Signal amplification of using a standardized translation initiation region.

is a genetic fragment that regulates the expression of the operon in bacteria, which is required for the metabolism of L-arabinose. It is widely used in bioengineering applications because it can drive regulatable and titratable expression of genes and genetic pathways in microbial cell factories. A notable limitation of is that it generates a low signal when induced with high concentrations of L-arabinose (the maximum ON state). Herein we have amplified the maximum ON state of by coupling it to a synthetically evolved translation initiation region ( ). The coupling maintains regulatable and titratable expression from and yet increases the maximal ON state by >5-fold. The general principle demonstrated in the study can be applied to amplify the signal from similar genetic modules. Graphical Abstract.