ORN activity patterns in Drosophila melanogaster larvae elicited by ecologically relevant odorants
Kellermeyer, Riley 2016 ORN activity patterns in Drosophila melanogaster larvae elicited by ecologically relevant odorants.pdf
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Most insects locate their food source primarily through olfaction. In Drosophila larvae, attraction and repulsion to environmental odorants are based on the activity of only 21 olfactory receptor neurons (ORNs). While a considerable amount of information has been generated regarding the ORN responses of worms, flies, and mammals to odorants, much less is known about their role in driving behavioral output. This gap in knowledge prevents the development of reliable odor coding models that can elucidate general principles of information processing, as well as instruct effective solutions for insect control. In this study, we examined the hypothesis that ecologically relevant attractive or repulsive odorants elicit specific patterns of ORN activity in the Drosophila melanogaster larva. To measure attractive or repellent odorants, a simple two-choice behavioral paradigm was used to test the behavioral response of wild type Drosophila melanogaster larvae to 54 odorants selected from its ecological habitat. Using this behavioral screen, a panel of 10 odorants that elicited the strongest attractive or repulsive responses in larvae was identified. This panel of odorants was then used to assess the response patterns among the 21 larval ORNs. For this, we expressed each larval odorant receptor in an in vivo expression system, the “empty neuron” system, and measured neural responses using single unit electrical recordings. At the test concentration, the panel of strong behavioral determinants elicited both excitatory and inhibitory responses from a variety of larval odor receptors expressed in the empty neuron system. Further, many of these receptor-odorant combinations exhibited varying response dynamics. Overall, our preliminary evidence suggests that ecologically relevant odorants elicit specific patterns of ORN activity. This study is significant because conserved patterns of sensory neuron activity may instruct downstream olfactory coding of behavioral valence. By comparing amplitude, temporal dynamics, and distribution of all 21 ORN responses, we aim to identify conserved patterns among sensory neuron activity elicited by attractants and repellents. The results from this study have the potential to impact development of more reliable odor coding models as well as to transform existing methods of insect control.