Legume plants do not depend on externally supplied nitrogen, because they can form a symbiosis with nitrogen-fixing bacteria, called rhizobia. The plants recognize the nitrogen-fixing bacteria and allow them to colonize specially formed organs called nodules. It has been known for many years that there are two Nod factor receptors, NFR1 and NFR5, which are responsible for recognizing the signaling molecules secreted by rhizobia. But how the receptors work together in signaling complexes was unknown until now.
