Joint engineering of SACE_Lrp and its target MarR enhances the biosynthesis and export of erythromycin in Saccharopolyspora erythraea.

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The Lrp and MarR families are two groups of transcriptional regulators widely distributed among prokaryotes. However, the hierarchical-regulatory relationship between the Lrp family and the MarR family remains unknown. Our previous study found that an Lrp (SACE_Lrp) from Saccharopolyspora erythraea indirectly repressed the biosynthesis of erythromycin. In this study, we characterized a novel MarR family protein (SACE_6745) from S. erythraea, which is controlled by SACE_Lrp and plays a direct regulatory role in erythromycin biosynthesis and export. SACE_Lrp directly regulated the expression of marR by specifically binding a precise site OM (5'-CTCCGGGAACCATT-3'). Gene disruption of marR increased the production of erythromycin by 45% in S. erythraea A226. We found that MarR has direct DNA-binding activity for the promoter regions of the erythromycin biosynthetic genes, as well as an ABC exporter SACE_2701-2702 which was genetically proved to be responsible for erythromycin efflux. Disruption of SACE_Lrp in industrial S. erythraea WB was an efficient strategy to enhance erythromycin production. Herein, we jointly engineered SACE_Lrp and its target MarR by deleting marR in WBΔSACE_Lrp, resulting in 20% increase in erythromycin yield in mutant WBΔLrpΔmarR compared to WBΔSACE_Lrp, and 39% to WB. Overall, our findings provide new insights into the hierarchical-regulatory relationship of Lrp and MarR proteins and new avenues for coordinating antibiotic biosynthesis and export by joint engineering regulators in actinomycetes. KEY POINTS: • The hierarchical-regulatory relationship between SACE_Lrp and MarR was identified. • MarR directly controlled the expression of erythromycin biosynthesis and export genes. • Joint engineering of SACE_Lrp-MarR regulatory element enhanced erythromycin production.