NOT Gate Genetic Circuits to Control Gene Expression in Cyanobacteria

To downregulate gene expression in
cyanobacteria, we constructed
NOT gate genetic circuits using orthogonal promoters and their cognate
repressors regulated translationally by synthetic riboswitches. Four
NOT gates were tested and characterized in five cyanobacterial strains
using fluorescent reporter-gene assays. In comparison to alternative
systems used to downregulate gene expression in cyanobacteria, these
NOT gates performed well, reducing YFP reporter expression by 4 to
50-fold. We further evaluated these NOT gates by controlling the expression
of the ftsZ gene, which encodes a prokaryotic tubulin
homologue that is required for cell division and is essential for Synechococcus elongatus PCC 7942. These NOT gates would
facilitate cyanobacterial genetic engineering or the study of essential
cellular processes.