De novo assembly and annotation of Popillia japonica's genome with initial clues to its potential as an invasive pest.

BACKGROUND: The spread of Popillia japonica in non-native areas (USA, Canada, the Azores islands, Italy and Switzerland) poses a significant threat to agriculture and horticulture, as well as to endemic floral biodiversity, entailing that appropriate control measures must be taken to reduce its density and limit its further spread. In this context, the availability of a high quality genomic sequence for the species is liable to foster basic research on the ecology and evolution of the species, as well as on possible biotechnologically-oriented and genetically-informed control measures. RESULTS: The genomic sequence presented and described here is an improvement with respect to the available draft sequence in terms of completeness and contiguity, and includes structural and functional annotations. A comparative analysis of gene families of interest, related to the species ecology and potential for polyphagy and adaptability, revealed a contraction of gustatory receptor genes and a paralogous expansion of some subgroups/subfamilies of odorant receptors, ionotropic receptors and cytochrome P450s. CONCLUSIONS: The new genomic sequence as well as the comparative analyses data may provide a clue to explain the staggering invasive potential of the species and may serve to identify targets for potential biotechnological applications aimed at its control.

IR76b-expressing neurons in Drosophila melanogaster are necessary for associative reward learning of an amino acid mixture.

Learning where to find nutrients while at the same time avoiding toxic food is essential for survival of any animal. Using Drosophila melanogaster larvae as a study case, we investigate the role of gustatory sensory neurons expressing IR76b for associative learning of amino acids, the building blocks of proteins. We found surprising complexity in the neuronal underpinnings of sensing amino acids, and a functional division of sensory neurons. We found that the IR76b receptor is dispensable for amino acid learning, whereas the neurons expressing IR76b are specifically required for the rewarding but not the punishing effect of amino acids. This unexpected dissociation in neuronal processing of amino acids for different behavioural functions provides a study case for functional divisions of labour in gustatory systems.

Genome-wide identification and expression pattern analysis of novel chemosensory genes in the German cockroach Blattella germanica.

The German cockroach Blattella germanica is an important urban insect pest worldwide. In many insects, chemosensation is essential for guiding their behaviors for survival. Although a large number of chemosensory-related genes have been identified in B. germanica, little information on tissue-specific and developmental expression patterns has not been uncovered yet. In this study, we performed transcriptome analysis of different B. germanica tissues to reveal novel chemosensory proteins (CSPs) and sensory neuron membrane proteins (SNMPs). In addition, a phylogenetic tree and gender-specific expression of multiple chemosensory gene families have been analyzed. We identified three CSPs genes (BgerCSP11, BgerCSP12, and BgerCSP13) and five SNMP genes in B. germanica. Tissue-specific expression profiling showed that CSP1, 8, and 9 exhibited significant expression levels in both adult and 5th instar nymph antennae. The results have paved the way for further functional study of the chemosensory mechanism in B. germanica and provided potential insecticide targets.

Kainate Receptor Antagonists: Recent Advances and Therapeutic Perspective.

Since the 1990s, ionotropic glutamate receptors have served as an outstanding target for drug discovery research aimed at the discovery of new neurotherapeutic agents. With the recent approval of perampanel, the first marketed non-competitive antagonist of AMPA receptors, particular interest has been directed toward 'non-NMDA' (AMPA and kainate) receptor inhibitors. Although the role of AMPA receptors in the development of neurological or psychiatric disorders has been well recognized and characterized, progress in understanding the function of kainate receptors (KARs) has been hampered, mainly due to the lack of specific and selective pharmacological tools. The latest findings in the biology of KA receptors indicate that they are involved in neurophysiological activity and play an important role in both health and disease, including conditions such as anxiety, schizophrenia, epilepsy, neuropathic pain, and migraine. Therefore, we reviewed recent advances in the field of competitive and non-competitive kainate receptor antagonists and their potential therapeutic applications. Due to the high level of structural divergence among the compounds described here, we decided to divide them into seven groups according to their overall structure, presenting a total of 72 active compounds.

Chemosensory-Related Genes in Marine Copepods.

