Insights on reproduction-related genes in the striped fruit fly, Zeugodacus scutellata (Hendel) (Diptera: Tephritidae).

The striped fruit fly, Zeugodacus scutellata is a significant pest in East and Southeast Asia by damaging Cucurbitaceae blossoms and fruits. To control this pest, a novel strategy to suppress the gene(s) associated with sexually dimorphic phenotypes has been devised and implemented in a laboratory scale. However, comprehensive transcriptomic analysis related to this sex differentiation of Z. scutellata was necessary to determine effective target genes for the genetic control. We performed de novo assembly of the transcript obtained by paired-end sequencing using an Illumina HiSeq platform and let to 217,967 unigenes (i.e., unique genes) with a minimum length of 200 bp. The female produced 31, 604, 442 reads with 97.93% of Q20, 94.76% of Q30, and the male produced 130, 592, 828 reads with 97.93% of Q20 and 94.76 of Q30%. The differentially expressed genes were used to predict genetic factors associated with sex differentiation, which included Rho1, extra-macrochaetae (emc), hopscotch (hop), doublesex (dsx), sex-lethal (sxl), transformer-2 (tra-2), testis-specific serine/threonine-protein kinase (tssk1), tektin1 (tkt1) and 2 (tkt2), odorant binding proteins (OBPs), fruitless (fru), vitellogenin receptor, and hormone receptors in Z. scutellata. In addition, this transcriptome analysis provides the additional gene associated with sex determination and mating behaviors, which would be applied to develop a novel sterile insect technique against Z. scutellata.

Host's guardian protein counters degenerative symbiont evolution.

Microbial symbioses significantly contribute to diverse organisms, where long-lasting associations tend to result in symbiont genome erosion, uncultivability, extinction, and replacement. How such inherently deteriorating symbiosis can be harnessed to stable partnership is of general evolutionary interest. Here, we report the discovery of a host protein essential for sustaining symbiosis. Plataspid stinkbugs obligatorily host an uncultivable and genome-reduced gut symbiont, Ishikawaella Upon oviposition, females deposit "capsules" for symbiont delivery to offspring. Within the capsules, the fragile symbiotic bacteria survive the harsh conditions outside the host until acquired by newborn nymphs to establish vertical transmission. We identified a single protein dominating the capsule content, which is massively secreted by female-specific intestinal organs, embedding the symbiont cells, and packaged into the capsules. Knockdown of the protein resulted in symbiont degeneration, arrested capsule production, symbiont transmission failure, and retarded nymphal growth, unveiling its essential function for ensuring symbiont survival and vertical transmission. The protein originated from a lineage of odorant-binding protein-like multigene family, shedding light on the origin of evolutionary novelty regarding symbiosis. Experimental suppression of capsule production extended the female's lifespan, uncovering a substantial cost for maintaining symbiosis. In addition to the host's guardian protein, the symbiont's molecular chaperone, GroEL, was overproduced in the capsules, highlighting that the symbiont's eroding functionality is compensated for by stabilizer molecules of host and symbiont origins. Our finding provides insight into how intimate host-symbiont associations can be maintained over evolutionary time despite the symbiont's potential vulnerability to degeneration and malfunctioning.

Identification of attractants for adult Spodoptera litura based on the interaction between odorant-binding protein 34 and host volatiles.

Odorant-binding proteins (OBPs) play key roles in host plant location by insects, and can accordingly serve as important targets for the development of attractants. In this study, we detected the high expression of SlitOBP34 in male antennae of Spodoptera litura. Subsequently, the fluorescence competitive binding experiments displayed that the SlitOBP34 protein has binding affinity for different ligands. Then, protein-ligand interaction analyses found the presence of six amino acid residues may serve as key recognition sites. Further electroantennographic and biobehavioral assessments revealed that the electrophysiological responses of male antennae were evoked in response to stimulation with the six identified host volatiles, and that these volatiles attracted male moths to varying extents. Notably, low concentrations of benzaldehyde, 1-hexanol, and cis-3-hexenyl acetate were found to have significant attractant effects on male moths, thereby identifying these three host volatiles as potential candidates for the development of male attractants. These findings advance our current understanding of the olfactory-encoded mechanisms of host plants selection in S. litura and have enabled us to develop novel adult attractants for controlling the pest in the future.

Different binding properties of odorant-binding protein 8 to insecticides in Orius sauteri.

