Receptor-mediated exopolysaccharide perception controls bacterial infection

Rhizobium bacteria infect the roots of legumes, where they induce the formation of nitrogen-fixing root nodules. This symbiotic relationship is of agricultural importance as it reduces the need for nitrogen fertilizers. But how do legumes recognize these beneficial partners among thousands of incompatible soil bacteria they encounter? It is known that exopolysaccharides on the surface of bacteria are important for interactions of these microorganisms with multicellular organisms and here Jens Stougaard and coworkers identify an exopolysaccharide receptor (EPR3) that mediates recognition of rhizobia in the wild legume Lotus japonicus. EPR3 expression is induced upon perception of bacterial signalling molecules known as Nod factors. The receptor recognizes compatible exopolysaccharides, thus controlling the symbiotic infection.