Synthetic riboswitches for the conditional control of gene expression in Streptomyces coelicolor.

We have demonstrated the portability of theophylline-dependent synthetic riboswitches for the conditional control of gene expression in Streptomyces coelicolor. The riboswitches mediate dose-dependent, up to 260-fold activation of reporter gene expression. Riboswitch regulation is a simple method requiring a sequence of only ~85 nt to be inserted between a transcriptional start site and the start codon; no additional auxiliary factors are necessary. The promoters galP2, ermEp1 and SF14 worked well in concert with the riboswitches. They allowed theophylline-dependent expression of not only the heterologous β-glucuronidase reporter gene but also dagA, an endogenous agarase gene. The successful combination of all tested promoters with the riboswitches underlines the orthogonality of riboswitch regulation. We anticipate that any additional natural or synthetic promoters can be combined with the riboswitch.