Living organisms deeply rely on the acquisition of chemical signals in any aspect of their life, from searching for food, mating and defending themselves from stressors. Copepods, the most abundant and ubiquitous metazoans on Earth, possess diversified and highly specified chemoreceptive structures along their body. The detection of chemical stimuli activates specific pathways, although this process has so far been analyzed only on a relatively limited number of species. Here, in silico mining of 18 publicly available transcriptomes is performed to delve into the copepod chemosensory genes, improving current knowledge on the diversity of this multigene family and on possible physiological mechanisms involved in the detection and analysis of chemical cues. Our study identifies the presence of ionotropic receptors, chemosensory proteins and gustatory receptors in copepods belonging to the Calanoida, Cyclopoida and Harpacticoida orders. We also confirm the absence in these copepods of odorant receptors and odorant-binding proteins agreeing with their insect specificity. Copepods have evolved several mechanisms to survive in the harsh marine environment such as producing proteins to respond to external stimulii. Overall, the results of our study open new possibilities for the use of the chemosensory genes as biomarkers in chemical ecology studies on copepods and possibly also in other marine holozooplankters.

Identification and expression of potential olfactory-related genes related to Niemann-Pick C2 protein and ionotropic receptors in Haemaphysalis longicornis.

Studies have shown that the main pathway for tick host localization and perception of mating information may be chemosensory. However, chemical communication in ticks is poorly understood, especially in those other than the Ixodes ticks. Niemann-Pick C2 (NPC2) protein and ionotropic receptors (IRs) are considered to be closely related to the perception of infochemicals in arthropods. Through bioinformatic analysis, eight NPC2 and four IR candidate genes were identified through screening and identification of the transcriptome sequencing database of Haemaphysalis longicornis. Phylogenetic tree analysis indicated that H. longicornis possesses similar homology to the genus Ixodes. A comparison of the expression of NPC2 and IR in tick forelegs (first pair of legs), hind legs (fourth pair of legs), and capitula using RT-PCR revealed that, barring HlonNPC2-8, 11 candidate genes were highly expressed in the foreleg and capitulum, which are the main sensory organs of ticks. They were also expressed in the hind legs, except for six genes that were not expressed in the males. RT-qPCR analysis showed upregulation and higher relative expression of HlonNPC2-1, HlonNPC2-3, HlonNPC2-6, and HlonNPC2-8 when stimulated by ammonium hydroxide, whereas the others were downregulated and demonstrated lower relative expression. These results further support the putative role of NPC2s as a new odorant carrier in ticks and present 12 promising candidate genes for understanding tick olfactory communication, enriching the data on these genes, especially outside the genus Ixodes.

Ion channel profiling of the Lymnaea stagnalis ganglia via transcriptome analysis.

BACKGROUND: The pond snail Lymnaea stagnalis (L. stagnalis) has been widely used as a model organism in neurobiology, ecotoxicology, and parasitology due to the relative simplicity of its central nervous system (CNS). However, its usefulness is restricted by a limited availability of transcriptome data. While sequence information for the L. stagnalis CNS transcripts has been obtained from EST libraries and a de novo RNA-seq assembly, the quality of these assemblies is limited by a combination of low coverage of EST libraries, the fragmented nature of de novo assemblies, and lack of reference genome. RESULTS: In this study, taking advantage of the recent availability of a preliminary L. stagnalis genome, we generated an RNA-seq library from the adult L. stagnalis CNS, using a combination of genome-guided and de novo assembly programs to identify 17,832 protein-coding L. stagnalis transcripts. We combined our library with existing resources to produce a transcript set with greater sequence length, completeness, and diversity than previously available ones. Using our assembly and functional domain analysis, we profiled L. stagnalis CNS transcripts encoding ion channels and ionotropic receptors, which are key proteins for CNS function, and compared their sequences to other vertebrate and invertebrate model organisms. Interestingly, L. stagnalis transcripts encoding numerous putative Ca2+ channels showed the most sequence similarity to those of Mus musculus, Danio rerio, Xenopus tropicalis, Drosophila melanogaster, and Caenorhabditis elegans, suggesting that many calcium channel-related signaling pathways may be evolutionarily conserved. CONCLUSIONS: Our study provides the most thorough characterization to date of the L. stagnalis transcriptome and provides insights into differences between vertebrates and invertebrates in CNS transcript diversity, according to function and protein class. Furthermore, this study provides a complete characterization of the ion channels of Lymnaea stagnalis, opening new avenues for future research on fundamental neurobiological processes in this model system.

Genomic content of chemosensory receptors in two sister blister beetles facilitates characterization of chemosensory evolution.

