Rhizobia and legume nodulation genes

Most legume plants are able to enter into a symbiotic relationship with nitrogen-fixing soil bacteria commonly referred to as rhizobia. This interaction leads to the formation of novel root organs called nodules in which the rhizobia are housed. The symbiosis provides the legume host with a tremendous competitive advantage over other plant species that are unable to acquire nitrogen in this manner. The rhizobia partner also benefits by being able to access food in the form of carbohydrates from their host plant. The process of nodule formation requires a number of highly specific signaling interactions between the plant and bacterial partners. In this article, a number of critical plant and bacterial genes and signal molecules that are required for nodule development and the regulation of nodule numbers are described