Article

The chemoreceptor superfamily in the honey bee, Apis mellifera: Expansion of the odorant, but not gustatory, receptor family

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Abstract

The honey bee genome sequence reveals a remarkable expansion of the insect odorant receptor (Or) family relative to the repertoires of the flies Drosophila melanogaster and Anopheles gambiae, which have 62 and 79 Ors respectively. A total of 170 Or genes were annotated in the bee, of which seven are pseudogenes. These constitute five bee-specific subfamilies in an insect Or family tree, one of which has expanded to a total of 157 genes encoding proteins with 15%-99% amino acid identity. Most of the Or genes are in tandem arrays, including one with 60 genes. This bee-specific expansion of the Or repertoire presumably underlies their remarkable olfactory abilities, including perception of several pheromone blends, kin recognition signals, and diverse floral odors. The number of Apis mellifera Ors is approximately equal to the number of glomeruli in the bee antennal lobe (160-170), consistent with a general one-receptor/one-neuron/one-glomerulus relationship. The bee genome encodes just 10 gustatory receptors (Grs) compared with the D. melanogaster and A. gambiae repertoires of 68 and 76 Grs, respectively. A lack of Gr gene family expansion primarily accounts for this difference. A nurturing hive environment and a mutualistic relationship with plants may explain the lack of Gr family expansion. The Or family is the most dramatic example of gene family expansion in the bee genome, and characterizing their caste- and sex-specific gene expression may provide clues to their specific roles in detection of pheromone, kin, and floral odors.

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... Firstly, 10 GRs genes (AmGr) and 3 AmGrs pseudogenes (i.e., which do not code for functional proteins) were identified, thus indicating the presence of 10 functional GRs (Robertson & Wanner, 2006). Later, the sequencing of bumble bee genomes (Bombus terrestris and Bombus impatiens) led to a revision of the honey bee genome, and the number of GR genes and of functional GRs was extended to 11 and the number of pseudogenes to 4 (Sadd et al., 2015). ...
... For instance, the fruit fly D. melanogaster possesses 68 functional GRs encoded by 60 Grs (Dunipace et al., 2001;Robertson et al., 2003;Scott et al., 2001), the mosquito Anopheles gambiae 76 functional GRs encoded by 52 Grs (Hill et al., 2002), and the Argentine ant (Linepithema humile) 96 functional GRs encoded by 116 Grs (Smith et al., 2011). The reduced number of Grs found in the honey bee has been interpreted as the result of a feeding specialization on floral products (Robertson & Wanner, 2006), which would be associated with a reduction in tastant diversity. This interpretation has been questioned as a similar reduction in the number of Grs has been found in other Hymenoptera with different, omnivorous feeding regimes (e.g., 11 Grs and 6 Grs in the carpenter ant Camponotus floridanus and the jumping ant Harpegnathos saltator, respectively; Bonasio et al., 2010). ...
... The sequencing of the honey bee genome allowed to identify the presence of GRs and IRs and enables, in addition, to use comparative analyses between species to address the evolution of taste mechanisms and search for orthologs guiding functional analyses of receptor function. To investigate the evolution of the GR multigenic family, we gathered all known 359 proteins of the GR family reported for 6 insect species, including 15 proteins for the honey bee, A. mellifera (AmGr); 25 proteins for the bumble bee, B. terrestris (BtGr); 76 proteins for the Malaria mosquito, A. gambiae (AgGr); 68 proteins for the fruit fly D. melanogaster (DmGr); 117 proteins for the Argentinean ant, L. humile (LhGr); and 58 proteins for the parasitoid wasp, Nasonia vitripennis (NvGr; Robertson & Wanner, 2006;Sadd et al., 2015;Smith et al., 2011). Some proteins are not functional and were labeled as pseudogenes (PSE) in our reconstruction. ...
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Understanding the neural principles governing taste perception in species that bear economic importance or serve as research models for other sensory modalities constitutes a strategic goal. Such is the case of the honey bee (Apis mellifera), which is environmentally and socioeconomically important, given its crucial role as pollinator agent in agricultural landscapes and which has served as a traditional model for visual and olfactory neurosciences and for research on communication, navigation and learning and memory. Here we review the current knowledge on honey bee gustatory receptors to provide an integrative view of peripheral taste detection in this insect, highlighting specificities and commonalities with other insect species. We describe behavioral and electrophysiological responses to several tastant categories and relate these responses, whenever possible, to known molecular receptor mechanisms. Overall, we adopted an evolutionary and comparative perspective to understand the neural principles of honey bee taste, and define key questions that should be answered in future gustatory research centered on this insect.
... The ORco lineage contained SnocORco and SnitORco (1.00 bootstrap support value), which further confirmed that these two ORs were ORcos. And the two ORcos were clustered with the honey bee ORco AmelOR2 [32] and other Hymenoptera ORco, suggesting they could function as a complex with other ORs in the woodwasps as the ORcos in other insects. The sirex-specific lineages contained SnocOR9, SnocOR12, SnocOR17, SnocOR20, SnocOR22a, SnocOR22b, SnocOR23 in S. noctilio and SnitOR1a, SnitOR1b, SnitOR9, SnitOR12, SnitOR17, SnitOR20a, SnitOR20b, SnitOR22a, SnitOR22b, SnitOR23 in S. nitobei. ...
... Amino acid sequence analysis revealed a highly conserved region at the end of the ORco sequence [31]. In our phylogenetic analysis, we found two genes, SnocORco and SnitORco, that were clustered with the honey bee ORco AmelOR2 [32] and other Hymenoptera ORco, suggesting they could function as a complex with other ORs in the woodwasps as the ORcos in other insects. ...
... We analyzed a total of 62 and 69 chemosensory genes in S. noctilio and in S. nitobei, respectively, including 41 ORs in S. noctilio and 43 ORs in S. nitobei. The numbers of ORs identified in S. noctilio and S. nitobei were less than those in most Hymenopteran species, such as M. mediator (60) [36], C. cinctus (72) [61], Chouioia cunea (80) [62], A. mellifera (174) [32], M. pulchricornis (99) [50], N. vitripennis (301) [63], M. cingulum (109) [64], and C. chlorideae (211) [60]. However, the numbers of ORs identified in S. noctilio and S. nitobei were greater than that of some Coleopteran species, such as Anoplophora glabripennis (37), Agrilus planipennis (2), and Monochamus alternatus (9) [65][66][67]. ...
Article
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Background The woodwasp Sirex noctilio Fabricius is a major quarantine pest worldwide that was first discovered in China in 2013 and mainly harms Pinus sylvestris var. mongolica Litv.. S. nitobei Matsumura is a native species in China and is closely related to S. noctilio . Recently, the two woodwasps species were found attacking the P. sylvestris var. mongolica Litv in succession. The olfactory system is the foundation of insect behavior. Olfactory genes were identified through antennal transcriptome analysis. The expression profiles odorant binding proteins (OBPs) were analyzed with RT-qPCR. Results From our transcriptome analysis, 16 OBPs, 7 chemosensory proteins (CSPs), 41 odorant receptors (ORs), 8 gustatory receptors (GRs), 13 ionotropic receptors (IRs), and one sensory neuron membrane protein (SNMP) were identified in S. noctilio , while 15 OBPs, 6 CSPs, 43 ORs, 10 GRs, 16 IRs, and 1 SNMP were identified in S. nitobei . Most of the olfactory genes identified in two species were homologous. However, some species-specific olfactory genes were identified from the antennal transcriptomes, including SnocOBP13 , SnocCSP6 , SnocOR26, SnocGR2 , SnocIR7 in S. noctilio and SnitGR9, SnitGR11, SnitIR17 in S. nitobei. In total, 14 OBPs were expressed primarily in the antennae. SnocOBP9 and SnitOBP9, identified as PBP homologues, were sex-biased expression in two siricid, but with different pattern. SnocOBP11 and SnitOBP11 were highly expressed in antennae and clearly expressed in external genitalia. SnocOBP7 and SnitOBP7 were highly expressed in male genitalia. SnocOBP3 and SnocOBP10 were highly expressed in female genitalia and male heads, while SnitOBP3 and SnitOBP10 did not show obvious tissue bias. Conclusion We analyzed 86 and 91 olfactory genes from S. noctilio and S. nitobei , respectively. Most of the olfactory genes identified were homologous, but also some species-specific olfactory genes were identified, which indicated the similarities and differences of the molecular mechanisms between the two closely-related species. Different expression in the antennae, external genitals or heads, exhibiting an obvious sex bias, suggested their different role in recognizing sex pheromones or plant volatiles. Species-specific expression for several OBPs genes may suggest that they strengthened or lost their original function during species differentiation, resulting in olfactory differences between the two species.
... From previous studies, we know that Wufu contains 81 olfactory receptors and 10 gustatory receptors [16], Korea contains 119 olfactory receptors and 13 gustatory receptors [17], and Baisha has not been systematically identified [18]. In A. mellifera, a total of 170 olfactory receptors and 10 taste receptors were identified [24]. ...
... The odorant receptor proteins of homo species, Bombyx mori, and mice were downloaded from NCBI [55]. The odorant receptor proteins of A. florea and A. mellifera were obtained, referring to another past study [24,56], as well the predicted odorant receptor proteins of two A. cerana strains. Ultimately, a total of 6535 predicted odorant receptor proteins from our collected protein sets were used as a database for the prediction of odorant receptor proteins of different A. cerana strains in this study. ...
... Bees are fed by nurse bees from a young age and do not need gustatory sensation to locate and recognize food. In addition, they can recognize objects by their antennae instead of gustatory sensation [24]. We believe that the loss/gain of gustatory receptors in bees could also result from adaptation to their environment. ...
Article
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Apis cerana abansis, widely distributed in the southeastern margin of the Qinghai-Tibet Plateau, is considered an excellent model to study the phenotype and genetic variation for highland adaptation of Asian honeybee. Herein, we assembled and annotated the chromosome-scale assembly genome of A. cerana abansis with the help of PacBio, Illumina and Hi-C sequencing technologies in order to identify the genome differences between the A. cerana abansis and the published genomes of different A. cerana strains. The sequencing methods, assembly and annotation strategies of A. cerana abansis were more comprehensive than previously published A. cerana genomes. Then, the intraspecific genetic diversity of A. cerana was revealed at the genomic level. We re-identified the repeat content in the genome of A. cerana abansis, as well as the other three A. cerana strains. The chemosensory and immune-related proteins in different A. cerana strains were carefully re-identified, so that 132 odorant receptor subfamilies, 12 gustatory receptor subfamilies and 22 immune-related pathways were found. We also discovered that, compared with other published genomes, the A. ceranaabansis lost the largest number of chemoreceptors compared to other strains, and hypothesized that gene loss/gain might help different A. cerana strains to adapt to their respective environments. Our work contains more complete and precise assembly and annotation results for the A. cerana genome, thus providing a resource for subsequent in-depth related studies.
... The number of chemosensory genes in A. dorsata and A. florea (Supplemental Table S6) was similar to the previously described gene sets in A. mellifera for all chemosensory gene families (Robertson and Wanner 2006;Karpe et al. 2016;Brand and Ramírez 2017), with a large number of 1:1:1 orthologous genes between the three species (from 66% in ORs to 100% in CSPs and IRs). Additionally, we found conservation of genes, such as the 9-ODA receptor gene OR11, across species. ...
... In addition to these patterns shared among gene families, we found that the number of GRs in the newly annotated A. florea and A. dorsata genomes differed substantially from A. mellifera. Previous annotations of the A. mellifera genome reported a total of 15 GR genes including 11 functional and four pseudogenized copies (Robertson and Wanner 2006;Smith et al. 2011). In addition to single copies for each of the functional GRs known from A. mellifera, we identified 19 and 15 GRs in A. dorsata and A. florea, respectively (Fig. 4). ...
... Several of the XYZ-homologous GRs showed 1:1 homology between A. dorsata and A. florea, as well as the A. mellifera pseudogenes. A reannotation of the A. mellifera GR gene family, including the previously reported >50 fragmented GR pseudogenes (Robertson and Wanner 2006), reconstructed all known functional GRs and 88 additional sequences with homology with the X, Y, and Z GR pseudogenes. Six of 11 GRs with a length of at least 300 amino acids contained premature stop codons, whereas the other five represent new, potentially functional GRs. ...
Article
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In contrast to the western honey bee, Apis mellifera, other honey bee species have been largely neglected despite their importance and diversity. The genetic basis of the evolutionary diversification of honey bees remains largely unknown. Here, we provide a genome-wide comparison of three honey bee species each representing one of the three subgenera of honey bees, namely the dwarf (Apis florea), giant (A. dorsata) and cavity-nesting (A. mellifera) honey bees with bumblebees as outgroup. Our analyses resolve the phylogeny of honey bees with the dwarf honey bees diverging first. We find that evolution of increased eusocial complexity in Apis proceeds via increases in the complexity of gene regulation, which is in agreement with previous studies. However, this process seems to be related to pathways other than transcriptional control. Positive selection patterns across Apis reveal a trade-off between maintaining genome stability and generating genetic diversity, with a rapidly evolving piRNA pathway leading to genomes depleted of transposable elements, and a rapidly evolving DNA repair pathway associated with high recombination rates in all Apis species. Diversification within Apis is accompanied by positive selection in several genes whose putative functions present candidate mechanisms for lineage-specific adaptations, such as migration, immunity, and nesting behavior.
... The impressive species diversity that insects have reached through their evolution shows a high capacity to adapt according to environmental heterogeneities and changing scenarios. In this sense, the dramatically different PPK repertoires reported here may reflect specific sensory abilities shaped by the particular niches where these animals thrive (McBride and Arguello 2007;Smadja et al. 2012;Sánchez-Gracia et al. 2011;Robertson and Wanner 2006) . The extreme examples of 59 PPK family members found in the genome of M. domestica, and only one in that of P. humanus capture the extent of the plasticity shown by these gene repertoires to adapt to environmental pressures. ...
