OpenPlant researchers advance a translational synthetic biology platform for rapid access to new drug-like molecules

Researchers in Prof Anne Osbourn's lab at the John Innes Centre, including Prof Osbourn and OpenPlant PDRA Dr Michael Stephenson, have published a new paper detailing their advances in rapidly creating and purifying gram-scale quantities of natural products that were previously not possible to synthesise. This has the potential to reinvigorate drug discovery pipelines by opening up whole regions of chemical diversity for testing and production of potentially medicinally important molecules.

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Reed, J., Stephenson, M.J., Miettinen, K., Brouwer, B., Leveau, A., Brett, P., Goss, R.J., Goossens, A., O’Connell, M.A. and Osbourn, A., 2017. A translational synthetic biology platform for rapid access to gram-scale quantities of novel drug-like moleculesMetabolic Engineering. DOI: 10.1016/j.ymben.2017.06.012

Fig 2 from paper: Generation of gram quantities of triterpene using vacuum infiltration a, Vacuum infiltration of N. benthamiana plants. Plants are retained by a bespoke holder, inverted into a bath containing 10 L of A. tumefaciens suspension, and a vacuum applied. Upon release of the vacuum the infiltration process is complete. b, GFP expression in leaves from a vacuum-infiltrated plant 5 days after infiltration (leaves arranged from top left to bottom right in descending order of their height on the plant). The youngest leaves (top left) were formed post-infiltration. c, β-Amyrin purified from vacuum-infiltrated plants following transient expression.

Fig 2 from paper: Generation of gram quantities of triterpene using vacuum infiltration a, Vacuum infiltration of N. benthamiana plants. Plants are retained by a bespoke holder, inverted into a bath containing 10 L of A. tumefaciens suspension, and a vacuum applied. Upon release of the vacuum the infiltration process is complete. b, GFP expression in leaves from a vacuum-infiltrated plant 5 days after infiltration (leaves arranged from top left to bottom right in descending order of their height on the plant). The youngest leaves (top left) were formed post-infiltration. c, β-Amyrin purified from vacuum-infiltrated plants following transient expression.

Abstract

Plants are an excellent source of drug leads. However availability is limited by access to source species, low abundance and recalcitrance to chemical synthesis. Although plant genomics is yielding a wealth of genes for natural product biosynthesis, the translation of this genetic information into small molecules for evaluation as drug leads represents a major bottleneck. For example, the yeast platform for artemisinic acid production is estimated to have taken >150 person years to develop. Here we demonstrate the power of plant transient transfection technology for rapid, scalable biosynthesis and isolation of triterpenes, one of the largest and most structurally diverse families of plant natural products. Using pathway engineering and improved agro-infiltration methodology we are able to generate gram-scale quantities of purified triterpene in just a few weeks. In contrast to heterologous expression in microbes, this system does not depend on re-engineering of the host. We next exploit agro-infection for quick and easy combinatorial biosynthesis without the need for generation of multi-gene constructs, so affording an easy entrée to suites of molecules, some new-to-nature, that are recalcitrant to chemical synthesis. We use this platform to purify a suite of bespoke triterpene analogs and demonstrate differences in anti-proliferative and anti-inflammatory activity in bioassays, providing proof of concept of this system for accessing and evaluating medicinally important bioactives. Together with new genome mining algorithms for plant pathway discovery and advances in plant synthetic biology, this advance provides new routes to synthesize and access previously inaccessible natural products and analogs and has the potential to reinvigorate drug discovery pipelines.