Characterization of the nodulation receptor kinase (NORK)

Legumes are able to establish root endosymbioses with rhizobial bacteria and arbuscular mycorrhizal fungi. These relationships enable these plants to fi x atmospheric nitrogen and acquire phosphorus from the soil, respectively. The legume-rhizobia relationship begins with a molecular dialog in the rhizosphere. Plant exudates (fl avonoids) induce the production of the so-called Nod factor (NF) in the bacteria (Dénarié et al. 1996). NFs induce nodule formation on roots and they are the major determinant of host specifi city of the interaction. Since responses are induced in the plant by NF concentrations in a nano- to picomolar range, it has been postulated that NFs are recognized by specifi c receptor(s). Recently, several genes have been identifi ed and characterized that are involved in the perception and early signal transduc-tion of the NF thereby in the nodulation process