Pantoea agglomerans YS19 poly(A) polymerase i gene possesses the indole-sensing sequence in the promoter region

Pantoea agglomerans YS19 is a predominant diazotrophic endophyte with multiple growth-promoting effects on its host plant that was isolated from rice. Indole is confirmed to induce many changes of physiological and biochemical characteristics in bacteria. Although YS19 cannot produce indole, it can sense indole in the environment and be regulated by indole. Here, using gfp as a reporter gene, we constructed a series of recombinant plasmids containing the promoter region of the poly(A) polymerase I gene (pcnB) fused with gfp, and compared the green fluorescence intensity at different concentrations of exogenous indole by a flow cytometer. In this research, we confirmed that exogenous indole significantly inhibited the expression of pcnB by its promoter; the regulation sequence sensitive to indole in the promoter region of the pcnB gene (In-pcnB) was between -129 and -88 bp. In-pcnB is widely distributed and strictly conserved in the same genus. These results suggest novel roles of In-pcnB in P. agglomerans YS19, showing its special relation to the indole regulatory pathway.