Identification of a hybrid PKS-NRPS required for the biosynthesis of NG-391 in Metarhizium robertsii

• Published in: Current genetics Vol. 56; no. 2; pp. 151 - 162
• Main Authors: Donzelli, Bruno Giuliano Garisto, Krasnoff, Stuart B, Churchill, Alice C. L, Vandenberg, John D, Gibson, Donna M
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.04.2010; Springer-Verlag; Springer Nature B.V
• Subjects: Animals; Biochemistry; Biomedical and Life Sciences; Biosynthesis; Cell Biology; Chimera - metabolism; Hydrogen peroxide; Immunologic Factors - biosynthesis; Immunologic Factors - genetics; Immunologic Factors - metabolism; Larvae; Life Sciences; Ligases - biosynthesis; Ligases - genetics; Ligases - metabolism; Metabolites; Metarhizium; Metarhizium - genetics; Metarhizium - metabolism; Microbial Genetics and Genomics; Microbiology; Multienzyme Complexes - biosynthesis; Multienzyme Complexes - genetics; Multienzyme Complexes - metabolism; Open Reading Frames; Oxidative stress; Peptide Synthases - biosynthesis; Peptide Synthases - genetics; Peptide Synthases - metabolism; Plant Sciences; Polyketide Synthases - biosynthesis; Polyketide Synthases - genetics; Polyketide Synthases - metabolism; Proteomics; Research Article; Secondary metabolites; Spodoptera exigua; NG-391; GFP reporter; Secondary metabolism; PKS–NRPS
• ISSN: 0172-8083; 1432-0983
• DOI: 10.1007/s00294-010-0288-0

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.