Abstract
Coumarins, also known as 1,2-benzopyrones, comprise a large class of secondary metabolites that are ubiquitously found throughout the plant kingdom. In many plant species, coumarins are particularly important for iron acquisition and plant defence. Here, we show that COUMARIN SYNTHASE (COSY) is a key enzyme in the biosynthesis of coumarins. Arabidopsis thaliana cosy mutants have strongly reduced levels of coumarin and accumulate o-hydroxyphenylpropanoids instead. Accordingly, cosy mutants have reduced iron content and show growth defects when grown under conditions in which there is a limited availability of iron. Recombinant COSY is able to produce umbelliferone, esculetin and scopoletin from their respective o-hydroxycinnamoyl-CoA thioesters by two reaction steps—a trans–cis isomerization followed by a lactonization. This conversion happens partially spontaneously and is catalysed by light, which explains why the need for an enzyme for this conversion has been overlooked. The combined results show that COSY has an essential function in the biosynthesis of coumarins in organs that are shielded from light, such as roots. These findings provide routes to improving coumarin production in crops or by microbial fermentation.
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Acknowledgements
We thank A. Bleys for help with preparing the manuscript. We acknowledge funding through the framework of the IWT-SBO (project ARBOREF), the Hercules program of Ghent University for the Synapt Q-Tof (grant no. AUGE/014), the Bijzonder Onderzoeksfonds-Zware Apparatuur of Ghent University for the FT-ICR-MS instrument (174PZA05) and the Multidisciplinary Research Partnership Biotechnology for a Sustainable Economy (01MRB510W) of Ghent University. R.V. was supported by the Research Foundation—Flanders with a postdoctoral fellowship; L.S., L.H. and B.D.M. by the Agency for Innovation by Science and Technology, Flanders (IWT-Vlaanderen); and X.L. and J.L. by the China Scholarship Council. H.K. and J.R. were funded by the DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science DE-SC0018409) and research in the Schmidt laboratory was supported by MoST.
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R.V., L.S., W.S. and W.B. designed the experiments. R.V., L.S., K.C.S., H.K., X.L., B.D.M., L.H., J.L., G.G., H.-H.T. and K.M. performed experiments. R.V., L.S., G.G., K.M., J.H., B.V., H.-H.T. and J.R. collected and analysed data; R.V. and W.B. wrote the manuscript with the help of all of the authors.
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A patent (Belgium Patent publication no: WO 2018/046526 Al) for the use of COSY for the production of coumarins in plants and microorganisms has been published.
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Peer review information: Nature Plants thanks Chang Jun Liu and **g Ke Weng and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Supplementary Figs. 1–23, legend of Supplementary Table 1, Supplementary Tables 2 and 3, Supplementary Table 4 legend, Supplementary Tables 5 and 6.
Supplementary Tables 1 and 4
Supplementary Table 1: a full list of peaks detected in the root extracts of cosy-1 and cosy-2. Supplementary Table 4: a full list of peaks detected in the inflorescence stem extracts of cosy-1 and cosy-2.
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Vanholme, R., Sundin, L., Seetso, K.C. et al. COSY catalyses trans–cis isomerization and lactonization in the biosynthesis of coumarins. Nat. Plants 5, 1066–1075 (2019). https://doi.org/10.1038/s41477-019-0510-0
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DOI: https://doi.org/10.1038/s41477-019-0510-0
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