"Rhizobium" sp. NGR234 establishes a symbiotic interaction with many legume plants. Regulatory cascade which is trigged by plant produced flavonoids is intricate and numerous factors participate including several transcriptional regulators to control the synthesis of Nod-factors, polysaccharides and T3SS. The striking effects of the NodV (sensor) and NodW (regulator) two-component system were observed on key symbiosis regulators of the regulatory cascade in the absence of flavonoids. The NodVW is repressor of main regulator to maintain the low expression level of symbiotic cascade. T3SS effector proteins generally alter cell signalling and thus host responses induced upon infection. In NGR234, the demonstration that NopM is an effector protein brings the total to five effector proteins which have been identified. The phenotype of the T3SS appears to be an equilibrium in the action of the individual effector proteins, and is also indicative that all five effectors are translocated into the target plant cells.