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Chemoreceptor Evolution in Hymenoptera and Its Implications for the Evolution of Eusociality.
Zhou X, Rokas A, Berger SL, Liebig J, Ray A, Zwiebel LJ
(2015) Genome Biol Evol 7: 2407-16
MeSH Terms: Animals, Ants, Bees, Evolution, Molecular, Gene Expression, Genomics, Hymenoptera, Molecular Sequence Annotation, Receptors, Odorant, Social Behavior, Taste
Show Abstract · Added February 15, 2016
Eusocial insects, mostly Hymenoptera, have evolved unique colonial lifestyles that rely on the perception of social context mainly through pheromones, and chemoreceptors are hypothesized to have played important adaptive roles in the evolution of sociality. However, because chemoreceptor repertoires have been characterized in few social insects and their solitary relatives, a comprehensive examination of this hypothesis has not been possible. Here, we annotate ∼3,000 odorant and gustatory receptors in recently sequenced Hymenoptera genomes and systematically compare >4,000 chemoreceptors from 13 hymenopterans, representing one solitary lineage (wasps) and three independently evolved eusocial lineages (ants and two bees). We observe a strong general tendency for chemoreceptors to expand in Hymenoptera, whereas the specifics of gene gains/losses are highly diverse between lineages. We also find more frequent positive selection on chemoreceptors in a facultative eusocial bee and in the common ancestor of ants compared with solitary wasps. Our results suggest that the frequent expansions of chemoreceptors have facilitated the transition to eusociality. Divergent expression patterns of odorant receptors between honeybee and ants further indicate differential roles of chemoreceptors in parallel trajectories of social evolution.
© The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
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3 Members
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11 MeSH Terms
Mutational analysis of cysteine residues of the insect odorant co-receptor (Orco) from Drosophila melanogaster reveals differential effects on agonist- and odorant-tuning receptor-dependent activation.
Turner RM, Derryberry SL, Kumar BN, Brittain T, Zwiebel LJ, Newcomb RD, Christie DL
(2014) J Biol Chem 289: 31837-45
MeSH Terms: Allosteric Site, Animals, Biotinylation, Calcium, Cysteine, DNA Mutational Analysis, Drosophila Proteins, Drosophila melanogaster, Epitopes, HEK293 Cells, Humans, Ion Channels, Kinetics, Mutagenesis, Site-Directed, Mutation, Odorants, Patch-Clamp Techniques, Protein Binding, Protein Structure, Tertiary, Receptors, Odorant, Thioglycolates, Triazoles
Show Abstract · Added February 19, 2015
Insect odorant receptors are heteromeric odorant-gated cation channels comprising a conventional odorant-sensitive tuning receptor (ORx) and a highly conserved co-receptor known as Orco. Orco is found only in insects, and very little is known about its structure and the mechanism leading to channel activation. In the absence of an ORx, Orco forms homomeric channels that can be activated by a synthetic agonist, VUAA1. Drosophila melanogaster Orco (DmelOrco) contains eight cysteine amino acid residues, six of which are highly conserved. In this study, we replaced individual cysteine residues with serine or alanine and expressed Orco mutants in Flp-In 293 T-Rex cells. Changes in intracellular Ca(2+) levels were used to determine responses to VUAA1. Replacement of two cysteines (Cys-429 and Cys-449) in a predicted intracellular loop (ICL3), individually or together, gave variants that all showed similar increases in the rate of response and sensitivity to VUAA1 compared with wild-type DmelOrco. Kinetic modeling indicated that the response of the Orco mutants to VUAA1 was faster than wild-type Orco. The enhanced sensitivity and faster response of the Cys mutants was confirmed by whole-cell voltage clamp electrophysiology. In contrast to the results from direct agonist activation of Orco, the two cysteine replacement mutants when co-expressed with a tuning receptor (DmelOR22a) showed an ∼10-fold decrease in potency for activation by 2-methyl hexanoate. Our work has shown that intracellular loop 3 is important for Orco channel activation. Importantly, this study also suggests differences in the structural requirements for the activation of homomeric and heteromeric Orco channel complexes.
© 2014 by The American Society for Biochemistry and Molecular Biology, Inc.
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1 Members
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22 MeSH Terms
A determinant of odorant specificity is located at the extracellular loop 2-transmembrane domain 4 interface of an Anopheles gambiae odorant receptor subunit.
