Abstract:The promoter sequences of nodA,nodB,nodD were cloned based on the genomic information of Mesorhizobium loti MAFF303099 and fused with the reporter gene lacZ to construct the nod-lacZ fusion separately. Then these fusions were separately transformed into M. loti MAFF303099 and Rhizobium sp. NGR234 to detect the expression of these nod genes after induced by Lotus japonicus root extract (RE). The results showed that there was no expression of nodA when treated with root extracts.RE induced expression of nodB and nodD1,but showed upregulation of just 2-3 times. nodD2 expressed constitutively in M. loti MAFF303099.Neither of these induced the expression of nodA in M. loti MAFF303099 induced by 5 different flavonoid compounds separately,but the expression of nodA was detected in NGR234 strain treated by Luteolin.