BACKGROUND: More than 2500 species belong to the Meloidae family (Coleoptera: Tenebrionoidea), members of which produce the potent defensive blistering agent cantharidin and are commonly known as blister beetles or Spanishflies. Cantharidin has recently been used for cancer therapy. Hycleus cichorii and Hycleus phaleratus have been used in traditional Chinese medicine for more than 2000 years due to their ability to biosynthesize cantharidin. To understand the role of the chemosensory system in beetle evolution, we comparatively analysed the chemosensory receptor families of both blister beetle species and compared them with those of other beetles. RESULTS: We identified 89 odorant receptors (ORs), 86 gustatory receptors (GRs), and 45 ionotropic receptors (IRs) in H. phaleratus and 149 ORs, 102 GRs and 50 IRs in H. cichorii. Nine groups of beetle ORs were recovered, and a similar pattern of ORs in Coleoptera emerged. Two evident expanded clades in Hycleus (Groups 5A and 3) were reconstructed in the phylogenetic tree. Four of eight genes with evidence of positive selection were clustered in the expanded clades of Group 5A. Three, eight and three orthologous pairs of CO2, sugar and fructose receptors, respectively, were identified in both blister beetles. Two evident expanded clades of putative bitter GRs in Hycleus were also found, and the GR in one clade had notably low divergence. Interestingly, IR41a was specifically expanded in blister beetles compared to other insects identified to date, and IR75 was also clearly expanded in both blister beetles based on our phylogenetic tree analysis. Moreover, evidence of positive selection was detected for eight ORs, three GRs and two IRs, half of which were from five duplicate clades. CONCLUSIONS: We first annotated the chemosensory receptor families in a pair of sister beetle genomes (Meloidae: Hycleus), which facilitated evolutionary analysis of chemosensory receptors between sibling species in the Coleoptera group. Our analysis suggests that changes in chemosensory receptors have a possible role in chemical-based species evolution in blister beetles. Future studies should include more species to verify this correlation, which will help us understand the evolution of blister beetles.

Acetoin is a key odor for resource location in the giant robber crab Birgus latro.

The terrestrial and omnivorous robber crab Birgus latro inhabits islands of the Indian Ocean and the Pacific Ocean. The animals live solitarily but occasionally gather at freshly opened coconuts or fructiferous arenga palms. By analyzing volatiles of coconuts and arenga fruit, we identified five compounds, including acetoin, which are present in both food sources. In a behavioral screen performed in the crabs' habitat, a beach on Christmas Island, we found that of 15 tested fruit compounds, acetoin was the only volatile eliciting significant attraction. Hence, acetoin might play a key role in governing the crabs' aggregation behavior at both food sources.

The Interplay between Ca2+ Signaling Pathways and Neurodegeneration.

Calcium (Ca2+) homeostasis is essential for cell maintenance since this ion participates in many physiological processes. For example, the spatial and temporal organization of Ca2+ signaling in the central nervous system is fundamental for neurotransmission, where local changes in cytosolic Ca2+ concentration are needed to transmit information from neuron to neuron, between neurons and glia, and even regulating local blood flow according to the required activity. However, under pathological conditions, Ca2+ homeostasis is altered, with increased cytoplasmic Ca2+ concentrations leading to the activation of proteases, lipases, and nucleases. This review aimed to highlight the role of Ca2+ signaling in neurodegenerative disease-related apoptosis, where the regulation of intracellular Ca2+ homeostasis depends on coordinated interactions between the endoplasmic reticulum, mitochondria, and lysosomes, as well as specific transport mechanisms. In neurodegenerative diseases, alterations-increased oxidative stress, energy metabolism alterations, and protein aggregation have been identified. The aggregation of α-synuclein, ß-amyloid peptide (Aß), and huntingtin all adversely affect Ca2+ homeostasis. Due to the mounting evidence for the relevance of Ca2+ signaling in neuroprotection, we would focus on the expression and function of Ca2+ signaling-related proteins, in terms of the effects on autophagy regulation and the onset and progression of neurodegenerative diseases.

Candidate ionotropic taste receptors in the Drosophila larva.