... The hymenopteran species analyzed herein are another example showing relatively small PPK sets in their genomes (6-9 genes), in coincidence with those observed for their GR and IR families (Supplementary Table S7). On the other hand, the large OR sets known for hymenopterans suggest that they rely mostly on olfaction to detect and discriminate floral/plant/prey-emitted compounds (Robertson and Wanner 2006;Zhou et al. 2015). ...
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Insect Pickpocket (PPK) receptors mediate the detection of stimuli of diverse sensory modalities, therefore having a relevant role for environmental sounding. Notwithstanding their relevance, studies on their evolution are scarce. We have analyzed the genomes of 26 species belonging to 8 insect orders (Blattodea, Orthoptera, Hemiptera, Phthiraptera, Hymenoptera, Lepidoptera, Coleoptera, and Diptera) to identify their PPK repertoires and study the evolution of this gene family. PPKs were detected in all genomes analyzed, with a total of 578 genes identified that distributed in 7 subfamilies. Our phylogenetic analysis allowed clarifying that the ppk17 gene appears to be the most divergent family member, composing a new group designed as subfamily VII. According to our analysis, PPKs evolved under a birth-and-death model that generated lineage‐specific expansions usually located in clusters and the effect of strong purifying selection was seen for several orthogroups. Subfamily V was the largest one, presenting half of all PPKs studied, including a mosquito-specific expansion that can be considered a new target for pest control. Consistently with their sensory role, PPKs present a high gene turnover that generated considerable variation in the size of insect repertoires: Musca domestica (59), Blattella germanica (41), Culex quinquefasciatus (48), and Aedes albopictus (51) presented the largest PPK repertoires, while Pediculus humanus (only ppk17), bees and ants (6-9) had the smallest ones. The expansions identified in M. domestica and Bl. germanica also show promise as specific targets for controlling these nuisance insects. Our phylogenetic analysis revealed a subset of prevalent PPKs across insect genomes, suggesting a very conserved function that resembles the case of antennal ionotropic receptors. Finally, we identified new highly conserved residues in the second transmembrane domain that may be key for receptor function. Besides, more than a hundred PPK sequences presented calmodulin binding motifs, suggesting that at least some members of this family may amplify sensory responses as previously proposed for D. melanogaster ppk25. Overall, our study is a first attempt to characterize the evolutionary history of this family of sensory receptors, revealing relevant unknown features and clade-specific expansions.
... While most Drosophila species and the mosquito Anopheles gambiae have eight SRs and some other insects like the beetle Tribolium castaneum even up to 16 SRs responding to several different sugars (e.g. sucrose, trehalose, glucose…), only two were identified for the parasitoid jewel wasp Nasonia vitripennis (Kent and Robertson 2009), the honeybee Apis mellifera (Robertson and Wanner 2006), and the bumblebee Bombus terrestris (Sadd et al. 2015). In general, 23 GR genes have been identified in B. terrestris (Sadd et al. 2015), while only ten GR genes have been identified for A. mellifera, leading to a discussion about an impoverished gustatory perception of the honeybee (Robertson and Wanner 2006). ...
... sucrose, trehalose, glucose…), only two were identified for the parasitoid jewel wasp Nasonia vitripennis (Kent and Robertson 2009), the honeybee Apis mellifera (Robertson and Wanner 2006), and the bumblebee Bombus terrestris (Sadd et al. 2015). In general, 23 GR genes have been identified in B. terrestris (Sadd et al. 2015), while only ten GR genes have been identified for A. mellifera, leading to a discussion about an impoverished gustatory perception of the honeybee (Robertson and Wanner 2006). However, besides alternative splicing, leading to more than one receptor type per GR gene and the fact that one receptor type can receive a broader variety of substances (de Brito Sanchez 2011), receptors can either work on their own, or together as co-receptors or heterodimers. ...
Thesis
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Nutrients belong to the key elements enabling life and influencing an organism’s fitness. The intake of nutrients in the right amounts and ratios can increase fitness; strong deviations from the optimal intake target can decrease fitness. Hence, the ability to assess the nutritional profile of food would benefit animals. To achieve this, they need the according nutrient receptors, the ability to interpret the receptor information via perceptive mechanisms, and the ability to adjust their foraging behavior accordingly. Additionally, eventually existing correlations between the nutrient groups and single nutrient compounds in food could help them to achieve this adjustment. A prominent interaction between food and consumer is the interaction between flowering plants (angiosperms) and animal pollinators. Usually both of the interacting partners benefit from this mutualistic interaction. Plants are pollinated while pollinators get a (most of the times) nutritional reward in form of nectar and/or pollen. As similar interactions between plants and animals seem to have existed even before the emergence of angiosperms, these interactions between insects and angiosperms very likely have co-evolved right from their evolutionary origin. Therefore, insect pollinators with the ability to assess the nutritional profile may have shaped the nutritional profile of plant species depending on them for their reproduction via selection pressure. In Chapter I of this thesis the pollen nutritional profile of many plant species was analyzed in the context of their phylogeny and their dependence on insect pollinators. In addition, correlations between the nutrients were investigated. While the impact of phylogeny on the pollen protein content was little, the mutual outcome of both of the studies included in this chapter is that protein content of pollen is mostly influenced by the plant’s dependence on insect pollinators. Several correlations found between nutrients within and between the nutrient groups could additionally help the pollinators to assess the nutrient profile of pollen. An important prerequisite for this assessment would be that the pollinators are able to differentiate between pollen of different plant species. Therefore, in Chapter II it was investigated whether bees have this ability. Specifically, it was investigated whether honeybees are able to differentiate between pollen of two different, but closely related plant species and whether bumblebees prefer one out of three pollen mixes, when they were fed with only one of them as larvae. Honeybees indeed were able to differentiate between the pollen species and bumblebees preferred one of the pollen mixes to the pollen mix they were fed as larvae, possibly due to its nutritional content. Therefore, the basis for pollen nutrient assessment is given in bees. However, there also was a slight preference for the pollen fed as larvae compared to another non-preferred pollen mix, at least hinting at the retention of larval memory in adult bumblebees. Chapter III looks into nutrient perception of bumblebees more in detail. Here it was shown that they are principally able to perceive amino acids and differentiate between them as well as different concentrations of the same amino acid. However, they do not seem to be able to assess the amino acid content in pollen or do not focus on it, but instead seem to focus on fatty acids, for which they could not only perceive concentration differences, but also were able to differentiate between. These findings were supported by feeding experiments in which the bumblebees did not prefer any of the pollen diets containing less or more amino acids but preferred pollen with less fatty acids. In no choice feeding experiments, bumblebees receiving a diet with high fatty acid content accepted undereating other nutrients instead of overeating fat, leading to increased mortality and the inability to reproduce. Hence, the importance of fat in pollen needs to be looked into further. In conclusion, this thesis shows that the co-evolution of flowering plants and pollinating insects could be even more pronounced than thought before. Insects do not only pressure the plants to produce high quality nectar, but also pressure those plants depending on insect pollination to produce high quality pollen. The reason could be the insects’ ability to receive and perceive certain nutrients, which enables them to forage selectively leading to a higher reproductive success of plants with a pollinator-suitable nutritional pollen profile.
... TpreOBP amino acid sequences (Supplementary Data) were used to create an entry file for phylogenetic analysis in MEGA-X with A. mellifera, Nasonia vitripennis and Diachasma alloeum OBP protein sequences [24][25][26][27]. Firstly, the amino acid sequences were aligned using ClustalW alignment with default settings: Gap Opening Penalty (10.00), ...
... For example, A. mellifera has 163 ORs but only ten gustatory receptors (GRs). Presumably a large number of ORs can enhance A. mellifera olfactory ability and facilitate the typical foraging and social behaviours while honeybees have limited need for GRs for plant secondary metabolite discrimination since flowering plants have evolved visual and olfactory cues to attract bees [26]. T. pretiosum has the lowest numbers of ORs in these four species. ...
Article
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Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) is a tiny natural egg parasitoid of several agricultural pest insects, which has been widely used in the biological control for Plutella xylostella, Helicoverpa armigera, Spodoptera frugiperda and Ectomyelois ceratoniae. However, limited studies have been conducted on T. pretiosum olfactory system, which is critical in regulating insect behaviours. In this study, T. pretiosum adult antennae were investigated under ascanning electron microscopy (SEM). Four types of olfactory sensilla were observed, including chaetica sensilla (CS), trichoid sensilla (TS), faleate sensilla (FS) and placoid sensilla (PS). Using T. pretiosum genome, 22 putative odorant binding proteins (OBPs) and 105 odorant receptors (ORs) were identified, which were further compared with olfactory genes of Apis mellifera, Nasonia vitripennis and Diachasma alloeum. The expression patterns of OBPs between T. pretiosum male and female adults were examined by quantitative real time PCR (qRT-PCR) approaches. Three female-specific OBPs (TpreOBP19, TpreOBP15 and TpreOBP3) were identified, which may play crucial roles in T. pretiosum host-seeking and oviposition behaviours. This study enriches our knowledge of T. pretiosum olfactory genes and improves our understanding of its olfactory system.
... Like the OR family, GRs are abundant and diverse 68, 65, 76, or 10 GR genes have been identified in Drosophila melanogaster, Bombyx mori, Anopheles gambiae, and Apis mellifera, respectively [12][13][14][15]. In D. melanogaster, Dmel-GR5a is expressed in taste organs and recognizes trehalose [16]. ...
... This count is similar to previously reported estimates for other Hemipteran insects, such as 83 ORs in Nysius ericae [39], 110 ORs in A. lucorum [40], and 88 ORs in A. lineolatus [41]. However, it is lower than counts of 259 ORs in T. castaneum [42], 170 ORs A. mellifera [14], and 142 ORs Locusta migratoria [43] and it is higher than estimates of 63 ORs in Sogatella furcifera [44] and 45 ORs in Aphis gossypii [45]. These differences may be explained by divergence among species. ...
Article
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Chemosensory receptors in the dendritic membrane of olfactory cells are critical for the molecular recognition and discrimination of odorants. Tropidothorax elegans is a major pest of agricultural, ornamental, and medicinal plants. However, very little is known about olfactory genes in T. elegans. The purpose of this study was to obtain chemosensory receptor genes by sequencing the antennal transcriptome of T. elegans using Illumina sequencing technology. We identified 153 candidate chemosensory receptors, including 121 olfactory receptors (including one olfactory receptor co-receptor), 10 ionotropic receptors (including one IR8a and one IR25a), and 22 gustatory receptors (GRs). TeleOR76, 104 and 112 displayed more highly expression level than TeleOrco. Other TeleGR genes were expressed at very low levels except TeleGR1 and 20. TeleIR76b was the most highly expressed among TeleIR genes. Our results provide valuable biological information for studies of the olfactory communication system of T. elegans.
... However, honeybees possess only 21 OBPs and 6 CSPs (Forêt and Maleszka, 2006), as compared with the 50 OBPs and 20 CSPs of T. castaneum (Dippel et al., 2014) These large differences are not compensated by NPC2 proteins, that are present with 5 and 9 genes in the two species, respectively . Similarly, when we look at chemoreceptor genes, the honeybee is less equipped with 170 ORs and only 10 GRs (Robertson and Wanner, 2006) than T. castaneum, which is endowed with 259 ORs and 220 GRs (Engsontia et al., 2008). ...
... These large differences in the number of chemoreception genes between species have been suggested to be related to different ecology. In particular, it has been suggested that the small number of GRs in the honey bee might reflect the fact that these insects locate plants based on their smell (Robertson and Wanner, 2006), while the large number of ORs in T. castaneum was http://mc.manuscriptcentral.com/gbe 13 required by this species before its diet became specialised and limited to stored grain (Engsontia et al., 2008). ...
Article
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Lipocalins represent one of the most successful superfamilies of proteins. Most of them are extracellular carriers for hydrophobic ligands across aqueous media, but other functions have been reported. They are present in most living organisms including bacteria. In animals they have been identified in mammals, molluscs and arthropods; sequences have also been reported for plants. A sub-group of lipocalins, referred to as odorant-binding proteins (OBPs), mediate chemical communication in mammals by ferrying specific pheromones to the vomeronasal organ. So far, these proteins have not been reported as carriers of semiochemicals in other living organisms; instead chemical communication in arthropods is mediated by other protein families structurally unrelated to lipocalins. A search in the databases has revealed extensive duplication and differentiation of lipocalin genes in some species of insects, crustaceans and chelicerates. Their large numbers, ranging from a handful to few dozens in the same species, their wide divergence, both within and between species, and their expression in chemosensory organs suggest that such expansion may have occurred under environmental pressure, thus supporting the hypothesis that lipocalins may be involved in chemical communication in arthropods.
... Nurse bees are less responsive than foragers to sugar stimuli (Scheiner et al., 2017), and they show differential expression of taste receptors in the antennae and brain, which might be involved in regulating division of labor through nutrition-related signaling pathways (Degirmenci et al., 2018). The honey bee genome encodes 10 gustatory receptors (Grs), among which AmGR1, AmGR2 and AmGR3 encode for putative sugar receptors (Robertson & Wanner, 2006). In this study, we found that Mblk-1 and AmGR1 had significantly higher expression in the brains of forager bees compared with nurse bees. ...
... Differential sensing of sugars were related to social organization in the honey bee. The honeybee genome contains a multitude of olfactory receptor genes that enable workers to perceive various floral odors; it contains less than a dozen gustatory receptor genes (Robertson & Wanner, 2006). Nurses and foragers perceive and evaluate different sugars differently, which is related to a differential expression of taste receptors in the antennae and brain (Degirmenci et al., 2018). ...
