Structure revision of cryptosporioptides and determination of the genetic basis for dimeric xanthone biosynthesis in fungi

• Published in: Chemical science (Cambridge) Vol. 1; no. 1; pp. 293 - 2939
• Main Authors: Greco, Claudio, de Mattos-Shipley, Kate, Bailey, Andrew M, Mulholland, Nicholas P, Vincent, Jason L, Willis, Christine L, Cox, Russell J, Simpson, Thomas J
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 14-03-2019
• Subjects: Annotations; Biosynthesis; Cytochromes P450; Dimers; Disruption; Fungi; Genomes; Metabolites; Methylation; Molecular structure; NMR; Nuclear magnetic resonance
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c8sc05126g

Three novel dimeric xanthones, cryptosporioptides A-C were isolated from
Cryptosporiopsis
sp. 8999 and their structures elucidated. Methylation of cryptosporioptide A gave a methyl ester with identical NMR data to cryptosporioptide, a compound previously reported to have been isolated from the same fungus. However, HRMS analysis revealed that cryptosporioptide is a symmetrical dimer, not a monomer as previously proposed, and the revised structure was elucidated by extensive NMR analysis. The genome of
Cryptosporiopsis
sp. 8999 was sequenced and the dimeric xanthone (
dmx
) biosynthetic gene cluster responsible for the production of the cryptosporioptides was identified. Gene disruption experiments identified a gene (
dmxR5
) encoding a cytochrome P450 oxygenase as being responsible for the dimerisation step late in the biosynthetic pathway. Disruption of
dmxR5
led to the isolation of novel monomeric xanthones. Cryptosporioptide B and C feature an unusual ethylmalonate subunit: a hrPKS and acyl CoA carboxylase are responsible for its formation. Bioinformatic analysis of the genomes of several fungi producing related xanthones,
e.g.
the widely occurring ergochromes, and related metabolites allows detailed annotation of the biosynthetic genes, and a rational overall biosynthetic scheme for the production of fungal dimeric xanthones to be proposed.
Three novel dimeric xanthones, cryptosporioptides A-C were isolated from
Cryptosporiopsis
sp. 8999 and their structures elucidated.