Dr. Tholl investigates the biosynthesis and function of volatile compounds (terpenoids) emitted by plants in response to pest and pathogen attack above and below ground, and uses this knowledge to develop alternative pest control strategies. She also studies the organization and regulation of chemical defenses in plant root systems.
Plants rely on a plethora of phytochemicals (specialized metabolites) to communicate with their environment and other organisms. Many of these metabolites are released as volatile compounds, which facilitate short and long distance plant interaction with both beneficial and harmful organisms as well as signaling within and between plants. The role of individual volatiles or complex volatile blends in these interactions is in many ways poorly understood. By using a combination of biochemical, molecular, and analytical tools paired with bioassays, the Tholl lab aims to explore the multi-functionality of volatile compounds and the plasticity of their biosynthesis in correlation with spatial and temporal regulation.
One current focus area is the biochemistry and defensive activities of insect-induced volatiles aboveground. Dr. Tholl investigates the biosynthesis of volatile homoterpenes (norterpenes), which are common compounds released by the foliage of flowering plants in response to herbivory. Homoterpenes have been implicated in attracting natural enemies (predators, parasitoids) of pests and thereby contributing to biological pest control. Moreover, homoterpenes have the potential to induce or prime defense responses in plant-plant interactions. The Tholl lab explores the evolution of the homoterpene biosynthetic pathway and identifies gene tools and possible regulatory elements (in Arabidopsis) for metabolic engineering of homoterpene formation. This transgenic approach will allow elucidating the role of homoterpenes more specifically as individual compounds and synergistically in blends with other volatiles. Knowledge gained from these experiments can be applied to improve plant volatile emissions in crops for developing alternative strategies in defense priming and pest control.
Another focus area is the organization and function of volatile metabolism in roots. Analysis of Arabidopsis roots has shown that volatile terpenes are produced in radial layers of specific root cell types. The Tholl lab investigates how this cell-type specificity correlates with the defensive activity of terpenes against soil-borne pests and pathogens. In addition, Dr. Tholl analyzes the role of biosynthetic modules in root-specific terpene formation and the evolutionary plasticity of biosynthetic pathways in volatile terpene formation above- and belowground. She further aims to explore metabolic and transcriptional networks integrating terpene defense mechanisms with other insect-induced or non-induced chemical defenses in roots.