Evolution of noctuid pheromone binding proteins: identification of PBP in the black cutworm moth, Agrotis ipsilon

CRISPR/Cas9: a cutting-edge solution for combatting the fall armyworm, Spodoptera frugiperda

The utilization of CRISPR/Cas9 in Spodoptera frugiperda, commonly known as fall armyworm, presents a groundbreaking avenue for pest management. With its ability to precisely modify the insect's genome, CRISPR/Cas9 offers innovative strategies to combat this destructive pest. The application of CRISPR/Cas9 in S. frugiperda holds immense potential. It enables the identification and functional analysis of key genes associated with its behavior, development, and insecticide resistance. This knowledge can unveil novel target sites for more effective and specific insecticides. Additionally, CRISPR/Cas9 can facilitate the development of population control methods by disrupting vital genes essential for survival. However, challenges such as off-target effects and the efficient delivery of CRISPR/Cas9 components remain. Addressing these obstacles is vital to ensure accurate and reliable results. Furthermore, ethical considerations, biosafety protocols, and regulatory frameworks must be integral to the adoption of this technology. Looking forward, CRISPR/Cas9-based gene drive systems hold the potential to promulgate desirable genetic traits within S. frugiperda populations, offering a sustainable and eco-friendly approach. This could curtail their reproductive capabilities or make them more susceptible to certain interventions. In conclusion, CRISPR/Cas9 presents a transformative platform for precise and targeted pest management in S. frugiperda. By deciphering the insect's genetic makeup and developing innovative strategies, we can mitigate the devastating impact of fall armyworm on agriculture while ensuring environmental sustainability.

AlepPBP2, but not AlepPBP3, may involve in the recognition of sex pheromones and maize volatiles in Athetis lepigone

Athetis lepigone Möschler (Lepidoptera, Noctuidae) is a common maize pest in Europe and Asia. However, there is no long-term effective management strategy is available yet to suppress its population. Adults rely heavily on olfactory cues to locate their optimal host plants and oviposition sites. Pheromone-binding proteins (PBPs) are believed to be responsible for recognizing and transporting different odorant molecules to interact with receptor membrane proteins. In this study, the ligand-binding specificities of two AlepPBPs (AlepPBP2 and AlepPBP3) for sex pheromone components and host plant (maize) volatiles were measured by fluorescence ligand-binding assay. The results demonstrated that AlepPBP2 had a high affinity with two pheromones [(Z)-7-dodecenyl acetate, Ki = 1.11 ± 0.1 μM, (Z)-9-tetradecenyl acetate, Ki = 1.32 ± 0.15 μM] and ten plant volatiles, including (-)-limonene, α-pinene, myrcene, linalool, benzaldehyde, nonanal, 2-hexanone, 3-hexanone, 2-heptanone and 6-methyl-5-hepten-2-one. In contrast, we found that none of these chemicals could bind to AlepPBP3. Our results clearly show no significant differences in the functional characterization of the binding properties between AlepPBP2 and AlepPBP3 to sex pheromones and host plant volatiles. Furthermore, molecular docking was employed for further detail on some crucial amino acid residues involved in the ligand-binding of AlepPBP2. These findings will provide valuable information about the potential protein binding sites necessary for protein-ligand interactions which appear as attractive targets for the development of novel technologies and management strategies for insect pests.

An Expanded Survey of the Moth PBP/GOBP Clade in Bombyx mori: New Insight into Expression and Functional Roles

We studied the expression profile and ontogeny (from the egg stage through the larval stages and pupal stages, to the elderly adult age) of four OBPs from the silkworm moth Bombyx mori. We first showed that male responsiveness to female sex pheromone in the silkworm moth B. mori does not depend on age variation; whereas the expression of BmorPBP1, BmorPBP2, BmorGOBP1, and BmorGOBP2 varies with age. The expression profile analysis revealed that the studied OBPs are expressed in non-olfactory tissues at different developmental stages. In addition, we tested the effect of insecticide exposure on the expression of the four OBPs studied. Exposure to a toxic macrolide insecticide endectocide molecule (abamectin) led to the modulated expression of all four genes in different tissues. The higher expression of OBPs was detected in metabolic tissues, such as the thorax, gut, and fat body. All these data strongly suggest some alternative functions for these proteins other than olfaction. Finally, we carried out ligand docking studies and reported that PBP1 and GOBP2 have the capacity of binding vitamin K1 and multiple different vitamins.

