MilliporeSigma

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

Sigma-Aldrich
Isopentyl acetate, mixture of isomers, reagent grade, 98%
Sigma-Aldrich
p-Cresol, puriss. p.a., ≥99.0% (GC)
Supelco
Naphthalene, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Butyraldehyde, analytical standard, contains ~0.1% 2,6-di-tert-butyl-4-methylphenol and ~1% water as stabilizer
Sigma-Aldrich
Ethyl hexanoate, natural, ≥98%, FCC, FG
Sigma-Aldrich
Decanoic acid, ≥99.5%, FCC, FG
Sigma-Aldrich
Ethyl lactate, natural, ≥98%, FCC, FG
Sigma-Aldrich
Ethyl butyrate, natural, ≥98%, FCC, FG
Sigma-Aldrich
Ethyl lactate, ≥98%, FCC, FG
Sigma-Aldrich
Decanoic acid, natural, ≥98%, FCC, FG
Sigma-Aldrich
Ethyl butyrate, ≥98%, FCC, FG
Sigma-Aldrich
Ethyl hexanoate, ≥98%, FCC, FG
Sigma-Aldrich
1-Butanol, BioRenewable, ACS reagent, ≥99.4%
Sigma-Aldrich
Ammonia solution, 2.0 M in methanol
Sigma-Aldrich
Acetic acid, glacial, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.8%
Sigma-Aldrich
Acetic acid, glacial, ≥99.99% trace metals basis
Sigma-Aldrich
1-Propanol, ≥99% (GC), purum
Sigma-Aldrich
1-Butanol, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.5% (GC)
Sigma-Aldrich
Acetic acid solution, suitable for HPLC
Sigma-Aldrich
Ammonia solution, 2.0 M in ethanol
Sigma-Aldrich
Ammonia solution, 7 N in methanol
Sigma-Aldrich
Ammonia solution, 2.0 M in isopropanol
Sigma-Aldrich
1-Butanol, ACS reagent, ≥99.4%
Sigma-Aldrich
1-Octanol, suitable for HPLC, ≥99%
Guaiacol, European Pharmacopoeia (EP) Reference Standard
Lauric acid, European Pharmacopoeia (EP) Reference Standard
Supelco
Pentyl acetate, analytical standard
Supelco
Heptaldehyde, analytical standard
Supelco
Acetophenone, certified reference material, TraceCERT®
Sigma-Aldrich
Heptyl alcohol, natural, 98%