title: Production of the Streptomyces scabies coronafacoyl phytotoxins involves a novel biosynthetic pathway with an F420 -dependent oxidoreductase and a short-chain dehydrogenase/reductase.
abstract: Coronafacoyl phytotoxins are secondary metabolites that are produced by various phytopathogenic bacteria, including several pathovars of the Gram-negative bacterium Pseudomonas syringae as well as the Gram-positive potato scab pathogen Streptomyces scabies. The phytotoxins are composed of the polyketide coronafacic acid (CFA) linked via an amide bond to amino acids or amino acid derivatives, and their biosynthesis involves the cfa and cfa-like gene clusters that are found in P. syringae and S. scabies, respectively. The S. scabies cfa-like gene cluster was previously reported to contain several genes that are absent from the P. syringae cfa gene cluster, including one (oxr) encoding a putative F420 -dependent oxidoreductase, and another (sdr) encoding a predicted short-chain dehydrogenase/reductase. Using gene deletion analysis, we demonstrated that both oxr and sdr are required for normal production of the S. scabies coronafacoyl phytotoxins, and structural analysis of metabolites that accumulated in the Δsdr mutant cultures revealed that Sdr is directly involved in the biosynthesis of the CFA moiety. Our results suggest that S. scabies and P. syringae use distinct biosynthetic pathways for producing coronafacoyl phytotoxins, which are important mediators of host-pathogen interactions in various plant pathosystems.
authors.affiliation: Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada.
authors.forename: Luke
authors.initials: L
authors.lastname: Bown
authors.affiliation: Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada.
authors.forename: Mead S
authors.initials: MS
authors.lastname: Altowairish
authors.affiliation: Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada.
authors.forename: Joanna K
authors.initials: JK
authors.lastname: Fyans
authors.affiliation: Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada.
authors.forename: Dawn R D
authors.initials: DR
authors.lastname: Bignell
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D053898:Biosynthetic Pathways; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D005798:Genes, Bacterial; D054884:Host-Pathogen Interactions; D007192:Indenes / Q000378:metabolism*; D005810:Multigene Family; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology; D017386:Sequence Homology, Amino Acid; D011198:Solanum tuberosum / Q000382:microbiology; D013302:Streptomyces / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D007192:Indenes; C084266:coronafacic acid; C036543:short chain trans-2-enoyl-CoA reductase; D009247:NADH, NADPH Oxidoreductases; C109941:F420-dependent NADP reductase; D064429:Fatty Acid Synthases