GOBP1 from the Variegated Cutworm Peridroma saucia (Hübner) (Lepidoptera: Noctuidae) Displays High Binding Affinities to the Behavioral Attractant (Z)-3-Hexenyl acetate

The variegated cutworm Peridroma saucia (Hübner) is a worldwide pest that causes serious damage to many crops. To recognize sex pheromones and host plant volatiles, insects depend on olfactory chemoreception involving general odorant-binding proteins (GOBPs). In this study, PsauGOBP1 was cloned from the adult antennae of P. saucia. RT-qPCR and Western-blot analysis showed that PsauGOBP1 was specifically and equally expressed in the adult antennae of both females and males. Fluorescence competitive-binding assays with sex pheromones and host plant volatiles demonstrated that PsauGOBP1 bound to six host plant volatiles: (Z)-3-hexenyl acetate (K_D = 4.0 ± 0.1 μM), citral (K_D = 5.6 ± 0.4 μM), farnesol (K_D = 6.4 ± 0.6 μM), nonanal (K_D = 6.8 ± 0.3 μM), (Z)-3-hexen-1-ol (K_D = 8.5 ± 0.6 μM), and benzaldehyde (K_D = 9.4 ± 0.5 μM). Electroantennogram recordings with the six host plant volatiles indicated that (Z)-3-hexenyl acetate elicited the strongest responses from both male and female antennae. Further bioassays using Y-tube olfactometers showed that (Z)-3-hexenyl acetate was attractive to adult P. saucia of both sexes. These results suggest that PsauGOBP1 might be involved in detecting host plant volatiles and that (Z)-3-hexenyl acetate might serve as a potential attractant for the biological control of P. saucia.

Chemosensory genes in the head of Spodoptera litura larvae

The tobacco cutworm Spodoptera litura (Lepidoptera: Noctuidae) is a polyphagous pest with a highly selective and sensitive chemosensory system involved in complex physiological behaviors such as searching for food sources, feeding, courtship, and oviposition. However, effective management strategies for controlling the insect pest populations under threshold levels are lacking. Therefore, there is an urgent need to formulate eco-friendly pest control strategies based on the disruption of the insect chemosensory system. In this study, we identified 158 putative chemosensory genes based on transcriptomic and genomic data for S. litura, including 45 odorant-binding proteins (OBPs, nine were new), 23 chemosensory proteins (CSPs), 60 odorant receptors (ORs, three were new), and 30 gustatory receptors (GRs, three were new), a number higher than those reported by previous transcriptome studies. Subsequently, we constructed phylogenetic trees based on these genes in moths and analyzed the dynamic expression of various genes in head capsules across larval instars using quantitative real-time polymerase chain reaction. Nine genes-SlitOBP8, SlitOBP9, SlitOBP25, SlitCSP1, SlitCSP7, SlitCSP18, SlitOR34, SlitGR240, and SlitGR242-were highly expressed in the heads of 3- to 5-day-old S. litura larvae. The genes differentially expressed in olfactory organs during larval development might play crucial roles in the chemosensory system of S. litura larvae. Our findings substantially expand the gene inventory for S. litura and present potential target genes for further studies on larval feeding in S. litura.

Interpopulational Variations of Odorant-Binding Protein Expression in the Black Cutworm Moth, Agrotis ipsilon

Simple Summary

Odorant-binding proteins (OBPs) are small soluble transporter proteins that are believed to play a key role in insect olfaction. However, there is an emerging set of data that shows a role in insecticide resistance for similar families of binding proteins. The black cutworm Agrotis ipsilon is a migrant species of moth known to feed on multiple types of crops (polyphagous) worldwide. It is therefore likely that the olfactory system of this species can be modulated to adapt to different environments. We compared gene expression between American and European continental populations of the moth. We found continental-specific expression of antennal binding protein X (ABPX) and general odorant-binding protein 2 (GOBP2), suggesting a function of these proteins in migration, environment recognition, crop change and adaptation that are required for a polyphagous species such as A. ipsilon.

