Host plant-induced changes in metabolism and osmotic regulation gene expression in Diaphorina citri adults.

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a worldwide citrus pest. It transmits the pathogen Candidatus Liberibacter spp. of Huanglongbing (HLB), causing severe economic losses to the citrus industry. Severalgenera of plants in the Rutaceae family are the hosts of D. citri. However, the impact of these hosts on the metabolism and osmotic regulation gene expression of the pest remains unexplored. In this study, the contents of total sugars, sucrose, fructose, and glucose in young shoots, old leaves, and young leaves of 'Shatangju' mandarin and Murraya exotica were analyzed. Metabolomic analysis found that sucrose and trehalose were more abundant in the gut samples of D. citri adults fed on M. exotica when compared to what's in 'Shatangju' mandarin. A total of six aquaporin genes were identified in D. citri through the genome and transcriptome data. Subsequently, the expression patterns of these genes were investigated with respect to their developmental stage and tissue specificity. Additionally, the expression levels of osmotic regulation and trehalose metabolism genes in adults fed on different plants were evaluated. Our results provide useful information on the transfer of sugar between plants and D. citri. Our results preliminary revealed the sugar metabolism regulation mechanism in D. citri adults.

Bamboo-like dual-phase nanostructured copper composite strengthened by amorphous boron framework.

Grain boundary engineering is a versatile tool for strengthening materials by tuning the composition and bonding structure at the interface of neighboring crystallites, and this method holds special significance for materials composed of small nanograins where the ultimate strength is dominated by grain boundary instead of dislocation motion. Here, we report a large strengthening of a nanocolumnar copper film that comprises columnar nanograins embedded in a bamboo-like boron framework synthesized by magnetron sputtering co-deposition, reaching the high nanoindentation hardness of 10.8 GPa among copper alloys. The boron framework surrounding copper nanograins stabilizes and strengthens the nanocolumnar copper film under indentation, benefiting from the high strength of the amorphous boron framework and the constrained deformation of copper nanocolumns confined by the boron grain boundary. These findings open a new avenue for strengthening metals via construction of dual-phase nanocomposites comprising metal nanograins embedded in a strong and confining light-element grain boundary framework.

Genome-wide identification, characterization and functional analysis of the chitianse and chitinase-like gene family in Diaphorina citri.

BACKGROUND: Insect chitinases play vital roles in postembryonic development, especially during the molting process, and are potential targets for the RNA interference (RNAi)-based insecticidal strategy. Systematic functional analyses of chitinase genes have already been conducted on numerous insect pests, but similar analyses have not been carried out on Diaphorina citri. RESULTS: Eleven chitinase/chitinase-like genes and one endo-ß-N-acetylglucosaminidase (ENGase) gene were identified in the Diaphorina citri genome using various bioinformatic tools. Transcriptomes of the integument and midgut from fifth-instar nymphs and freshly-emerged adults of Diaphorina citri were generated and sequenced. Potential functions of 12 chitinase/chitinase-like genes were examined during nymph-adult transitions. Four chitinase genes, including DcCht5, DcCht7, DcCht10-1 and DcCht10-2, were mainly expressed in the integument of fifth-instar nymphs. These four genes were also up-regulated significantly under 20-hydroxyecdysone (20E) treatments. RNAi-mediated knockdown of these four genes suggests that they are essential for nymph-adult transition. CONCLUSION: Our results demonstrated essential roles of the chitinase/chitinase-like genes during the nymph-adult transition in Diaphorina citri, which are potentially useful targets for controlling the Diaphorina citri pest. © 2022 Society of Chemical Industry.

Proteomic and transcriptomic analyses of saliva and salivary glands from the Asian citrus psyllid, Diaphorina citri.

