FIG 4.

c-di-GMP regulates transcriptional activity of tfoY promoters in a VpsR-dependent manner. (A) Expression from the indicated reporters was assayed in a ΔvpsR mutant V. cholerae strain. The dual P_tac-vpsR, P_tac-qrgB strain carries a single overexpression vector in which vpsR and qrgB have unique ribosome binding sites but are under the transcriptional control of the same inducible promoter. Error bars for all graphs indicate the standard deviation among three biological replicates. *, P < 0.05 in a comparison of QrgB to QrgB* or VC1086 to VC1086*. (B) Western blot of PAGE-separated protein isolated from a V. cholerae ΔvpsR mutant carrying the P₁₂₃₄-TL-FULL gfp reporter fusion. Blots were hybridized with anti-GFP primary antibody and HRP-conjugated secondary antibody and detected using ECL. The blot shown is representative of multiple experiments. L, low; I, intermediate; H, high.