A modular and tunable genetic amplifier for the modulation of transcriptional signals

View all posters

Baojun Wang, Prof Mauricio Barahona, Prof Martin Buck

Imperial College London, United Kingdom

Here we report the design and construction of a modular and tunable genetic amplifier in E. coli that can amplify weak transcriptional input signals in linear analogue mode with continuous tunable gain control. The three-terminal transcriptional device comprises orthogonal genetic components (hrpRS, hrpV and PhrpL) from the hrp (hypersensitive response and pathogenicity) gene regulatory network in Pseudomonas syringae. In contrast to other work, our design approach focuses on controlling the amounts of in trans acting protein components to achieve tunable devices. Our results show that the amplifier can linearly amplify 20-fold the transduced transcriptional signal of an arsenic-responsive sensor without observable response delay, thus greatly enhancing the sensitivity and dynamic range of the biosensor. To showcase the flexibility of the device, we generated a set of genetic amplifiers with different gains and input dynamic ranges by varying the expression levels of the underlying activator proteins in the device. Furthermore, we appended a third modular terminal to control the expression of an inhibitor protein for the output transcriptional rate, thus acting as a gain-tuning knob for our amplifier. As a result, the amplifier was able to modulate transcriptional signals with a continuous tunable gain depending on this additional external signal input. The device was demonstrated to be modular since it can amplify the transcriptional inputs from a set of constitutive promoters of different strengths with the same gain as the one measured for the arsenic sensor. To our knowledge, the engineered genetic amplifier is the first analogue device in the field that allows linear transcriptional signal amplification with a tunable high gain and a large dynamic range output. The device could have a wide range of applications for tuning transcriptional signals in gene circuits, e.g. for enhanced biosensing, and in metabolic pathways for improved bioproduction.