Salivary secretions play critical roles in interactions among insects, insect-vectored pathogens, and host plants. The Asian citrus psyllid Diaphorina citri is a sap-sucking Hemipteran that serves as a vector for Candidatus Liberibacter asiaticus, the causal agent of citrus greening disease ("Huanglongbing" or HLB). D. citri continuously injects saliva into host plants using specialized stylets so as to feed and transmit the HLB pathogen. Knowledge on the composition and function of salivary proteins of this pest is very limited. In this study, proteomic and transcriptomic approaches were adopted to characterize the protein composition of the saliva and salivary glands in D. citri. A total of 246 and 483 proteins were identified in saliva and dissected salivary glands, respectively, via LC-MS/MS analyses. Comparative analyses of the identified proteins were performed between D. citri and other reported Hemipteran insect species. Transcription levels of the genes coding for the identified proteins were determined via RNA-sequencing among different tissues including salivary glands and other digestive tissues. Identification of putative effectors that are expressed exclusively or abundantly in salivary glands provides the foundation for future functional studies towards the understanding of their roles in interactions among D. citri, HLB pathogen, and their citrus host. BIOLOGICAL SIGNIFICANCE: This is a systematic analysis on proteins in saliva and dissected salivary glands. A high percentage of novel proteins have been identified due to the large amounts of samples collected. This report gives a more comprehensive repertoire of potential effector proteins that may be possibly involved in modulating host defense, altering nutrient metabolism, and facilitating Ca. L. asiaticus transmission.

Effects of the entomopathogenic fungus Clonostachys rosea on mortality rates and gene expression profiles in Diaphorina citri adults.

Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a serious pest of citrus. The insect also transmits Candidatus Liberibacter asiaticus, the pathogen of a devastating citrus disease called Huanglongbing. Clonostachys rosea is a versatile fungus that possesses nematicidal and insecticidal activities. The effect of C. rosea against D. citri remains unclear. Here we examined the pathogenicity of C. rosea against D. citri adults. A mortality rate of 46.67% was observed in adults treated with 1 × 108 conidia/mL spore suspension. Comparative transcriptomic analyses identified 259 differentially-expressed genes (DEGs) between controls and samples treated with fungi. Among the DEGs, 183 were up-regulated and 76 down-regulated. Genes with altered expression included those involved in immunity, apoptosis and cuticle formation. Our preliminary observation indicated that C. rosea is virulent against ACP adults and has the potential as a biological control agent for ACP management in the field.

Identification and Expression Profiling of Chemosensory Genes in Hermetia illucens via a Transcriptomic Analysis.

The black soldier fly, Hermetia illucens, is a cosmopolitan insect of the family Stratiomyidae (Diptera). Chemosensory genes encode proteins involved directly in the detection of odorants. In this study, we sequenced the antennal transcriptome of H. illucens adults to identify chemosensory genes. Putative unigenes encoding 27 odorant binding proteins (OBPs), five chemosensory proteins (CSPs), 70 odorant receptors (ORs), 25 ionotropic receptors (IRs), 10 gustatory receptors (GRs) and two sensory neuron membrane proteins (SNMPs) were identified. Tissue-specific expression profiles of the identified OBPs, CSPs and SNMPs were investigated using RT-PCR. Eight OBPs (HillOBP1-2, 9, 11-14, and 17), one CSP (HillCSP5) and one SNMP (HillSNMP1) were predominantly expressed in antennae. Further real-time quantitative PCR analyses revealed that the antennae-enriched unigenes also exhibited significant differences in expression between males and females. Among the sex-biased unigenes, six ORs showed female-biased expression, suggesting that these genes might participate in female-specific behaviors such as oviposition site searching. Sixteen ORs and two OBPs showed male-biased expression, indicating that they may play key roles in the detection of female sex pheromones. Our study is the first attempt to delineate the molecular basis of chemoreception in H. illucens. Our data provide useful information for comparative studies on the differentiation and evolution of Dipteran chemosensory gene families.

Transcriptome analysis of putative detoxification genes in the Asian citrus psyllid, Diaphorina citri.