Chemical sensing systems are vital in the growth and development of insects. Orius sauteri (Poppius) (Hemiptera: Anthocoridae) is an important natural enemy of many pests. The molecular mechanism of odorant binding proteins (OBPs) binding with common insecticides is still unknow in O. sauteri. In this study, we expressed in vitro OsauOBP8 and conducted fluorescence competition binding assay to investigate the function of OsauOBP8 to insecticides. The results showed that OsauOBP8 could bind with four common insecticides (phoxim, fenitrothion, chlorpyrifos, deltamethrin). Subsequently, we used molecular docking to predict and obtained candidate six amino acid residues (K4, K6, K13, R31, K49, K55) and then mutated. The result showed that three key residues (K4, K6, R31) play important role in OsauOBP8 bound to insecticides. Our study identified the key binding sites of OsauOBP8 to insecticides and help to better understand the molecular mechanism of OBPs to insecticides in O. sauteri.

Role of odorant binding protein C12 in the response of Tribolium castaneum to chemical agents.

Tribolium castaneum is a worldwide pest of stored grain that mainly damages flour, and not only causes serious loss of flour quality but also leads to deterioration of flour quality. Chemical detection plays a key role in insect behavior, and the role of odorant-binding proteins (OBPs) in insect chemical detection has been widely studied. OBPs can interact with small molecule compounds and thereby modulate variation in insecticide susceptibility in insects. In this study, a total of 65 small molecule compounds are selected to investigate the bound effect with TcOBP C12. The molecular docking results showed that ß-caryophyllene, (-)-catechin, butylated hydroxytoluene, diphenyl phthalate and quercetin were the top five compounds, with docking binding energies of -6.11, -5.25, -5.09, -5.05, and - 5.03 Kcal/mol, respectively. Molecular dynamics analysis indicated that odorant binding protein C12 (TcOBP C12) exhibited high binding affinity to all five tested chemical ligands, evidenced by fluorescence quenching assay in vitro. In addition, the contact toxicity assay results suggested that these chemical agents caused a dose-dependent increase in mortality rate for T. castaneum adults. The TcOBP C12 gene was upregulated >2 times after a 24-h exposure, indicating that OBP C12 may play an important role for T. castaneum in response to these chemical agents. In conclusion, our results provide a theoretical basis for future insecticide experiments and pest management.

Reverse Chemical Ecology Suggests Putative Primate Pheromones.

Pheromonal communication is widespread among living organisms, but in apes and particularly in humans there is currently no strong evidence for such phenomenon. Among primates, lemurs use pheromones to communicate within members of the same species, whereas in some monkeys such capabilities seem to be lost. Chemical communication in humans appears to be impaired by the lack or malfunctioning of biochemical tools and anatomical structures mediating detection of pheromones. Here, we report on a pheromone-carrier protein (SAL) adopting a "reverse chemical ecology" approach to get insights on the structures of potential pheromones in a representative species of lemurs (Microcebus murinus) known to use pheromones, Old-World monkeys (Cercocebus atys) for which chemical communication has been observed, and humans (Homo sapiens), where pheromones and chemical communication are still questioned. We have expressed the SAL orthologous proteins of these primate species, after reconstructing the gene encoding the human SAL, which is disrupted due to a single base mutation preventing its translation into RNA. Ligand-binding experiments with the recombinant SALs revealed macrocyclic ketones and lactones as the best ligands for all three proteins, suggesting cyclopentadecanone, pentadecanolide, and closely related compounds as the best candidates for potential pheromones. Such hypothesis agrees with the presence of a chemical very similar to hexadecanolide in the gland secretions of Mandrillus sphinx, a species closely related to C. atys. Our results indicate that the function of this carrier protein has not changed much during evolution from lemurs to humans, although its physiological role has been certainly impaired in humans.

Modeling disruption of Apis mellifera (honey bee) odorant-binding protein function with high-affinity binders.

Chemical toxins pose a great threat to honey bee health because they affect memory and cognition, diminish immunity, and increase susceptibility to infection, resulting in decreased colony performance, reproduction, and survival. Although the behavioral effects of sub-lethal chemical exposure on honey bees have been intensively studied, how xenobiotics affect olfaction, at the molecular level, still needs to be elucidated. In the present work, in silico tools, such as molecular docking, binding free energy calculations, and molecular dynamics simulations are used to predict if environmental chemicals have stronger binding affinities to honey bee antennal odorant-binding protein 14 (OBP14) than the representative floral odors citralva, eugenol, and the fluorescent probe 1-N-phenylnaphthylamine. Based on structural analysis, 21 chemicals from crop pesticides, household appliances, cosmetics, food, public health-related products, and other sources, many of which are pervasive in the hive environment, have higher binding affinities than the floral odors. These results suggest that chemical exposures are likely to interfere with the honey bee's sense of smell and this disruptive mechanism may be responsible for the lower associative learning and memory based on olfaction found in bees exposed to pesticides. Moreover, bees mainly rely on olfactory cues to perceive their environment and orient themselves as well as to discriminate and identify their food, predators, nestmates, and diseased individuals that need to be removed with hygienic behavior. In summary, sub-lethal exposure to environmental toxins can contribute to colony collapse in several ways from the disruption of proper olfaction functioning.

