Methods

We investigate odors from various natural sources via GC-MS (Gas Chromatography–Mass Spectrometry) in order to identify their chemical components. Basing on the specific properties of an odor sample we can employ different techniques like liquid injection, solid-phase micro extraction or thermal desorption with our array of specialized GCs.

We use a large set of behavioral assays to test whether and how odors affect the behavior of flies, moths, or other insects. These assays range from simple trap assays for a quick test of odorant valence to huge wind tunnels with 3D tracking systems for the characterization of odor guided behavior in sphingid moths and – finally –  to fully automated high-throughput systems like the Flywalk (where we quantify detailed response characteristics of large numbers of individual flies to an extensive screen of odorants).

We use immunohistochemistry to morphologically label and characterize populations of olfactory neurons in all parts of the insect brain. We employ photoactivatable GFP to trace single neurons, which we subsequently reconstruct with the segmentation software Amira and incorporate into our standard fly brain using image registration. In order to analyze synaptic connectivity of specific neuronal populations, we use scanning electron microscopy (SEM) or apply the GRASP technique at light microscopic resolution.

We use a variety of neurogenetic methods, such as fly lines carrying mutations, transgenes, and binary systems of expression, in order to visualize, manipulate, and monitor the activity of neurons sustaining chemosensory behavior. We get hold of a battery of available genetic tools in Drosophila melanogaster, and using state-of-the-arts technology for genetically modifying organisms (transposable P elements, PhiC31 integrase-mediated site-specific transgenesis, CRISPR/Cas9) we create fly lines of specific interest in a variety of Drosophila species.

We employ optical recording techniques via calcium-, chloride- or cAMP-sensitive probes at the widefield or two-photon microscope to visualize spatial as well as temporal aspects of odor representations in populations of olfactory neurons in the insect brain. In addition, we perform patch clamp experiments with olfactory sensory neurons as well as cultured cells expressing ion channels or olfactory receptor proteins.