BACKGROUND: The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a notorious pest that transmits the causal agent of huanglongbing (also called citrus greening disease). Resistance to insecticide in this destructive pest poses a serious threat to the citrus industry. To date, no systemic studies on genes coding for detoxification enzymes has been carried out on D. citri. RESULTS: Multiple transcriptomes were generated through deep sequencing of RNA libraries. Candidate genes potentially involved in detoxification including cytochrome P450 monooxygenases (CYPs), glutathione S-transferases (GSTs), and esterases (ESTs) were systematically identified by searching the transcriptomes and a draft genome assembly. A total of 49, 14 and 20 genes were found encoding CYPs, GSTs, and ESTs, respectively, in D. citri. The total numbers of candidate detoxification genes were much smaller than the counterparts reported in other insect species, which may reflect the strict oligophagy of this insect species. Developmental stage- and tissue-specific expression patterns of the identified genes as well as their responses to insecticide treatments identified a small set of genes that could participate in detoxifying plant secondary metabolites and insecticides. CONCLUSION: Our studies represent the most comprehensive investigation to date on identification, characterization and expression profiling of detoxification genes in D. citri. The information revealed in this study shall be useful in designing strategies to manage this important insect pest. © 2020 Society of Chemical Industry.

Analyses of chemosensory genes provide insight into the evolution of behavioral differences to phytochemicals in Bactrocera species.

Insect olfactory systems have evolved to recognize phytochemicals and respond to olfactory-triggered cues that vary depending on needs. Several Bactrocera species are attracted explicitly to particular phytochemicals, including methyl eugenol (ME) and cue lure/raspberry ketone (CL/RK). The attraction of Bactrocerans to ME/RK is primarily driven by olfaction. Therefore, the divergent behavioral phenotypes are due to the differences in genes expressed in antennae. High quality transcriptomes were generated with mRNA from dissected antennae, to analyze the differences in olfaction-related genes of three ME-responders B. dorsalis, B. papayae and B. correcta and two RK-responders B. cucurbitae and B. tau. Many distinct quantitative and qualitative differences were identified in their respective chemosensory repertoires. Tissue- and sex-specific expression analyses identified antennae-predominant and sex-biased chemosensory genes. Sequence comparison revealed variations among family members of odorant-binding proteins and odorant-receptors between ME-responders and RK-responders. Differences in composition, expression levels, and sequence of proteins encoded by olfactory-related genes were identified between ME-responders and RK-responders. Some of the differences might contribute to the divergence in response to plant-derived odorants. Taken together, our results provide insights into the evolution of an olfactory system at molecular level in Bactrocera ME- and CL/RK-responding species.

Odorant-binding proteins and chemosensory proteins potentially involved in host plant recognition in the Asian citrus psyllid, Diaphorina citri.

BACKGROUND: Odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are two families of small water-soluble proteins involved in odor detection and subsequent signal transmission. Determination of their binding mechanisms and specificity towards different odorants is important for developing OBPs/CSPs as targets in pest control management. RESULTS: We re-annotated genes encoding putative OBPs and CSPs in the Asian citrus psyllid (Diaphorina citri) draft genome using various bioinformatic tools. Genes encoding nine OBPs (seven Classic and two Plus-C) and 12 CSPs were identified, consistent with our previous transcriptomic results. Tissue-specific and developmental expression analyses suggested that genes encoding six OBPs and four CSPs were predominantly expressed in antennae, and displayed various expression patterns in different development stages, suggesting potential involvement in olfactory perception. Competitive fluorescence binding assays with 13 candidate ligands, including known host plant volatiles, sex pheromone components and repellents, showed that DcitOBP3 could bind to various odorants, whereas DcitOBP6, 8 and 9 bound specifically to host plant terpenoids. DcitCSP1 and 12 could also bind to certain terpenoids with high binding specificity. CONCLUSION: OBP- and CSP-encoding genes were systematically identified by annotating the draft D. citri genome and those potentially involved in odorant detection and signal transmission were identified by analyzing their tissue-expression profiles and odorant-binding affinities, particularly to the peripheral molecular perception of host plant terpenoids. The identified genes may provide potential targets for efficient pest control. © 2020 Society of Chemical Industry.

