Transcriptional regulation of cpsQ-mfpABC and mfpABC by CalR in Vibrio parahaemolyticus.

The cpsQ-mfpABC locus is transcribed as two operons, i.e., cpsQ-mfpABC and mfpABC, in Vibrio parahaemolyticus, and both of them are all required for biofilm formation. CalR belongs to the LysR-type transcriptional regulator family, and was originally identified as a repressor of the swarming motility and T3SS1 genes expression in V. parahaemolyticus. In the present work, a combination of qRT-PCR, primer extension, LacZ fusion expression, electrophoretic mobility shift assay, and DNase I footprinting assays were employed to elucidate the regulatory mechanisms of cpsQ-mfpABC and mfpABC by CalR. One transcription start site for each operon was detected and their activities were activated by CalR. His-CalR protected two DNA regions upstream of mfpABC against DNase I digestion, but no binding sites were detected in the promoter region of cpsQ-mfpABC, suggesting a direct and an indirect regulatory manner for mfpABC and cpsQ-mfpABC transcription by CalR, respectively. Collectively, the results presented here confirmed a new physiological role for CalR that acts as an activator for cpsQ-mfpABC and mfpABC transcription.