Candidate odorant-binding protein and chemosensory protein genes in the turnip aphid Lipaphis erysimi.

The turnip aphid, Lipaphis erysimi Kaltenbach, inflicts heavy damage on cruciferous crops worldwide. In these insects, olfactory perception is crucial for mating, host location, and oviposition. Both odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are responsible for the delivery of host odorants and pheromones during initial molecular interactions. In this study, antennal and body transcriptomes of L. erysimi were generated through the deep sequencing of RNA libraries. A dataset of 11 LeryOBP and four LeryCSP transcripts was identified among assembled unigenes and subjected to sequence analysis. Phylogenetic analysis found a one-to-one orthologous relationship between LeryOBP/LeryCSP and its corresponding homologs from other aphid species. Further quantitative real-time PCR analyses across developmental stages and tissues showed that five LeryOBP genes (i.e., LeryGOBP, LeryOBP6, LeryOBP7, LeryOBP9, and LeryOBP13) and LeryCSP10 were specifically or significantly elevated in the antennae compared with other tissues. Moreover, two transcripts (i.e., LeryGOBP and LeryOBP6) exhibited remarkably higher expression levels in alate aphids, implying their potentially functional role in the perception of new host plant locations. These results present the identification and expression of OBP/CSP genes in L. erysimi, providing valuable insights into their putative role in olfactory signal transduction.

Identification and expression analyses of the olfactory-related genes in different tissues' transcriptome of a predacious soldier beetle, Podabrus annulatus (Coleoptera, Cantharidae).

We sequenced and analyzed the transcriptomes from different tissues of the soldier beetle, Podabrus annulatus (Coleoptera: Cantharidae), and obtained 75.74 Gb clean reads which were assembled into 95,274 unigenes. Among these transcripts, 25,484 unigenes of highly quality were annotated. Based on annotation and tBLASTn results, we identified a total of 101 candidate olfactory-related genes for the first time, including 11 putative odorant-binding proteins (OBPs), 6 chemosensory proteins (CSP), 50 olfactory receptors (ORs), 25 gustatory receptors (GRs), 6 ionotropic receptors (IRs), and 3 sensory neuron membrane proteins (SNMPs). BLASTX best-hit results indicated that these chemosensory genes were most identical to their respective orthologs from Photinus pyralis. Phylogenetic analyses also revealed that the ORs, GRs, and IRs of Podabrus annulatus are closely related to those of Photinus pyralis. The fragment per kilobase per million mapped fragments (FPKM) values showed that the PannOBP2, PannOBP3, and PannOBP10 were predominantly expressed in the antennae, PannOBP1 in the abdomen-thorax, while others were not identified to be tissue-specific. These olfactory-related differentially expressed genes (DEGs) demonstrated different roles in the olfactory system of Podabrus annulatus. This study establishes the groundwork for future research into the molecular mechanism of olfactory recognition in Podabrus annulatus.

Functional differentiation of two general odorant-binding proteins to sex pheromones in Spodoptera frugiperda.

A precise chemosensory system can help insects complete various important behavioral responses by accurately identifying different external odorants. Therefore, deeply understanding the mechanism of insect recognition of important odorants will help us develop efficient and environmentally-friendly behavioral inhibitors. Spodoptera frugiperda is a polyphagous pest that feeds on >350 different host plants worldwide and also harms maize production in China. However, the molecular mechanism of the first step for males to use odorant-binding proteins (OBPs) to recognize sex pheromones remains unclear. Here, we obtained 50 OBPs from the S. frugiperda genome, and the expression level of SfruGOBP1 in females was significantly higher than that in males, whereas SfruGOBP2 displayed male-biased expression. Fluorescence competitive binding assays showed that only SfruGOBP2 showed binding affinities for the four sex pheromones of female S. frugiperda. Subsequently, we identified some key amino acid residues that can participate in the interaction between SfruGOBP2 and sex pheromones using molecular docking and site-directed mutagenesis methods. These findings will help us explore the interaction mechanism between GOBPs and sex pheromones in moths, and provide important target genes for developing new mating inhibitors of S. frugiperda in the future.

