Exogenous cAMP upregulates the expression of glnII and glnK-amtB genes in Sinorhizobium meliloti 1021

The existence of multiple adenylate cyclase encoding genes implies the importance of cAMP in Sinorhizobium meliloti 1021. In this study, as a pioneer step of understanding CAMP roles, microarray analysis on S. meliloti was carried out for the function of exogenous CAMP. To our surprise, the result showed that the transcriptions of gInII and gInK genes were significantly upshifted in the presence of exogenous CAMP in S. meliloti. This phenomenon is further confirmed in S. meliloti that the expression of either glnll or gInK promoter-lacZ translational fusion is higher in the presence of exogenous cAMP. Therefore, for the first time, we have identified genes from S. meliloti whose expression is activated by CAMP. The potential physiological role of upregulation of glnll and g1nK by cAMP is discussed.