Abstract

A long-range migrant species of moth (Agrotis ipsilon) has served as a model to compare the expression profiles of antennal proteins between different continental populations. Our results showed that the American and French populations of the black cutworm moth, A. ipsilon, expressed the same odorant-binding proteins (OBPs), but apparently in different levels. Electrophoretic analysis of antennal protein profiles and reverse transcription polymerase chain reaction using RNA as a template showed significant differences between the two populations in the expression of antennal binding protein-X (ABPX) and general odorant-binding protein-2 (GOBP2). However, the two A. ipsilon populations showed no differences in RNA levels coding for pheromone binding proteins (PBPs), suggesting that the expression of generalist OBPs is population-specific and could be affected by specific odor and/or chemical changes in external environmental conditions. To support the role of ABPX and GOBP2 with expression, the role of ABPX and GOBP2 is discussed in regard to odor detection, memorization and/or degradation of toxic chemical insecticides.

CRISPR/Cas9-mediated PBP1 and PBP3 mutagenesis induced significant reduction in electrophysiological response to sex pheromones in male Chilo suppressalis

Pheromone-binding proteins (PBPs) are thought to bind and transport sex pheromones onto the olfactory receptors on the dendrite membrane of olfactory neurons, and thus play a vital role in sex pheromone perception. However, the function of PBPs has rarely been demonstrated in vivo. In this study, two PBPs (PBP1 and PBP3) of Chilo suppressalis, one of the most notorious pyralid pests, were in vivo functionally characterized using insects with the PBP gene knocked out by the CRISPR/Cas9 system. First, through direct injection of PBP-single guide RNA (sgRNA)/Cas9 messenger RNA into newly laid eggs, a high rate of target-gene editing (checked with polled eggs) was induced at 24 h after injection, 21.3% for PBP1-sgRNA injected eggs and 19.5% for PBP3-sgRNA injected eggs. Second, by an in-crossing strategy, insects with mutant PBP1 or PBP3 (both with a premature stop codon) were screened, and homozygous mutants were obtained in the G3 generation. Third, the mutant insects were measured for electroantennogram (EAG) response to female sex pheromones. As a result, both PBP mutant males displayed significant reduction in EAG response, and this reduction in PBP1 mutants was higher than that in PBP3 mutants, indicating a more important role of PBP1. Finally, the relative importance of two PBPs and the possible off target effect induced by sgRNA-injection are discussed. Taken together, our study provides a deeper insight into the function of and interaction between different PBP genes in sex pheromone perception of C. suppressalis, as well as a valuable reference in methodology for gene functional study in other genes and other moth species.

Pheromone-binding proteins in the Asian gypsy moth females, Lymantria dispar, recognizing the sex pheromone and plant volatiles

Lepidopterans are known to have different pheromone-binding proteins with differential expression patterns that facilitate specific signal transduction of semiochemicals. Two PBPs of the Asian gypsy moth, Lymantria dispar, were reported to express in both females and males, but their physiological functions were unknown. Results showed that LdisPBP1 and LdisPBP2 were expressed in the sensilla trichodea of males and the s. trichodea and s. basiconica of females. When LdisPBP1 gene was targeted by RNA interference (RNAi) in males, the expression of LdisPBP1 and LdisPBP2 decreased by 69 and 76%, respectively, and when LdisPBP2 gene was targeted by RNAi, they decreased by 60 and 42%, respectively. In females, after treatment with LdisPBP1 dsRNA, LdisPBP1 and LdisPBP2 levels were reduced by 26 and 69%, respectively, and LdisPBP2 dsRNA reduced the relative expression of them by 4 and 62%, respectively. The expression of LdisPBP1 and LdisPBP2 was interdependent. Electroantennogram (EAG) recordings showed that LdisPBPs participate in the recognition of the sex pheromone in males, and the sex pheromone and plant volatiles in females. The function of LdisPBPs represents the sex-specific roles.

