For decades DEET has been successfully used to repel biting insects. Scientists from Rockefeller University, New York, in collaboration with the Max Planck Institute for Chemical Ecology in Jena, Germany, have now clarified DEET’s (N,N-diethyl-meta-toluamide) mechanism of action. The substance does not block the insects’ recognition of attracting odor signals or cause an active avoidance behavior in mosquitoes and fruit flies, as has been assumed previously.
Mosquito (Aedes aegypti) feeding on human skin
Rickard Ignell, SLU Alnarp, Sweden
In fact, the substance is such an effective repellent because it disrupts the insects’ odor code. So-called odorant receptors (OR) function to detect special odor signals that enable the insect to locate a potential host or food source. DEET corrupts messages from attractive scents, and as a consequence mosquitoes or fruit flies lose their orientation. (NATURE, ahead of print publication, DOI 10.1038/nature10438)
Used as a repellent since 1946
The research results achieved by neurobiologists from Leslie Vosshall’s group at Rockefeller University, USA, helped now settle a scientific dispute over DEET's mode of action that has been ongoing for decades. DEET was developed in 1946 as an effective repellent against insect bites and has been used worldwide since. It does, however, neither function as a stimulus blocker nor as an active repellent. The substance, which is only slightly perceptible to humans, is very likely an insect confusant. In collaboration with Bill Hansson and Marcus Stensmyr from the Max Planck Institute for Chemical Ecology in Jena, Germany, who analyzed the odor substances, the scientists elucidated DEET’s mechanism of action by means of modern molecular, neurobiological and chemical techniques.
One neuron, one receptor
The requirements of the experiments fortunately matched the anatomy of the odor reception apparatus. The antenna of the fruit fly Drosophila melanogaster carry sensilla which house olfactory sensory neurons (OSNs) expressing specific odorant receptors (OR). At least two such OSNs are housed in one sensillum. In the experiments, the electric signals of both OSNs were recorded simultaneously and compared to each other. If a selected odor substance, such as linalool, was used as a stimulus, the presence of DEET had a stimulating effect on OSNs expressing receptor Or59b, whereas simultaneously an inhibiting effect on OSNs expressing receptor Or85a could be observed. Altogether, the reactions of four OSNs to ten different odor substances were compared. All substances, except for three, elicited different reactions in the presence of DEET, actually depending on the concentration of the odors in the environment. If no odor substance was used for stimulation, DEET alone did hardly cause any reaction. This means that DEET corrupts the odor code of the insects, which react confused as a result.
Natural variability of odorant receptors as a possible key to DEET’s broad range of activity against different insect species
To decode DEET’s mechanism of action the receptor Or59b was analyzed in more detail. 18 strains of fruit flies, which had been collected in different places of the world, were compared for their reaction to odor stimuli and showed similar results in comparison to the laboratory strain – with the exception of one Brazilian strain: This strain seemed insensitive to DEET and showed different activation patterns to specific odor stimuli. The Or59b encoding gene from the South American strain was compared to the gene from the laboratory strain and showed several deviations in the derived amino acid sequences. Analysis of individual amino acid exchanges using transgenic fruit flies showed that a valine-to-alanine substitution in the Brazilian strain was sufficient to annihilate the effect of DEET – evidence that DEET directly interacts with an odorant receptor and not with the conserved subunits that are also present in the receptor complexes, such as Orco (olfactory receptor coreceptor). The broad repertoire of different ORs in various insect species and their ecotypes may hold the key to the enormously broad range of activity of DEET. [JWK, AO]
Maurizio Pellegrino, Nicole Steinbach, Marcus C. Stensmyr, Bill S. Hansson, Leslie B. Vosshall: A natural polymorphism alters odour and DEET sensitivity in an insect odorant receptor. NATURE, ahead of print publication, DOI 10.1038/nature10438
Further Information:Bill S. Hansson, MPI for Chemical Ecology, Jena
Dr. Jan-Wolfhard Kellmann | Max-Planck-Institut
Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel
The Nagoya Protocol Creates Disadvantages for Many Countries when Applied to Microorganisms
05.12.2016 | Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
05.12.2016 | Power and Electrical Engineering
05.12.2016 | Materials Sciences
05.12.2016 | Power and Electrical Engineering