Comparative transcriptomic analyses revealed genes and pathways responsive to heat stress in Diaphorina citri.

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is a serious pest that feeds on plant phloem sap of citrus trees, and transmits Candidatus Liberibacter asiaticus, a bacterium that induces the destructive disease called Huanglongbing. Increasing evidence suggests that high temperatures could affect various biological traits, including size, longevity, mortality, behavior and metabolism of D. citri. However, the relevant mechanisms of heat stress remain unclear. In this study, a large set of transcriptomic data derived from D. citri adults were generated and differentially expressed genes (DEGs) after heat stress were identified by RNA sequencing. A total of 118, 399 unigenes were obtained, from which 37, 665 were mapped to sequences from at least one database. Seven hundreds and twenty-two unigenes were affected by high temperature of 40 °C for 4 h, in which 486 up-regulated and 236 down-regulated, and part of heat shock proteins, antioxidant and detoxification genes and cathepsins were identified as the DEGs. KEGG pathway enrichment analysis demonstrated that part of genes involved in protein synthesis and processing, metabolism, immunity, and signal transduction were differentially expressed under heat stress. Furthermore, the mRNA expression levels of 20 DEGs were confirmed by qRT-PCR, which verified the accuracy of high-throughput sequencing. Our results revealed that the response of D. citri adults to high temperatures is associated with a range of changes involved in various physiological and biochemical processes. Our data provide a basis for future research to improve our understanding on the molecular mechanism for heat responses in D. citri adults.

Identification and expression analysis of odorant binding proteins and chemosensory proteins from dissected antennae and mouthparts of the rice bug Leptocorisa acuta.

The rice bug, Leptocorisa acuta (Tunberg) (Hemiptera: Alydidae), is a notorious pest in Asia, and it is significantly attracted by the volatiles derived from host plants. However, it remains unknown how L. acuta recognizes host volatile compounds at the molecular level. Odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are thought to be responsible for the initial biochemical recognition during olfactory perception. Here, we followed the RNA Sequencing (RNA-Seq) approach to identify candidate genes encoding OBPs and CSPs from dissected antennae and mouthparts of L. acuta. In total, 26 unigenes were identified coding for OBPs (22 Classic OBPs and four Plus-C OBPs), and 17 unigenes coding for CSPs. Real-time quantitative PCR (RT-qPCR) revealed that 11 OBPs (LacuOBP1, 5, 6, 7, 9, 11, 13, 14, 17, 20 and 23) and nine CSPs (LacuCSP2, 3, 4, 5, 6, 8, 9, 10 and 12) were predominantly expressed in antennae, indicating that they might be essential for detection of general odorants and pheromones. Among these antennae-predominantly expressed genes, LacuOBP11 and LacuOBP13 showed male-biased expression and therefore may play crucial roles in the detection of sex pheromones. Seven LacuOBPs (LacuOBP4, 8, 10, 12, 21, 25 and 26) and two CSPs (LacuCSP7 and LacuOBP11) were predominantly expressed in mouthparts, suggesting that these genes might be involved in taste perception. Our work provides a starting point to facilitate functional study of these OBPs and CSPs in L. acuta at the molecular level in the future.

Identification and Expression Analyses of Olfactory Gene Families in the Rice Grasshopper, Oxya chinensis, From Antennal Transcriptomes.

