The complex interplay between bacterium and plant that results in nodulation of legumes--and thus the facility for the symbiosis to fix nitrogen--depends on the Nod factors, lipo-chitooligosaccharides of a variety of distinctive specificities. Limpens et al. (see the Perspective by Cullimore and Dénarié) have now identified two genes of the legume Medicago trunculata that encode putative receptors for the Nod factors. In M. trunculata, the receptors that regulate bacterial entry into the plant root-hair cells seem to be more selective than the receptors that regulate the earlier responses of root-hair curling. The LYK genes identified here function in the process of bacterial entry and subsequent growth of the infection thread.
E. Limpens, C. Franken, P. Smit, J. Willemse, T. Bisseling, R. Geurts, LysM domain receptor kinases regulating rhizobial Nod factor-induced infection. Science 302, 630-633 (2003). [Abstract] [Full Text]