Unearthing a sesterterpene biosynthetic repertoire in the Brassicaceae through genome mining reveals convergent evolution

Ancheng C. Huang, Satria A. Kautsar, Young J. Hong, Marnix H. Medema, Andrew D. Bond, Dean J. Tantillo, Anne Osbourn*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

46 Citations (Scopus)

Abstract

Sesterterpenoids are a rare terpene class harboring untapped chemo-diversity and bioactivities. Their structural diversity originates primarily from the scaffold-generating sesterterpene synthases (STSs). In fungi, all six known STSs are bifunctional, containing C-terminal trans-prenyltransferase (PT) and N-terminal terpene synthase (TPS) domains. In plants, two colocalized PT and TPS gene pairs from Arabidopsis thaliana were recently reported to synthesize sesterterpenes. However, the landscape of PT and TPS genes in plant genomes is unclear. Here, using a customized algorithm for systematically searching plant genomes, we reveal a suite of physically colocalized pairs of PT and TPS genes for the biosynthesis of a large sesterterpene repertoire in the wider Brassicaceae. Transient expression of seven TPSs from A. thaliana, Capsella rubella, and Brassica oleracea in Nicotiana benthamiana yielded fungal-type sesterterpenes with tri-, tetra-, and pentacyclic scaffolds, and notably (−)-ent-quiannulatene, an enantiomer of the fungal metabolite (+)-quiannulatene. Protein and structural modeling analysis identified an amino acid site implicated in structural diversification. Mutation of this site in one STS (AtTPS19) resulted in premature termination of carbocation intermediates and accumulation of bi-, tri-, and tetracyclic sesterterpenes, revealing the cyclization path for the pentacyclic sesterterpene (−)-retigeranin B. These structural and mechanistic insights, together with phylogenetic analysis, suggest convergent evolution of plant and fungal STSs, and also indicate that the colocalized PT–TPS gene pairs in the Brassicaceae may have originated from a common ancestral gene pair present before speciation. Our findings further provide opportunities for rapid discovery and production of sesterterpenes through metabolic and protein engineering.
Original languageEnglish
Pages (from-to)E6005-E6014
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number29
DOIs
Publication statusPublished - 2017

Keywords

  • Brassicaceae
  • Convergent evolution
  • Cyclization mechanism
  • Plant natural products
  • Sesterterpene biosynthesis

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  • Datasets

    CCDC 1539193: Experimental Crystal Structure Determination

    Huang, A. C. (Creator), Kautsar, S. A. (Creator), Hong, Y. J. (Creator), Medema, M. (Creator), Bond, A. D. (Creator), Tantillo, D. J. (Creator) & Osbourn, A. (Creator), 20 Mar 2017

    Dataset

    CCDC 1535306: Experimental Crystal Structure Determination

    Huang, A. C. (Creator), Kautsar, S. A. (Creator), Hong, Y. J. (Creator), Medema, M. (Creator), Bond, A. D. (Creator), Tantillo, D. J. (Creator) & Osbourn, A. (Creator), 28 Feb 2017

    Dataset

    CCDC 1535308: Experimental Crystal Structure Determination

    Huang, A. C. (Creator), Kautsar, S. A. (Creator), Hong, Y. J. (Creator), Medema, M. (Creator), Bond, A. D. (Creator), Tantillo, D. J. (Creator) & Osbourn, A. (Creator), 28 Feb 2017

    Dataset

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