Article
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Brain transcriptional regulatory network for behavior demonstrates that brain gene expression in the honey bee can be accurately predicted from the expression transcription factors (TFs), but roles for specific TFs are less understood. Mushroom bodies (MBs) are important for learning, memory and sensory integration in the honey bee brain. A transcription factor, Mblk-1, expressed preferentially in the large-type Kenyon cells of the honeybee MBs is predicted to be involved in brain function by regulating transcription of its target genes in honey bee. However its function and the mechanism of regulation in behavior of honey bee is still obscure. Here we show that Mblk-1 had significantly higher expression in the brains of forager bees relative to nurse bees. Mblk-1 was significantly inhibited in bees fed siRNA. In addition, inhibition of Mblk-1 decreased sucrose responsiveness in foragers. Finally, we determined that Mblk-1 regulated the mRNA of AmGR1. These findings suggest that Mblk-1 may target AmGR1 to regulate the sucrose responsiveness of foragers. This article is protected by copyright. All rights reserved
... La taille de la famille de gènes d'OR chez un insecte est liée probablement à la complexité de son environnement chimique. Par exemple l'abeille Apis mellifera possède 163 OR en comparaison aux 62 OR chez Drosophila melanogaster et 79 OR chez Anopheles gambiae (Vosshall et al. 1999, Robertson and Wanner 2006). Cela peut s'expliquer par le fait que les abeilles sont confrontées à un environnement très complexe, où elles doivent être capables de percevoir plusieurs mélanges de phéromones, de signaux de reconnaissance de parenté et de diverses odeurs florales. ...
... Cela peut s'expliquer par le fait que les abeilles sont confrontées à un environnement très complexe, où elles doivent être capables de percevoir plusieurs mélanges de phéromones, de signaux de reconnaissance de parenté et de diverses odeurs florales. Cela pourrait expliquer l'expansion de la famille des OR chez les Hyménoptère sociaux (Robertson and Wanner 2006). ...
Thesis
Les insectes détectent, grâce à leurs récepteurs olfactifs (OR), une diversité de composées volatils présents dans l’environnement, qu’ils utilisent pour des activités vitales comme l’identification des sources de nourritures et des partenaires sexuels. Identifier des sémiochimiques qui ont un effet attractif ou répulsif est un enjeu pour manipuler le comportement des insectes nuisibles à des fins de biocontrôle. Appliquées aux Lépidoptères, de telles stratégies visent essentiellement les adultes, alors que le stade ravageur est principalement la chenille.Ainsi mon travail de thèse a consisté à rechercher des sémiochimiques actifs sur le comportement des chenilles chez un ravageur modèle, la noctuelle Spodoptera littoralis, en mettant en œuvre une approche d’écologie chimique inverse à partir des OR. Tout d’abord, une étude transcriptomique a permis d’identifier le répertoire des gènes chimiosensoriels exprimés chez la chenille. Nous avons ensuite étudié la fonction de certains récepteurs en utilisant un système d’expression hétérologue in vivo chez la drosophile, afin d’identifier quels sont les volatils détectés par l’insecte. Enfin, nous avons combiné des approches de modélisation in silico ligand-ciblée, des analyses fonctionnelles in vivo chez la drosophile et des tests comportementaux, afin d’identifier de nouveaux ligands des OR ciblés actifs sur le comportement.Ce travail a permis de valider l’utilisation des OR pour accélérer de découverte de nouveaux sémiochimiques actifs sur les comportements qui, à terme, pourraient servir au bioncontrôle des chenilles herbivores. Les données obtenues apportent également des connaissances fondamentales dans le domaine de la neurobiologie et de l’éthologie des larves.
... Likewise, it is unlikely that adult honeybees, which obtain food from several plants, are capable to associate a carbohydrate source with a larval intoxication within the colony. Nor can it be ruled out that honeybees, a generalist species that have few gustatory receptors, do not detect the low concentrations of xanthoxylin that are present in E. cestri secretions (Robertson and Wanner 2006). ...
Article
Full-text available
The “River Disease” (RD), a disorder impacting honeybee colonies located close to waterways with abundant riparian vegetation (including Sebastiania schottiana, Euphorbiaceae), kills newly hatched larvae. Forager bees from RD-affected colonies collect honeydew excretions from Epormenis cestri (Hemiptera: Flatidae), a planthopper feeding on trees of S. schottiana. First-instar honeybee larvae fed with this honeydew died. Thus, we postulated that the nectars of RD-affected colonies had a natural toxin coming from either E. cestri or S. schottiana. An untargeted metabolomics characterization of fresh nectars extracts from colonies with and without RD allowed to pinpoint xanthoxylin as one of the chemicals present in higher amounts in nectar from RD-affected colonies than in nectars from healthy colonies. Besides, xanthoxylin was also found in the aerial parts of S. schottiana and the honeydew excreted by E. cestri feeding on this tree. A larva feeding assay where xanthoxylin-enriched diets were offered to 1st instar larvae showed that larvae died in the same proportion as larvae did when offered enriched diets with nectars from RD-colonies. These findings demonstrate that a xenobiotic can mimic the RD syndrome in honeybee larvae and provide evidence of an interspecific flow of xanthoxylin among three trophic levels. Further, our results give information that can be considered when implementing measures to control this honeybee disease.
... Only few of the chemosensory genes identified in our study were commonly expressed across ant, honeybee and fruit fly larvae. This is probably due to sequence divergence between lineages, as most of the sequences were identified from studies on ant gene expression, and insects are known to vary widely in the number and sequence divergence of genes from gene families involved in sensory perception (Robertson and Wanner, 2006;Engsontia et al., 2008;Brand and Ramírez, 2017;Slone et al., 2017;McKenzie and Kronauer, 2018). This study is therefore only a first step in understanding larval perception in social insects, with three potential avenues for future research. ...
Article
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Social insects depend on communication to regulate social behaviour. This also applies to their larvae, which are commonly exposed to social interactions and can react to social stimulation. However, how social insect larvae sense their environment is not known. Using RNAseq we characterized expression of sensory‐related genes in larvae of the ant Formica fusca, upon exposure to two social environments: isolation without contact to other individuals, and stimulation via the presence of other developing individuals. Expression of key sensory‐related genes was higher following social stimulation, and larvae expressed many of the same sensory‐related genes as adult ants and larvae of other insects, including genes belonging to the major insect chemosensory gene families. Our study provides first insights into the molecular changes associated with social information perception in social insect larvae.
... The impressive species diversity that insects have reached through their evolution attests a high capacity to adapt to diverse environmental conditions. In this sense, the dramatically different PPK repertoires reported herein may reflect specific adaptations to the ecological niches where these animals thrive (Robertson and Wanner 2006;McBride et al. 2007;S anchez-Gracia et al. 2011;Smadja et al. 2012). The extreme examples of 59 PPK family members found in the genome of M. domestica, and only one in that of P. humanus capture the extent of the plasticity shown by these gene repertoires to adapt to environmental pressures. ...
Article
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Insect pickpocket (PPK) receptors mediate diverse functions, among them the detection of mechano-and chemo-sensory stimuli. Notwithstanding their relevance, studies on their evolution only focused on Drosophila. We have analyzed the genomes of 26 species of 8 orders including holometabolous and 2 hemimetabolous insects (Blattodea, Orthoptera, Hemiptera, Phthiraptera, Hymenoptera, Lepidoptera, Coleoptera, and Diptera), to characterize the evolution of this gene family. PPKs were detected in all genomes analyzed, with 578 genes distributed in 7 subfamilies. According to our phylogeny ppk17 is the most divergent member, composing the new subfamily VII. PPKs evolved under a gene birth-and-death model that generated lineage-specific expansions usually located in clusters, while purifying selection affected several orthogroups. Subfamily V was the largest, including a mosquito-specific expansion that can be considered a new target for pest control. PPKs present a high gene turnover generating considerable variation. On one hand, Musca domestica (59), Aedes albopictus (51), Culex quinquefasciatus (48), and Blattella germanica (41) presented the largest PPK repertoires. On the other hand, Pediculus humanus (only ppk17), bees and ants (6-9) had the smallest PPK sets. A subset of prevalent PPKs was identified, indicating very conserved functions for these receptors. Finally, at least twenty percent of the sequences presented calmodulin-binding motifs, suggesting that these PPKs may amplify sensory responses similarly as proposed for D. melanogaster ppk25. Overall, this work characterized the evolutionary history of these receptors revealing relevant unknown gene sequence features and clade-specific expansions.
... Analogously, in honey bees, ORs with a male-biased expression might function as PRs mediating the perception of queen-emitted sex pheromones in drones. Honey bees possess a large repertoire of approximately 170 genes encoding potential ORs (Robertson & Wanner, 2006). Based on quantitative polymerase chain reaction (qPCR), RNA sequencing, and microarray analyses, the honey bee OR types OR11, OR10, OR18, and OR170 were previously reported to have a male-biased expression in the antenna (Wanner et al., 2007;Jain & Brockmann, 2020). ...
Article
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In the European honey bee (Apis mellifera), the olfactory system is essential for foraging and intraspecific communication via pheromones. Honey bees are equipped with a large repertoire of olfactory receptors belonging to the insect odorant receptor (OR) family. Previous studies have indicated that the transcription level of a few OR types including OR11, a receptor activated by the queen-released pheromone compound (2E)-9-oxodecenoic acid (9-ODA), is significantly higher in the antenna of males (drones) than in female workers. However, the number and distribution of antennal cells expressing male-biased ORs is elusive. Here, we analyzed antennal sections from bees by in situ hybridization for the expression of the male-biased receptors OR11, OR18, and OR170. Our results demonstrate that these receptors are expressed in only moderate numbers of cells in the antennae of females (workers and queens), whereas substantially higher cell numbers express these ORs in drones. Thus, the reported male-biased transcript levels are due to sex-specific differences in the number of antennal cells expressing these receptors. Detailed analyses for OR11 and OR18 in drone antennae revealed expression in two distinct subsets of olfactory sensory neurons (OSNs) that in total account for about 69% of the OR-positive cells. Such high percentages of OSNs expressing given receptors are reminiscent of male-biased ORs in moths that mediate the detection of female-released sex pheromone components. Collectively, our findings indicate remarkable similarities between male antenna of bees and moths and support the concept that male-biased ORs in bee drones serve the detection of female-emitted sex pheromones. This article is protected by copyright. All rights reserved
... Bees are unique among insects because they possess few genes for gustatory receptors (Robertson and Wanner, 2006;Sadd et al., 2015). Adult bees have specialized mouthparts for collecting floral nectar, a sugary reward offered by plants to pollinators. ...
Article
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The sense of taste permits the recognition of valuable nutrients and the avoidance of potential toxins. Previously, we found that bumblebees have a specialized mechanism for sensing sugars whereby two gustatory receptor neurons (GRNs) within the galeal sensilla of the bees’ mouthparts exhibit burst of spikes. Here, we show that the temporal firing patterns of these GRNs separate sugars into four distinct groups that correlate with sugar nutritional value and palatability. We also identified a third GRN that responded to stimulation with relatively high concentrations of fructose, sucrose, and maltose. Sugars that were non-metabolizable or toxic suppressed the responses of bursting GRNs to sucrose. These abilities to encode information about sugar value are a refinement to the bumblebee’s sense of sweet taste that could be an adaptation that enables precise calculations of the nature and nutritional value of floral nectar.
... The number of OR genes identified from insect species varied greatly. In the present study, a total of 44 candidate ORs (including one Orco) were screened in the antennae of A. confusum, which was less than that in A. mellifera (174) (Robertson and Wanner, 2006) and C. vestalis (158) (Liu et al., 2020). Moreover, Zhou et al. (2015) identified only eight ORs in antennal transcripts of Sclerodermus sp. while a huge difference was found in N. vitripennis (225) (Robertson et al., 2010). ...
Article
The endoparasitoid wasp, Aulacocentrum confusum (Hymenoptera: Braconidae), is a preponderant natural enemy of the larvae of Glyphodes pyloalis Walker (Lepidoptera: Pyralidae), which is a destructive pest of mulberry trees. We first constructed the antennal transcriptome database of A. confusum. In total, we obtained 48,262,304 clean reads from the dataset and assembled 24,324 unigenes. A total of 12,690 (52.17%) unigenes indicated significant similarity (E-value ˂ 10⁻⁵) compared to known protein sequences of other species from the NCBI non-redundant protein database. Gene ontology (GO) and cluster of orthologous groups (COG) analyses were used to determine the functional categories of these genes. A total of 84 putative chemosensory genes were identified from the antennal transcriptome of A. confusum, including 11 putative odorant-binding protein (OBP) genes, six chemosensory protein (CSP) genes, 44 olfactory receptor (OR) genes (including one olfactory co-receptor, Orco), 19 ionotropic receptor (IR) genes, and four sensory neuron membrane protein (SNMP) genes. Results of qPCR assays indicated that among of 11 AconOBPs, nine AconOBP genes were significantly expressed in the antennae of A. confusum adults. AconOBP8 was significantly expressed in the abdomen and AconOBP10 was highly expressed in the thorax. These findings can build a basis for further study on the processes of chemosensory perception in A. confusum at the molecular level.
... KCl). By contrast, we found no 365 clear evidence of specific detection systems, consistently with the limited molecular repertoire 366 of gustatory receptors in this species [58]. Thus, reduced neural activity might result from non-367 specific toxic effects, such as oxidative stress and ion channel dysfunction [59,60]. ...
