Comparative analysis of inducible promoters in cyanobacteria

Abstract

Research in the field of synthetic biology highly depends on efficient, well-characterized promoters. While great progress has been made with other model organisms such as Escherichia coli, photosynthetic cyanobacteria still lag behind. Commonly used promoters that have been tested in cyanobacteria show weaker dynamic range or no regulation at all. Alternatives such as native metal-inducible promoters pose the problem of inducer toxicity.\n\nHere, we evaluate four different inducible promoters, both previously published and new, using the modular plasmid pSHDY, in the model cyanobacterium Synechocystis sp. PCC 6803 - namely the vanillate-inducible promoter PvanCC, the rhamnose-inducible Prha, and the aTc-inducible PL03, and the Co2+-inducible PcoaT. We estimate individual advantages and disadvantages, as well as dynamic range and strength of each promoter in comparison with well-established constitutive systems. We observed a delicate balance between transcription factor toxicity and sufficient expression to obtain a dose-dependent response to the inducer. In summary, we expand the current understanding and employability of inducible promoters in order to facilitate the construction of more complex regulatory synthetic networks, as well as more complicated biotechnological pathways for cyanobacteria.