Identification of Chemosensory Genes Based on the Transcriptomic Analysis of Six Different Chemosensory Organs in Spodoptera exigua

Insects have a complex chemosensory system that accurately perceives external chemicals and plays a pivotal role in many insect life activities. Thus, the study of the chemosensory mechanism has become an important research topic in entomology. Spodoptera exigua Hübner (Lepidoptera: Noctuidae) is a major agricultural polyphagous pest that causes significant agricultural economic losses worldwide. However, except for a few genes that have been discovered, its olfactory and gustatory mechanisms remain uncertain. In the present study, we acquired 144,479 unigenes of S. exigua by assembling 65.81 giga base reads from 6 chemosensory organs (female and male antennae, female and male proboscises, and female and male labial palps), and identified many differentially expressed genes in the gustatory and olfactory organs. Analysis of the transcriptome data obtained 159 putative chemosensory genes, including 24 odorant binding proteins (OBPs; 3 were new), 19 chemosensory proteins (4 were new), 64 odorant receptors (57 were new), 22 ionotropic receptors (16 were new), and 30 new gustatory receptors. Phylogenetic analyses of all genes and SexiGRs expression patterns using quantitative real-time polymerase chain reactions were investigated. Our results found that several of these genes had differential expression features in the olfactory organs compared to the gustatory organs that might play crucial roles in the chemosensory system of S. exigua, and could be utilized as targets for future functional studies to assist in the interpretation of the molecular mechanism of the system. They could also be used for developing novel behavioral disturbance agents to control the population of the moths in the future.

Conservation and lineage-specific rearrangements in the GOBP/PBP gene complex of distantly related ditrysian Lepidoptera

General odorant binding proteins (GOBPs) and pheromone binding proteins (PBPs) form a monophyletic subfamily of insect odorant binding proteins (OBPs) specific for Lepidoptera, butterflies and moths. The GOBP/PBP genes include six subgroups (GOBP1–2, PBP-A–D) previously reported to form a complex arrayed in a conserved order in representative moths (superfamily Bombycoidea) and butterflies (Nymphalidae). Although our knowledge of lepidopteran genomes has increased greatly recently, the structure of the GOBP/PBP complex has been studied only for species that represent limited lineages of the highly diverged Ditrysia. To understand the evolution of this functionally important gene complex, we determined 69–149 kb genomic sequences that include GOBP2 and five PBP genes in three Ostrinia moths (Pyraloidea), O. nubilalis, O. furnacalis, and O. latipennis, using bacterial artificial chromosome (BAC) and fosmid clones. The structure of the GOBP2/PBP gene cluster was well conserved despite the different sex pheromone composition utilized by the three moths. Five expressed PBP genes in Ostrinia moths were the result of two duplications of PBP-A genes. Surprisingly, an allele containing a fusion gene between tandemly arrayed PBP-A genes was observed in O. nubilalis. We also revealed duplication and intra-chromosomal translocation of the GOBP1 gene in P. xylostella by fluorescence in situ hybridization (FISH) analysis. Additionally, we compared the structure of the GOBP/PBP gene complex of seventeen species covering six superfamilies and twelve families of the lepidopteran clade, Ditrysia, and found the gene order was basically conserved despite the frequent occurrence of lineage-specific gains, losses, inversions and translocations of these genes, compared with their neighboring genes. Our findings support the hypothesis that the structure of the GOBP/PBP gene complex was already established in the common ancestor of Ditrysia.

The developmental transcriptome of the bamboo snout beetle Cyrtotrachelus buqueti and insights into candidate pheromone-binding proteins