Preprint
Whether animals can actively avoid food contaminated with harmful compounds through taste is key to understand their ecotoxicological risks. Here, we investigated the ability of honey bees to perceive and avoid food resources contaminated with common metal pollutants known to impair their cognition at low concentrations (lead, zinc and arsenic). In behavioural assays, bees did not discriminate food contaminated with field-realistic concentrations of these metals. Bees only reduced their food consumption and displayed aversive behaviours at very high, unrealistic concentrations of lead and zinc that they perceived through their antennae and proboscis. Electrophysiological analyses confirmed that high concentrations of the three metals in sucrose solution induced a reduced neural response to sucrose in their antennae. Our results thus show that honey bees can avoid metal pollutants in their food, but only at very high concentrations above regulatory levels. Their inability to detect lower, yet harmful, concentrations in a field-realistic range suggests that metal pollution is a major threat for pollinators.
... Likewise, it is unlikely that adult honeybees, which obtain food from several plants, are capable to associate a carbohydrate source with a larval intoxication within the colony. Nor can it be ruled out that honeybees, a generalist species that have few gustatory receptors, do not detect the low concentrations of xanthoxylin that are present in E. cestri secretions (Robertson and Wanner 2006). ...
Preprint
Full-text available
The "River Disease” (RD), a disorder impacting honeybee colonies located closed to waterways with abundant riparian vegetation (including Sebastiania schottiana , Euphorbiaceae), kills newly hatched larvae. Forager bees from RD-affected colonies collect honeydew excretions from Epormenis cestri (Hemiptera: Flatidae), a planthopper feeding on trees of S. schottiana . First-instar honeybee larvae fed with this honeydew died. Thus, we postulated that the nectars of RD-affected colonies had a natural toxin coming from either E. cestri or S. schottiana . An untargeted metabolomics characterization of fresh nectars extracts from colonies with and without RD allowed to pinpoint xanthoxylin as one of the chemicals present in higher amounts in nectar from RD-affected colonies than in nectars from healthy colonies. Besides, xanthoxylin was also found in the aerial parts of S. schottiana and in the honeydew excreted by E. cestri feeding on this tree. A larva feeding assay where xanthoxylin-enriched diets were offered to 1st instar larvae showed that larvae died in the same proportion as larvae did when offered enriched diets with nectars from RD-colonies. These findings demonstrate that a xenobiotic can mimic the RD syndrome in honeybee larvae and provide evidence of an interspecific flow of xanthoxylin among three trophic levels. Further, our results give information that can be considered when implementing measures to control this honeybee disease.
... Ozaki et al., 2005). The antennae, in particular, play important functions in social insect behavior, both within and outside the colony, such as mediating pheromone signaling (Nagari & Bloch, 2012;Vergoz et al., 2009;Grozinger et al., 2003;Pankiw, 2004), nestmate recognition (Ozaki et al., 2005; Zweden & D'Ettorre, 2010) and odor learning (Robertson et al., 2006;Rogers & Vallortigara, 2008). ...
Article
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Communication is essential for social animals, but deciding how to utilize information provided by conspecifics is a complex process that depends on environmental and intrinsic factors. Honey bees use a unique form of communication, the waggle dance, to inform nestmates about the location of food sources. However, as in many other animals, experienced individuals often ignore this social information and prefer to rely on prior experiences, i.e. private information. The neurosensory factors that drive the decision to use social information are not yet understood. Here we test whether the decision to use social dance information or private information is linked to gene expression differences in different parts of the nervous system. We trained bees to collect food from sugar water feeders and observed whether they utilize social or private information when exposed to dances for a new food source. We performed transcriptome analysis of four brain parts (11‐16 bees per tissue type) critical for cognition: the subesophageal ganglion, the central brain, the mushroom bodies, and the antennal lobes but, unexpectedly, detected no differences between social or private information users. In contrast, we found 413 differentially expressed genes in the antennae, suggesting that variation in sensory perception mediates the decision to use social information. Social information users were characterized by the upregulation of dopamine and serotonin genes, while private information users upregulated several genes coding for odor perception. These results highlight that decision making in honey bees might also depend on peripheral processes of perception rather than higher‐order brain centers of information integration.
... During this time, more than 50 Hymenopteran genomes have come online, and sequencing efforts for many more are currently underway [106,107]. One of the most notable scientific discoveries resulting from this evergrowing repository of genomic data was the identification of significant changes in the chemoreceptor families [21,22,[108][109][110][111][112][113][114]. Specifically, there has been a massive expansion of ORs through gene birth-and-death evolution across Apocrita that directly correlates to the degree of eusociality [21,22]. ...
Article
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Over the past decade, spurred in part by the sequencing of the first ant genomes, there have been major advances in the field of olfactory myrmecology. With the discovery of a significant expansion of the odorant receptor gene family, considerable efforts have been directed toward understanding the olfactory basis of complex social behaviors in ant colonies. Here, we review recent pivotal studies that have begun to reveal insights into the development of the olfactory system as well as how olfactory stimuli are peripherally and centrally encoded. Despite significant biological and technical impediments, substantial progress has been achieved in the application of gene editing and other molecular techniques that notably distinguish the complex olfactory system of ants from other well-studied insect model systems, such as the fruit fly. In doing so, we hope to draw attention not only to these studies but also to critical knowledge gaps that will serve as a compass for future research endeavors.
... Laodelphax striatellus (133) (He et al., 2020), Sogatella furcifera (135) (He et al., 2018), and A. mellifera (170) (Robertson and Wanner, 2006), suggesting that different sequencing methods and depths may affect the outcome of studies; the lack of genomic and transcriptomic information in the databases may influence the annotation results for C. sacchariphagus, and some ORs expressed at low levels may be difficult to detect Wang et al., 2017). In the neighbor-joining tree of ORs, CsacOR1 and CsacOR5 are orthologs of BmorOR1; CsacOR4 is the ortholog of BmorOR19; and CsacOR10 clustered close to BmorOR56. ...
Article
Full-text available
Insect chemoreception involves many families of genes, including odourant/pheromone binding proteins (OBP/PBPs), chemosensory proteins (CSPs), odourant receptors (ORs), ionotropic receptors (IRs), and sensory neuron membrane proteins (SNMPs), which play irreplaceable roles in mediating insect behaviors such as host location, foraging, mating, oviposition, and avoidance of danger. However, little is known about the molecular mechanism of olfactory reception in Chilo sacchariphagus, which is a major pest of sugarcane. A set of 72 candidate chemosensory genes, including 31 OBPs/PBPs, 15 CSPs, 11 ORs, 13 IRs, and two SNMPs, were identified in four transcriptomes from different tissues and genders of C. sacchariphagus. Phylogenetic analysis was conducted on gene families and paralogs from other model insect species. Quantitative real-time PCR (qRT-PCR) showed that most of these chemosensory genes exhibited antennae-biased expression, but some had high expression in bodies. Most of the identified chemosensory genes were likely involved in chemoreception. This study provides a molecular foundation for the function of chemosensory proteins, and an opportunity for understanding how C. sacchariphagus behaviors are mediated via chemical cues. This research might facilitate the discovery of novel strategies for pest management in agricultural ecosystems.
... The ORs, such as the olfactory receptor co-receptor (Orco) and conventional ligand-binding odorant receptors, play key roles in olfactory behavior [8]. Since the first identification of insect ORs in Drosophila melanogaster in 1999, many OR genes have now been identified in species from at least seven insect orders, which include Diptera, Lepidoptera, Hymenoptera, Coleoptera, Homoptera, Orthoptera and Blattodea [9][10][11][12][13][14][15][16][17][18][19][20][21]. In mosquitoes, OR repertoires have been identified in Anopheles gambiae, Anopheles darlingi, Aedes aegypti, Culex quinquefasciatus and Aedes albopictus through genome-wide identification [9,11,13,17,22]. ...
Article
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Background The olfactory system plays a crucial role in regulating insect behaviors. The detection of odorants is mainly mediated by various odorant receptors (ORs) that are expressed in the dendrites of olfactory neurons of chemosensilla. Anophelessinensis is a major malaria vector in Eastern Asia and its genome has recently been successfully sequenced and annotated. In this study, we present genome-wide identification and expression profiling of OR genes in different chemosensory tissues of An.sinensis. Methods The OR genes were identified using the available genome sequences of An.sinensis. A series of bioinformatics analyses were conducted to investigate the structure, genome distribution, selective pressure and phylogenetic relationships of OR genes, the conserved domains and specific functional sites in the OR amino acid sequences. The expression levels of OR genes were analyzed from transcriptomic data from An.sinensis antennae, proboscis and maxillary palps of both sexes. Results A total of 59 putative OR genes have been identified and characterized in An.sinensis. This number is significantly less than that in An.gambiae. Whether this difference is caused by the contraction or expansion of OR genes after divergence of the two species remains unknown. The RNA-seq analysis showed that AsORs have obvious tissue- and sex-specific expression patterns. Most AsORs are highly expressed in the antennae and the expression pattern and number of AsORs expressed in antennae are similar in males and females. However, the relative levels of AsOR transcripts are much higher in female antennae than in male antennae, which indicates that the odor sensitivity is likely to be increased in female mosquitoes. Based on the expression patterns and previous studies, we have speculated on the functions of some OR genes but this needs to be validated by further behavioral, molecular and electrophysiological studies. Further studies are necessary to compare the olfactory-driven behaviors and identify receptors that respond strongly to components of human odors that may act in the process of human recognition. Conclusions This is the first genome-wide analysis of the entire repertoire of OR genes in An.sinensis. Characterized features and profiled expression patterns of ORs suggest their involvement in the odorous reception of this species. Our findings provide a basis for further research on the functions of OR genes and additional genetic and behavioral targets for more sustainable management of An.sinensis in the future. Graphical Abstract
... Genome analysis shows that there are many genes encoding olfactory sensilla in bees, and there are as many as 163 olfactory receptor genes in Apis mellifera, so bees are highly sensitive to compounds and exhibit different sound characteristics (Como et al., 2017;Robertson and Wanner, 2006). In order to better understand the health, living habits and behavior of bees, the development of an effective and practical bee monitoring system has become a hot topic in recent years. ...
Article
As honey bees are extremely sensitive to a variety of chemicals and emit typical sound when exposed to environmental chemical, the sound of beehive may be explored as signal to monitor atmospheric pollutants. In the study, the beehives were exposed to the common air pollution chemicals of acetone, Trichloromethane, Glutaric dialdehyde and ethyl ether, and collect beehive sound data using a beehive sound acquisition device developed by ourselves. We found that the sound of honey bees has a certain relationship with the surrounding chemistry and pollution. Based on the features of Mel frequency cepstral coefficients (MFCCs) extracted from beehive sound data, we have builted the support vector machine (SVM) model provided the accuracy rate of 93.7% for classifying beehive sounds associated with different compounds. Our method outperformed other classification algorithms in terms of accuracy when applied to preprocessed teat data (93.7% average accuracy compared to the 83.8% achieved by KNN and the 83.6% achieved by RF). The results indicated that the beehive sound analysis can provide qualitative chemical information about the air surrounding the beehives. The study suggestd that monitoring the beehive sounds would become a promising way to monitor the air quality
... Insect antennae are covered with different types of olfactory sensilla (Schneider and Steinbrecht, 1968), which contain the sensitive dendrites of the olfactory sensory neurons (Zacharuk, 1980;Couto et al., 2005). Olfactory stimulation occurs when odor molecules enter through pores or slits on the antenna surface (Steinbrecht, 1997) and are directed by odorant binding proteins (OBPs) that bind together with the volatile to olfactory receptors (ORs) situated in the membrane of these dendrites (Hallem and Carlson, 2006;Robertson and Wanner, 2006). These olfactory receptors vary in the type of molecules that activate them, their chemical tuning spectrum and the molecular receptive ranges (Hallem and Carlson, 2006;Getahun et al., 2013). ...
Article
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Male euglossine bees exhibit unique adaptations for the acquisition and accumulation of chemical compounds from “perfume flowers” and other sources. During courtship display, male bees expose perfume mixtures, presumably to convey species-specific recognition and/or mate choice signals to females. Because olfaction regulates both signal production (in males) and signal detection (in females) in this communication system, strong selective pressures are expected to act on the olfactory system, which could lead to sensory specialization in favor of an increased sensitivity to specific chemical compounds. The floral scents of euglossine-pollinated plants are hypothesized to have evolved in response to the preexisting sensory biases of their male euglossine bee pollinators. However, this has never been investigated at the peripheral olfactory circuitry of distinct pollinating genera. Here, we present a comparative analysis using electroantennography (EAG) of males across the phylogeny of 29 euglossine bee species, among them Euglossa and Eulaema species. First, we tested whether antennal responses differ among different euglossine genera, subgenera and species. Secondly, we conducted a comparative phylogenetic analysis to investigate the macroevolutionary patterns of antennal responses across the euglossine bee phylogeny. We found that antennal response profiles are very unique on the species level and differ on the subgenus and the genus level. The differences can be explained by chemical compounds typically found in the floral scent bouquets of perfume flowers and specific compounds of species either pollinated by Euglossa (e.g., ipsdienol) or Eulaema bees (e.g., (−)-(E)-carvone epoxide). Also, we detected a phylogenetic signal in mean antennal responses and found that especially at the species level of our simulation the overall antennal responses exhibit greater disparity relative to a null model of pure Brownian-motion across the phylogeny. Altogether, our results suggest that (1) euglossine bee species exhibit species-specific antennal responses that differ among euglossine genera and subgenera, (2) antennal responses diverge early after speciation events, and (3) scent composition of perfume flowers evolved in response to pollinator-mediated selection imposed by preexisting sensory biases in euglossine bees.
... A change in volume of glomerular units likely corresponds to differences in elaboration of neuronal processes and is found to be influenced by inputs from olfactory sensory neurons (ORNs). The total number of glomeruli roughly corresponds to the total number of olfactory receptor genes (ORs) Drosophila (Robertson and Wanner 2006). However, recent studies have revealed exceptions to this canonical rule in olfaction (Dobritsa et al. 2003;Hallem et al. 2004;Couto et al. 2005). ...
