Effect of fcl gene for butenyl-spinosyn biosynthesis and growth of Saccharopolyspora pogona / 生物工程学报

The fcl gene encodes GDP-fucose synthase, which catalyzes two-step differential isomerase and reductase reactions in the synthesis of GDP-L-fucose from GDP-D-mannose. It also participates in the biosynthesis of amino sugar and ribose sugar, and is one of the key enzymes to regulate the metabolism of sugar and nucleotides in organisms. The presence of fcl gene in Saccharopolyspora pogona was found through sequencing result of genome. The mutant S. pogona-fcl and S. pogona-Δfcl were constructed by gene engineering technology. The results showed that the gene had an effects on growth and development, protein expression and transcriptional level, insecticidal activity, and biosynthesis of butenyl-spinosyn of Saccharopolyspora pogona. The results of HPLC analysis showed that the yield of butenyl-spinosyn in S. pogona-Δfcl was 130% compared with that in S. pogona, which reduced by 25% in S. pogona-fcl. The results of determination of insecticidal activity showed that S. pogona-Δfcl had a stronger insecticidal activity against Helicoverpa armigera than that of S. pogona, while the S. pogona-fcl had a lower insecticidal activity against Helicoverpa armigera compared with S. pogona. Scanning electron microscopy (SEM) was used to observe the morphology of the mycelia. It was found that the surface of the S. pogona-Δfcl was wrinkled, and the mycelium showed a short rod shape. There was no significant difference in mycelial morphology between S. pogona-fcl and S. pogona. Aboved all showed that deletion of fcl gene in S. pogona hindered the growth and development of mycelia, but was beneficial to increase the biosynthesis of butenyl-spinosyn and improve insecticidal activity. Whereas the fcl gene over-expression was not conducive to the biosynthesis of butenyl-spinosyn and reduced their insecticidal activity. SDS-PAGE results showed that the difference of protein expression among the three strains was most obvious at 96 hours, which was identified by real-time fluorescence quantitative polymerase chain reaction, the results showed that there were significant differences of related genes in transcriptional levels among the three strains. Based on the results of the study, a network metabolic control map was constructed to analyze the effect of fcl gene on growth and the regulation pathway of butenyl-spinosyn biosynthesis, which provided an experimental basis for revealing the regulation mechanism of butenyl-spinosyn biosynthesis and related follow-up studies.

Effect of ribosome engineering on butenyl-spinosyns synthesis of Saccharopolyspora pogona / 生物工程学报

Through introducing mutations into ribosomes by obtaining spontaneous drug resistance of microorganisms, ribosome engineering technology is an effective approach to develop mutant strains that overproduce secondary metabolites. In this study, ribosome engineering was used to improve the yield of butenyl-spinosyns produced by Saccharopolyspora pogona by screening streptomycin resistant mutants. The yields of butenyl-spinosyns were then analyzed and compared with the parent strain. Among the mutants, S13 displayed the greatest increase in the yield of butenyl-spinosyns, which was 1.79 fold higher than that in the parent strain. Further analysis of the metabolite profile of S13 by mass spectrometry lead to the discovery of Spinosyn α1, which was absent from the parent strain. DNA sequencing showed that there existed two point mutations in the conserved regions of rpsL gene which encodes ribosomal protein S12 in S13. The mutations occurred a C to A and a C to T transversion mutations occurred at nucleotide pair 314 and 320 respectively, which resulted in the mutations of Proline (105) to Gultamine and Alanine (107) to Valine. It also demonstrated that S13 exhibited genetic stability even after five passages.

[Localization and identification of crystal protein genes in Bacillus thuringiensis strain 4.0718].

OBJECTIVE: To localize and identify the insecticidal crystal protein genes (cry genes) in high-toxic Bacillus thuringiensis strain 4.0718. METHODS: The genomic DNA of B. thuringiensis strain 4.0718 was isolated by pulse field gel electrophoresis (PFGE), and the PFGE pattern and plasmid pattern were characterized. The cry genes in the strain were analyzed by Southern blot and the cry gene types on the chromosome and plasmid were identified by PCR and restriction fragment length polymorphism patterns of the PCR-amplified fragments (PCR-RFLP). RESULTS: Southern blots showed that the cry genes in B. thuringiensis strain 4.0718 are present on both chromosome and plasmid. PCR and RFLP patterns showed that the chromosome and plasmid contain four cry genes, cry1Aa, crylAc, cry2Aa, and cry2Ab. However, the cry genes on the chromosome may be incomplete, while the cry1Aa and cry1Ac genes localized on the plasmid were found to contain the full coding sequence. CONCLUSION: The abundant cry genes were first found on chromosome of B. thuringiensis strain 4.0718, and the cry-type genes are the same as the plasmid.