Cellular and molecular basis of IR3535 perception in Drosophila

Abstract

BACKGROUND: IR3535 is among the most widely used synthetic insect repellents, particularly for the mitigation of mosquitoborne diseases such as malaria, yellow fever, dengue and Zika, as well as to control flies, ticks, fleas, lice and mites. These insects are well-known vectors of deadly diseases that affect humans, livestock and crops. Moreover, global warming could increase the populations of these vectors.RESULTS: Here, we performed IR3535 dose-response analyses on Drosophila melanogaster, a well-known insect model organism, using electrophysiology and binary food choice assays. Our findings indicated that bitter-sensing gustatory receptor neurons (GRNs) are indispensable to detect IR3535. Further, potential candidate gustatory receptors were screened, among which GR47a was identified as a key molecular sensor. IR3535 concentrations in the range 0.1-0.4% affected larval development and mortality. In addition, N,N-diethyl-m-toluamide (DEET, another commonly used insecticide) was found to exert synergistic effects when co-administered with IR3535. CONCLUSION: Our findings confirmed that IR3535 directly activates bitter-sensing GRNs, which are mediated by GR47a. This relatively safe and highly potent insecticide can be largely used in combination with DEET to increase its efficiency to protect livestock and crops. Collectively, our findings suggest that the molecular sensors elucidated herein could be used as targets for the development of alternative insecticides.

Molecular Basis of Hexanoic Acid Taste in Drosophila melanogaster

“…Tip-recording tests were undertaken, as previously described ( Shrestha et al, 2022 ). We collected 4- to 7-day-old flies and tranquilized them on ice.…”

“…L- and S-type sensilla have four gustatory receptor neurons (GRNs), whereas I-type sensilla have only two GRNs. Gustatory receptors (GRs) and ionotropic receptors (IRs) are major chemoreceptors that detect sweet, amino acid, bitter, salty, nitrogenous waste, fermented histamine, vitamin C, and sour tastants in flies ( Aryal et al, 2022a ; Aryal and Lee, 2021 ; 2022 ; Dahanukar et al, 2007 ; Dhakal et al, 2021 ; Ganguly et al, 2017 ; Lee et al, 2010 ; McDowell et al, 2022 ; Rimal et al, 2019 ; 2020 ; Sang et al, 2019 ; 2021 ; Shrestha and Lee, 2021a ; 2021b ; Shrestha et al, 2022 ; 2023 ; Stanley et al, 2021 ; Thorne et al, 2004 ; Zhang et al, 2013a ). Furthermore, transient receptor potential (TRPA1, TRPL, and painless) channels are involved in detecting pungent and aversive chemicals: aristolochic acid, wasabi, and camphor ( Al-Anzi et al, 2006 ; Kang et al, 2010 ; Kim et al, 2010 ; Zhang et al, 2013b ).…”

In Vitro Evaluation of Essential Oils and Saturated Fatty Acids for Repellency against the Old-World Sand Fly, Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae)

“…Weeks et al [ 7 ] reported that P. papatasi sand flies were observed to approach human skin treated with IR3535, but to suddenly veer away, suggesting a limited spatial component of repellency. Shrestha et al [ 42 ] reported that bitter-sensing gustatory receptor neurons were essential for IR3535 detection, and that together, DEET and IR3535 exerted synergistic effects. Low concentrations of IR3535 act on the muscarinic acetylcholine receptors of the insect neurosecretory cells, inducing increased intracellular calcium, resulting in an increased sensitivity of the nicotinic acetylcholine receptors to thiacloprid [ 42 ].…”

“…Shrestha et al [ 42 ] reported that bitter-sensing gustatory receptor neurons were essential for IR3535 detection, and that together, DEET and IR3535 exerted synergistic effects. Low concentrations of IR3535 act on the muscarinic acetylcholine receptors of the insect neurosecretory cells, inducing increased intracellular calcium, resulting in an increased sensitivity of the nicotinic acetylcholine receptors to thiacloprid [ 42 ]. Some terpene constituents of essential oils have been shown to inhibit arthropod acetylcholinesterase [ 44 , 68 ].…”

“…Ethyl butylacetylaminopropionate, or EBAAP, also known as IR3535, is another synthetic insect repellent structurally similar to β-alanine or pantothenic acid, which is widely used in Europe [ 40 , 41 , 42 ]. IR3535 repels and deters biting by P. duboscqi , P. mascittii , and P. papatasi [ 7 , 43 ].…”