title: Cloning and analysis of the spinosad biosynthetic gene cluster of Saccharopolyspora spinosa.
abstract: BACKGROUND
  Spinosad is a mixture of novel macrolide secondary metabolites produced by Saccharopolyspora spinosa. It is used in agriculture as a potent insect control agent with exceptional safety to non-target organisms. The cloning of the spinosyn biosynthetic gene cluster provides the starting materials for the molecular genetic manipulation of spinosad yields, and for the production of novel derivatives containing alterations in the polyketide core or in the attached sugars.
  
  
  RESULTS
  We cloned the spinosad biosynthetic genes by molecular probing, complementation of blocked mutants, and cosmid walking, and sequenced an 80 kb region. We carried out gene disruptions of some of the genes and analyzed the mutants for product formation and for the bioconversion of intermediates in the spinosyn pathway. The spinosyn gene cluster contains five large open reading frames that encode a multifunctional, multi-subunit type I polyketide synthase (PKS). The PKS cluster is flanked on one side by genes involved in the biosynthesis of the amino sugar forosamine, in O-methylations of rhamnose, in sugar attachment to the polyketide, and in polyketide cross-bridging. Genes involved in the early common steps in the biosynthesis of forosamine and rhamnose, and genes dedicated to rhamnose biosynthesis, were not located in the 80 kb cluster.
  
  
  CONCLUSIONS
  Most of the S. spinosa genes involved in spinosyn biosynthesis are found in one 74 kb cluster, though it does not contain all of the genes required for the essential deoxysugars. Characterization of the clustered genes suggests that the spinosyns are synthesized largely by mechanisms similar to those used to assemble complex macrolides in other actinomycetes. However, there are several unusual genes in the spinosyn cluster that could encode enzymes that generate the most striking structural feature of these compounds, a tetracyclic polyketide aglycone nucleus.
authors.affiliation: Dow AgroSciences, Indianapolis, IN 46268, USA. cwaldron@dowagro.com
authors.forename: C
authors.initials: C
authors.lastname: Waldron
authors.forename: P
authors.initials: P
authors.lastname: Matsushima
authors.forename: P R
authors.initials: PR
authors.lastname: Rosteck
authors.forename: M C
authors.initials: MC
authors.lastname: Broughton
authors.forename: J
authors.initials: J
authors.lastname: Turner
authors.forename: K
authors.initials: K
authors.lastname: Madduri
authors.forename: K P
authors.initials: KP
authors.lastname: Crawford
authors.forename: D J
authors.initials: DJ
authors.lastname: Merlo
authors.forename: R H
authors.initials: RH
authors.lastname: Baltz
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D003001:Cloning, Molecular; D004338:Drug Combinations; D006595:Hexosamines / Q000096:biosynthesis; D018942:Macrolides / Q000378:metabolism*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism; D005810:Multigene Family / Q000235:genetics*; D016254:Mutagenesis, Insertional / Q000235:genetics*; D016366:Open Reading Frames / Q000235:genetics; D012210:Rhamnose / Q000096:biosynthesis / Q000737:chemistry; D016930:Saccharopolyspora / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D004338:Drug Combinations; D006595:Hexosamines; D018942:Macrolides; D009097:Multienzyme Complexes; C012325:forosamine; D012210:Rhamnose; C415329:spinosad