Hughes DT, Wang G, Zwiebel LJ, Luetje CW
(2014) Chem Senses 39: 761-9
MeSH Terms: Amino Acid Sequence, Animals, Anopheles, Cells, Cultured, Gene Expression, Insect Proteins, Molecular Sequence Data, Mutation, Odorants, Protein Structure, Tertiary, Receptors, Odorant, Smell, Xenopus
Show Abstract · Added February 19, 2015
To explore the structural basis for odorant specificity in odorant receptors of the human malaria vector mosquito, Anopheles gambiae, odorant-binding subunits (Agam\Ors) expressed in Xenopus oocytes in combination with Agam\Orco (coreceptor subunit) were assayed by 2-electrode voltage clamp against 25 structurally related odorants. Agam\Or13 and Agam\Or15 display 82% amino acid identity and had similar, but somewhat distinct odorant response profiles. The ratio of acetophenone to 4-methylphenol responses was used in a mutation-based analysis of Agam\Or15, interchanging 37 disparate residues between Agam\Or15 and Agam\Or13. Eleven mutations caused significant changes in odorant responsiveness. Mutation of alanine 195 resulted in the largest shift in response ratio from Agam\Or15 toward Agam\Or13. Concentration-response analysis for a series of mutations of residue 195 revealed a large effect on acetophenone sensitivity, with EC50 values varying by >1800-fold and correlating with residue side chain length. Similar results were obtained for propiophenone and benzaldehyde. But, for other odorants, such as 4-methylphenol, 4-methylbenzaldehyde, and 4-methylpropiophenone, the effect of mutation was much smaller (EC50 values varied by ≤16-fold). These results show that alanine 195, putatively located at the second extracellular loop/fourth transmembrane domain interface, plays a critical role in determining the odorant response specificity of Agam\Or15.
© The Author 2014. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
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1 Members
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13 MeSH Terms
Narrow SAR in odorant sensing Orco receptor agonists.
Romaine IM, Taylor RW, Saidu SP, Kim K, Sulikowski GA, Zwiebel LJ, Waterson AG
(2014) Bioorg Med Chem Lett 24: 2613-6
MeSH Terms: Animals, Drosophila melanogaster, Indoles, Molecular Structure, Receptors, Odorant, Structure-Activity Relationship, Triazoles
Show Abstract · Added May 27, 2014
The systematic exploration of a series of triazole-based agonists of the cation channel insect odorant receptor is reported. The structure-activity relationships of independent sections of the molecules are examined. Very small changes to the compound structure were found to exert a large impact on compound activity. Optimal substitutions were combined using a 'mix-and-match' strategy to produce best-in-class compounds that are capable of potently agonizing odorant receptor activity and may form the basis for the identification of a new mode of insect behavior modification.
Copyright © 2014 Elsevier Ltd. All rights reserved.
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1 Members
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7 MeSH Terms
Odorant receptor-mediated sperm activation in disease vector mosquitoes.
Pitts RJ, Liu C, Zhou X, Malpartida JC, Zwiebel LJ
(2014) Proc Natl Acad Sci U S A 111: 2566-71
MeSH Terms: Animals, Anopheles, Biological Assay, Insect Vectors, Male, Receptors, Odorant, Sequence Analysis, RNA, Sperm Capacitation, Sperm Tail, Statistics, Nonparametric, Testis
Show Abstract · Added May 27, 2014
Insects, such as the malaria vector mosquito, Anopheles gambiae, depend upon chemoreceptors to respond to volatiles emitted from a range of environmental sources, most notably blood meal hosts and oviposition sites. A subset of peripheral signaling pathways involved in these insect chemosensory-dependent behaviors requires the activity of heteromeric odorant receptor (OR) ion channel complexes and ligands for numerous A. gambiae ORs (AgOrs) have been identified. Although AgOrs are expressed in nonhead appendages, studies characterizing potential AgOr function in nonolfactory tissues have not been conducted. In the present study, we explore the possibility that AgOrs mediate responses of spermatozoa to endogenous signaling molecules in A. gambiae. In addition to finding AgOr transcript expression in testes, we show that the OR coreceptor, AgOrco, is localized to the flagella of A. gambiae spermatozoa where Orco-specific agonists, antagonists, and other odorant ligands robustly activate flagella beating in an Orco-dependent process. We also demonstrate Orco expression and Orco-mediated activation of spermatozoa in the yellow fever mosquito, Aedes aegypti. Moreover, we find Orco localization in testes across distinct insect taxa and posit that OR-mediated responses in spermatozoa may represent a general characteristic of insect reproduction and an example of convergent evolution.
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1 Members
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11 MeSH Terms
Antennal transcriptome profiles of anopheline mosquitoes reveal human host olfactory specialization in Anopheles gambiae.
