Lotus japonicus in legumes is one of the model plants in the study of the system on the symbiotic nitrogen fixation.The research of the symbiotic signaling pathway and the mechanism of interaction of rhizobial bacteria helps to discover the secret about the establishment of symbiotic relationship and the formation of the symbiont between rhizobial bacteria with legumes.In this study,the interaction of the two GRAS family proteins,nodulation signaling pathway1 (NSP1) and nodulation signaling pathway2(NSP2),was confirmed in vivo and vitro using a yeast two-hybrid system and protein-protein interaction in vitro.The interacting loci were assessed to be the LHRI domain of NSP2 and LHRII domain of NSP1.