Screening and engineering of high-activity promoter elements through transcriptomics and red fluorescent protein visualization in .

The versatile photosynthetic α-proteobacterium , has recently been extensively engineered as a novel microbial cell factory (MCF) to produce pharmaceuticals, nutraceuticals, commodity chemicals and even hydrogen. However, there are no well-characterized high-activity promoters to modulate gene transcription during the engineering of . In this study, several native promoters from JDW-710 (JDW-710), an industrial strain producing high levels of co-enzyme Q (Q) were selected on the basis of transcriptomic analysis. These candidate promoters were then characterized by using as a reporter gene. Two native promoters, and , showed 620% and 800% higher activity, respectively, than the promoter, which has previously been used for gene overexpression in In addition, a -derived synthetic promoter library with strengths ranging from 54% to 3200% of that of the promoter, was created on the basis of visualization of red fluorescent protein (RFP) expression in . Finally, as a demonstration, the synthetic pathway of Q was modulated by the selected promoter T334* in JDW-710; the Q yield in shake-flasks increased 28% and the production reached 226 mg/L These well-characterized promoters should be highly useful in current synthetic biology platforms for refactoring the biosynthetic pathway in -derived MCFs.