Odorant-binding Protein 10 From Bradysia odoriphaga (Diptera: Sciaridae) Binds Volatile Host Plant Compounds.

Bradysia odoriphaga (Diptera: Sciaridae) is a major insect pest of seven plant families including 30 commercial crops in Asia. The long-term use of chemical pesticides leads to problems such as insect resistance, environmental issues, and food contamination. Against this background, a novel pest control method should be developed. In insects, odorant-binding proteins (OBPs) transport odor molecules, including pheromones and plant volatiles, to olfactory receptors. Here, we expressed and characterized the recombinant B. odoriphaga OBP BodoOBP10, observing that it could bind the sulfur-containing compounds diallyl disulfide and methyl allyl disulfide with Ki values of 8.01 µM and 7.00 µM, respectively. Homology modeling showed that the BodoOBP10 3D structure was similar to that of a typical OBP. Both diallyl disulfide and methyl allyl disulfide bound to the same site on BodoOBP10, mediated by interactions with six hydrophobic residues Met70, Ile75, Thr89, Met90, Leu93, and Leu94, and one aromatic residue, Phe143. Furthermore, silencing BodoOBP10 expression via RNAi significantly reduced the electroantennogram (EAG) response to diallyl disulfide and methyl allyl disulfide. These findings suggest that BodoOBP10 should be involved in the recognition and localization of host plants.

Identification and sex-specific expression of chemosensory genes in the antennal transcriptomes of Pachyrhinus yasumatsui (Coleoptera: Curculionidae).

Pachyrhinus yasumatsui Kono et Morimoto is a major pest of Chinese jujube, which is widespread in northern China and causes severe economic losses in the jujube industry. Chemosensory genes play crucial roles in insect behaviors. Currently, little is known about chemosensory genes in P. yasumatsui. In the present study, antennal transcriptomes of female and male adult P. yasumatsui were annotated. In total, 113 genes involved in chemosensory functions were identified, including 41 odorant receptors, 28 odorant-binding proteins, 16 ionotropic receptors, 15 chemosensory proteins, 9 gustatory receptors, and 4 sensory neuron membrane proteins. Subsequently, the phylogenetic analyses of these olfactory-related proteins in P. yasumatsui were conducted using multiple sequence alignment. Furthermore, sex-specific expression levels of 113 genes were analyzed based on fragments per kilobase of transcript per million mapped reads (FPKM). Then, the quantitative real-time PCR (RT-qPCR) was used to quantify gene expression profiles of 28 P. yasumatsui OBPs (PyasOBPs) and 15 CSPs (PyasCSPs). The results revealed that 20 PyasOBPs and 13 PyasCSPs exhibited significantly higher expression in the antennae than in the bodies, suggesting that they might have functions in olfaction. Moreover, some OBPs and CSPs (PyasOBP6, PyasOBP7, PyasOBP16, PyasOBP21, and PyasCSP4) exhibited female-biased expression, indicating that they might take part in several female-specific behaviors. This study will promote the understanding of olfactory mechanism in P. yasumatsui, and our findings lay the groundwork for developing environmentally friendly pest management measures.

Transcriptome analysis used to identify and characterize odorant binding proteins in Agasicles hygrophila (Coleoptera: Chryspmelidae).

The transcriptomes of Agasicles hygrophila eggs and first instar larvae were analyzed to explore the olfactory mechanism of larval behavior. The analysis resulted in 135,359 unigenes and the identification of 38 odorant-binding proteins (OBPs), including 23 Minus-C OBPs, 8 Plus-C OBPs, and 7 Classic OBPs. Further analysis of differentially expressed genes (DEGs) revealed 10 DEG OBPs, with 5 (AhygOBP5, AhygOBP9, AhygOBP12, AhygOBP15 and AhygOBP36) up-regulated in first instar larvae. Verification of expression patterns of these 5 AhygOBPs using qPCR showed that AhygOBP9 and AhygOBP36 were mainly expressed in the adult stage with gradually increasing expression in the larval stage. AhygOBP5, AhygOBP12, and AhygOBP15 were not expressed in eggs and pupae, and their expression in larvae and adults showed no clear pattern. These 5 AhygOBPs may play an olfactory role in larval behavior, providing a basis for further investigation of their specific functions and clarifying the olfactory mechanism of A. hygrophila.

