title: Identification of a hybrid PKS-NRPS required  for the biosynthesis of NG-391 in Metarhizium robertsii.
abstract: The fungal entomopathogen Metarhizium robertsii (formerly known as M. anisopliae var. anisopliae) is a prolific producer of secondary metabolites of which very little is known at the genetic level. To establish the genetic bases for the biosynthesis of the mutagenic compound NG- 391, we identified a 19,818 kb genomic region harboring the predicted hybrid polyketide synthase-nonribosomal peptide synthetase NGS1, plus five additional ORFs. NGS1 knockouts generated by Agrobacterium-mediated transformation failed to produce detectable levels of NG-391, indicating the involvement of this locus in its biosynthesis. NGS1 deletion mutants had no significant changes in virulence levels against larvae of Spodoptera exigua and in resistance to hydrogen peroxide-generated oxidative stress compared to the wild-type strain. All 6 ORFs were expressed in medium supporting production of NG-391, and NGS1 was expressed during the interaction with the S. exigua host. The use of an NGS1 promoter-GFP reporter fusion showed that during in vitro growth in still broth cultures, NGS1 expression is restricted to the early exponential phase and is affected by M. robertsii cell density.
authors.affiliation: Biological Integrated Pest Management Research Unit, Robert W. Holley Center for Agriculture and Health, USDA-ARS, Tower Road, Ithaca, NY 14853, USA. Bruno.Donzelli@ars.usda.gov
authors.forename: Bruno Giuliano Garisto
authors.initials: BG
authors.lastname: Donzelli
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Krasnoff
authors.forename: Alice C L
authors.initials: AC
authors.lastname: Churchill
authors.forename: John D
authors.initials: JD
authors.lastname: Vandenberg
authors.forename: Donna M
authors.initials: DM
authors.lastname: Gibson
mesh_terms: D000818:Animals; D002678:Chimera / Q000378:metabolism*; D007155:Immunologic Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D008025:Ligases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D052981:Metarhizium / Q000235:genetics / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D016366:Open Reading Frames; D010453:Peptide Synthases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D048630:Polyketide Synthases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D007155:Immunologic Factors; D009097:Multienzyme Complexes; D048630:Polyketide Synthases; D008025:Ligases; C066234:enterobactin synthetase; D010453:Peptide Synthases; C026269:2,3-dihydroxybenzoate - serine ligase