P Ramakrishnan, JJ Tabor – ACS Synthetic Biology, 2016
We have previously engineered green/red and red/far red photoreversible E. coli phytochrome and cyanobacteriochrome (CBCR) two component systems (TCSs) and utilized them to program tailor-made gene expression signals for gene circuit characterization. Here, we transport the UV-violet/green photoreversible CBCR TCS UirS-UirR from Synechocystis PCC6803 to E. coli . We demonstrate that the promoter of the small RNA csiR1, previously shown to be activated by inorganic carbon stress, is a UirS-UirR output. Additionally, in contrast to a recently proposed sequestration model, we show that the sensor histidine kinase UirS phosphorylates the response regulator UirR to activate PcsiR1 transcription in response to UV-violet light. Finally, we measure UirS-UirR output changes minutes after a change in light input and exploit these rapid dynamics to program a challenging gene expression signal with high predictability. UirS-UirR is the first photoreversible optogenetic tool that responds in the UV-blue region of the spectrum and has numerous optogenetic applications.