Antennal transcriptome analysis of olfactory genes and tissue expression profiling of odorant binding proteins in Semanotus bifasciatus (cerambycidae: coleoptera).

BACKGROUND: Insect olfactory proteins can transmit chemical signals in the environment that serve as the basis for foraging, mate searching, predator avoidance and oviposition selection. Semanotus bifasciatus is an important destructive borer pest, but its olfactory mechanism is not clear. We identified the chemosensory genes of S. bifasciatus in China, then we conducted a phylogenetic analysis of the olfactory genes of S. bifasciatus and other species. And the expression profiles of odorant binding proteins (OBPs) genes in different tissues and different genders of S. bifasciatus were determined by quantitative real-time PCR for the first time. RESULTS: A total of 32 OBPs, 8 chemosensory proteins (CSPs), 71 odorant receptors (ORs), 34 gustatory receptors (GRs), 18 ionotropic receptors (IRs), and 3 sensory neuron membrane proteins (SNMPs) were identified. In the tissue expression analysis of OBP genes, 7 OBPs were higher expressed in antennae, among them, SbifOBP2, SbifOBP3, SbifOBP6, SbifOBP7 and SbifOBP20 were female-biased expression, while SbifOBP1 was male-biased expression and SbifOBP22 was no-biased expression in antennae. In addition, the expressed levels of SbifOBP4, SbifOBP12, SbifOBP15, SbifOBP27 and SbifOBP29 were very poor in the antennae, and SbifOBP4 and SbifOBP29 was abundant in the head or legs, and both of them were male-biased expression. While SbifOBP15 was highly expressed only at the end of the abdomen with its expression level in females three times than males. Other OBPs were expressed not only in antennae but also in various tissues. CONCLUSION: We identified 166 olfactory genes from S. bifasciatus, and classified these genes into groups and predicted their functions by phylogenetic analysis. The majority of OBPs were antenna-biased expressed, which are involved in odor recognition, sex pheromone detection, and/or host plant volatile detection. However, also some OBPs were detected biased expression in the head, legs or end of the abdomen, indicating that they may function in the different physiological processes in S. bifasciatus.

Binding properties of odorant-binding protein 4 from bean bug Riptortus pedestris to soybean volatiles.

The bean bug Riptortus pedestris is a notorious insect pest that can damage various crops, especially soybean, in East Asia. In insects, the olfactory system plays a crucial role in host finding and feeding behaviour in which the odorant-binding proteins (OBPs) are believed to be involved in initial step in this system. In this study, we produced the R. pedestris adult antennae-expressed RpedOBP4 protein using a recombinant expression system in E. coli. Fluorescence competitive binding confirmed that RpedOBP4 has binding affinities to 7 of 20 soybean volatiles (ligands), and that a neutral condition is the best environment for it. The binding property of RpedOBP4 to these ligands was further revealed by integrating data from molecular docking, site-directed mutagenesis and ligand binding assays. This demonstrated that five amino acid residues (I30, L33, Y47, I57 and Y121) are involved in the binding process of RpedOBP4 to corresponding ligands. These findings will not only help us to more thoroughly explore the olfactory mechanism of R. pedestris during feeding on soybean, but also lead to the identification of key candidate targets for developing environmental and efficient behaviour inhibitors to prevent population expansion of R. pedestris in the future.

Silencing of an odorant binding protein (SaveOBP10) involved in the behavioural shift of the wheat aphid Sitobion avenae (Fabricius).

Insects are highly reliant on their active olfactory system in which odorant binding proteins play a role to selectivity and sensitivity during odour perception and processing. This study sets out to determine whether and to which extent the antennal loaded SaveOBP10 in English grain aphid Sitobion avenae, contributes in olfactory processing during host selection. To understand this possible relationship, we purified the SaveOBP10 recombinant protein and performed fluorescence ligand binding tests, molecular docking, RNA interference (RNAi) and behavioural trials. The results showed that SaveOBP10 had strong binding affinities (Ki ≤5 µM) with most of wheat plant volatiles at pH 5.0 as compared to pH 7.4. In Y-tube olfactometer bioassays, the S. avenae was attracted behaviourally towards pentadecane, butylated hydroxytoluene, tetradecane and ß-caryophyllene however repelled by naphthalene. After RNAi of SaveOBP10, the aphid showed nonattraction towards ß-caryophyllene and nonsignificant behavioural response to pentadecane, butylated hydroxytoluene and tetradecane. Furthermore, the three-dimensional structure modelling and molecular docking of SaveOBP10 were performed to the volatiles with high binding abilities. Together these findings indicate that SaveOBP10 can bind more strongly to the volatiles that involved in S. avenae behaviour regulation and possibly will contribute effectively in S. avenae integrated pest management.