Article
Antennal lobes (AL) are the primary olfactory centres of the insect brain, the organisation of which reflects the chemosensory repertoire of the insect. The sensory neurons from the antenna, local neurons (LNs), and projection neurons (PNs) constitute the neuropilar organisation of the AL, which often varies according to the ecology and behaviour of the insects. We explored the organisation of the AL in the ant Oecophylla smaragdina through Golgi analysis and other standard histological procedures. Six topographically distinct glomerular clusters were noticed in the AL. AL volume, total number of glomeruli and its spatial organisation were different in the castes of Oecophylla smaragdina. We could count 220 glomeruli in the AL of the major worker, whereas only 140 glomeruli were located in AL of minor workers. LNs with their cell body located on the dorsal, dorso-lateral, ventral, ventro-lateral, and medial position of the AL were characterised. Most of the LNs are oligoglomerular. Uniglomerular and multiglomerular PNs were also identified. The results underline a caste specific organisation of the AL in Oecophylla smaragdina. The characterised LNs and PNs further reveals the complex neural circuitry involved in the processing of important chemical cues related to the lifestyle of the ant.
... In fact, recent research has shown that honeybees can be used as environmental bioindicators for heavy metals and polycyclic aromatic hydrocarbons [104]. The work in [28], for example, showed that honeybee hive acoustics could be used to detect a Varroa mite infestation, whereas the work in [105,106] showed that hive acoustics could be used to detect certain atmospheric pollutants. Using four features, namely, spectral centroid, peak frequency, frequency standard deviation, and bandwidth (range of predominant frequencies with the threshold of −9 dB), coupled with a machine learning framework could lead to Varroa mite detection [28] with an accuracy of 81%. ...
Article
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Bees play an important role in agriculture and ecology, and their pollination efficiency is essential to the economic profitability of farms. The drastic decrease in bee populations witnessed over the last decade has attracted great attention to automated remote beehive monitoring research, with beehive acoustics analysis emerging as a prominent field. In this paper, we review the existing literature on bee acoustics analysis and report on the articles published between January 2012 and December 2021. Five categories are explored in further detail, including the origin of the articles, their study goal, experimental setup, audio analysis methodology, and reproducibility. Highlights and limitations in each of these categories are presented and discussed. We conclude with a set of recommendations for future studies, with suggestions ranging from bee species characterization, to recording and testing setup descriptions, to making data and codes available to help advance this new multidisciplinary field.
... Orco can support OrX proteins located to the dendritic as a chaperone (Larsson et al., 2004). In total, 180 ORs in Apis florae (Snehal et al., 2016), 177 ORs in Apis mellifera (Robertson and Wanner, 2006;Wanner et al., 2007), and 119 ORs in Apis cerana cerana (Park et al., 2015) have been identified. However, there are only a few studies on their function. ...
Article
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Bees rely on their sensitive olfactory system to perform foraging activities in the surrounding environment. This ability is associated with the existence of olfactory receptors (ORs). In this study, we identified the AcerOr2 (ortholog to the Orco) protein in Apis cerana cerana , which contains a conserved, putative calmodulin (CaM)-binding site (CBS) indicating that CaM is involved in its function. We used immunofluorescence, Western blot, and Ca 2 + imaging to monitor changes in the expression and activation of the signaling pathway associated with Ca 2 + and Ca 2 + /CaM-dependent protein kinase II (CaMKII) in Sf9 cells heterologously expressing AcerOr2 and a CaM-binding mutant. We used the synthetic Orco agonist VUAA1 to stimulate the cells or the antagonist W7 to inhibit CaM activity. The AcerOr2 CaM-binding mutant has a point mutation in the putative CBS (K331N). When heterologously expressed in Sf9 cells, the mutant should have less CaM activity. When the cells expressing AcerOr2 were treated with W7, the Ca 2 + response of AceOr2 was similar to that of the mutant stimulated by VUAA1, and the expression of the CaM, CaMKII, and p-CaMKII has similar effects. Our results suggest that CaM activity affects the function of AceOr2 in vitro and can be used to further study the interaction between the AcerOr2 and calcium/CaM signaling pathway in the pollen collection behavior of bees.
... Both established structures are tetramers, which indicates that OR and Orco subunits form a heterotetramer. Although there is a single Orco gene in most insect species, the number of tuning ORs is greatly variable, ranging from three in the dragonfly ladona fulva [67] to hundreds in eusocial insects, such as ants and honeybees [68,69]. Orco is highly conserved across insect lineages, and the amino-acid identity of Orco from evolutionarily distant insects is above 70% [70,71]. ...
Article
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Insects use olfaction to detect ecologically relevant chemicals in their environment. To maintain useful responses over a variety of stimuli, olfactory receptor neurons are desensitized to prolonged or high concentrations of stimuli. Depending on the timescale, the desensitization is classified as short-term, which typically spans a few seconds; or long-term, which spans from minutes to hours. Compared with the well-studied mechanisms of desensitization in vertebrate olfactory neurons, the mechanisms underlying invertebrate olfactory sensitivity regulation remain poorly understood. Recently, using a large-scale functional screen, a conserved critical receptor phosphorylation site has been identified in the model insect Drosophila melanogaster, providing new insight into the molecular basis of desensitization in insects. Here, we summarize the progress in this area and provide perspectives on future directions to determine the molecular mechanisms that orchestrate the desensitization in insect olfaction.
... In addition, honeybees have extraordinary olfactory capabilities and are highly sensitive to toxic substances. The honey bee genome sequence revealed that 170 odorant receptors were annotated in the bee (Robertson & Wanner, 2006). When exposed to low-dose insecticides, honeybees may be induced to produce nitric oxide as a defense mechanism (Bartling et al., 2021). ...
Preprint
Honey bees ( Apis spp.) are widely used as biological indicators of environmental changes. Recently, bees have been explored by researchers to monitor air contamination by listening to their hive sound. However, no study has determined whether beehive sound reflects the responses of bees to in-hive or out-hive chemicals. In this study, we conducted a feeding experiment to address this. First, we fed colonies with pure syrup (PS), syrup containing acetone (SA) or syrup containing ethyl acetate (SE) to collect beehive sound to establish multiple classifications using machine learning (ML) models. Then, we orderly fed colonies with PS, followed by SE, SA and PS. Next, we fed colonies in PS, SA, SE and PS order. Eventually, we evaluated the recall and precision of the model in detecting each syrup type. The result built on orderly feeding had a recall of 99%, 80%, 30%, 53% in detecting PS, SE, SA, PS, respectively. In the reverse feeding experiment, the ML model has a recall of 99%, 89%, 37% and 44% in detecting PS, SA, SE, and PS, respectively. Because the collected syrup in the two orderly feeding sessions was not removed from the frames during the experiment, the results indicate that beehive sound responds to chemicals in or out of the beehive.
... By contrast, we found no clear evidence of additional selective responses to metal ions similar to the activation of a specific set of receptors by calcium in Drosophila (Lee et al., 2018). This is consistent with the limited number of gustatory receptor genes in bees (Robertson and Wanner, 2006;Sadd et al., 2015;Bestea et al., 2021), as well as with the similar responses upon antennal stimulations with either metal in our devaluation assay. Thus, this provides additional evidence that bees are not more sensitive to As and Pb, despite the high toxicity of these compounds. ...
Article
Whether animals can actively avoid food contaminated with harmful compounds through taste is key to assess their ecotoxicological risks. Here, we investigated the ability of honey bees to perceive and avoid food resources contaminated with common metal pollutants known to impair behaviour at low concentrations. In laboratory assays, bees did not discriminate food contaminated with arsenic, lead or zinc and ingested it readily, up to estimated doses of 929.1 μg g⁻¹ As, 6.45 mg g⁻¹ Pb and 72.46 mg g⁻¹ Zn. A decrease of intake and appetitive responses indicating metal detection was only observed at the highest concentrations of lead (3.6 mM) and zinc (122.3 mM) through contact with the antennae and the proboscis. Electrophysiological analyses confirmed that only high concentrations of the three metals in a sucrose solution induced a consistently reduced neural response to sucrose in antennal taste receptors (As: >0.1 μM, Pb: >1 mM; Zn: >100 mM). Overall, cellular and behavioural responses did not provide evidence for specific mechanisms that would support selective detection of toxic metals (arsenic, lead), as compared to zinc, which has important biological functions. Our results thus show that honey bees can avoid metal pollutants in their food only at high concentrations unlikely to be encountered in the environment. By contrast, they appear to be unable to detect low, yet harmful, concentrations found in flowers. Metal pollution at trace levels is therefore a major threat for pollinators.
... Drosophila has been associated with rapid changes in genes associated with olfaction and taste (McBride 2007, McBride & Arguello 2007. Comparative studies with bees and mosquitoes have revealed large-scale extensive changes in the chemosensory system, particularly in the olfactory and gustatory receptors (Robertson et al. 2003, Robertson & Wanner 2006, Amrein & Thorne 2005, McBride & Arguello 2007. Therefore, differential resource use in insects is associated with adaptations that enhance their ability to respond to resource-associated chemical stimuli. ...
Thesis
A fundamental prediction of ecological theory is that competition for resources can drive the evolution of specialised resource use. One way in which costly competition can be avoided is via individual specialisation, i.e., the persistence of specialised individuals within a generalist population that utilise a smaller subset of the entire population’s resource base. This could occur through the evolution of genetic morphs that specialise on different resources. Although correlational evidence exists that is consistent with this prediction, there is surprisingly little evidence that competition causes resource specialisation. Burying beetles are an ideal species for testing this prediction. They require the carcass of a small vertebrate such as a mouse or a songbird for reproduction, but carcasses can be unpredictably distributed and competition to secure ownership is correspondingly intense. For my PhD project in Prof. Rebecca Kilner’s lab, I tested whether this fierce competition for a carcass breeding resource has driven the evolution of beetles that specialise in breeding on dead mammals or dead birds. With field experiments at three different woodlands, I tested for evidence of a bias in the type of carcass favoured by Nicrophorus vespilloides and if this bias changed across the burying beetle season (from April to October each year). I found spatial and seasonal variation within each of the three populations in the preference for dead mice over dead birds. In two populations, beetles were more likely to be trapped upon dead mice overall, but were occasionally trapped with greater frequencies on dead birds. This trend was completely reversed for the third population, where beetles were more likely to be found in traps baited with dead birds than dead mice. The patterns of resource use I observed in the field could be due to adaptive partitioning of resource type within populations. To test this hypothesis, I measured the reproductive success of wild beetles induced to breed on different types of carrion. Although I found seasonal variation in beetle reproductive success on different types of carrion, I found no evidence that this resulted from variation in carrion preferences at the individual or population level. Instead, it is more likely to be explained by variation in individual quality. In collaboration with Dr Michael Sheehan at Cornell University, we sequenced females trapped on each type of carrion within all three woodlands, to test whether carrion specialisation was associated with genetic differences. Consistent with this possibility, we found divergence at ~ 50 loci in each of the three populations. Several of these loci were associated with olfaction and sensory-system development. In the lab, I set up replicate experimentally evolving populations of N. vespilloides which were bred either on mice or chicks for ~ 20 generations. I used these populations to test whether, in principle, beetles within a natural population could become divergently adapted to specialise on different types of carrion. I found no evidence to support this possibility, perhaps because there was insufficient standing genetic variation in the founding populations to select upon. However, there was some indication that the experimental populations might have diverged in cryptic ways that I did not measure directly. To understand the chemical basis for differential resource use, I carried out several analyses in collaboration with Prof. Patrizia d'Ettorre at Université Paris, using mass spectrometric techniques. We found little evidence that the volatiles emitted from carrion differ substantially between birds and mice. We also found little evidence that a beetle’s cuticular hydrocarbons predict the carrion it will be attracted to in nature. However, we did find seasonal variation in the cuticular hydrocarbon profiles of wild-caught beetles that could be related to beetle quality or breeding status. In short, although we found some evidence for differential carrion use within wild burying beetle populations and some indication that this is associated with genetic differences among individuals, some of this variation is also due to phenotypic variation in individual quality. While it is possible that carrion specialists could evolve within natural populations, we found no strong evidence to suggest that this happens routinely.
... Studies of olfactory mechanisms in insects are largely based on model insects (D. melanogaster, Anopheles gambiae, Bombyx mori, Tribolium castaneum, Schistocerca gregaria, Bemisia tabaci, Aedes aegypti, Apis mellifera and Hermetia illucens, etc.) [11,13,[21][22][23][24][25][26][27]. Chemosensory genes can be targeted to develop environmentally friendly pest management strategies [28,29]. ...
Article
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The red-necked longicorn beetle, Aromia bungii (Faldermann) (Coleoptera: Cerambycidae), is a major destructive, wood-boring pest, which is widespread throughout the world. The sex pheromone of A. bungii was reported earlier; however, the chemosensory mechanism of the beetle remains almost unknown. In this study, 45 AbunORs, 6 AbunGRs and 2 AbunIRs were identified among 42,197 unigenes derived from the antennal transcriptome bioinformatic analysis of A. bungii adults. The sequence of putative Orco (AbunOR25) found in this study is highly conserved with the known Orcos from other Coleoptera species, and these Orco genes might be potentially used as target genes for the future development of novel and effective control strategies. Tissue expression analysis showed that 29 AbunOR genes were highly expressed in antennae, especially in the antennae of females, which was consistent with the idea that females might express more pheromone receptors for sensing pheromones, especially the sex pheromones produced by males. AbunOR5, 29, 31 and 37 were clustered with the pheromone receptors of the cerambycid Megacyllene caryae, suggesting that they might be putative pheromone receptors of A. bungii. All six AbunGRs were highly expressed in the mouthparts, indicating that these GRs may be involved in the taste perception process. Both AbunIRs were shown to be female-mouthparts-biased, suggesting that they might also be related to the tasting processes. Our study provides some basic information towards a deeper understanding of the chemosensing mechanism of A. bungii at a molecular level.
