Construction of the co-expression plasmids of fostriecin polyketide synthases and heterologous expression in Streptomyces

Context: Polyketides are bioactive natural products with diverse bioactivities, and heterologous production of polyketides in easily engineered microbial hosts is preferred for the production of structurally diverse and the therapeutically active polyketides. Objective: In this study, heterologous expression of the biosynthetic genes encoding type I polyketide synthases (PKS) involved in biosynthesis of fostriecin, a unique phosphate monoester polyketide antibiotic, was attempted. Materials and methods: Fostriecin PKS (Fos-PKS) biosynthetic gene cluster in a total of 48.4 kb were cloned downstream of the act I promoter in two compatible Streptomyces vectors using Red/ET recombination. The co-expression plasmids were sequentially transferred into Streptomyces lividans and Streptomyces coelicolor. Active transcription of the polyketide genes was confirmed by reverse transcription PCR (RT-PCR) analysis, and the metabolites were detected using high-performance liquid chromatography (HPLC). Results: The recombinant strains S. lividans TK24/p6-fosAB-p4-fosCDEF and S. coelicolor M512/p6-fosAB-p4-fosCDEF were obtained for heterologous expression in Streptomyces. Pigmentation was observed in the recombinant strains, whereas the control strain with empty vector displayed no change in pigment production. Active transcription of the polyketide genes was confirmed by RT-PCR analysis and subsequent sequencing. Conclusion: The present study is the first attempt to overexpress Fos-PKS biosynthetic gene cluster in Streptomyces. More studies on heterologous expression of the fostriecin biosynthetic gene cluster would be beneficial for further understanding the mechanisms of its structural as well as the potential pharmaceutically effect.