Merck

Mosquito odorant receptor for DEET and methyl jasmonate.

Proceedings of the National Academy of Sciences of the United States of America (2014-10-29)
Pingxi Xu, Young-Moo Choo, Alyssa De La Rosa, Walter S Leal
ABSTRACT

Insect repellents are important prophylactic tools for travelers and populations living in endemic areas of malaria, dengue, encephalitis, and other vector-borne diseases. DEET (N,N-diethyl-3-methylbenzamide) is a 6-decade-old synthetic repellent, which is still considered the gold standard of mosquito repellents. Mosquitoes use their sense of smell to detect DEET, but there are currently two hypotheses regarding its mode of action: activation of ionotropic receptor IR40a vs. odorant receptor(s). Here, we demonstrate that DEET, picaridin, insect repellent 3535, and p-menthan-3,8-diol activate the odorant receptor CquiOR136 of the southern house mosquito, Culex quinquefasciatus. Electrophysiological and behavioral assays showed that CquiIR40a knockdown had no significant effect on DEET detection and repellency. By contrast, reduction of CquiOR136 transcript levels led to a significant decrease in electroantennographic responses to DEET and a complete lack of repellency. Thus, direct activation of an odorant receptor, not an ionotropic receptor, is necessary for DEET reception and repellency in Culex mosquitoes. Interestingly, methyl jasmonate, a repellent derived from the nonvolatile jasmonic acid in the signaling pathway of plant defenses, elicited robust responses in CquiOR136•CquiOrco-expressing Xenopus oocytes, thus suggesting a possible link between natural products with long insect-plant evolutionary history and synthetic repellents.

MATERIALS
Product Number
Brand
Product Description

Caprylic acid, European Pharmacopoeia (EP) Reference Standard
Supelco
1-Hexanol, analytical standard
Supelco
Geranyl acetate, analytical standard
Supelco
2-Heptanone, analytical standard
Supelco
m-Cresol, analytical standard
Sigma-Aldrich
Phenol, puriss., meets analytical specification of Ph. Eur., BP, USP, 99.5-100.5% (GC)
Sigma-Aldrich
Isobutyric acid, puriss. p.a., ≥99.5%
Supelco
Cyclohexanone, Selectophore, ≥99.5%
Sigma-Aldrich
Cyclohexanone, puriss. p.a., ≥99.5% (GC)
Supelco
Propionic acid, analytical standard
Sigma-Aldrich
Phenol, puriss., meets analytical specification of Ph. Eur., BP, USP, ≥99.5% (GC), crystalline (detached)
Sigma-Aldrich
Phenol, ≥96.0% (calc. on dry substance, T)
Sigma-Aldrich
Octylamine, ≥99.5%
Supelco
1-Dodecanol, Selectophore, ≥98.0%
Sigma-Aldrich
DL-Lactic acid, ~90% (T)
Supelco
3-Methylbutanol, analytical standard
Supelco
Cyclohexanone, analytical standard
Sigma-Aldrich
1-Heptanol, ≥99.5% (GC)
Supelco
Methyl acetate, analytical standard
Supelco
Octylamine, analytical standard
Sigma-Aldrich
1-Nonanol, purum, ≥98.0% (GC)
Sigma-Aldrich
3-Methylbutanol, BioUltra, for molecular biology, ≥99.0% (GC)
Supelco
Hexyl acetate, analytical standard
Supelco
Valeric acid, analytical standard
Supelco
2-Butanone, analytical standard
Supelco
Butyric acid, analytical standard
Sigma-Aldrich
Methyl acetate, ≥98%, FG
Sigma-Aldrich
Dodecanoic acid, 98%
Sigma-Aldrich
Undecanal, FCC, ≥96%
Sigma-Aldrich
Isoamyl acetate, natural, ≥97%, FCC, FG