Species-specific microsymbiont discrimination mediated by a receptor kinase.

Host range specificity is a prominent feature of the legume-rhizobial symbiosis. and are two closely related species that engage in root nodule symbiosis with legume plants of the genus, but certain species exhibit selectivity in their interactions with the two rhizobial species. We have identified a receptor-like kinase, which can discriminate between the two bacterial species, acting as a genetic barrier against infection by most strains. Activation of this receptor-mediated nodulation restriction requires a bacterial gene that encodes a glycine-rich octapeptide repeat protein with distinct variants capable of distinguishing from . This study sheds light on the coevolution of host plants and rhizobia, shaping symbiotic selectivity in their respective ecological niches.