We examine in Drosophila a group of ∼35 ionotropic receptors (IRs), the IR20a clade, about which remarkably little is known. Of 28 genes analyzed, GAL4 drivers representing 11 showed expression in the larva. Eight drivers labeled neurons of the pharynx, a taste organ, and three labeled neurons of the body wall that may be chemosensory. Expression was not observed in neurons of one taste organ, the terminal organ, although these neurons express many drivers of the Gr (Gustatory receptor) family. For most drivers of the IR20a clade, we observed expression in a single pair of cells in the animal, with limited coexpression, and only a fraction of pharyngeal neurons are labeled. The organization of IR20a clade expression thus appears different from the organization of the Gr family or the Odor receptor (Or) family in the larva. A remarkable feature of the larval pharynx is that some of its organs are incorporated into the adult pharynx, and several drivers of this clade are expressed in the pharynx of both larvae and adults. Different IR drivers show different developmental dynamics across the larval stages, either increasing or decreasing. Among neurons expressing drivers in the pharynx, two projection patterns can be distinguished in the CNS. Neurons exhibiting these two kinds of projection patterns may activate different circuits, possibly signaling the presence of cues with different valence. Taken together, the simplest interpretation of our results is that the IR20a clade encodes a class of larval taste receptors.

Molecular cloning and expression of a GABA receptor subunit from the crayfish Procambarus clarkii.

Molecular cloning has introduced an unexpected, large diversity of neurotransmitter hetero- oligomeric receptors. Extensive research on the molecular structure of the γ-aminobutyric acid receptor (GABAR) has been of great significance for understanding how the nervous system works in both vertebrates and invertebrates. However, only two examples of functional homo-oligomeric GABA-activated Cl(-) channels have been reported. In the vertebrate retina, the GABAρ1 subunit of various species forms homo-oligomeric receptors; in invertebrates, a cDNA encoding a functional GABA-activated Cl(-) channel has been isolated from a Drosophila melanogaster head cDNA library. When expressed in Xenopus laevis oocytes, these subunits function efficiently as a homo-oligomeric complex. To investigate the structure-function of GABA channels from the crayfish Procambarus clarkii, we cloned a subunit and expressed it in human embryonic kidney cells. Electrophysiological recordings show that this subunit forms a homo-oligomeric ionotropic GABAR that gates a bicuculline-insensitive Cl(-) current. The order of potency of the agonists was GABA > trans-4-amino-crotonic acid = cis-4-aminocrotonic acid > muscimol. These data support the notion that X-organ sinus gland neurons express at least two GABA subunits responsible for the formation of hetero-oligomeric and homo-oligomeric receptors. In addition, by in situ hybridization studies we demonstrate that most X-organ neurons from crayfish eyestalk express the isolated pcGABAA ß subunit. This study increases the knowledge of the genetics of the crayfish, furthers the understanding of this important neurotransmitter receptor family, and provides insight into the evolution of these genes among vertebrates and invertebrates.

Molecular Mechanisms of Reception and Perireception in Crustacean Chemoreception: A Comparative Review.

This review summarizes our present knowledge of chemoreceptor proteins in crustaceans, using a comparative perspective to review these molecules in crustaceans relative to other metazoan models of chemoreception including mammals, insects, nematodes, and molluscs. Evolution has resulted in unique expansions of specific gene families and repurposing of them for chemosensation in various clades, including crustaceans. A major class of chemoreceptor proteins across crustaceans is the Ionotropic Receptors, which diversified from ionotropic glutamate receptors in ancient protostomes but which are not present in deuterostomes. Representatives of another major class of chemoreceptor proteins-the Grl/GR/OR family of ionotropic 7-transmembrane receptors-are diversified in insects but to date have been reported in only one crustacean species, Daphnia pulex So far, canonic 7-transmembrane G-protein coupled receptors, the principal chemoreceptors in vertebrates and reported in a few protostome clades, have not been identified in crustaceans. More types of chemoreceptors are known throughout the metazoans and might well be expected to be discovered in crustaceans. Our review also provides a comparative coverage of perireceptor events in crustacean chemoreception, including molecules involved in stimulus acquisition, stimulus delivery, and stimulus removal, though much less is known about these events in crustaceans, particularly at the molecular level.

Calcium Signalling through Ligand-Gated Ion Channels such as P2X1 Receptors in the Platelet and other Non-Excitable Cells.

Ligand-gated ion channels on the cell surface are directly activated by the binding of an agonist to their extracellular domain and often referred to as ionotropic receptors. P2X receptors are ligand-gated non-selective cation channels with significant permeability to Ca(2+) whose principal physiological agonist is ATP. This chapter focuses on the mechanisms by which P2X1 receptors, a ubiquitously expressed member of the family of ATP-gated channels, can contribute to cellular responses in non-excitable cells. Much of the detailed information on the contribution of P2X1 to Ca(2+) signalling and downstream functional events has been derived from the platelet. The underlying primary P2X1-generated signalling event in non-excitable cells is principally due to Ca(2+) influx, although Na(+) entry will also occur along with membrane depolarization. P2X1 receptor stimulation can lead to additional Ca(2+) mobilization via a range of routes such as amplification of G-protein-coupled receptor-dependent Ca(2+) responses. This chapter also considers the mechanism by which cells generate extracellular ATP for autocrine or paracrine activation of P2X1 receptors. For example cytosolic ATP efflux can result from opening of pannexin anion-permeable channels or following damage to the cell membrane. Alternatively, ATP stored in specialised secretory vesicles can undergo quantal release via the process of exocytosis. Examples of physiological or pathophysiological roles of P2X1-dependent signalling in non-excitable cells are also discussed, such as thrombosis and immune responses.