Cyrtotrachelus buqueti is an extremely harmful bamboo borer, and the larvae of this pest attack clumping bamboo shoots. Pheromone-binding proteins (PBPs) play an important role in identifying insect sex pheromones, but the C. buqueti genome is not readily available for PBP analysis. Developmental transcriptomes of eggs, larvae from the first instar to the prepupal stage, pupae, and adults (females and males) from emergence to mating were built by RNA sequencing (RNA-Seq) in the present study to establish a sequence background of C. buqueti to help understand PBPs. Approximately 164.8 million clean reads were obtained and annotated into 108,854 transcripts. These were assembled into 24,338, 21,597, 24,798, 21,886, 24,642, and 83,115 unigenes for eggs, larvae, pupae, females, males, and the combined datasets, respectively. Unigenes were annotated against NCBI non-redundant protein sequences, NCBI non-redundant nucleotide sequences, Gene Ontology (GO), Protein family, Clusters of Orthologous Groups of Proteins/ Clusters of Eukaryotic Orthologous Groups (KOG), Swiss-Prot, and KEGG Orthology databases. A total of 17,213 unigenes were annotated into 55 sub-categories belonging to three main GO categories; 10,672 unigenes were classified into 26 functional categories by KOG classification, and 8,063 unigenes were classified into five functional KEGG categories. RSEM software for RNA sequencing showed that 4,816, 3,176, 3,661, 2,898, 4,316, 8,019, 7,273, 5,922, 5,844, and 4,570 genes were differentially expressed between larvae and males, larvae and eggs, larvae and pupae, larvae and females, males and females, males and eggs, males and pupae, females and eggs, females and pupae, and eggs and pupae, respectively. Of these, three were confirmed to be significantly differentially expressed between larvae, females, and males. Furthermore, PBP Cbuq7577_g1 was highly expressed in the antenna of males. A comprehensive sequence resource of a desirable quality was constructed from developmental transcriptomes of C. buqueti eggs, larvae, pupae, and adults. This work enriches the genomic data of C. buqueti, and facilitates our understanding of its metamorphosis, development, and response to environmental change. The identified candidate PBP Cbuq7577_g1 might play a crucial role in identifying sex pheromones, and could be used as a targeted gene to control C. buqueti numbers by disrupting sex pheromone communication.

Molecular characterization and functional analysis of pheromone binding protein 1 from Cydia pomonella (L.)

A full-length cDNA encoding Cydia pomonella pheromone binding protein 1 (CpomPBP1) was cloned and characterized. CpomPBP1, possessing the typical characteristics of lepidopteran odorant binding proteins, was detected to be specifically expressed in the antennae of male and female moths at the mRNA and protein level. Soluble recombinant CpomPBP1 was subjected to in vitro binding to analyse its binding properties and to search for potentially active semiochemicals. A competitive binding assay showed that three 12-carbon ligands, codlemone, 1-dodecanol and E,E-2,4-dodecadienal, were able to bind to CpomPBP1 in decreasing order of affinity. Moreover, unlike the wild-type CpomPBP1, the C-terminus truncated CpomPBP1 exhibited high affinity to ligands even in an acidic environment, suggesting that the C-terminus plays a role in preventing ligands from binding to CpomPBP1 in a lower pH environment.

Functional characterization of a pheromone-binding protein from rice leaffolder Cnaphalocrocis medinalis in detecting pheromones and host plant volatiles

Pheromone-binding proteins (PBPs) are believed to be involved in the recognition of semiochemicals. In the present study, western blot analysis, fluorescence-binding characteristics and immunolocalization of CmedPBP4 from the rice leaffolder, Cnaphalocrocis medinalis, were investigated. Western blot analysis revealed that CmedPBP4 showed obvious antenna-specific expression patterns in female and male antenna, and made a clearly different sex-biased expression. Immunocytochemical labeling revealed that CmedPBP4 showed specific expression in the trichoid sensilla. Competitive fluorescence binding assays indicated that CmedPBP4 could selectively recognize three sex pheromone components (Z13-18:Ac, Z11-16:Al and Z13-18:OH) and eleven rice plant volatiles, including cyclohexanol, nerolidol, cedrol, dodecanal, ionone, (-)-α-cedrene, (Z)-farnesene, β-myrcene, R-(+)-limonene, (-)-limonene, and (+)-3-carene. Meanwhile the CmedPBP4 detection of sex pheromones and host odorants was pH-dependent. Our results, for the first time, provide further evidence that trichoid sensilla might be play an important role in detecting sex pheromones and host plant volatiles in the C. medinalis moth. Our systematic studies provided further detailed evidence for the function of trichoid sensilla in insect semiochemical perception.

