Further Studies on Structure of nodD3 Gene in Rhizobium meliloti——Analysis of 5’Non-Coding Region of nodD3 and Its Evolutionary Implications

R.meliloti nodD3 gene is transcriptionally controlled by two promoters.Gel retardationexperiments show that SyrM and NodD3 are binding to the first promoter region of nodD3,while no proteinfactor is found to bind to the second promoter region of the gene.Comparison has been made between 5′ non-coding region of nodD3 and the corresponding region upstream of nodD1.The presence of nod-box andnodA-like sequences in the 5′ noncoding region of nodD3 supports the hypothesis that nodD3 evolves withthe duplication of the nodD1-nodA fragment during the speciation of R.meliloti.