title: Activation of a plasmid-situated type III PKS gene cluster by deletion of a wbl gene in deepsea-derived Streptomyces somaliensis SCSIO ZH66.
abstract: BACKGROUND
  Actinomycete genome sequencing has disclosed a large number of cryptic secondary metabolite biosynthetic gene clusters. However, their unavailable or limited expression severely hampered the discovery of bioactive compounds. The whiB-like (wbl) regulatory genes play important roles in morphological differentiation as well as secondary metabolism; and hence the wblA so gene was probed and set as the target to activate cryptic gene clusters in deepsea-derived Streptomyces somaliensis SCSIO ZH66.
  
  
  RESULTS
  wblA so from deepsea-derived S. somaliensis SCSIO ZH66 was inactivated, leading to significant changes of secondary metabolites production in the ΔwblA so mutant, from which α-pyrone compound violapyrone B (VLP B) was isolated. Subsequently, the VLP biosynthetic gene cluster was identified and characterized, which consists of a type III polyketide synthase (PKS) gene vioA and a regulatory gene vioB; delightedly, inactivation of vioB led to isolation of another four VLPs analogues, among which one was new and two exhibited improved anti-MRSA (methicillin-resistant Staphylococcus aureus, MRSA) activity than VLP B. Moreover, transcriptional analysis revealed that the expression levels of whi genes (whiD, whiG, whiH and whiI) and wbl genes (wblC, wblE, wblH, wblI and wblK) were repressed by different degrees, suggesting an intertwined regulation mechanism of wblA so in morphological differentiation and secondary metabolism of S. somaliensis SCSIO ZH66.
  
  
  CONCLUSIONS
  wblA orthologues would be effective targets for activation of cryptic gene clusters in marine-derived Streptomyces strains, notwithstanding the regulation mechanisms might be varied in different strains. Moreover, the availability of the vio gene cluster has enriched the diversity of type III PKSs, providing new opportunities to expand the chemical space of polyketides through biosynthetic engineering.
authors.affiliation: Key Laboratory of Marine Drugs, Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, 266003, China.
authors.forename: Huiming
authors.initials: H
authors.lastname: Huang
authors.affiliation: Key Laboratory of Marine Drugs, Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, 266003, China.
authors.forename: Lukuan
authors.initials: L
authors.lastname: Hou
authors.affiliation: Key Laboratory of Marine Drugs, Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, 266003, China.
authors.forename: Huayue
authors.initials: H
authors.lastname: Li
authors.affiliation: Key Laboratory of Marine Drugs, Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, 266003, China.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: CAS Key Laboratory of Marine Bio-resources Sustainable Utilization, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou, 510301, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Ju
authors.affiliation: Key Laboratory of Marine Drugs, Ministry of Education of China, School of Medicine and Pharmacy, Ocean University of China, Qingdao, 266003, China. liwenli@ouc.edu.cn.
authors.forename: Wenli
authors.initials: W
authors.lastname: Li
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D005810:Multigene Family; D010957:Plasmids / Q000235:genetics* / Q000378:metabolism; D048630:Polyketide Synthases / Q000235:genetics* / Q000378:metabolism / Q000600:supply & distribution*; D061065:Polyketides / Q000378:metabolism; D012623:Seawater / Q000382:microbiology*; D013302:Streptomyces / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D061065:Polyketides; D048630:Polyketide Synthases
keywords: Cryptic gene cluster; Deepsea-derived Streptomyces; Type III polyketide synthase (PKS); Violapyrones (VLPs); whiB-like (wbl) gene