Richard A. Dixon, M.A., D. Phil., DSC Noble Foundation Senior Vice President and Plant Biology Division Director email: radixon@noble.org

D. Phil., Botany, 1976, University of Oxford, UK.
Joined the Noble Foundation in 1988

Research Video: Molecular Biology of Plant Natural Products Flash Player is required

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The research interests of my laboratory center on understanding how plants produce natural products, and how this understanding can be applied to generate improved plants with altered natural product profiles. Three major classes of natural products are currently being studied; flavonoids/isoflavonoids, triterpene saponins, and the cell wall polymer lignin. Our target species for these studies is the forage legume alfalfa, but we also make use of the extensive genomics resources available at the Noble Foundation for the closely related model legume Medicago truncatula. Our approaches are multidisciplinary, ranging from organic chemistry through biochemistry, molecular biology, genetics, genomics and structural biology.

Isoflavonoids help protect the plant from fungal infection, but may also have health beneficial effects as components of the human diet. We are currently investigating how the isoflavonoid pathway can be moved into plant species that do not naturally make isoflavonoids, how the pathway is regulated at the transcriptional and cellular levels, and how glycosyltransferase enzymes acquire specificity for isoflavonids. Related compounds called condensed tannins help reduce the incidence of pasture bloat in ruminant animals, and we are working to understand the pathway for condensed tannin biosynthesis and thereby manipulate its expression to develop bloat-safe alfalfa. We are also interested in the potential of tannins and related compounds for chemoprevention of human diseases. Triterpene saponins act as anti-feedants and can seriously impact forage quality. However, some triterpenes have potent anticancer activity, and may be valuable lead compounds for drug or nutraceutical development. We are using genomics approaches in M. truncatula to discover the genes involved in the synthesis and regulation of triterpene saponin production. Our work on lignin is driven by the fact that this cell wall polymer negatively impacts forage digestibility in both legumes and grasses. We have developed methods for improving digestibility through the genetic manipulation of lignin content and composition, and are now applying a range of biochemical and genetics/genomics approaches to decipher the exact manner in which the building blocks of lignin are made in the plant. A new goal in the lab is to apply this understanding towards reducing the recalcitrance of biofuel crops for ethanol production. Through collaborations, we are utilizing information on the crystal structures of lignin and flavonoid biosynthetic enzymes to design new enzymes for the genetic modification of these pathways.