Section for Plant Biochemistry
Thorvaldsensvej 40, 1871 Frb. C, Building: R126
An essential driving component in the co-evolution of plants and insects is the ability to produce and handle bioactive compounds. Plants produce bioactive natural products for defense, but some insects detoxify and/or sequester the compounds, opening up for new niches with fewer competitors. We are investigating the interactions between Lotus corniculatus and Zygaena filipendulae. They both contain cyanogenic glucosides which liberate toxic hydrogen cyanide upon breakdown. Moths belonging to the Zygaena family are the only insects known, able to carry out both de novo biosynthesis and sequestration of the same cyanogenic glucosides as those from their feed plants. The cyanogenic glucosides linamarin and lotaustralin are amino acid derived secondary metabolites that carry out several important functions in the life cycle of Z. filipendulae apart from being used in defense. The transfer of a nuptial gift of cyanogenic glucosides during mating of Zygaena has been demonstrated as well as the possible involvement of hydrogen cyanide in mate attraction and nitrogen metabolism. The ratio and content of cyanogenic glucosides is tightly regulated in Zygaena filipendulae, and Zygaena larvae prefer to feed on highly cyanogenic Lotus plants over low cyanogenic or acyanogenic Lotusplants, probably to optimize the amount of cyanogenic glucosides available for sequestering. We have solved the biosynthetic pathway of cyanogenic glucosides in Zygaena, and it turns out that the pathway is remarkably similar to the pathway in plants, although clearly convergently evolved. We have also elucidated when and where in Z. filipendulae tissues and life-stages the biosynthetic pathway is expressed. Furthermore, we have recently shown that cyanogenic glucosides are taken up intact during sequestration by Z. filipendulae and are rapidly distributed to all tissues, mingling freely with cyanogenic glucosides originating from biosynthesis. Z. filipendulae have evolved several adaptations to facilitate sequestration of intact cyanogenic glucosides, namely a high pH in the gut, fast feeding and the use of a leaf-snipping feeding mode.
We are currently investigating how cyanogenic glucosides are bio-activated, transported and how they are involved in fitness and nitrogen metabolism in Z. filipendulae. Our long term goal is to elucidate all the functions of cyanogenic glucosides in the Z. filipendulae life-cycle, as well as how, when and from what the pathway evolved in butterflies and moths.