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Finding Diamonds in the Rough: Resistance-Gene-Directed Discovery of Fungal Natural Products

  • Author(s): Yan, Yan
  • Advisor(s): Tang, Yi
  • et al.
Abstract

Bioactive natural products have evolved to inhibit specific cellular targets and have served as lead molecules for health and agricultural applications for the last century. The post-genomics era has brought a renaissance in natural product discovery using synthetic biology tools. However, compared to traditional bioactivity-guided approaches, genome mining of natural products with specific and potent biological activities remains challenging. Here we proposed a resistance gene directed strategy to discover new natural products of desired bioactivity from genomic data. Our approach is based on the co-clustering of a self-resistance gene in the natural product biosynthetic gene cluster, which serves as a window to potential biological activity of the encoded compound. To demonstrate the feasibility, we first successfully located and verified the biosynthetic gene cluster of a glyceraldehyde-3-phosphate dehydrogenase inhibitor heptelidic acid by using a resistance gene. We showed the glyceraldehyde-3-phosphate dehydrogenase homolog hepG, co-localized with biosynthetic genes, is able to confer self-resistance to the producing organism using in vitro biochemical analysis. Next we present the discovery and validation of a highly potent herbicide lead that targets a critical metabolic enzyme that is required for plant survival. We queried dihydroxyacid dehydratase in the branched-chain amino acid biosynthetic pathway in plants, which is often targeted for herbicide development. We also showed that the fungal sesquiterpenoid aspterric acid discovered using this method is a submicromolar inhibitor of DHAD and is effective as an herbicide in spray applications. The self-resistance gene astD was validated to be insensitive to aspterric acid and was deployed as a transgene in the establishment of plants that are resistant to aspterric acid. This herbicide-resistance gene combination complements urgent efforts in overcoming weed resistance. Our discovery demonstrates the potential of using a resistance-gene directed approach in the mining of bioactive natural products.

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