Pyrethrins from pyrethrum, Tanacetum cinerariifolium, and polygodial from Persicaria hydropiper are potent botanical insecticides, which are expected to contribute significantly to deterrence of potential herbivores. Both compounds affect ion channels of neurons causing depolarization of the membrane potential and muscle paralysis or a pungent taste. Pyrethrins affect voltage-gated ion channels which are present in all types of neurons.Polygodial, on the other hand, is specific for TRPA1 channels which occur in heat-sensing neurons. They are also the target of allylisothiocyanate and black pepper.
To investigate the contribution of pyrethrins and polygodial to insect resistance and to potentially transfer the pathway to other crops we dissect the pathway and clone the main biosynthetic genes. In the case of pyrethrins the pathway is very complex involving the esterification of an irregular monoterpene, chrysanthemic acid and jasmolone, a derivative of the jasmonate pathway. Polygodial is made in at least two steps from farnesyl diphosphate, first by the enzyme drimenol synthase, and subsequently by a P450 to first introduce a hydroxylation and subsequently oxidation into two aldehydes on the drimenol backbone.
Both the pyrethrum and persicaria projects are funded since 2008 by the Technological Top Institute Green Genetics. They are carried out in close cooperation with the Laboratories of Plant Physiology and Entomology as well as a range of plant breeding companies.
- Metabolic engineering of geranic acid in maize to achieve fungal resistance is compromised by novel glycosylation patterns: Metabolic Engineering 13: 414-425 (2011)
- Pyrethrins protect pyrethrum leaves against attack by western flower thrips, Frankliniella occidentalis: Journal of Chemical Ecology (2012) (in press).