A Nod of recognition: How the ups and downs of Ca2+ lead to nodule development during the initiation of rhizobial-legume symbioses

One of the most sensitive Ca2+-signalling pathways identified in nature is that which is activated by rhizobia during the initiation of symbiotic nitrogen-fixing nodules on legume roots. Leguminous plants owe much of their ecological success to their symbiosis with rhizobia, because rhizobia provide NH3 to plants by reducing N2 within specialized root organs called nodules. Rhizobia induce nodule development by activating a plant signalling pathway that requires oscillations of Ca2+ within the nucleus.