title: Enhanced production of avermectin by deletion of type III polyketide synthases biosynthetic cluster rpp in Streptomyces avermitilis.
abstract: The rpp biosynthetic gene cluster (sav7130-7131) in Streptomyces avermitilis contains a type III polyketide synthases (PKSs) and a cytochrome P450 and was reportedly involved in producing a diffusible brown pigment. Since the same precursor malonyl-CoA was used as substrate for the type I PKSs and type III PKSs, there might be a competition for precursor between rpp gene cluster and avermectin biosynthetic cluster. In this work, rpp biosynthetic gene cluster deletion mutants were constructed to improve avermectin production. In an industrial strain AV-LP, rpp deletion improved avermectin production from 1024 to 1262 mg l-1without any effect on the cell growth. In the same way, the production of an industrial overproducer increased from 3582 to 4450 mg l-1. Transcriptional analysis suggested that the deletion of rpp gene cluster stimulated transcription of aveR, leading to increased transcription of biosynthetic gene aveA1 and a consequent increase in avermectin production.
  
  
  CONCLUSIONS
  Because of the wide use of avermectins, many efforts have been made to improve the productivity via conventional genetic engineering technique. However, due to the lack of the molecular and genetic basis underlying such a yield enhancement after iterative rounds of mutagenesis and selection, it is often difficult to improve the titre in overproducers. Here, we report knocking out rpp biosynthetic gene cluster improved the production of an industrial overproducer by 24%. This work enriched the strategy to improve the production of antibiotics in industrial strains and may help further understanding of the interaction between type III polyketide synthases and other types.
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China.|Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors.forename: L
authors.initials: L
authors.lastname: Meng
authors.affiliation: School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Xiong
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China.
authors.forename: J
authors.initials: J
authors.lastname: Chu
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China. yongwang@sibs.ac.cn.|Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China. yongwang@sibs.ac.cn.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000217:Acyltransferases / Q000235:genetics*; D017353:Gene Deletion; D005818:Genetic Engineering; D007218:Industrial Microbiology / Q000379:methods*; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000378:metabolism; D008316:Malonyl Coenzyme A / Q000378:metabolism; D005810:Multigene Family; D048630:Polyketide Synthases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism*
chemical_list: D008316:Malonyl Coenzyme A; D007559:Ivermectin; C019264:avermectin; D048630:Polyketide Synthases; D000217:Acyltransferases; C020141:flavanone synthetase
keywords: 
  Streptomyces avermitili
  ; 
  rppA
  ; avermectin production; biosynthesis cluster; industrial overproducer; type III polyketide synthases