The rice grasshopper Oxya chinensis is an important agricultural pest of rice and other gramineous plants. Chemosensory genes are crucial factors in direct interactions with odorants in the olfactory process. Here we identified genes encoding 18 odorant-binding proteins (OBPs), 13 chemosensory proteins (CSPs), 94 olfactory receptors (ORs), 12 ionotropic receptors (IRs), and two sensory neuron membrane proteins (SNMPs) from O. chinensis using an transcriptomic approach. Semi-quantitative RT-PCR assays revealed that six OBP-encoding genes (OchiOBP4, 5, 8, 9, 10, and 14), one CSP gene (OchiOBP10) and two IR genes (OchiIR28 and 29) were exclusively expressed in antennae, suggesting their roles in olfaction. Real-time quantitative PCR analyses revealed that genes expressed exclusively or predominantly in antennae also displayed significant differences in expression levels between males and females. Among the differentially expressed genes, 17 OR-encoding genes, one CSP- and one SNMP-gene showed female-biased expression, suggesting that they may be involved in some female-specific behaviors such as seeking oviposition site; whereas the three remaining OR-encoding genes showed male-biased expression, indicating their possible roles in sensing female sex pheromones. Our results laid a solid foundation for future studies to reveal olfactory mechanisms as well as designing strategies for controlling this rice pest.

Candidates for chemosensory genes identified in the Chinese citrus fly, Bactrocera minax, through a transcriptomic analysis.

BACKGROUND: The males of many Bactrocera species (Diptera: Tephritidae) respond strongly to plant-derived chemicals (male lures) and can be divided into cue lure/raspberry ketone (CL/RK) responders, methyl eugenol (ME) responders and non-responders. Representing a non-responders, Bactrocera minax display unique olfactory sensory characteristics compared with other Bactrocera species. The chemical senses of insects mediate behaviors that are associated with survival and reproduction. Here, we report the generation of transcriptomes from antennae and the rectal glands of both male and female adults of B. minax using Illumina sequencing technology, and annotated gene families potentially responsible for chemosensory. RESULTS: We developed four transcriptomes from different tissues of B. minax and identified a set of candidate genes potentially responsible for chemosensory by analyzing the transcriptomic data. The candidates included 40 unigenes coding for odorant receptors (ORs), 30 for ionotropic receptors (IRs), 17 for gustatory receptors (GRs), three for sensory neuron membrane proteins (SNMPs), 33 for odorant-binding proteins (OBPs), four for chemosensory proteins (CSPs). Sex- and tissue-specific expression profiles for candidate chemosensory genes were analyzed via transcriptomic data analyses, and expression profiles of all ORs and antennal IRs were investigated by real-time quantitative PCR (RT-qPCR). Phylogenetic analyses were also conducted on gene families and paralogs from other insect species together. CONCLUSIONS: A large number of chemosensory genes were identified from transcriptomic data. Identification of these candidate genes and their expression profiles in various tissues provide useful information for future studies towards revealing their function in B. minax.

Candidate genes coding for odorant binding proteins and chemosensory proteins identified from dissected antennae and mouthparts of the southern green stink bug Nezara viridula.

The southern green stink bug Nezara viridula (Hemiptera: Pentatomidae) is a highly polyphagous pest that can significantly impact many major crops worldwide. Insect odorant binding proteins (OBPs) and chemosensory proteins (CSPs) transport chemicals and play critical roles in chemoreception. Studies on N. viridula OBPs and CSPs should increase our overall understandings on chemosensory systems and chemical ecology of stink bugs, which may lead to improved pest control. In this study, we identified candidate genes encoding putative OBPs and CSPs in N. viridula by generating transcriptomes from dissected antennae and mouthparts. In total, the 42 unigenes were identified coding for OBPs (34 Classic OBPs and eight Plus-C OBPs) and 13 unigenes coding for CSPs. Expression profiles of OBP- and CSP -encoding genes were compared between antennae and mouthparts based on FKPM values. Candidates for antenna-predominant OBPs and CSPs were selected for real-time quantitative PCR analyses. Analyses of tissue expression profiles revealed that 17 OBP-encoding genes, and four CSP genes were primarily expressed in antennae, suggesting their putative roles in perception of volatiles. The sex-biased expression patterns of these antenna-predominant genes suggested that they may have important functions in reproduction of the insect. This is a systematic analysis on OBPs and CSPs in a stink bug, providing a comprehensive resource for future functional studies not only for N. viridula, but also for other stink bugs as well.

