Key Odorants Regulate Food Attraction in Drosophila melanogaster

Abstract

In insects, the search for food is highly dependent on olfactory sensory input. Here, we investigated whether a single key odorant within an odor blend or the complexity of the odor blend influences the attraction of Drosophila melanogaster to a food source. A key odorant is defined as an odorant that elicits a difference in the behavioral response when two similar complex odor blends are offered. To validate that the observed behavioral responses were elicited by olfactory stimuli, we used olfactory co-receptor Orco mutants. We show that within a food odor blend, ethanol functions as a key odorant. In addition to ethanol other odorants might serve as key odorants at specific concentrations. However, not all odorants are key odorants. The intensity of the odor background influences the attractiveness of the key odorants. Increased complexity is only more attractive in a concentration-dependent range for single compounds in a blend. Orco is necessary to discriminate between two similarly attractive odorants when offered as single odorants and in food odor blends, supporting the importance of single odorant recognition in odor blends. These data strongly indicate that flies use more than one strategy to navigate to a food odor source, depending on the availability of key odorants in the odor blend and the alternative odor offered.

2‐Pentylfuran: a novel repellent of Drosophila suzukii

“…This unexpected repellency from compounds isolated from the headspace of an attractive bait may be explained by differences in the chemical concentration of 2‐pentylfuran emitted from bread dough compared to the pure compound released from vials during the subsequent behavioral assay. Similar concentration‐dependent antagonistic and agonistic responses to semiochemicals are well known in insects and reflect the need for detailed behavioral assessments at a range of concentrations and release rates in order to establish the unique chemical ecology of species 45,46 . Indeed, in our dose–response tests, 2‐pentylfuran did not show repellent activities under 0.6 mg h −1 .…”

Alcohol boosts pheromone production in male flies and makes them sexier

“…In order to examine how flies interact with sources of alcohol, we conducted behavioral studies of attraction (Figure 1a,b,c). As shown previously 4,5,7,8 , male flies were acutely attracted to sources of ethanol. Furthermore, we confirmed that mating status created variability in this attractive behavior 5 , namely that virgin males were more attracted to sources of ethanol than recently mated males (Figure 1b).…”

Octopamine Shifts the Behavioral Response From Indecision to Approach or Aversion in Drosophila melanogaster

“…In a binary choice assay, flies choose between two equal food odor traps (Ogueta et al, 2010 ). The presence of an attractive key odorant within the food odor biases the decision to move towards and enter the food odor trap containing the key odorant (Giang et al, 2017 ). The attraction for one odor trap in comparison to an equal second food odor trap can also be induced by activation of tyraminergic/octopaminergic neurons using the UAS -ChR2 transgene under the control of the dTdc2-Gal4 driver (Schneider et al, 2012 ; Figure 1A ).…”

“…Given the choice between two similar attractive food odor sources, male and female Drosophila are more attracted to ethanol-enriched food odors than to a similar odor without ethanol (Ogueta et al, 2010 ). The low ethanol concentration that elicits approach functions as a key odorant in the food odor mixture (Giang et al, 2017 ). The approach depends on the positive reinforcing action of the octopaminergic/tyraminergic neurotransmitter system, as neuronal activation of neurons expressing tyrosine decarboxylase 2 (dTdc2)—the enzyme required for tyramine and indirectly for octopamine synthesis (Cole et al, 2005 )—results in attraction (Schneider et al, 2012 ).…”