Electroantennographic activity of 21 aliphatic compounds that bind well to a locust odorant-binding protein.

Odorants that bind well to odorant-binding proteins (OBPs) often trigger olfactory responses and have important biological significance. The locust Locusta migratoria (Meyen) (Orthoptera: Acrididae) is a serious agricultural pest. Twenty-one saturated aliphatic compounds with carbon-oxygen bonds and straight chains of 10-17 carbon atoms bind well to an L. migratoria OBP. In this study, olfactory activities of these aliphatic compounds on L. migratoria adult males were tested by electroantennography (EAG) and comparatively analyzed. Four alcohols (undecanol, dodecanol, tridecanol, and tetradecanol), two ketones (2-dodecanone and 2-tridecanone), and two esters (ethyl octanoate and ethyl nonanoate) triggered strong EAG responses, and there was no significant difference between them. The results suggest that the eight compounds are more likely to have important biological significance than the other compounds. Moreover, we found that there is not necessarily a positive correlation between the olfactory activity of odorants and their binding ability with OBP. The study contributes to understanding the odorants with biological significance for L. migratoria and the molecular mechanism of the locust's olfaction.

Morphological and odorant-binding protein 1 gene intron 1 sequence variations in Anopheles stephensi from Jaffna city in northern Sri Lanka.

Three Anopheles stephensi biotypes have historically been differentiated through variations in the mode numbers of egg ridges and adult spiracular indices. Anopheles stephensi odorant-binding protein 1 gene (AsteObp1) sequences in Iran and Afghanistan have been recently interpreted to suggest that the three biotypes are sibling species. AsteObp1 intron 1 sequences, mode numbers of egg ridges and spiracular indices of An. stephensi in Jaffna city in Sri Lanka were therefore investigated in field-collected mosquitoes and short-term laboratory colonies established from them. AsteObp1 intron 1 sequences revealed the region to be polymorphic with four unique sequences, ASJF1-4, present in both short-term laboratory colonies and field-collected An. stephensi. The spiracular index did not relate to the mode number of egg ridges in Jaffna An. stephensi. The results suggested that numbers of egg ridges, spiracular indices and AsteObp1 intron 1 sequences were not useful for differentiating An. stephensi biotypes in Jaffna. It is proposed that the observed differences between An. stephensi mosquitoes in Jaffna now result from normal population variance in the context of rapidly changing bionomics in India and northern Sri Lanka.

Identification and characterization of olfactory genes in the parasitoid wasp Diadegma semiclausum (Hellén) (Hymenoptera: Ichneumonidae).

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.

Combined transcriptomic, proteomic and genomic analysis identifies reproductive-related proteins and potential modulators of female behaviors in Spodoptera litura.

The common cutworm, Spodoptera litura, is a polyandrous moth with high reproductive ability. Sexual reproduction is a unique strategy for survival and reproduction of population in this species. However, to date available information about its reproductive genes is rare. Here, we combined transcriptomics, genomics and proteomics approaches to characterize reproductive-related proteins in S. litura. Illumina sequencing in parallel with the reference genome led to the yields of 12,161 reproductive genes, representing 47.83% of genes annotated in the genome. Further, 524 genes of 19 specific gene families annotated in the genome were detected in reproductive tissues of both sexes, some of which exhibited sex-biased and/or tissue-enriched expression. Of these, manual efforts together with the transcriptome analyses re-annotated 54 odorant binding proteins (OBPs) and 23 chemosensory proteins (CSPs) with an increase of 18 OBPs and one CSP compared to those previously annotated in the genome. Interestingly, at least 35 OBPs and 22 CSPs were transcribed in at least one reproductive tissue, suggestive of their involvement in reproduction. Further proteomic analysis revealed 2381 common proteins between virgin and mated female reproductive systems, 79 of which were differentially expressed. More importantly, 74 proteins exclusive to mated females were identified as transferred relatives, coupled with their specific or high expression in male reproductive systems. Of the transferred proteins, several conserved protein classes across insects were observed including OBPs, serpins, trypsins and juvenile hormone-binding proteins. Our current study has extensively surveyed reproductive genes in S. litura with an emphasis on the roles of OBPs and CSPs in reproduction, and identifies potentially transferred proteins serving as modulators of female post-mating behaviors.