Candidate genes involved in spiroacetal biosynthesis in the oriental fruit fly, Bactrocera dorsalis.

Spiroacetals are widespread in nature as components of volatile semiochemical secretions from many insect species. The general pathway for spiroacetal biosynthesis in Bactrocera sp. is preliminarily established, but many genes involved in this pathway remain to be characterized. By analyzing transcriptomes of the rectal glands (RGs) from immature and mature females of the oriental fruit fly, Bactrocera dorsalis, a set of genes encoding two acetyl-CoA carboxylases (ACCs), two fatty acid synthases (FASs), eight desaturases (DESs), twelve fatty acyl-CoA reductases (FARs), seventy-two cytochrome P450 enzymes (CYPs), and twenty-three odorant binding proteins (OBPs) were identified. We investigated the expression of candidate genes in immature and mature stages based on the RNA-seq data and Real-time quantitative PCR. Expression profiling revealed that some of these genes were primarily expressed in female rectal glands among different tissues, and were up-regulated in mature females. Semi-quantitative RT-PCR assays were also adapted to examine tissue-specific expression of selected candidate genes. Additionally, their putative functions in spiroacetal synthesis and transportation are proposed. Our study provided large-scale sequence information for further functional studies on spiroacetal biosynthetic pathways.

Tuning Superhydrophobic Materials with Negative Surface Energy Domains.

Hydrophobic/superhydrophobic materials with intrinsic water repellence are highly desirable in engineering fields including anti-icing in aerocrafts, antidrag and anticorrosion in ships, and antifog and self-cleaning in optical lenses, screen, mirrors, and windows. However, superhydrophobic material should have small surface energy (SE) and a micro/nanosurface structure which can reduce solid-liquid contact significantly. The low SE is generally found in organic materials with inferior mechanical properties that is undesirable in engineering. Intriguingly, previous theoretical calculations have predicted a negative SE for θ-alumina (θ-Al2O3), which inspires us to use it as a superhydrophobic material. Here, we report the experimental evidence of the small/negative SE of θ-Al2O3 and a θ-Al2O3-based superhydrophobic coating prepared by one-step scalable plasma arcing oxidation. The superhydrophobic coating has complete ceramic and desired micro/nanostructure and therefore exhibits excellent aging resistance, wear resistance, corrosion resistance, high-temperature tolerance, and burning resistance. Owing to the rarity of the small/negative SE in inorganic materials, the concept to reduce SE by θ-Al2O3 may foster a blowout to develop robust superhydrophobicity by complete inorganic materials.

Selection of Reference Genes for Optimal Normalization of Quantitative Real-Time Polymerase Chain Reaction Results for Diaphorina citri Adults.

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), can cause direct damage to citrus trees and is the main vector for the devastating disease, citrus greening disease or huanglongbing. Most molecular studies on this important insect pest use real-time reverse-transcription quantitative polymerase chain reaction (RT-qPCR) to quantify gene expression, including analyzing molecular basis for insecticide resistance in field populations. One critical factor to cause inaccuracy in RT-qPCR results is the lack of appropriate internal reference genes for optimal data normalization. In this study, the expression levels of 10 selected reference genes were evaluated in different tissue samples of psyllid adults and in the insects treated with different temperatures and insecticides. Data were analyzed using different computational algorithms, including Delta Ct, BestKeeper, NormFinder, geNorm, and RefFinder. According to our results, at least two reference genes should be used for the normalization of RT-qPCR data in this insect. The best choices of reference genes for different samples are as follows: ACT1 and Ferritin for different tissue samples, RPS20 and Ferritin for samples treated with different temperatures, TBP and EF1α for samples treated with imidacloprid, and Ferritin and TBP for samples treated with beta-cypermethrin. The reference genes identified in this study should be useful for future studies to analyze the expression patterns of target genes, especially for genes linked with temperature adaptability and insecticide resistance in this insect species in the future.