Rinker DC, Zhou X, Pitts RJ, AGC Consortium, Rokas A, Zwiebel LJ
(2013) BMC Genomics 14: 749
MeSH Terms: Animals, Anopheles, Arthropod Antennae, Evolution, Molecular, Female, Genome, Humans, Molecular Sequence Annotation, Receptors, Odorant, Sequence Analysis, RNA, Transcriptome
Show Abstract · Added May 27, 2014
BACKGROUND - Two sibling members of the Anopheles gambiae species complex display notable differences in female blood meal preferences. An. gambiae s.s. has a well-documented preference for feeding upon human hosts, whereas An. quadriannulatus feeds on vertebrate/mammalian hosts, with only opportunistic feeding upon humans. Because mosquito host-seeking behaviors are largely driven by the sensory modality of olfaction, we hypothesized that hallmarks of these divergent host seeking phenotypes will be in evidence within the transcriptome profiles of the antennae, the mosquito's principal chemosensory appendage.
RESULTS - To test this hypothesis, we have sequenced antennal mRNA of non-bloodfed females from each species and observed a number of distinct quantitative and qualitative differences in their chemosensory gene repertoires. In both species, these gene families show higher rates of sequence polymorphisms than the overall rates in their respective transcriptomes, with potentially important divergences between the two species. Moreover, quantitative differences in odorant receptor transcript abundances have been used to model potential distinctions in volatile odor receptivity between the two sibling species of anophelines.
CONCLUSION - This analysis suggests that the anthropophagic behavior of An. gambiae s.s. reflects the differential distribution of olfactory receptors in the antenna, likely resulting from a co-option and refinement of molecular components common to both species. This study improves our understanding of the molecular evolution of chemoreceptors in closely related anophelines and suggests possible mechanisms that underlie the behavioral distinctions in host seeking that, in part, account for the differential vectorial capacity of these mosquitoes.
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2 Members
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11 MeSH Terms
A conserved aspartic acid is important for agonist (VUAA1) and odorant/tuning receptor-dependent activation of the insect odorant co-receptor (Orco).
Kumar BN, Taylor RW, Pask GM, Zwiebel LJ, Newcomb RD, Christie DL
(2013) PLoS One 8: e70218
MeSH Terms: Amino Acid Substitution, Animals, Anopheles, Drosophila Proteins, Drosophila melanogaster, Insect Proteins, Mutagenesis, Protein Structure, Tertiary, Receptors, Odorant, Thioglycolates, Triazoles
Show Abstract · Added May 27, 2014
Insect odorant receptors function as heteromeric odorant-gated cation channels comprising a conventional odorant-sensitive tuning receptor, and a conserved co-receptor (Orco). An Orco agonist, VUAA1, is able to activate both heteromeric and homomeric Orco-containing channels. Very little is known about specific residues in Orco that contribute to cation permeability and gating. We investigated the importance of two conserved Asp residues, one in each of transmembrane domains 5 and 7, for channel function by mutagenesis. Drosophila melanogaster Orco and its substitution mutants were expressed in HEK cells and VUAA1-stimulated channel activity was determined by Ca(2+) influx and whole-cell patch clamp electrophysiology. Substitution of D466 in transmembrane 7 with amino acids other than glutamic acid resulted in a substantial reduction in channel activity. The D466E Orco substitution mutant was ~2 times more sensitive to VUAA1. The permeability of the D466E Orco mutant to cations was unchanged relative to wild-type Orco. When D466E Orco is co-expressed with a conventional tuning odorant receptor, the heteromeric complex also shows increased sensitivity to an odorant. Thus, the effect of the D466E mutation is not specific to VUAA1 agonism or dependent on homomeric Orco assembly. We suggest the gain-of-activation characteristic of the D466E mutant identifies an amino acid that is likely to be important for activation of both heteromeric and homomeric insect odorant receptor channels.
0 Communities
1 Members
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11 MeSH Terms
Blood meal-induced changes to antennal transcriptome profiles reveal shifts in odor sensitivities in Anopheles gambiae.
