A green fluorescent protein (GFP)-based plasmid system to study post-transcriptional control of gene expression in vivo.

Small non-coding RNAs (sRNAs) are an emerging class of regulators of bacterial gene expression, which mainly modulate the translation of trans-encoded mRNAs. Typically, these molecules are 50-200 nucleotides in size and do not contain expressed open reading frames (ORFs). In Escherichia coli, about 70 members of this group have been identified to date and further estimates assume hundreds of sRNAs per bacterial genome. Regulation of gene expression by sRNAs is predominantly mediated by physical sRNA/target mRNA interactions that are based on short and imperfect complementarity. Although the contribution of sRNAs to overall bacterial gene regulation is now being appreciated, the function of many sRNAs is still unknown and their targets await to be uncovered. We recently developed a modular two-plasmid system, based on the green fluorescent protein (GFP) as non-invasive reporter of gene expression, to rapidly monitor the regulatory potential of sRNA/target mRNA pairs under investigation in vivo. The specialized reporter plasmid series also provides a suitable platform to study the function of cis-encoded riboregulators such as natural riboswitches, thermosensors, or engineered aptamer-based regulatory switches.