Nod factor signaling in symbiotic nodulation

Abstract

In the rhizobial legume symbiosis, an exchange of signals leads to the specific infection of the host plant by its rhizobial symbiont and the development of specialized organs, the nodules, in which rhizobia fix nitrogen. In response to flavonoids secreted by legume roots, rhizobia notably produce lipochitooligosaccharidic molecules called Nod factors (NFs). Following extensive research, we now understand better the mechanisms of perception and transduction of the NF signal by the legume host. NF signaling results in a wide transcriptional reprogramming that leads to coordinated multistep processes of infection and nodule organogenesis, involving many plant and bacterial molecular components. Recent data suggest that the NF biosynthesis pathway evolved from non rhizobial bacteria and that NF perception/signaling in legumes adapted components preexisting in plant signaling pathways controlling in particular the establishment of the more ancient arbuscular mycorrhizal symbiosis.