Rinker DC, Pitts RJ, Zhou X, Suh E, Rokas A, Zwiebel LJ
(2013) Proc Natl Acad Sci U S A 110: 8260-5
MeSH Terms: Animals, Anopheles, Arthropod Antennae, Blood, Cluster Analysis, Computational Biology, Female, Gene Expression Regulation, Odorants, RNA, Receptors, Odorant, Sequence Analysis, DNA, Transcription, Genetic, Transcriptome
Show Abstract · Added May 27, 2014
Olfactory-driven behaviors are central to the lifecycle of the malaria vector mosquito Anopheles gambiae and are initiated by peripheral signaling in the antenna and other olfactory tissues. To continue gaining insight into the relationship between gene expression and olfaction, we have performed cohort comparisons of antennal transcript abundances at five time points after a blood meal, a key event in both reproduction and disease transmission cycles. We found that more than 5,000 transcripts displayed significant abundance differences, many of which were correlated by cluster analysis. Within the chemosensory gene families, we observed a general reduction in the level of chemosensory gene transcripts, although a subset of odorant receptors (AgOrs) was modestly enhanced in post-blood-fed samples. Integration of AgOr transcript abundance data with previously characterized AgOr excitatory odorant response profiles revealed potential changes in antennal odorant receptivity that coincided with the shift from host-seeking to oviposition behaviors in blood-fed female mosquitoes. Behavioral testing of ovipositing females to odorants highlighted by this synthetic analysis identified two unique, unitary oviposition cues for An. gambiae, 2-propylphenol and 4-methylcyclohexanol. We posit that modest, yet cumulative, alterations of AgOr transcript levels modulate peripheral odor coding resulting in biologically relevant behavioral effects. Moreover, these results demonstrate that highly quantitative, RNAseq transcript abundance data can be successfully integrated with functional data to generate testable hypotheses.
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2 Members
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14 MeSH Terms
Blockade of insect odorant receptor currents by amiloride derivatives.
Pask GM, Bobkov YV, Corey EA, Ache BW, Zwiebel LJ
(2013) Chem Senses 38: 221-9
MeSH Terms: Amiloride, Animals, Anopheles, Cell Line, HEK293 Cells, Humans, Insect Proteins, Patch-Clamp Techniques, Receptors, Odorant, Thioglycolates, Transfection, Triazoles
Show Abstract · Added May 27, 2014
Insect odorant receptors (ORs) function as heteromeric odorant-gated ion channels consisting of a conserved coreceptor, Orco, and an odorant-sensitive tuning subunit. Although some OR modulators have been identified, an extended library of pharmacological tools is currently lacking and would aid in furthering our understanding of insect OR complexes. We now demonstrate that amiloride and several derivatives, which have been extensively used as blockers for various ion channels and transporters, also block odorant-gated currents from 2 OR complexes from the malaria vector mosquito Anopheles gambiae. In addition, both heteromeric and homomeric ORs were susceptible to amiloride blockade when activated by VUAA1, an agonist that targets the Orco channel subunit. Amiloride derivatives therefore represent a valuable class of channel blockers that can be used to investigate the pharmacological and biophysical properties of insect OR function.
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1 Members
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12 MeSH Terms
Phylogenetic and transcriptomic analysis of chemosensory receptors in a pair of divergent ant species reveals sex-specific signatures of odor coding.
Zhou X, Slone JD, Rokas A, Berger SL, Liebig J, Ray A, Reinberg D, Zwiebel LJ
(2012) PLoS Genet 8: e1002930
MeSH Terms: Animals, Ants, Behavior, Animal, Female, Gene Expression Profiling, Gene Expression Regulation, Male, Pheromones, Phylogeny, Receptors, Ionotropic Glutamate, Receptors, Odorant, Sex Characteristics, Social Behavior, Species Specificity
Show Abstract · Added May 27, 2014
Ants are a highly successful family of insects that thrive in a variety of habitats across the world. Perhaps their best-known features are complex social organization and strict division of labor, separating reproduction from the day-to-day maintenance and care of the colony, as well as strict discrimination against foreign individuals. Since these social characteristics in ants are thought to be mediated by semiochemicals, a thorough analysis of these signals, and the receptors that detect them, is critical in revealing mechanisms that lead to stereotypic behaviors. To address these questions, we have defined and characterized the major chemoreceptor families in a pair of behaviorally and evolutionarily distinct ant species, Camponotus floridanus and Harpegnathos saltator. Through comprehensive re-annotation, we show that these ant species harbor some of the largest yet known repertoires of odorant receptors (Ors) among insects, as well as a more modest number of gustatory receptors (Grs) and variant ionotropic glutamate receptors (Irs). Our phylogenetic analyses further demonstrate remarkably rapid gains and losses of ant Ors, while Grs and Irs have also experienced birth-and-death evolution to different degrees. In addition, comparisons of antennal transcriptomes between sexes identify many chemoreceptors that are differentially expressed between males and females and between species. We have also revealed an agonist for a worker-enriched OR from C. floridanus, representing the first case of a heterologously characterized ant tuning Or. Collectively, our analysis reveals a large number of ant chemoreceptors exhibiting patterns of differential expression and evolution consistent with sex/species-specific functions. These differentially expressed genes are likely associated with sex-based differences, as well as the radically different social lifestyles observed between C. floridanus and H. saltator, and thus are targets for further functional characterization. Our findings represent an important advance toward understanding the molecular basis of social interactions and the differential chemical ecologies among ant species.
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2 Members
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14 MeSH Terms