Damage to crops in agriculture and the transmission of vector-borne diseases by insect pests have become a global threat today. Chemical treatments such as insecticides and repellents have been a crucial strategy against insect pests for centuries. However, due to a limited understanding of the mechanisms of insect avoidance behavior, the development of insect repellents has been delayed. In order to discover compounds that effectively repel insect pests, it is important to focus on key molecules associated with sensory, especially aversive reactions. In this study, researchers identified a compound that elicits strong aversive reactions through multiple sensory pathways in the fruit fly Drosophila melanogaster.
Among the sensory receptors, TRP cation channels (Transient Receptor Potential) play a key role in noxious behavior against various stimuli in many insect species. In particular, the TRPA1 channel has been extensively studied as it is activated by various harmful chemicals. Therefore, insect TRPA1 stimulants are promising leads for novel repellents with a broad spectrum of activity. Takaaki Sokabe and his colleagues from the National Institute for Physiological Sciences/Exploratory Research Center on Life and Living Systems (ExCELLS) found that 2-methylthiazoline (2MT), an analog of a volatile compound in fox urine, effectively repels flies, revealing the molecular and cellular mechanisms of 2MT-induced aversions in flies. Their results were recently published in „Frontiers in Molecular Neuroscience“.
„It has been reported that 2MT induces innate fear responses in mice through TRPA1, so we expected that the chemical might have an aversive effect on insects. And it worked even more than we expected.“
– Takaaki Sokabe, National Institute for Physiological Sciences/Exploratory Research Center
The avoidance behavior of flies demonstrated that 2MT stimulates multiple sensory modalities: 2MT vapor acts on odor receptors (ORs) in an olfactory signaling pathway, and direct contact with 2MT activates TRPA1 in the gustatory and nociceptive signaling pathway. This caused male flies to clearly escape from the chemical source, and female flies did not lay eggs. Furthermore, the researchers showed that TRPA1 is activated by 2MT through the direct interaction of 2MT with certain two amino acids in TRPA1.
„The effect of 2MT on multiple sensory pathways seems to be a key to its high efficacy,“ says Takaaki Sokabe. „Since the amino acids essential for TRPA1 activation are highly conserved in a variety of insect species, including agricultural pests and disease vectors, it will be important to test 2MT on many other insect pests to assess its spectrum.“
This new work could advance the development of novel insect repellents by focusing on TRP channels and other types of receptors as promising targets.
National Institute for Physiological Sciences
Sato, S., et al. (2023). Aversion of thiazoline compound depends on multiple sensory pathways mediated by TrpA1 and ORs in Drosophila. Frontiers in Molecular Neuroscience. doi.org/10.3389/fnmol.2023.1249715.