Zinc as Allosteric Ion Channel Modulator: Ionotropic Receptors as Metalloproteins.

Zinc is an essential metal to life. This transition metal is a structural component of many proteins and is actively involved in the catalytic activity of cell enzymes. In either case, these zinc-containing proteins are metalloproteins. However, the amino acid residues that serve as ligands for metal coordination are not necessarily the same in structural proteins compared to enzymes. While crystals of structural proteins that bind zinc reveal a higher preference for cysteine sulfhydryls rather than histidine imidazole rings, catalytic enzymes reveal the opposite, i.e., a greater preference for the histidines over cysteines for catalysis, plus the influence of carboxylic acids. Based on this paradigm, we reviewed the putative ligands of zinc in ionotropic receptors, where zinc has been described as an allosteric modulator of channel receptors. Although these receptors do not strictly qualify as metalloproteins since they do not normally bind zinc in structural domains, they do transitorily bind zinc at allosteric sites, modifying transiently the receptor channel's ion permeability. The present contribution summarizes current information showing that zinc allosteric modulation of receptor channels occurs by the preferential metal coordination to imidazole rings as well as to the sulfhydryl groups of cysteine in addition to the carboxyl group of acid residues, as with enzymes and catalysis. It is remarkable that most channels, either voltage-sensitive or transmitter-gated receptor channels, are susceptible to zinc modulation either as positive or negative regulators.

Calcium ion influx in microglial cells: physiological and therapeutic significance.

Microglial cells, the immunocompetent cells of the central nervous system (CNS), exhibit a resting phenotype under healthy conditions. In response to injury, however, they transform into an activated state, which is a hallmark feature of many CNS diseases. Factors or agents released from the neurons, blood vessels, and/or astrocytes could activate these cells, leading to their functional and structural modifications. Microglial cells are well equipped to sense environmental changes within the brain under both physiological and pathological conditions. Entry of calcium ions (Ca(2+)) plays a critical role in the process of microglial transformation; several channels and receptors have been identified on the surface of microglial cells. These include store-operated channel, Orai1, and its sensor protein, stromal interaction molecule 1 (STIM1), in microglial cells, and their functions are modulated under pathological stimulations. Transient receptor potential (TRP) channels and voltage- and ligand-gated channels (ionotropic and metabotropic receptors) are also responsible for Ca(2+) influx into the microglial cells. An elevation of intracellular Ca(2+) concentration subsequently regulates microglial cell functions by activating a diverse array of Ca(2+)-sensitive signaling cascades. Perturbed Ca(2+) homeostasis contributes to the progression of a number of CNS disorders. Thus, regulation of Ca(2+) entry into microglial cells could be a pharmacological target for several CNS-related pathological conditions. This Review addresses the recent insights into microglial cell Ca(2+) influx mechanisms, their roles in the regulation of functions, and alterations of Ca(2+) entry in specific CNS disorders.

Ionotropic receptors mediate olfactory learning and memory in Drosophila.

Phenylacetaldehyde (PAH), an aromatic compound, is present in a diverse range of fruits including overripe bananas and prickly pear cactus, the two major host fruits for Drosophila melanogaster. PAH acts as a potent ligand for the ionotropic receptor 84a (IR84a) in the adult fruit fly and it is detected by the IR84a/IR8a heterotetrameric complex. Its role in the male courtship behavior through IR84a as an environmental aphrodisiac is of additional importance. In D. melanogaster, two distinct kinds of olfactory receptors, that is, odorant receptors (ORs) and ionotropic receptors (IRs), perceive the odorant stimuli. They display unique structural, molecular, and functional characteristics in addition to having different evolutionary origins. Traditionally, olfactory cues detected by the ORs such as ethyl acetate, 1-butanol, isoamyl acetate, 1-octanol, 4-methylcyclohexanol, etc. classified as aliphatic esters and alcohols have been employed in olfactory classical conditioning using fruit flies. This underlines the participation of OR-activated olfactory pathways in learning and memory formation. Our study elucidates that likewise ethyl acetate (EA) (an OR-responsive odorant), PAH (an IR-responsive aromatic compound) too can form learning and memory when associated with an appetitive gustatory reinforcer. The association of PAH with sucrose (PAH/SUC) led to learning and formation of the long-term memory (LTM). Additionally, the Orco1, Ir84aMI00501, and Ir8a1 mutant flies were used to confirm the exclusive participation of the IR84a/IR8a complex in PAH/SUC olfactory associative conditioning. These results highlight the involvement of IRs via an IR-activated pathway in facilitating robust olfactory behavior.

