Figure 2.
SGCs are examples of the complex behavior that arises when combining genetic elements. (A) A serial transcriptional activation cascade that produces deGFP. Each σ factor activates its successor by interacting with its promoter, as indicated by solid arrows. (B) This circuit generates a pulse in deGFP production due to two competing expression cascades. Addition of σ70 induces deGFP production by the stimulatory (lower) circuit, but the inhibitory (upper) circuit is triggered simultaneously and causes a delayed suppression. (C) An inducible transcriptional repression unit that can switch outputs. In the presence of IPTG, deCFP is produced; replacement by ATc represses deCFP production and stimulates deGFP expression. Adapted with permission from refs (17 and 18). Copyright 2012 and 2016 American Chemical Society.