Legume roots secure nitrogen by forming a symbiosis with soil rhizobia but remain resistant to pathogenic bacteria1–4. How this tolerance to rhizobia is achieved without compromising plant immunity is largely unknown. Here we identify the cytoplasmic kinase MtLICK1/2, which interacts with nodulation factor receptor MtLYK3 to drive symbiotic signalling and suppress plant immunity. Rhizobial infection and nodule development are defective in Mtlick1/2, phenocopying the Mtlyk3-1 mutant. MtLICK1/2 and MtLYK3 undergo reciprocal transphosphorylation during rhizobial symbiosis. Phosphorylated MtLYK3 activates the receptor-like kinase MtDMI2 to stimulate symbiotic signalling. MtLICK1/2 is activated in the rhizobial infection area to suppress plant immunity. Thus, MtLICK1/2 and MtLYK3 together amplify symbiotic signalling and dampen host immunity to enable legume–rhizobium symbiosis.