Arthropod repellent interactions with olfactory receptors and ionotropic receptors analyzed by molecular modeling.

The main insect chemoreceptors are olfactory receptors (ORs), gustatory receptors (GRs) and ionotropic receptors (IRs). The odorant binding sites of many insect ORs appear to be occluded and inaccessible from the surface of the receptor protein, based on the three-dimensional structure of OR5 from the jumping bristletail Machilis hrabei (MhraOR5) and a survey of a sample of vinegar fly (Drosophila melanogaster) OR structures obtained from artificial intellegence (A.I.) modeling. Molecular dynamics simulations revealed that the occluded site can become accessible through tunnels that transiently open and close. The present study extends this analysis to examine seventeen ORs and one GR docking with ligands that have known valence: nine that signal attraction and nine that signal aversion. All but one of the receptors displayed occluded ligand binding sites analogous to MhraOR5, and docking software predicted the known attractant and repellent ligands will bind to the occluded sites. Docking of the repellent DEET was examined, and more than half of the OR ligand sites were predicted to bind DEET, including receptors that signal aversion as well as those that signal attraction. However, DEET may not actually have access to all the attractant binding sites. The larger size and lower flexibility of repellent molecules may restrict their passage through the tunnel bottlenecks, which could act as filters to select access to the ligand binding sites. In contrast to ORs and GRs, the IR ligand binding site is in an extracellular domain known to undergo a large conformational change from an open to a closed state. A.I. models of two D. melanogaster IRs of known valence and two blacklegged tick (Ixodes scapularis) IRs having unknown ligands were computationally tested for attractant and repellent binding. The ligand-binding sites in the closed state appear inaccessible to the protein surface, so attractants and repellents must bind initially at an accessible site in the open state before triggering the conformational change. In some IRs, repellent binding sites were identified at exterior sites adjacent to the ligand-binding site. These may be allosteric sites that, when occupied by repellents, can stabilize the open state of an attractant IR, or stabilize the closed state of an IR in the absence of its activating ligand. The model of D. melanogaster IR64a suggests a possible molecular mechanism for the activation of this IR by H+. The amino acids involved in this proposed mechanism are conserved in IR64a from several Dipteran pest species and disease vectors, potentially offering a route to discovery of new repellents that act via the allosteric site.

Comparative transcriptomic analysis of chemoreceptors in two sympatric scarab beetles, Hylamorpha elegans and Brachysternus prasinus.

Chemoreception through odorant receptors (ORs), ionotropic receptors (IRs) and gustatory receptors (GRs) represents the functions of key proteins in the chemical ecology of insects. Recent studies have identified chemoreceptors in coleopterans, facilitating the evolutionary analysis of not only ORs but also IRs and GRs. Thus, Cerambycidae, Tenebrionidae and Curculionidae have received increased attention. However, knowledge of the chemoreceptors from Scarabaeidae is still limited, particularly for those that are sympatric. Considering the roles of chemoreceptors, this analysis could shed light on evolutionary processes in the context of sympatry. Therefore, the aim of this study was to identify and compare the repertoires of ORs, GRs and IRs between two sympatric scarab beetles, Hylamorpha elegans and Brachysternus prasinus. Here, construction of the antennal transcriptomes of both scarab beetle species and analyses of their phylogeny, molecular evolution and relative expression were performed. Thus, 119 new candidate chemoreceptors were identified for the first time, including 17 transcripts for B. prasinus (1 GR, 3 IRs and 13 ORs) and 102 for H. elegans (22 GRs, 14 IRs and 66 ORs). Orthologs between the two scarab beetle species were found, revealing specific expansions as well as absence in some clades. Purifying selection appears to have occurred on H. elegans and B. prasinus ORs. Further efforts will be focused on target identification to characterize kairomone and/or pheromone receptors.