Symbiotic nitrogen fixation is a high energy consumption procession, legumes must has a machansim to balance growth and symbiotic nodulation. We show that the Compact Root Architecture 2 (MtCRA2) receptor-like kinase is essential to promote the initiation of early symbiotic nodulation and to inhibit root growth in response to low-N.stress On the one hand, MtCEP1-activated MtCRA2 receptor represses transcriptionally the expression of the MtYUC2 gene, which is correlated with reduced auxin content in roots, and increased main root growth and decreased lateral root formation. On the other hand, the MtCEP1-activated MtCRA2 receptor transphosphorylates MtEIN2, which inhibits MtEIN2 cleavage depending on N-availability and thus interrupts the ethylene signaling pathway which inhibits rhizobial infections under low-N, making the plant roots more actively susceptible to rhizobium. The image shows the transgenic hairy roots overexpressing MtYUC2 and marked by GUS staining. The image was photographed by Fugui Zhu.