A Sugar Gustatory Receptor Identified from the Foregut of Cotton Bollworm Helicoverpa armigera

CSIRO Ecosystem Sciences, Black Mountain, Australian Capital Territory, 2601, Australia.
Journal of Chemical Ecology (Impact Factor: 2.75). 12/2012; 38(12). DOI: 10.1007/s10886-012-0221-8
Source: PubMed


Helicoverpa armigera (Hübner) is one of the most polyphagous and cosmopolitan pest species, the larvae of which feed on numerous important crops. The gustatory system is critical in guiding insect feeding behavior. Here, we identified a gustatory receptor from H. armigera, HaGR9, which shows high levels of identity to DmGR43a from Drosophila melanogaster and BmGR9 from Bombyx mori. Reverse transcriptase PCR (RT-PCR) revealed HaGR9 is highly expressed in larval foregut, with little or no expression in other chemosensory tissues. Membrane topology studies indicated that, like two previously studied B. mori GRs, BmGR8 and BmGR53, HaGR9 has an inverted topology relative to G protein-coupled receptors (GPCRs), an intracellular N-terminus and an extracellular C-terminus. Calcium imaging studies confirmed HaGR9 is a sugar receptor showing dose-dependent responses to D-galactose, D-maltose, and D-fructose. This highly-expressed foregut-specific gustatory receptor may contribute to the regulation of larval feeding behavior.

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Available from: Hui-Jie Zhang, Apr 02, 2014
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    • "In vitro studies on other GRs, such as BmGR8 (Zhang et al. 2011), BmGR9, DmelGR43a (Sato et al. 2011) and HarmGR9 (Xu et al. 2012), show their responses to myo-inositol or Dfructose did not require the coexpression of other GRs in insect cell or Xenopus oocytes, which is consistent with our HarmGR3 studies here (Fig. 4). Previously, Sf9 cells have been successfully used to functionally characterise insect sugar receptors (Xu et al. 2012; Zhang et al. 2011) and insect ORs (Anderson et al. 2009; Smart et al. 2008). Sf9 cells are derived from ovarian tissue of a lepidopteran species (Spodoptera frugiperda) and may therefore be more suitable than other systems like the Bempty neuron^ from Drosophila (Dobritsa et al. 2003), Xenopus oocytes with patch clamp technologies (Sakurai et al. 2004) and human cells (HEK293T cells) (Sato et al. 2008) for studying lepidopteran chemosensory receptors, including CO 2 receptors, because they better support lepidopteran chemoreceptor function. "
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    ABSTRACT: Carbon dioxide (CO2) is important in insect ecology, eliciting a range of behaviours across different species. Interestingly, the numbers of CO2 gustatory receptors (GRs) vary among insect species. In the model organism Drosophila melanogaster, two GRs (DmelGR21a and DmelGR63a) have been shown to detect CO2. In the butterfly, moth, beetle and mosquito species studied so far, three CO2 GR genes have been identified, while in tsetse flies, four CO2 GR genes have been identified. In other species including honeybees, pea aphids, ants, locusts and wasps, no CO2 GR genes have been identified from the genome. These genomic differences may suggest different mechanisms for CO2 detection exist in different insects but, with the exception of Drosophila and mosquitoes, limited attention has been paid to the CO2 GRs in insects. Here, we cloned three putative CO2 GR genes from the cotton bollworm Helicoverpa armigera and performed phylogenetic and expression analysis. All three H. armigera CO2 GRs (HarmGR1, HarmGR2 and HarmGR3) are specifically expressed in labial palps, the CO2-sensing tissue of this moth. HarmGR3 is significantly activated by NaHCO3 when expressed in insect Sf9 cells but HarmGR1 and HarmGR2 are not. This is the first report characterizing the function of lepidopteran CO2 receptors, which contributes to our general understanding of the molecular mechanisms of insect CO2 gustatory receptors.
    Full-text · Article · Apr 2015 · The Science of Nature
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    • "Moreover, the expression of HarmGR4 also in larval foregut suggests that HarmGR4 may be also involved in the control of sugar consumption. In view of the wide distribution of HarmGR4 orthologs across various insect species, we think that the physiological function of fructose receptor is very important (Xu et al., 2012). Fig. 4. Two-electrode voltage-clamp recordings of Xenopus oocytes expressing HarmGR4 isolated in the present study. "
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    ABSTRACT: Insect gustatory systems play important roles in food selection and feeding behaviors. In spite of the enormous progress in understanding gustation in Drosophila, for other insects one of the key elements in gustatory signaling, the gustatory receptor (GR), is still elusive. In this study, we report that fructose elicits behavioral and physiological responses in Helicoverpa armigera (Harm) to fructose and identify the gustatory receptor for this sugar. Using the proboscis extension reflex (PER) assays we found that females respond to fructose following stimulation of the distal part of the antenna, where we have identified contact chemosensilla tuned to fructose in tip recording experiments. We isolated three full-length cDNAs encoding candidate HarmGRs based on comparison with orthologous GR sequences in Heliothis virescens and functionally characterized the responses of HarmGR4 to 15 chemicals when this receptor was expressed in Xenopus oocytes with two-electrode voltage-clamp recording. Among the tastants tested, the oocytes dose-dependently responded only to D-fructose (EC50 = 0.045M). By combining behavioral, electrophysiological and molecular approaches, these results provide basic knowledge for further research on the molecular mechanisms of gustatory reception. Copyright © 2015. Published by Elsevier Ltd.
    Full-text · Article · Mar 2015 · Insect biochemistry and molecular biology
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    • "HassGR4–8 are members of the insect 'sugar' receptor subfamily and share ∼10–64% identity to B. mori 'sugar' GRs. HassGR9, one member of 'GR43a-like' receptors, is an orthologous gene of HarmGR9 (Xu et al., 2012b). Nine 'bitter' receptors (HassGR10–18) were detected in our transcriptome, which have no identical homologies in H. armigera (Fig. 4). "
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    ABSTRACT: The Oriental tobacco budworm (Helicoverpa assulta) is a specialist herbivore moth and its larvae feed on Solanaceous plants. (Z)-9-hexadecenal (Z9-16: Ald) is the major sex pheromone component in H. assulta but the specific pheromone receptor (PR) against Z9-16: Ald has not yet been identified. In the present study, we integrated transcriptomic, bioinformatic and functional characterization approaches to investigate the chemosensory receptor genes of H. assulta. We identified seven potential PRs with 44 olfactory receptors, 18 gustatory receptors and 24 ionotropic receptors, which were further studied by in silico gene expression profile, phylogenetic analysis, reverse transcription PCR and calcium imaging assays. The candidate PR, HassOR13, showed a strong response to the minor sex pheromone component, (Z)-11-hexadecenal, but not the major component, Z9-16: Ald, in calcium imaging assays. This study provides the molecular basis for comparative studies of chemosensory receptors between H. assulta and other Helicoverpa species and will advance our understanding of the evolution and function of Lepidoptera insect chemosensation. © 2014 The Royal Entomological Society.
    Full-text · Article · Nov 2014 · Insect Molecular Biology
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