The tarsal segments at the end of the insect legs are the contact and uptake site of xenobiotics, including plant secondary metabolites and insecticides. The following project is based on our hypothesis that the tarsi control xenobiotic uptake and metabolism.

The tarsus is a cuticular tube equipped with sensory cells to taste the substratum and with setae required for adhesion. These structures and their function have been well studied to date; by contrast, our understanding of the tarsal cuticle and the underlying epidermal cells is limited. Here, we address the problem of tarsi as a critical organ of xenobiotic processing using the fruit flies Drosophila melanogaster (non-pest) and D. suzukii (pest) as model insects. We will analyze the histology of tarsal segments by transmission and scanning electron microscopy to learn about the cuticle and the epidermis. By proteomics and transcriptomics, we will identify proteins and genes present in the tarsi. In pilot experiments, we isolated cytochrome P450s, glutathione S-transferases involved in xenobiotic detoxification, and proteins required for forming the cuticle (chitin/chitosan matrix) in the tarsi of D. melanogaster and D. suzukii. Candidate proteins will be tagged with fluorescence by gene editing (CRISPR/Cas9) to monitor their expression and localization behavior during exposure to contact insecticides such as cyhalothrin. We will generate mutant versions of the respective genes to study their roles in the defense and detoxification of insecticides.
The results of this project will constitute crucial information to the fundamental question of how the insect tarsi are used in contact with the proximal environment of the animal body during orientation in its ecological niche and will allow us to formulate smart strategies for controlling insect pests by manipulating this interactive process.