Systemic Signalling in Legume Nodulation: Nodule Formation and Its Regulation

Legume plants are able to enter into a symbiotic relationship with rhizobia bacteria. This results in the formation of a novel organ on the root called the nodule, where the rhizobia are housed. The rhizobia provide the host plant with nitrogen in exchange for carbohydrates. Successful nodule formation and sustainable nodulation involve complex signalling events. This includes systemic signalling between the symbiotic partners, and also signalling between the root and shoot of the plant. Factors such as plant hormone levels and environmental conditions for growth influence these systemic signalling pathways. This chapter investigates the different types of long-distance signalling events that are necessary for the development and regulation of legume nodulation.