... Whereas pheromones or kairomones must be volatile, long-chain HC are not volatile and, therefore, can play individually customized roles. The antenna's basiconica sensilla of insects act as signal receptors of CHCs (Robertson and Wanner, 2006;Blomquist and Bagnères, 2010). However, it is still entirely unclear whether the change in the concentrations of distinct hydrocarbons causes a specific effect (i.e., in this case, the removal behavior of nurse bees) or whether the observed behavior is triggered by the blend of the whole hydrocarbon bouquet. ...
Article
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We were intrigued by reported observations of reduced brood production and a high number of empty brood cells in bee colonies exposed to sublethal pesticide doses, which could suggest an active removal of larvae. Higher numbers of oenocytes, insect cells responsible for lipid processing and detoxification, were also found in pesticide-exposed larvae. Oenocytes are involved in hydrocarbon metabolism and chemical communication, and we hypothesized that these larvae could display altered cuticular hydrocarbon (CHC) profiles when exposed to pesticides as compared to control larvae. In addition, we proposed that these chemical cues could trigger specific behavioral responses in colony nurses. To test these hypotheses, we analyzed the CHC profiles of artificially reared larvae that had been fed sublethal doses of either dimethoate or clothianidin or fed on lipopolysaccharide (LPS) using gas chromatography-mass spectrometry. We found significant differences in the CHC profiles of these differently treated larvae. In a subsequent behavioral experiment, we transferred clothianidin-treated or LPS-treated larvae into the brood combs of surrogate colonies. Larvae that had been fed either the pesticide or LPS were removed at a significantly higher rate than control larvae. Our results demonstrate that larvae exposed to clothianidin possess altered CHC profiles, are detected in the colony by nurse bees via chemical cues and are actively removed.
... Consequently, the number of glomeruli closely correlates with the number of olfactory receptor genes expressed within a species and is thought to reflect the general olfactory discrimination power. For instance, consistently with the one-receptor/one-glomerulus, ~ 170 functional OR genes were annotated in the honeybee, which has about 165 olfactory glomeruli in the antennal lobe 74,75 . Social insects deal with a highly complex olfactory environment in which they must be able to discriminate among numerous different odorants. ...
Article
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Olfaction is a crucial sensory modality underlying foraging, social and mating behaviors in many insects. Since the olfactory system is at the interface between the animal and its environment, it receives strong evolutionary pressures that promote neuronal adaptations and phenotypic variations across species. Hornets are large eusocial predatory wasps with a highly developed olfactory system, critical for foraging and intra-specific communication. In their natural range, hornet species display contrasting ecologies and olfactory-based behaviors, which might match to adaptive shifts in their olfactory system. The first olfactory processing center of the insect brain, the antennal lobe, is made of morphological and functional units called glomeruli. Using fluorescent staining, confocal microscopy and 3D reconstructions, we compared antennal lobe structure, glomerular numbers and volumes in four hornet species (Vespa crabro, Vespa velutina, Vespa mandarinia and Vespa orientalis) with marked differences in nesting site preferences and predatory behaviors. Despite a conserved organization of their antennal lobe compartments, glomeruli numbers varied strongly between species, including in a subsystem thought to process intraspecific cuticular signals. Moreover, specific adaptations involving enlarged glomeruli appeared in two species, V. crabro and V. mandarinia, but not in the others. We discuss the possible function of these adaptations based on species-specific behavioral differences.
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The rapa whelk Rapana venosa, an economically important marine fishery resource in China but a major invader all over the world, changes from a phytophagous to a carnivorous form following settlement and metamorphosis. However, the low settlement and metamorphosis rates (<1%) of larvae limit the abundance of R. venosa. This critical step (settlement and metamorphosis) remains poorly characterized but may be related to how larvae perceive the presence of shellfish, their new source of food. Here, we report that larvae may use olfactory perception to sense shellfish. Olfactory receptor (OR) genes are involved in odor sensing in animals. We identified a total of 463 OR genes, which could be grouped into nine clades based on phylogenetic analysis. When assessing the attraction of larvae at different developmental stages to oyster odor, R. venosa showed active settlement and metamorphosis behavior only at the J4 stage and in the presence of shellfish odor at the same time. Expression of OR gene family members differed between stage 2 (four-spiral whorl stage) and stage 1 (single- to three-spiral whorl stage), indicating significant changes in the olfactory system during larval development. These findings broaden our understanding of olfactory perception, settlement, and metamorphosis in gastropods and can be used to improve R. venosa harvesting, as well as the sustainable development and utilization of this resource.
Chapter
Es ist schwer vorstellbar, dass ein so kleines Tier wie ein Rebhuhn irgendeine verfolgbare Spur hinterlässt, wenn es am Waldrand entlangläuft. Schaut man aber genauer hin, passiert tatsächlich eine Menge bei jedem einzelnen Tritt, und eine vielgestaltige Geruchsfährte bietet einem Fuchs die Möglichkeit, das Rebhuhn zu verfolgen. Eine zentrale Rolle spielen dabei Kleinstlebewesen wie Bakterien, Algen, Pilze und Protozoen, die den gesamten Boden bewohnen. Beschädigt das Rebhuhn das Blatt einer Pflanze, wird als erste Geruchsquelle ein wenig Pflanzensaft freigesetzt. Neben dem frischen Pflanzengeruch entsteht nach kurzer Zeit der Geruch von bakteriellen Ausscheidungen, denn Mikroorganismen nutzen den Pflanzensaft als Nahrung. Es dauert nicht lange, bis die Pflanzen die kleinen Blattwunden geschlossen und die Mikroorganismen den ausgetretenen Pflanzensaft vergoren haben. Eine Abfolge der Duftnoten „Gras“ – „Heu“ – „Fäulnis“ ist also immer zu erwarten, wenn eine krautige Pflanze verletzt wird. Mikroorganismen und kleine Wirbellose werden aber auch selbst durch den Rebhuhntritt zerquetscht, und ihre Bestandteile sind ihrerseits wieder Nahrung für Bakterien. Einige typische Stoffwechselprodukte, die bei solchen bakteriellen Aktivitäten anfallen, sind kurzkettige Fettsäuren wie Buttersäure, organische Verbindungen, für welche die Nasen vieler Jagdtiere besonders empfindlich sind. Der Rotfuchs (◘ Abb. 10.1) hat demzufolge, wie auch die anderen Mitglieder der Familie der Hunde (Canidae), eine feine Nase für mikrobielle Stoffwechselaktivitäten, die von den Trittspuren der Rebhühner ausgehen. Besonders interessant ist dabei, dass sich die Geruchsspur mit der Zeit verändert. Ganz am Anfang, in den ersten Minuten, gibt es noch wenig bakterielle Aktivität („Grasgeruch“). Im Verlauf der Zeit wird sie stärker und die bakteriellen Gerüche werden intensiver („Heugeruch“). Schließlich ist alles Verfügbare verstoffwechselt, und ein schwerer Bakteriengestank („Fäulnisgeruch“) liegt über dem Biofilm auf dem Rebhuhntritt. Der Fuchs hat dadurch die Möglichkeit abzuschätzen, wann das Rebhuhn hier gewesen ist – eine wichtige Information für den Jäger. Dass die Tritte von einem Rebhuhn stammen und nicht von einem anderen Tier, kann der Fuchs natürlich auch riechen. Denn jedes Tier hat einen Eigengeruch, der letztlich vor allem durch die Sekrete von holokrinen oder apokrinen Drüsen verursacht wird. Beim Rebhuhn ist das die Bürzeldrüse, eine holokrine Drüse, deren Drüsenzellen kontinuierlich zu einem öligen Sekret abgebaut werden, welches unter dem Einfluss bakterieller Stoffwechselaktivität Geruchsstoffe freisetzt. Spuren dieses Sekrets haften an Pflanzen und Steinen entlang der Fährte und sind wohl auch im aufgewirbelten Staub und vielleicht sogar in der Luft zu riechen. Andere Tiere haben andere Sekrete. Säugetiere wie Mäuse oder Eichhörnchen, die vielleicht die Rebhuhnfährte kreuzen, besitzen hauptsächlich apokrine Drüsen, bei denen die Drüsenzellen bei der Sekretion nicht zugrunde gehen. Die Haut dieser Tiere wird von anderen Bakterien bewohnt, und deren Stoffwechsel produziert andere Geruchscocktails, die der Fuchs leicht vom Rebhuhngeruch unterscheiden kann. Der Fuchs liest also aus der Rebhuhnfährte vielschichtige Information, und er ist klug genug, die chemosensorischen Signale zur Verfolgung der Rebhühner einzusetzen.
Article
Background Olfaction plays a central role in mating, spawning, obtaining food and escaping predators, which is essential for survival and reproduction of animals. The nature of the olfactory perception in crabs, which is a major group of crustaceans, has remained elusive.Objective This project aims to explore the molecular mechanism of olfaction in crabs and further improve our understanding of olfactory perception in crustaceans.Methods The olfactory receptors and ingestion-related gene expression in Eriocheir japonica sinensis were studied by transcriptomic techniques. The de novo assembly, annotation and functional evaluation were performed with bioinformatics tools.ResultsA series of chemosensory receptors associated with olfaction were identified including 33 EsIRs, 24 EsIGluRs, 58 EsVIGluRs, 1 EsOR and 1 EsGC-D. We found IRs were key odorant receptors demonstrating a specific species evolutionary trend in crustaceans. Furthermore, we identified ORs in E. j. sinensis and Litopenaeus vannamei. The incomplete EsOR and LvOR1 structures implied that ORs exist in crustaceans, and may have been degenerated or even lost in the olfactory evolutionary process. In addition, comparative transcriptome analysises demonstrated two possible olfactory transduction pathways of E. j. sinensis: the cGMP-mediated olfactory pathway related to vegetable odor molecules and the cAMP-mediated olfactory pathway related to meat odor molecules. The above results were consistent with its omnivorous ingestion of E. j. sinensis.Conclusions Our study revealed the unique olfactory molecular mechanism of omnivorous crabs and provided valuable information for further functional research on the chemoreception mechanisms in crustaceans.
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Insect pickpocket (PPK) receptors mediate diverse functions, among them the detection of mechano- and chemo-sensory stimuli. Notwithstanding their relevance, studies on their evolution only focused on Drosophila. We have analyzed the genomes of 26 species of 8 orders including holometabolous and hemimetabolous insects (Blattodea, Orthoptera, Hemiptera, Phthiraptera, Hymenoptera, Lepidoptera, Coleoptera, and Diptera), to characterize the evolution of this gene family. PPKs were detected in all genomes analyzed, with 578 genes distributed in 7 subfamilies. According to our phylogeny ppk17 is the most divergent member, composing the new subfamily VII. PPKs evolved under a gene birth-and-death model that generated lineage-specific expansions usually located in clusters, while purifying selection affected several orthogroups. Subfamily V was the largest, including a mosquito-specific expansion that can be considered a new target for pest control. PPKs present a high gene turnover generating considerable variation. On one hand, Musca domestica (59), Aedes albopictus (51), Culex quinquefasciatus (48), and Blattella germanica (41) presented the largest PPK repertoires. On the other hand, Pediculus humanus (only ppk17), bees and ants (6-9) had the smallest PPK sets. A subset of prevalent PPKs was identified, indicating very conserved functions for these receptors. Finally, at least twenty percent of the sequences presented calmodulin-binding motifs, suggesting that these PPKs may amplify sensory responses similarly as proposed for D. melanogaster ppk25. Overall, this work characterized the evolutionary history of these receptors revealing relevant unknown gene sequence features and clade-specific expansions.
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Insect pests consume tastants as their necessary energy and nutrient sources. Gustatory receptors play important roles in insect life and can form within an extremely complicated regulatory network. However, there are still many gustatory genes that have a significant impact on insect physiology, but their functional mechanism is still unknown. Here, we purified and characterized a gustatory receptor (protein) coding gene, NlGr7, from the brown planthopper (BPH) Nilaparvata lugens, which is an important insect pest of rice. Our results revealed that NlGr7 has an active association with various ligands, such as lectins, lipids (phospho- and sphingolipid) and copper. The mass-spectrometry result showed that NlGr7 is a sugar receptor, and NlGr7 is validated by different types of insoluble polysaccharides and a varied range of tastants. Further, we observed that NlGr7-bound ATP hydrolysed on the ATPase activity assay, which indicated that NlGr7 may be associated with important biological functions in the BPH. Furthermore, an injection of NlGr7 (protein), into newly emerged female adults of BPH, showed the reduced vitellogenin in ovary. The important NlGr7 for chemoreception has now been characterized in the BPH. We showed that NlGr7 in the BPH is required for various protein-ligands, as well as protein-sugars interactions, and for regulation of fecundity marker to play crucial roles in this pest. This study will provide valuable information for further functional studies of chemoreception mechanisms in this important agricultural pest.
