrid
Communication and signal exchange in the Rhizobium bradyrhizobium legume system.
In: Endocytobiosis and Cell Research, Vol. 10, No. 1-2: pp. 5-15
A new comprehensive communication concept in the Rhizobium/Bradyrhizobium legume symbiosis was developed. It includes a root zone specific flavonoid exudation, the differential activity of phenylpropane/acetate pathway derivatives on chemotaxis, nod-gene inducing activity and phytoalexin resistance induction on the microsymbiont side (Bradyrhizobium). Nod factor production from the microsymbiont affects the host plant in root hair curling and meristem induction. Phytoalexin production in the host plant is also an early response, however repressed to a low level after a few hours. Another strategy of the microsymbiont to overcome phytoalexin effects is degradation of phytoalexins in Rhizobium leguminosarum bv. vicieae. Competitiveness within the same infection group of the microsymbiont was studied with gus-gene fusion, using the blue coloured nodules to easily discriminate marked strains from unmarked competitors. New exopolysaccharide (EPS) mutants of Bradyrhizobium japonicum were reconstructed homologous with a DNA region to exoB gene of Rhizobium meliloti. Their clearly reduced competitiveness of nodulation, demonstrates that exopolysaccharides of Bradyrhizohium japonicum also have an important function during the early stages of this symbiotic interaction.