A Robust and Orthogonal Far-Red Light Sensor for Gene Expression Control in Escherichia coli

Area of Science:

• Synthetic Biology
• Microbiology
• Biotechnology

Background:

• Optogenetics offers noninvasive control of cellular processes.
• Far-red light (FRL) is advantageous for optogenetics due to low toxicity and deep tissue penetration.
• Existing FRL sensors lack robustness and orthogonality in bacteria.

Purpose of the Study:

• To establish an orthogonal FRL sensor in *Escherichia coli*.
• To leverage the RfpA-RfpC-RfpB (RfpABC) signaling system from cyanobacteria.
• To enable precise FRL-inducible gene expression in bacterial synthetic biology.

Main Methods:

• Identified a conserved far-red light-regulatory (FLR) motif in cyanobacterial FaRLiP gene clusters.
• Engineered simplified FLR-containing promoters for FRL-responsive gene activation.
• Characterized the dynamic range and activation/suppression capabilities of the FRL sensor.

Main Results:

• Established an orthogonal FRL sensor in *E. coli* with a dynamic range exceeding 230-fold.
• Demonstrated FRL-inducible gene expression via the FLR motif and RfpB interaction.
• Identified additional FRL-inducible promoter resources within the FaRLiP gene cluster.

Conclusions:

• The study provides a robust and orthogonal FRL sensor for bacterial synthetic biology.
• Advances understanding of far-red light photoacclimation (FaRLiP) regulatory mechanisms in cyanobacteria.
• Offers versatile FRL-inducible promoter tools for diverse synthetic biology applications.