Molecular Characterization and Sex Distribution of Chemosensory Receptor Gene Family Based on Transcriptome Analysis of Scaeva pyrastri

Chemosensory receptors play key roles in insect behavior. Thus, genes encoding these receptors have great potential for use in integrated pest management. The hover fly Scaeva pyrastri (L.) is an important pollinating insect and a natural enemy of aphids, mainly distributed in the Palearctic and Nearctic regions. However, a systematic identification of their chemosensory receptor genes in the antennae has not been reported. In the present study, we assembled the antennal transcriptome of S. pyrastri by using Illumina sequencing technology. Analysis of the transcriptome data identified 60 candidate chemosensory genes, including 38 for odorant receptors (ORs), 16 for ionotropic receptors (IRs), and 6 for gustatory receptors (GRs). The numbers are similar to those of other Diptera species, suggesting that we were able to successfully identify S. pyrastri chemosensory genes. We analyzed the expression patterns of all genes by using reverse transcriptase PCR (RT-PCR), and found that some genes exhibited sex-biased or sex-specific expression. These candidate chemosensory genes and their tissue expression profiles provide information for further studies aimed at fully understanding the molecular basis behind chemoreception-related behaviors in S. pyrastri.

Identification and characterisation of two general odourant-binding proteins from the litchi fruit borer, Conopomorpha sinensis Bradley

BACKGROUND

The litchi fruit borer, Conopomorpha sinensis Bradley, is one of the most destructive pests of litchi and longan fruits in south-east Asia and southern China, yet the molecular biology and physiology of this pest remain poorly understood. Control of this insect pest may be achieved by interfering with its recognition of host plants.

RESULTS

In this study, two cDNAs encoding CsGOBP1 and CsGOBP2 were identified from the antennae of C. sinensis, and a comparative study on these two C. sinensis GOBPs (CsGOBPs) was conducted. The secondary structure of these two CsGOBPs mainly consists of six α-helices, but three-dimensional structural predictions of CsGOBP1 and CsGOBP2 indicated significant difference in the final 3D models. Results in real-time PCR assays indicated that the two CsGOBPs had different tissue- and sex-dependent expression patterns. A competitive binding assay revealed that CsGOBP1 considerably prefer the component exhibited in Guiwei or Feizixiao litchi cultivar, while CsGOBP2 bind to general volatile components from nine litchi cultivars. Additionally, ethyl acetate has higher binding affinities to CsGOBP2 protein than to CsGOBP1, and has remarkable attraction to female C. sinensis moths in Y-tube olfactometer assays.

CONCLUSION

These results strongly suggest functional difference between these two CsGOBPs in perception of host plant odourants.

Pheromone Autodetection: Evidence and Implications

Olfactory communication research with insects utilizing sex pheromones has focused on the effects of pheromones on signal receivers. Early pheromone detection studies using the silkworm moth, Bombyx mori L., and Saturniids led to the assumption that emitters, especially females, are unable to detect their own pheromone. Pheromone anosmia, i.e., the inability of females to detect their conspecific sex pheromone, was often assumed, and initially little attention was paid to female behaviors that may result from autodetection, i.e., the ability of females to detect their sex pheromone. Detection of conspecific pheromone plumes from nearby females may provide information to improve chances of mating success and progeny survival. Since the first documented example in 1972, numerous occurrences of autodetection have been observed and verified in field and laboratory studies. We summarize here a significant portion of research relating to autodetection. Electrophysiological and behavioral investigations, as well as expression patterns of proteins involved in pheromone autodetection are included. We discuss problems inherent in defining a boundary between sex and aggregation pheromones considering the occurrence of autodetection, and summarize hypothesized selection pressures favoring autodetection. Importance of including autodetection studies in future work is emphasized by complications arising from a lack of knowledge combined with expanding the use of pheromones in agriculture.

Candidate chemosensory genes identified in Colaphellus bowringi by antennal transcriptome analysis

BACKGROUND

Since chemosensory genes play key roles in insect behaviour, they can potentially be used as new targets for pest control. The cabbage beetle, Colaphellus bowringi, is a serious insect pest of cruciferous vegetables in China and other Asian countries. However, a systematic identification of the chemosensory genes expressed in the antennae has not been reported.

