Ionotropic receptor 8a is involved in the attraction of Helicoverpa armigera to acetic acid

Abstract

Ionotropic receptors (IRs) were first found in Drosophila melanogaster, and derive from ionotropic glutamate receptors (iGluRs), which are implicated in detecting acids, ammonia, amine, temperature and humidity. Although IRs are involved in sensing acid odors in a few insects, such as D. melanogaster, Aedes aegypti, and Manduca sexta, the function of IRs in Helicoverpa armigera is still unknown. IR8a was confirmed to be a co‐receptor associated with acid detection. From the results of phylogenetic analysis, HarmIR8a displayed high similarity compared to homologs in D. melanogaster, M. sexta, and A. aegypti, suggesting that HarmIR8a might have a consistent function as a co‐receptor for acid detection. In this study, clustered regularly interspaced palindromic repeats (CRISPR) / CRISPR‐associated protein 9 (Cas9)‐mediated genome editing was implemented to knockout HarmIR8a for in vivo functional analysis. Electrophysiological and behavioral assays were performed to compare the differences between HarmIR8a knockout mutants and wild type individuals. From electroantennogram (EAG) analysis, we found that wild type H. armigera adults could detect short‐chain carboxylic acids. In addition, wind tunnel experiments showed that 1% acetic acid attracted wild type H. armigera adults. However, acid sensing and attraction were reduced or abolished in the HarmIR8a knockout mutants. Our data suggest that HarmIR8a is important for H. armigera to detect short‐chain carboxylic acids and mediate attraction behavior to acetic acid.

Characterization of Antennal Chemosensilla and Associated Chemosensory Genes in the Orange Spiny Whitefly, Aleurocanthus spiniferus (Quaintanca)

“…et al, 2019 ). Apart from the GRs, some IRs are also expressed in gustatory organs and are involved in gustation perception ( Zhang et al, 2021 ). For example, IRs expressed in D. melanogaster leg sensilla also showed a response to food components such as sugar, salts, polyamines and bitter compounds ( Ling et al, 2014 ; Hussain et al, 2016 ).…”

“…For example, IRs expressed in D. melanogaster leg sensilla also showed a response to food components such as sugar, salts, polyamines and bitter compounds ( Ling et al, 2014 ; Hussain et al, 2016 ). In H. armigera , knockout of IR8a reduced the EAG responses and trend behavior to acetic acid ( Zhang et al, 2021 ). Additionally, IR8a was found to be essential to detect human odors and water detection in Aedes aegypti ( Raji et al, 2019a , b ).…”

Recent Insights into Insect Olfactory Receptors and Odorant-Binding Proteins

“…While spearheaded by Drosophila , the advent of CRISPR technology has expanded the range of species amenable to genetic targeting, providing a much more reliable loss-of-function phenotype compared with RNA interference methods. Indeed, genetic lesioning in Aedes and Anopheles mosquitoes [ 5 , 6 , 7 ] and moths, including Bombyx [ 8 ], Helicoverpa [ 9 ], Manduca [ 10 , 11 , 12 ], and others, contributes to our understanding of these remarkable chemical detectors. This review will provide context for recent findings in the insect chemosensation field.…”

Mutagenesis of the odorant receptor co-receptor (Orco) reveals severe olfactory defects in the crop pest moth Helicoverpa armigera

“…As a typical polyphagous insect, the cotton bollworm, Helicoverpa armigera, is an important agricultural pest globally. A total of 84 candidate OR genes have been identified in the published genomic data of H. armigera [44] and at least 65 candidate OR transcripts (1 Orco, 7 PRs, at least 55 conventional Ors), and at least 21 Irs have been identified in the transcriptome data of H. armigera [45][46][47][48][49]. Seven PRs are involved in sex pheromone communication between male and female H. armigera, which are mainly expressed in three types of trichoid sensilla in male antennae.…”