(271b) Gene-Centric Discovery of a Novel Coumarin Biosynthetic Pathway in Higher Plants

As sessile organisms, plants have evolved a remarkable array of specialized biochemical pathways in order to interact with and manipulate their environment. The products of specialized metabolism have been a rich source of bioactive molecules used for therapeutic and agrochemical applications, among others. However, the discovery and utilization of novel plant biochemistries has traditionally been a slow process.

Here, we present one instance of the application of a “gene-centric” approach for pathway discovery in plants. Leveraging large amounts of freely available genomic and transcriptomic data enables us to make predictions about the function of biosynthetic genes of interest, while metabolomic analysis of plant tissue allows for the direct testing of such predictions, leading to marked acceleration of the pathway discovery process. In particular, we report the elucidation of the biosynthesis of sideretin, a novel, highly oxidized coumarin with unusual redox properties involved in soil iron uptake. Starting with a single candidate gene from the cytochrome P450 family in the model plant Arabidopsis thaliana, we have systematically uncovered the biosynthesis of sideretin from phenylpropanoid precursors, and have managed to reconstitute the pathway in a heterologous host as well as in vitro. We have further shown that this pathway is widespread among evolutionarily distant clades of flowering plants, and therefore represents a conserved strategy for iron uptake, with implications for engineering crops with enhanced nutritional uptake capability. Finally, we present a chemical synthesis of sideretin from commercially available precursors and its detailed physical and chemical characterization. Overall, our work demonstrates the power of a gene-centric approach for understanding and harnessing plant specialized metabolism.