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Gustatory receptors (GRs) are critical for multiple life activities of insects. Owing to the rapid development of genome and transcriptome sequencing, numerous insect GRs have been identified. However, the expression patterns and functions of these receptors are poorly understood. In this study, we analyzed the expression pattern of GRs in Helicoverpa armigera and found that the fructose receptor HarmGR9 was highly expressed in the foregut and abdomen. The function of HarmGR9 was identified using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system. Knockout of the HarmGR9 gene shortened the developmental period of the larval stages and increased food consumption in both larvae and adults. This study revealed the tissue distribution of sugar-sense-related receptors in H. armigera and thereby expanded the understanding of insect feeding regulation. This article is protected by copyright. All rights reserved
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In social insects colony fitness is determined in part by individual worker phenotypes. Across ant species, colony size varies greatly and is thought to affect worker trait variation in both proximate and ultimate ways. Little is known about the relationship between colony size and worker trait evolution, but hypotheses addressing the role of social structure in brain evolution suggest workers of small-colony species may have larger brains or larger brain regions necessary for complex behaviors. In previous work on odorous ants (Formicidae: Dolichoderinae) we found no correlation between colony size and these brain properties, but found that relative antennal lobe size scaled negatively with colony size. Therefore, we now test whether sensory systems scale with colony size, with particular attention to olfactory components thought to be involved in nestmate recognition. Across three species of odorous ants, Forelius mccooki , Dorymyrmex insanus , and D. bicolor , which overlap in habitat and foraging ecology but vary in colony size, we compare olfactory sensory structures, comparing those thought to be involved in nestmate recognition. We use the visual system, a sensory modality not as important in social communication in ants, as a control comparison. We find that body size scaling largely explains differences in eye size, antennal length, antennal sensilla density, and total number of olfactory glomeruli across these species. However, sensilla basiconica and olfactory glomeruli in the T6 cluster of the antennal lobe, structures known to be involved in nestmate recognition, do not follow body size scaling observed for other structures. Instead, we find evidence from the closely related Dorymyrmex species that the larger colony species, D. bicolor , invests more in structures implicated in nestmate recognition. To test for functional consequences, we compare nestmate and non-nestmate interactions between these two species and find D. bicolor pairs of either type engage in more interactions than D. insaus pairs. Thus, we do not find evidence supporting a universal pattern of sensory system scaling associated with changes in colony size, but hypothesize that observed differences in the olfactory components in two closely related Dorymyrmex species are evidence of a link between colony size and sensory trait evolution.
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Visual and olfactory floral signals play key roles in plant-pollinator interactions. In recent decades, studies investigating the evolution of either of these signals have increased considerably. However, there are large gaps in our understanding of whether or not these two cue modalities evolve in a concerted manner. Here, we characterized the visual (i.e., color) and olfactory (scent) floral cues in bee-pollinated Campanula species by spectrophotometric and chemical methods, respectively, with the aim of tracing their evolutionary paths. We found a species-specific pattern in color reflectance and scent chemistry. Multivariate phylogenetic statistics revealed no influence of phylogeny on floral color and scent bouquet. However, univariate phylogenetic statistics revealed a phylogenetic signal in some of the constituents of the scent bouquet. Our results suggest unequal evolutionary pathways of visual and olfactory floral cues in the genus Campanula. While the lack of phylogenetic signal on both color and scent bouquet points to external agents (e.g., pollinators, herbivores) as evolutionary drivers, the presence of phylogenetic signal in at least some floral scent constituents point to an influence of phylogeny on trait evolution. We discuss why external agents and phylogeny differently shape the evolutionary paths in floral color and scent of closely related angiosperms.
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Social parasitism describes a fascinating way of life in which species exploit the altruistic behaviour of closely related, social species. Social parasites have repeatedly evolved in the social Hymenoptera, including ants, bees, and wasps. The common ancestry and shared (social) environment with their hosts facilitates the study of molecular adaptations to the parasitic lifestyle. Moreover, when social parasites are widespread and virulent, they exert strong selection pressure on their hosts, leading to the evolution of defense mechanisms and triggering a coevolutionary arms race. Recent advances in sequencing technology now make it possible to study the molecular basis of this coevolutionary process. In addition to describing the latest developments, we highlight open research questions that could be tackled with genomic, transcriptomic, or epigenetic data.
Thesis
In this cumulative habilitation thesis, I have collected and discussed the publications that came out of my research during the last ten years. Evolving around the main theme of genome annotation, key achievements of my research line are the development of pipelines and web services for fully automated structural annotation of protein coding genes in novel genomes. The presented methods improve gene prediction accuracy in the respective fields of application. Furthermore, our work has provided the scientific community with summarized background knowledge on genome annotation, and with detailed instructions for the application of our tools. The presented work has received impulses from the annotation of several eukaryotic genomes. Corresponding publications are referenced where appropriate.
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Plants produce diverse secondary compounds as natural protection against microbial and insect attack. Most of these compounds, including bitters and acids, are sensed by insect gustatory receptors (Grs). Acids are potentially toxic to insects, but there are few reports on sour compounds as ligands of insect Grs. Here, using two different heterologous expression systems, the insect Sf9 cell line and the mammalian HEK293T cell line, we started from crude extracts of rice ( Oryza sativa ) and successfully identified oxalic acid (OA) as a ligand of NlGr23a, a Gr in the brown planthopper Nilaparvata lugens . The antifeedant effect of OA on the brown planthopper was dose dependent, and NlGr23a is essential for OA’s antifeedant activity in both artificial diets and rice plants. NlGr23a is also indispensable for tarsal OA sensing. To our knowledge, OA is the first identified ligand starting from plant crude extracts and the first known strong acid for insect Grs. These findings on rice-planthopper interactions will be of broad interest for pest control in agriculture and also for better understanding of how insects select host plants. Research organism Nilaparvata lugens
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Sociality is classified as one of the major transitions in evolution, with the largest number of eusocial species found in the insect order Hymenoptera, including the Apini (honey bees) and the Bombini (bumble bees). Bumble bees and honey bees not only differ in their social organization and foraging strategies, but comparative analyses of their genomes demonstrated that bumble bees have a slightly less diverse family of olfactory receptors than honey bees, suggesting that their olfactory abilities have adapted to different social and/or ecological conditions. However, unfortunately, no precise comparison of olfactory coding has been performed so far between honey bees and bumble bees, and little is known about the rules underlying olfactory coding in the bumble bee brain. In this study, we used in vivo calcium imaging to study olfactory coding of a panel of floral odorants in the antennal lobe of the bumble bee Bombus terrestris. Our results show that odorants induce reproducible neuronal activity in the bumble bee antennal lobe. Each odorant evokes a different glomerular activity pattern revealing this molecule’s chemical structure, i.e. its carbon chain length and functional group. In addition, pairwise similarity among odor representations are conserved in bumble bees and honey bees. This study thus suggests that bumble bees, like honey bees, are equipped to respond to odorants according to their chemical features.
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Diadegma semiclausum is an important parasitoid wasp and widely used in the biological control of the diamondback moth, Plutella xylostella, one of the most destructive pests of cruciferous plants. Insect olfactory system is critical in guiding behaviors including feeding, mating, and oviposition, in which odorant binding proteins (OBPs) and odorant receptors (ORs) are two key components. However, limited attention has been paid to D. semiclausum olfactory genes. In this study, a transcriptome sequencing was performed on the RNA samples extracted from D. semiclausum male and female adult antennae. A total of 17 putative OBP and 67 OR genes were annotated and further compared to OBPs and ORs from P. xylostella, and other hemipteran parasitoid species. The expression patterns of D. semiclausum OBPs between male and female antennae were examined using reverse transcription polymerase chain reaction (RT-PCR) and quantitative real-time PCR. Six OBPs (DsemOBP 6, 7, 8, 9, 10, and 14) demonstrated significantly higher expression levels in females than in males, which may assist in female D. semiclausum host-seeking and oviposition behaviors. This study advances our understanding of the olfactory system of D. semiclausum at the molecular level and paves the way for future functional studies aiming at increasing the efficacy to control P. xylostella by using D. semiclausum.
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Ore mineral and host lithologies have been sampled with 89 oriented samples from 14 sites in the Naica District, northern Mexico. Magnetic parameters permit to charac- terise samples: saturation magnetization, density, low- high-temperature magnetic sus- ceptibility, remanence intensity, Koenigsberger ratio, Curie temperature and hystere- sis parameters. Rock magnetic properties are controlled by variations in titanomag- netite content and hydrothermal alteration. Post-mineralization hydrothermal alter- ation seems the major event that affected the minerals and magnetic properties. Curie temperatures are characteristic of titanomagnetites or titanomaghemites. Hysteresis parameters indicate that most samples have pseudo-single domain (PSD) magnetic grains. Alternating filed (AF) demagnetization and isothermal remanence (IRM) ac- quisition both indicate that natural and laboratory remanences are carried by MD-PSD spinels in the host rocks. The trend of NRM intensity vs susceptibility suggests that the carrier of remanent and induced magnetization is the same in all cases (spinels). The Koenigsberger ratio range from 0.05 to 34.04, indicating the presence of MD and PSD magnetic grains. Constraints on the geometry of the intrusive source body devel- oped in the model of the magnetic anomaly are obtained by quantifying the relative contributions of induced and remanent magnetization components.
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Here we report the genome sequence of the honeybee Apis mellifera, a key model for social behaviour and essential to global ecology through pollination. Compared with other sequenced insect genomes, the A. mellifera genome has high A+T and CpG contents, lacks major transposon families, evolves more slowly, and is more similar to vertebrates for circadian rhythm, RNA interference and DNA methylation genes, among others. Furthermore, A. mellifera has fewer genes for innate immunity, detoxification enzymes, cuticle-forming proteins and gustatory receptors, more genes for odorant receptors, and novel genes for nectar and pollen utilization, consistent with its ecology and social organization. Compared to Drosophila, genes in early developmental pathways differ in Apis, whereas similarities exist for functions that differ markedly, such as sex determination, brain function and behaviour. Population genetics suggests a novel African origin for the species A. mellifera and insights into whether Africanized bees spread throughout the New World via hybridization or displacement.
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The BLAST programs are widely used tools for searching protein and DNA databases for sequence similarities. For protein comparisons, a variety of definitional, algorithmic, and statistical refinements permits the execution time of the BLAST programs to be decreased substantially while enhancing their sensitivity to weak similarities. A new criterion for triggering the extension of word hits, combined with a new heuristic for generating gapped alignments, yields a gapped BLAST program that runs at approximately three times the speed of the original. In addition, a method is described for automatically combining statistically significant alignments produced by BLAST into a position-specific score matrix, and searching the database using this matrix. The resulting Position Specific Iterated BLAST (PSLBLAST) program runs at approximately the same speed per iteration as gapped BLAST, but in many cases is much more sensitive to weak but biologically relevant sequence similarities.
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The BLAST programs are widely used tools for searching protein and DNA databases for sequence similarities. For protein comparisons, a variety of definitional, algorithmic and statistical refinements described here permits the execution time of the BLAST programs to be decreased substantially while enhancing their sensitivity to weak similarities. A new criterion for triggering the extension of word hits, combined with a new heuristic for generating gapped alignments, yields a gapped BLAST program that runs at approximately three times the speed of the original. In addition, a method is introduced for automatically combining statistically significant alignments produced by BLAST into a position-specific score matrix, and searching the database using this matrix. The resulting Position-Specific Iterated BLAST (PSIBLAST) program runs at approximately the same speed per iteration as gapped BLAST, but in many cases is much more sensitive to weak but biologically relevant sequence similarities. PSI-BLAST is used to uncover several new and interesting members of the BRCT superfamily.
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Insects provide an attractive system for the study of olfactory sensory perception. We have identified a novel family of seven transmembrane domain proteins, encoded by 100 to 200 genes, that is likely to represent the family of Drosophila odorant receptors. Members of this gene family are expressed in topographically defined subpopulations of olfactory sensory neurons in either the antenna or the maxillary palp. Sensory neurons express different complements of receptor genes, such that individual neurons are functionally distinct. The isolation of candidate odorant receptor genes along with a genetic analysis of olfactory-driven behavior in insects may ultimately afford a system to understand the mechanistic link between odor recognition and behavior.
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A novel family of candidate gustatory receptors (GRs) was recently identified in searches of the Drosophila genome. We have performed in situ hybridization and transgene experiments that reveal expression of these genes in both gustatory and olfactory neurons in adult flies and larvae. This gene family is likely to encode both odorant and taste receptors. We have visualized the projections of chemosensory neurons in the larval brain and observe that neurons expressing different GRs project to discrete loci in the antennal lobe and subesophageal ganglion. These data provide insight into the diversity of chemosensory recognition and an initial view of the representation of gustatory information in the fly brain.
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The antennae of moths have been an invaluable model for studying the principles of odour perception. In spite of the enormous progress in understanding olfaction on the molecular level, for the moth one of the key elements in olfactory signalling, the odourant receptors, are still elusive. We have assessed a genome database of a heliothine moth (Heliothis virescens, Noctuidae) and employed exon-specific probes to screen an antennal cDNA library of this species. Analysis of isolated cDNA-clones led to the discovery of a divergent gene family encoding putative seven-transmembrane domain proteins. The notion that they may encode candidate olfactory receptors of the moth, was supported by a tissue-specific expression; several of the subtypes were exclusively expressed in antennae. By means of double-labelling in situ hybridization studies it was demonstrated that the receptors are indeed expressed in antennal sensory neurons; moreover, each receptor subtype appears to be expressed in a distinct population of sensory cells. The results strongly suggest that the newly discovered gene family indeed encodes olfactory receptors of moth.
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We used bioinformatic approaches to identify a total of 276 G protein–coupled receptors (GPCRs) from the Anopheles gambiae genome. These include GPCRs that are likely to play roles in pathways affecting almost every aspect of the mosquito's life cycle. Seventy-nine candidate odorant receptors were characterized for tissue expression and, along with 76 putative gustatory receptors, for their molecular evolution relative to Drosophila melanogaster. Examples of lineage-specific gene expansions were observed as well as a single instance of unusually high sequence conservation.
