Plants need to defend themselves against a plethora of biotic stresses such as herbivores and pathogens. To this end, plants produce a large variety of different chemical structures, so called specialized metabolites. Our research group studies the function and evolution of these metabolites in the interaction of the plant with herbivores and microbes. Using a combination of molecular, ecological and evolutionary approaches, we aim to understand the mechanistic basis underlying ecological interactions.
1. Activation of specialized metabolites by herbivorous insects
Toxic secondary metabolites are of central importance to protect plants against herbivores. Many toxins are stored as precursors, so called protoxins, and are activated by compartmentalized enzymes upon tissue disruption. Curiously, protoxins are not always activated by plant-derived enzymes: in many cases, they seem to be cleaved by digestive enzymes from the herbivores. To date, the genetic basis of this phenomenon as well as its ecological implications are not well understood. To shed light into these aspects, we are studying the metabolization of taraxinic acid β-D-glucopyranosyl ester (TA-G), a sesquiterpene of the common dandelion (Taraxacum officinale) that repels its major root herbivore, the common cockchafer larva (Melolontha melolontha). Using a combination of heterologous expression and RNA interference, we aim to identify the genetic basis of TA-G deglycosylation during M. melolontha feeding, which will allow us to elucidate the ecological consequences of this phenomenon. This project will thereby assess the importance of the insect digestive system in mediating plant-herbivore interactions.
2. The function of natural rubber in biotic interactions
Natural rubber - a cis-1,4-polyisoprene with more than 10,000 isoprene units – is one of the most important plant polymers for industrial use. While natural rubber production increases each year and has reached 13,500 tons in 2017, the ecological functions of natural rubber remain a mystery. A long-standing but untested hypothesis is that natural rubber, which can accumulate to high concentrations in specialized defense reservoirs, so called laticifers, may protect plants by gluing the herbivore’s mouthparts or trapping entire insects. In addition, it is assumed that natural rubber seals the wounds made by attacking herbivores and thereby prevents the entry of pathogenic microorganisms; however, experimental evidence for these hypotheses are lacking. We investigate the function of natural rubber in herbivore and microbial defense by studying the interaction of the root feeding larvae of the common cockchafer (Melolontha melolontha) and the Russian dandelion (Taraxacum kok-saghyz), which accumulates particularly high concentrations of high-molecular mass rubber in its root laticifers. Using a combination of molecular and ecological approaches, we aim to elucidate the long-standing mystery why plants produce this polymer in nature. In addition, this project will shed light on how specialized metabolites modify the tripartite interaction between plants, microbes and herbivores.
3. Eco-evolutionary feedbacks of plant-herbivore-microbe interactions in duckweeds
Plants, herbivores and microbes simultaneously interact in nature. While recent research highlights the importance of microbes for plant defense against herbivores, it remains little understood how herbivore-mediated evolution of plant-associated microbes affects plant phenotype and fitness. Using real-time experimental evolution experiments outdoors, we investigate changes in the microbial networks that are associated with the common duckweed (Spirodela polyrhiza) upon exposure of its native herbivore, the great pond snail (Lymnaea stagnalis). By testing the effects of the evolved microbes for plant defense and growth, we aim to elucidate the functional importance of microbial network evolution during ecological interactions. This project will thereby shed light on the ecological importance of short-term evolutionary responses.