A Blue Light-Activated Sensor System Enables Dynamic and Reversible Control of Gene Expression in Streptomyces.

Programmable control of bacterial gene expression is critical for advancing applications in synthetic biotechnology. This is particularly true for the genus Streptomyces, a well-recognized prolific producer of diverse natural products. Although several inducible regulatory systems have been developed for Streptomyces, there remains an escalating demand to expand the repertoire of high-performance induction tools. Herein, we present Strep-LitRS, a light-sensing system for Streptomyces that exhibits pronounced activation under blue and green light, with only weak induction under yellow light. Moreover, blue light was more effective than green light in triggering transcriptional activation. This system enables tunable, reversible, and spatially controlled gene expression upon blue-light illumination. It demonstrates effective programmable control of morphological differentiation via CRISPR/dCas9-mediated interference. Its utility is further validated through the blue light-inducible production of actinorhodin and violacein in Streptomyces chassis strains. Furthermore, by coupling Strep-LitRS with the Cre-loxP recombination system, we achieve precise and conditional gene activation in response to blue light. A synthetic genetic circuit also allows light-induced control to be gated by rhamnose, enabling multi-input regulatory logic. Collectively, this work establishes a versatile light-sensing module and highlights its broad applicability for the programmable manipulation of diverse target genes across Streptomyces species.