Nodule diversity, evolution, organogenesis and identity
Résumé
Some plants can engage symbiosis with nitrogen fixing soil bacteria, allowing them to grow when soils are poor in nitrogen. This symbiotic association results in the formation of a unique plant root organ called the nodule. In these nodules, bacteria can convert atmospheric dinitrogen into ammonia that can be used by the plant. Establishment of a successful symbiosis requires the two symbiotic partners to be compatible with each other throughout the process of symbiotic development. Nodulating plants include actinorhizal plants, Parasponia and the economically important legume family. In this chapter, we will describe the diversity of nodule shapes, the molecular mechanisms underlying the inception of nodule primordia, as well as the development and the maintenance of the symbiotic organ. We will also describe the molecular actors involved in these processes with an emphasis on the NOOT-BOP-COCH-LIKE (NBCL) genes controlling the identity of the symbiotic organ.