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Anopheles gambiae is a highly anthropophilic mosquito responsible for the majority of malaria transmission in Africa. The biting and host preference behavior of this disease vector is largely influenced by its sense of smell, which is presumably facilitated by G protein-coupled receptor signaling [Takken, W. & Knols, B. (1999) Annu. Rev. Entomol. 44, 131-157]. Because of the importance of host preference to the mosquitoes' ability to transmit disease, we have initiated studies intended to elucidate the molecular mechanisms underlying olfaction in An. gambiae. In the course of these studies, we have identified a number of genes potentially involved in signal transduction, including a family of candidate odorant receptors. One of these receptors, encoded by GPRor7 (hereafter referred to as AgOr7), is remarkably similar to an odorant receptor that is expressed broadly in olfactory tissues and has been identified in Drosophila melanogaster and other insects [Krieger, J., Klink, O., Mohl, C., Raming, K. & Breer, H. (2003) J. Comp. Physiol. A 189, 519-526; Vosshall, L. B., Amrein, H., Morozov, P. S., Rzhetsky, A. & Axel, R. (1999) Cell 96, 725-736]. We have observed AgOr7 expression in olfactory and gustatory tissues in adult An. gambiae and during several stages of the mosquitoes' development. Within the female adult peripheral chemosensory system, antiserum against the AgOR7 polypeptide labels most sensilla of the antenna and maxillary palp as well as a subset of proboscis sensilla. Furthermore, AgOR7 antiserum labeling is observed within the larval antenna and maxillary palpus. These results are consistent with a role for AgOr7 in both olfaction and gustation in An. gambiae and raise the possibility that AgOr7 orthologs may also be of general importance to both modalities of chemosensation in other insects.
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Little is known about the molecular mechanisms of taste perception in animals, particularly the initial events of taste signaling. A large and diverse family of seven transmembrane domain proteins was identified from the Drosophila genome database with a computer algorithm that identifies proteins on the basis of structure. Eighteen of 19 genes examined were expressed in theDrosophila labellum, a gustatory organ of the proboscis. Expression was not detected in a variety of other tissues. The genes were not expressed in the labellum of a Drosophila mutant,pox-neuro70 , in which taste neurons are eliminated. Tissue specificity of expression of these genes, along with their structural similarity, supports the possibility that the family encodes a large and divergent family of taste receptors.
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— We studied sequence variation in 16S rDNA in 204 individuals from 37 populations of the land snail Candidula unifasciata (Poiret 1801) across the core species range in France, Switzerland, and Germany. Phylogeographic, nested clade, and coalescence analyses were used to elucidate the species evolutionary history. The study revealed the presence of two major evolutionary lineages that evolved in separate refuges in southeast France as result of previous fragmentation during the Pleistocene. Applying a recent extension of the nested clade analysis (Templeton 2001), we inferred that range expansions along river valleys in independent corridors to the north led eventually to a secondary contact zone of the major clades around the Geneva Basin. There is evidence supporting the idea that the formation of the secondary contact zone and the colonization of Germany might be postglacial events. The phylogeographic history inferred for C. unifasciata differs from general biogeographic patterns of postglacial colonization previously identified for other taxa, and it might represent a common model for species with restricted dispersal.
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The response properties of the antennal CO2-receptors in workers ofApis mellifera L. were studied electrophysiologically by extracellular recordings from single cells.1.For a proportion (>50%) of the receptors, the absolute sensitivities to CO2 are higher than previously observed.2.The spontaneous spike discharge and the response to C02 are reversibly inhibited by the inert gases N2O and Xe; N2O has a marginally stronger effect than Xe.3.For a gas mixture containing a given CO2-concentration above threshold the inhibition consists primarily of an increase in the response latency which is found to be proportional to the inhibitor concentration.4.For a given concentration of N2O or Xe, the magnitude of this effect decreases proportionally with an increase in CO2-concentration.5.A simple empirical equation for the latency as a function of the concentrations of excitatory stimulus and inhibitor is derived from the data.6.It is investigated to what extent the experimental findings are consistent with kinetic models based on the law of mass-action.7.It is suggested that the inhibition occurs via molecular ordering effects in the aqueous or lipid phases of either the cell membrane or the surrounding medium.
Article
1. Die Sensillen auf der Arbeiterinnenantenne lassen sich morphologisch in neun Typenklassen einteilen. Die lichtmikroskopisch untersuchten Sensillentypen auf der Drohnenantenne weisen keine prinzipiellen Unterschiede zu den Sensillentypen der Arbeiterinnenantenne auf. Die unterschiedliche Verteilung der einzelnen Sensillentypen auf den Antennen der Arbeiterin und der Drohne wird qualitativ angegeben. 2. Optisch kontrollierte, extrazellulre Ableitungen gelangen an den cuticularen Sensillen von der Antennenoberflche her. Die Antenne blieb dabei am lebenden Tier. Ein neuartiges Olfaktometer diente zur Reizung mit Geruchsstoffen, CO2-Luftmischungen und mit Luft verschiedener relativer Feuchte. Temperaturreize wurden mit einer Nieder-voltlampe gegeben. 3. Die entsprechenden Sensillentypen bei der Arbeiterin und der Drohne zeigen elektrophysiologisch gleichartige Reaktionen. Jeder der untersuchten Rezeptortypen ist auf nur eine Reizmodalitt spezialisiert, manche Typen zeigen jedoch zustzlich eine Temperaturabhngigkeit der Ruheaktivitt. 4. Die Porenplatten (Sensilla placodea) bei Arbeiterin und Drohne sind Geruchsrezeptoren. Sie zeigen eine Ruheaktivitt. Einzelne Sinneszellen bilden bei Reizung mit verschiedenen Geruchsstoffen einen phasisch-tonischen, nur selten einen rein phasischen Frequenzverlauf aus. Reaktionen auf Einzelreize und Dauerreize mit vorwiegend blumigaromatischen Geruchsstoffen werden beschrieben. Bei den Geruchsrezeptoren nimmt die Ruheaktivitt mit zunehmender Temperatur ab. Die Rezeptoren zeigen bei Reizung mit vielen verschiedenen Geruchs-stoffen ein breites Reaktionsspektrum. Alle diese Spektren sind voneinander verschieden und berlappen sich stark. Auch bei Reizung mit homologen Stoffen (Aldehyd C 10 bis C 18, Fettsure C 3 bis C 7 u.a.) treten voneinander verschiedene Reaktionsspektren auf. 5. Manche Grubenkegel (unbekannt, ob S. ampullacea oder S. coeloconica) bei Arbeiterin und Drohne sind CO2-Rezeptoren. Sie zeigen eine Ruheaktivitt, die mit steigender Temperatur zunimmt. Bei Reizung wird ein phasisch-tonischer Frequenzverlauf ausgebildet. Die Hhe der Erregungsspitze und des stationren Niveaus steigt annhernd logarithmisch mit der Reizintensitt. Einzel-, Dauerreize und die Narkosewirkung des reinen CO2 werden untersucht. 6. Manche Grubenkegel (unbekannt, ob S. ampullacea oder S. coeloconica) bei Arbeiterin und Drohne sind Feuchtigkeitsrezeptoren. Bei Reizsprngen in Richtung hherer Feuchte wird ein phasisch-tonischer Frequenzverlauf ausgebildet. Bei Reizung mit trockener Luft tritt in manchen Fllen ein Impulsausfall auf. Die Hhe des stationren Niveaus steigt bei konstanter Temperatur annhernd linear mit der relativen bzw. absoluten Feuchte. 7. Ebenfalls zu den Grubenkegeln zhlen bei Arbeiterin und Drohne Temperaturrezeptoren. Auf eine rasche Temperaturerniedrigung reagieren sie mit einem phasisch-tonischen Frequenzverlauf. Der Rezeptor zeigt bei steigender Temperatur ein fallendes stationres Niveau. Bei 40–45 C ist die Impulsaktivitt meistens erloschen. Der Rezeptor ist als Kaltrezeptor zu klassifizieren. 8. Die Sensilla trichodea (small, thick-walled hair und thick-walled peg) bei der Arbeiterin sind Mechanorezeptoren, die bei Reizung einen phasischen Erregungsverlauf zeigen. The antennal sense organs of the honey bee worker and drone were investigated morphologically and electrophysiologically.1. The sensilla of the antennae of the worker can be classified into nine morphologically distinct types. Light microscopical investigation of these sense organs of both worker and drone revealed no principle sexual difference in structure. The distribution of these sensilla types is described for the worker and the drone. 2. Electrical activity from cuticle sense organs was recorded extracellularly with microelectrodes which penetrated the antennal surface under optical control. The antenna remained in connection with the living animal. A new type of Olfactometer was used to present the stimuli of various aromatic odors, CO2-air mixtures, and air of different relative humidities. Heat emission from a regulated, low voltage lamp was used as a source of temperature stimulation. 3. The electrophysiological reactions of corresponding morphological sensory types are similar for the worker and the drone. Each of the investigated receptor types is specialized for only one stimulus modality, although some types show an additional temperature dependence at resting activity. 4. The plate organs (Sensilla placodea) of the worker and the drone are olfactory receptors. They show a resting activity. The sensory cells under stimulation with various odorous substances generally show a phasic-tonic frequency response, but in a few cases, a pure phasic response. Reactions to repetitive and continuous stimuli by chiefly aromatic flowery odors are described. The resting activity of these chemoreceptors decreases with increasing temperature. The receptors show a wide reaction spectrum. The spectra of the individual cells differ from one another but there is a considerable amount of overlap. Different receptors under stimulation with homologous series of substances (aldehydes, C 10 to C 18, fatty acids from C 3 to C 7) show different reaction spectra. 5. Many pit pegs (identification as S. ampullacea or S. coeloconica uncertain) are CO2 receptors in both worker and drone. Under CO2 stimulation they respond phasic-tonically. The height of the reaction, in both the phasic and tonic portion of the response, is approximately a logarithmic function of the stimulus intensity. Reactions to repetitive and continuous stimuli and the narcotic effects of pure CO2 were investigated. In addition, the receptors show a resting activity which increases with increasing temperature. 6. Many pit pegs (identification as S. ampullacea or S. coeloconica uncertain) in the worker and the drone are hygroreceptors. Each stepwise increase in humidity causes a phasic-tonic frequency response. In some cases, under stimulation with dried air, the nerve impulses disappear. The height of the excitation plateau increases approximately linearly with increasing relative and absolute humidity at constant temperature. 7. The pit pegs are also temperature receptors in both the worker and the drone. They react with a phasic-tonical increase of impulse frequency to a sudden decrease in temperature, whereas an increasing temperature causes a decrease in the stationary plateau of the receptors. Therefore, these pit pegs have to be classified as cold receptors. The impulse activity is generally abolished at 40–15 C. 8. Both the small, thick-walled hairs and the thick-walled pegs (Sensilla trichodea) of the worker respond to mechanical stimulation with a phasic increase of their impulse frequency.
Article
We have taken advantage of the availability of a large amount of Drosophila genomic DNA sequence in the Berkeley Drosophila Genome Project database (∼1/5 of the genome) to identify a family of novel seven transmembrane domain encoding genes that are putative Drosophila olfactory receptors. Members of the family are expressed in distinct subsets of olfactory neurons, and certain family members are restricted to distinct portions of the olfactory system. This pattern of expression has interesting similarities to and differences from the expression patterns observed for olfactory receptors in vertebrates. The Drosophila olfactory system is simpler than mammalian systems, yet it is complex enough to present a fascinating system in which to study neural information processing. Moreover, the powerful genetic manipulations available in Drosophila, when combined with electrophysiological and behavioral analyses, make this an attractive model system in which to study olfactory discrimination.
Article
Odours are received by olfactory receptors, which send their axons to the first sensory neuropils, the antennal lobes (in insects) or the olfactory bulb (in vertebrates). From here, processed olfactory information is relayed to higher-order brain centres. A striking similarity in olfactory systems across animal phyla is the presence of glomeruli in this first sensory neuropil. Various experiments have shown that odours elicit a mosaic of activated glomeruli, suggesting that odour quality is coded in an ‘across-glomeruli’ activity code. In recent years, studies using optical recording techniques have greatly improved our understanding of the resulting ‘across-glomeruli pattern’, making it possible to simultaneously measure responses in several, often identifiable, glomeruli. For the honeybee Apis mellifera, a functional atlas of odour representation is being created: in this atlas, the glomeruli that are activated by different odorants are named. However, several limitations remain to be investigated. In this paper, we review what optical recording of odour-evoked glomerular activity patterns has revealed so far, and discuss the necessary next steps, with emphasis on the honeybee.
Article
The str family of genes encoding seven-transmembrane G-protein-coupled or serpentine receptors related to the ODR-10 diacetyl chemoreceptor is very large, with at least 197 members in the Caenorhabditis elegans genome. The closely related stl family has 43 genes, and both families are distantly related to the srd family with 55 genes. Analysis of the structures of these genes indicates that a third of them are clearly or likely pseudogenes. Preliminary surveys of other candidate chemoreceptor families indicates that as many as 800 genes and pseudogenes or 6% of the genome might encode 550 functional chemoreceptors constituting 4% of the C. elegans protein complement. Phylogenetic analyses of the str and stl families, and comparisons with a few orthologs in Caenorhabditis briggsae, reveal ongoing processes of gene duplication, diversification, and movement. The reconstructed ancestral gene structures for these two families have eight introns each, four of which are homologous. Mapping of intron distributions on the phylogenetic tree reveals that each intron has been lost many times independently. Most of these introns were lost individually, which might best be explained by precise in-frame deletions involving nonhomologous recombination between short direct repeats at their termini. [Alignment of the putatively functional proteins in the str and stl families is available from Pfam ( http://genome.wustl.edu/Pfam ); alignments of all translations are available at http://cshl.org/gr ; alignments of the genes are available from the author at hughrobe@uiuc.edu ]
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