RESULTS

We assembled the antennal transcriptome of C. bowringi by using Illumina sequencing technology and identified 104 candidate chemosensory genes by analyzing transcriptomic data, which included transcripts encoding 26 odorant-binding proteins (OBPs), 12 chemosensory proteins (CSPs), four sensory neuron membrane proteins (SNMPs), 43 odorant receptors (ORs), nine ionotropic receptors (IRs), and ten gustatory receptors (GRs). The data obtained are similar to those found in other coleopteran species, suggesting that our approach successfully identified the chemosensory genes of C. bowringi. The expression patterns of 43 OR genes, some of which were predominately found in the antenna or associated with sex-biased expression, were analyzed using quantitative real time RT-PCR (qPCR).

CONCLUSIONS

Our study revealed that a large number of chemosensory genes are expressed in C. bowringi. These candidate chemosensory genes and their expression profiles in various tissues provide further information on understanding their function in C. bowringi as well as other insects, and identifying potential targets to disrupt the odorant system in C. bowringi so that new methods for pest management can be developed.

Field Evaluation of Agrotis ipsilon (Lepidoptera: Noctuidae) Pheromone Blends and Their Application to Monitoring Moth Populations in China

The attractiveness of a series of mixtures of (Z)-7-dodecenyl acetate (Z7-12:Ac), (Z)-9-tetradecenyl acetate (Z9-14:Ac), and (Z)-11-hexadecenyl acetate (Z11-16:Ac), the Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) pheromone, were evaluated in four locations in China. The ternary blend of Z7-12:Ac, Z9-14:Ac, and Z11-16:Ac was the complete pheromone blend for A. ipsilon and the ratio of Z7-12:Ac and Z9-14:Ac was optimal at 3:1. The most attractive ratio of Z11-16:Ac to the other components depended on geographic location. The optimal ratio was 3:1:6 in Yunnan and Shanxi, 3:1:2 in Sichuan and ranged from 3:1:2 to 3:1:12 in Shanghai, which differs significantly from the ratio of 3:1:16 in Japan. The dose of the blend in the pheromone lure influenced attractiveness to male moths and was related to the temperature in the test locations. Attractiveness of sugar-acetic acid-baited and pheromone-baited traps to male and female moths was different before and after the start of flowering of the oilseed rape crop; large numbers of female moths were attracted to sugar-acetic acid traps before flowering but none after flowering had started. This was similar for male moths and there was no synergistic effect when sugar-acetic acid solutions and pheromone were used together. These studies suggest that pheromone trapping based on the blends of three components can be an effective tool to improve the efficiency of monitoring of this pest in China.

Two subclasses of odorant-binding proteins in Spodoptera exigua display structural conservation and functional divergence

Although many studies on lepidopteran pheromone-binding proteins (PBPs)/ general odorant-binding proteins (GOBPs) have been reported, the functional differentiation within and between the two odorant-binding protein (OBP) subclasses is still elusive. Here we conducted a comparative study on three SexiPBPs and two SexiGOBPs in Spodoptera exigua. Results showed that all five SexiPBP/GOBP genes have the same intron numbers and conserved exon/intron splice sites. Reverse transcription PCR results showed that these five SexiPBP/GOBPs were primarily expressed in antennae of both sexes and some were also detected in other tissues. Further, quantitative real-time PCR showed that five SexiPBP/GOBPs had different sex-biased expression patterns, with PBP1 being highly male-biased (5.96-fold difference) and PBP3 slightly female-biased (2.43-fold difference), while PBP2 and two GOBPs were approximately sex-equivalent (the absolute value<1.90-fold difference). Binding assays showed that all three SexiPBPs could bind all six sex pheromone components, but SexiPBP1 had much higher affinities [dissociation constant (Ki ) <1.10 μM] than did the other two SexiPBPs (Ki  >1.20 μM). Very intriguingly, SexiGOBP2 displayed even stronger binding to five sex pheromone components (Ki  <0.40 μM) than SexiPBP1. In contrast, SexiGOBP1 only exhibited weak binding to three alcohol-pheromone components. Similar results were obtained for tested pheromone analogues. In addition, each of SexiPBP/GOBPs selectively bound some plant odorants with considerable affinities (Ki  <10.0 μM). Taken together, of the three SexiPBPs, SexiPBP1 may play the most important role in female sex pheromone reception, and additionally all three SexiPBPs can detect some plant odorants, while SexiGOBP2 may be involved in the detection of female sex pheromones in addition to plant odorants. The results strongly suggest functional differentiation within and between the two OBP sub-classes.

