title: Genome-based deletion analysis reveals the prenyl xanthone biosynthesis pathway in Aspergillus nidulans.
abstract: Xanthones are a class of molecules that bind to a number of drug targets and possess a myriad of biological properties. An understanding of xanthone biosynthesis at the genetic level should facilitate engineering of second-generation molecules and increasing production of first-generation compounds. The filamentous fungus Aspergillus nidulans has been found to produce two prenylated xanthones, shamixanthone and emericellin, and we report the discovery of two more, variecoxanthone A and epishamixanthone. Using targeted deletions that we created, we determined that a cluster of 10 genes including a polyketide synthase gene, mdpG, is required for prenyl xanthone biosynthesis. mdpG was shown to be required for the synthesis of the anthraquinone emodin, monodictyphenone, and related compounds, and our data indicate that emodin and monodictyphenone are precursors of prenyl xanthones. Isolation of intermediate compounds from the deletion strains provided valuable clues as to the biosynthetic pathway, but no genes accounting for the prenylations were located within the cluster. To find the genes responsible for prenylation, we identified and deleted seven putative prenyltransferases in the A. nidulans genome. We found that two prenyltransferase genes, distant from the cluster, were necessary for prenyl xanthone synthesis. These genes belong to the fungal indole prenyltransferase family that had previously been shown to be responsible for the prenylation of amino acid derivatives. In addition, another prenyl xanthone biosynthesis gene is proximal to one of the prenyltransferase genes. Our data, in aggregate, allow us to propose a complete biosynthetic pathway for the A. nidulans xanthones.
authors.affiliation: Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, School of Pharmacy, 1985 Zonal Avenue, Los Angeles, California 90089, United States.
authors.forename: James F
authors.initials: JF
authors.lastname: Sanchez
authors.forename: Ruth
authors.initials: R
authors.lastname: Entwistle
authors.forename: Jui-Hsiang
authors.initials: JH
authors.lastname: Hung
authors.forename: Junko
authors.initials: J
authors.lastname: Yaegashi
authors.forename: Sofina
authors.initials: S
authors.lastname: Jain
authors.forename: Yi-Ming
authors.initials: YM
authors.lastname: Chiang
authors.forename: Clay C C
authors.initials: CC
authors.lastname: Wang
authors.forename: Berl R
authors.initials: BR
authors.lastname: Oakley
mesh_terms: D001233:Aspergillus nidulans / Q000235:genetics / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D016681:Genome, Fungal; D017368:Protein Prenylation; D017384:Sequence Deletion; D013056:Spectrophotometry, Ultraviolet; D044004:Xanthones / Q000378:metabolism*
chemical_list: D044004:Xanthones; C009689:xanthone