Heterologous expression of predicted promoter site for paraquat-inducible genes of the bacterium Chromobacterium violaceum is increased by plumbagin

Abstract

The aim of this study was to evaluate functionally the effect of plumbagin on the heterologous expression of a predicted promoter region of open reading frames of paraquat-inducible (pqi) genes revealed during genome annotation analyses of the bacterium Chromobacterium violaceum. First, the promoter of interest was amplified using specific primers and cloned into a conjugative vector carrying the Escherichia coli lacZ gene without a promoter. The heterologous expression of the predicted promoter region was then examined in the presence of 50 µg/mL plumbagin by β-galactosidase expression assays. Significant differences were detected in the levels of β-galactosidase as a result of the activation of the promoter region of interest in response to plumbagin at the concentration tested. On the other hand, no growth of the wild strain of C. violaceum was found during its incubation in nutrient broth medium containing different concentrations of plumbagin compared to control group. The findings described herein demonstrate that the heterologous expression of a predicted promoter site of pqi genes of C. violaceum is induced by plumbagin in a fusion strain, giving insights into the functional characterization of intrinsic regulatory DNA motifs annotated in this bacterial genome.

Keywords

• Functional genome
• Heterologous expression
• Oxidizing agent