Antennal transcriptome and expression analyses of olfactory genes in the sweetpotato weevil Cylas formicarius.

The sweetpotato weevil, Cylas formicarius (Fabricius), is a serious pest of sweetpotato. Olfaction-based approaches, such as use of synthetic sex pheromones to monitor populations and the bait-and-kill method to eliminate males, have been applied successfully for population management of C. formicarius. However, the molecular basis of olfaction in C. formicarius remains unknown. In this study, we produced antennal transcriptomes from males and females of C. formicarius using high-throughput sequencing to identify gene families associated with odorant detection. A total of 54 odorant receptors (ORs), 11 gustatory receptors (GRs), 15 ionotropic receptors (IRs), 3 sensory neuron membrane proteins (SNMPs), 33 odorant binding proteins (OBPs), and 12 chemosensory proteins (CSPs) were identified. Tissue-specific expression patterns revealed that all 54 ORs and 11 antennal IRs, one SNMP, and three OBPs were primarily expressed in antennae, suggesting their putative roles in olfaction. Sex-specific expression patterns of these antenna-predominant genes suggest that they have potential functions in sexual behaviors. This study provides a framework for understanding olfaction in coleopterans as well as future strategies for controlling the sweetpotato weevil pest.

Transcriptome sequencing of Tessaratoma papillosa antennae to identify and analyze expression patterns of putative olfaction genes.

Studies on insect olfaction have increased our understanding of insect's chemosensory system and chemical ecology, and have improved pest control strategies based on insect behavior. In this study, we assembled the antennal transcriptomes of the lychee giant stink bug, Tessaratoma papillosa, by using next generation sequencing to identify the major olfaction gene families in this species. In total, 59 odorant receptors, 14 ionotropic receptors (8 antennal IRs), and 33 odorant binding proteins (28 classic OBPs and 5 plus-C OBPs) were identified from the male and female antennal transcriptomes. Analyses of tissue expression profiles revealed that all 59 OR transcripts, 2 of the 8 antennal IRs, and 6 of the 33 OBPs were primarily expressed in the antennae, suggesting their putative role in olfaction. The sex-biased expression patterns of these antenna-predominant genes suggested that they may have important functions in the reproductive behavior of these insects. This is the first report that provides a comprehensive resource to future studies on olfaction in the lychee giant stink bug.

Antennal and abdominal transcriptomes reveal chemosensory gene families in the coconut hispine beetle, Brontispa longissima.

Antennal and abdominal transcriptomes of males and females of the coconut hispine beetle Brontispa longissima were sequenced to identify and compare the expression patterns of genes involved in odorant reception and detection. Representative proteins from the chemosensory gene families likely essential for insect olfaction were identified. These include 48 odorant receptors (ORs), 19 ionotropic receptors (IRs), 4 sensory neuron membrane proteins (SNMPs), 34 odorant binding proteins (OBPs) and 16 chemosensory proteins (CSPs). Phylogenetic analysis revealed the evolutionary relationship of these proteins with homologs from Coleopterans or other insects, and led to the identification of putative aggregation pheromone receptors in B. longissima. Comparative expression analysis performed by calculating FPKM values were also validated using quantitative real time-PCR (qPCR). The results revealed that all ORs and antennal IRs, two IR co-receptors (BlonIR8a and BlonIR25a) and one SNMP (BlonSNMP1a) were predominantly expressed in antennae when compared to abdomens, and approximately half of the OBPs (19) and CSPs (7) were enriched in antennae. These findings for the first time reveal the identification of key molecular components in B. longissima olfaction and provide a valuable resource for future functional analyses of olfaction, and identification of potential targets to control this quarantine pest.