Characterization of the positive SARP family regulator PieR for improving piericidin A1 production in Streptomyces piomogeues var.Hangzhouwanensis

Piericidin A1,a member ofɑ-pyridone antibiotic,exhibits various biological activities such as antimicrobial,antifungal,and antitumor properties and possesses potent respiration-inhibitory activity against insects due to its competitive binding capacity to mitochondrial complex I.The biosynthetic pathway of piericidin A1 has been reported in Streptomyces piomogeues var.Hangzhouwanensis,while the regulatory mechanism remains poorly understood.In this study,a Streptomyces antibiotic regulatory protein(SARP)family transcriptional regulator PieR was characterized.Genetic disruption and complementation manipulations revealed that PieR positively regulated the production of piericidin A1.Moreover,the overexpression of pieR contributed to the improvement of piericidin A1 productivity.The real-time quantitative PCR(RT-qPCR)was carried out and the data showed that pieR stimulated the transcription of all the biosynthesis-related genes for piericidin A1.In order to explore the regulatory mechanism,electrophoresis mobility shift assays(EMSA)and DNase I footprinting experiments have been conducted.A protected region covering 50 nucleotides within the upstream region of pieR was identified and two 5-nt direct repeat sequences(5′-CCGGA-3′)in the protected region were found.These findings,taken together,set stage for transcriptional control engineering in the view of optimizing piericidin A1 production and thus provide a viable potent route for the construction of strains with high productivity.