Butenyl-spinosyn, a secondary metabolite produced by Saccharopolyspora pogona, exhibits strong insecticidal activity than spinosyn. However, the low synthesis capacity and unknown metabolic characteristics of butenyl-spinosyn in wild-type S. pogona limit its broad application and metabolic engineering. Here, we showed that S. pogona exhibited increased glucose consumption ability and growth rate compared with S. spinosa, but the production of butenyl-spinosyn was much lower than that of spinosyn. To further elucidate the metabolic mechanism of these different phenotypes, we performed a comparative proteomic and metabolomic study on S. pogona and S. spinosa to identify the change in the abundance levels of proteins and metabolites. We found that the abundance of most proteins and metabolites associated with glucose transport, fatty acid metabolism, tricarboxylic acid cycle, amino acid metabolism, energy metabolism, purine and pyrimidine metabolism, and target product biosynthesis in S. pogona was higher than that in S. spinosa. However, the overall abundance of proteins involved in butenyl-spinosyn biosynthesis was much lower than that of the high-abundance protein chaperonin GroEL, such as the enzymes related to rhamnose synthesis. We speculated that these protein and metabolite abundance changes may be directly responsible for the above phenotypic changes in S. pogona and S. spinosa, especially affecting butenyl-spinosyn biosynthesis. Further studies revealed that the over-expression of the rhamnose synthetic genes and methionine adenosyltransferase gene could effectively improve the production of butenyl-spinosyn by 2.69-and 3.03fold, respectively, confirming the reliability of this conjecture. This work presents the first comparative proteomics and metabolomics study of S. pogona and S. spinosa, providing new insights into the novel links of phenotypic change and metabolic difference between two strains. The result will be valuable in designing strategies to promote the biosynthesis of butenyl-spinosyn by metabolic engineering.

Background: Saccharopolyspora pogona is a prominent industrial strain due to its production of butenyl-spinosyn, a high-quality insecticide against a broad spectrum of insect pests. TetR family proteins are diverse in a tremendous number of microorganisms and some are been researched to have a key role in metabolic regulation. However, specific functions of TetR family proteins in S. pogona are yet to characterize. Results: In the present study, the overexpression of the tetR-like gene sp1418 in S. pogona resulted in marked effects on vegetative growth, sporulation, butenyl-spinosyn biosynthesis, and oxidative stress. By using qRT-PCR analysis, mass spectrometry, enzyme activity detection, and sp1418 knockout verification, we showed that most of these effects could be attributed to the overexpression of Sp1418, which modulated enzymes related to the primary metabolism, oxidative stress and secondary metabolism, and thereby resulted in distinct growth characteristics and an unbalanced supply of precursor monomers for butenyl-spinosyn biosynthesis. Conclusion: This study revealed the function of Sp1418 and enhanced the understanding of the metabolic network in S. pogona, and provided insights into the improvement of secondary metabolite production.

Purpose To generate a AfsR-like (AfsR-L) overexpression strain Saccharopolyspora pogona-AfsR-L and investigate its effects on the morphology and metabolism of S. pogona. Methods Firstly, we generated the overexpression vector pOJ260-P ermE-afsR-L via overlap extension PCR. Then, the recombination strain S. pogona-AfsR-L was constructed via conjugal transfer. To monitor the growth and morphology, mycelia and sporulation were observed. The distinctive proteins and butenyl-spinosyn biosynthesis were investigated by SDS-PAGE, HPLC, and mass spectrometry. And the transcriptional level of afsR-L and other relative functional genes in S. pogona-AfsR-L was analyzed by qRT-PCR. Western blot verified the increased amount of AfsR-L protein in the overexpression strain. Result Growth curve and mycelia observation showed that afsR-L overexpression make the stationary phase of S. pogona-AfsR-L longer than that of wild S. pogona by approximate 3 days. Moreover, S. pogona-AfsR-L exhibited a more obvious white phenotype on the solid medium, which means afsR-L overexpression affects the sporulation ability of S. pogona. HPLC analysis revealed that the peak area of the butenyl-spinosyn yield of S. pogona-AfsR-L was 293.6, while that of S. pogona was 250.9. SDS-PAGE analysis showed that the two strains had different whole protein expression profiles, and the distinctive proteins were further identified by LC-MS/MS identification, which showed the possible control mechanism of afsR-L gene in S. pogona. Conclusion We concluded that AfsR could directly or indirectly positively regulate the biosynthesis of butenyl-spinosyn and affect the growth features of S. pogona. We envisioned that this result can be expanded to other Streptomyces for strain improvement.

No abstract