Species-specific microsymbiont discrimination mediated by a Medicago receptor kinase | Science Advances
Abstract
Host range specificity is a prominent feature of the legume-rhizobial symbiosis.
Sinorhizobium meliloti
and
Sinorhizobium medicae
are two closely related species that engage in root nodule symbiosis with legume plants of the
Medicago
genus, but certain
Medicago
species exhibit selectivity in their interactions with the two rhizobial species. We have identified a
Medicago
receptor–like kinase, which can discriminate between the two bacterial species, acting as a genetic barrier against infection by most
S. medicae
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
S. medicae
from
S. meliloti
. This study sheds light on the coevolution of host plants and rhizobia, shaping symbiotic selectivity in their respective ecological niches.