Different roles suggested by sex-biased expression and pheromone binding affinity among three pheromone binding proteins in the pink rice borer, Sesamia inferens (Walker) (Lepidoptera: Noctuidae)

Pheromone binding proteins (PBPs) are thought to bind and transport hydrophobic sex pheromone molecules across the aqueous sensillar lymph to specific pheromone receptors on the dendritic membrane of olfactory neurons. A maximum of 3 PBP genes have been consistently identified in noctuid species, and each of them shares high identity with its counterparts in other species within the family. The functionality differences of the 3 proteins are poorly understood. In the present study, 3 PBP cDNAs (SinfPBP1, 2, 3) were identified from the pink rice borer, Sesamia inferens, for the first time. The quantitative real-time PCR indicated that the 3 PBPs displayed similar temporal but very different sex related expression profiles. Expression of SinfPBP1 and SinfPBP2 were highly and moderately male biased, respectively, while SinfPBP3 was slightly female biased, as SinfPBPs were expressed at very different levels (PBP1>PBP2≫PBP3) in male antennae, but at similar levels in female antennae. Furthermore, the 3 SinfPBPs displayed different ligand binding profiles in fluorescence competitive binding assays. SinfPBP1 exhibited high and similar binding affinities to all 3 sex pheromone components (Ki=0.72-1.60 μM), while SinfPBP2 showed selective binding to the alcohol and aldehyde components (Ki=0.78-1.71 μM), and SinfPBP3 showed no obvious binding to the 3 sex pheromone components. The results suggest that SinfPBP1 plays a major role in the reception of female sex pheromones in S. inferens, while SinfPBP3 plays a least role (if any) and SinfPBP2 functions as a recognizer of alcohol and aldehyde components.

Molecular characterization, expression pattern, and ligand-binding property of three odorant binding protein genes from Dendrolimus tabulaeformis

Odorant binding proteins (OBPs) play important roles in insect olfactory processes. The Chinese pine caterpillar moth, Dendrolimus tabulaeformis (Lepidoptera, Lasiocampidae) is a serious economic pest in China, and the pheromones of this species have been identified to monitor their presence. However, the molecular mechanisms by which D. tabulaeformis perceive pheromones and host volatiles remain unknown. In this study, we identified and characterized three new OBPs, including one pheromone binding protein (PBP1) and two general odor binding proteins (GOBPs), from antennal cDNA of D. tabulaeformis. The deduced amino acid sequences of DtabPBP1, DtabGOBP1, and DtabGOBP2 revealed mature proteins of 140, 147, and 140 amino acids, respectively. Each has six cysteine residues in conserved positions relative to other known OBPs. Amino-acid alignments indicated that the two GOBPs are more conserved (DtabGOBP1 is 52.9–67.4 % identical to orthologs from other Lepidoptera, and DtabGOBP2 is 55.2–81.8 % identical) than the PBP (32.5–46.0 %). Real-time PCR indicated tissue- and sex-specific expression patterns of the three genes. DtabPBP1 was mainly expressed in the antennae of males, whereas female antennae had only 1.09 % the expression in male antennae. Both DtabGOBP1 and DtabGOBP2 were more highly expressed in antennae than in other tissues, while DtabGOBP1 was more abundant in male antennae and DtabGOBP2 in female antennae. In addition, the binding specificities of the three proteins were investigated, and all three OBPs exhibited high binding affinities for the pheromone component (5Z,7E)-5,7-dodecadien-1-yl propionate (Z5,E7-12:OPr). This suggests a role in binding pheromone for GOBPs, as well as PBP1, in D. tabulaeformis.

Differential expression patterns in chemosensory and non-chemosensory tissues of putative chemosensory genes identified by transcriptome analysis of insect pest the purple stem borer Sesamia inferens (Walker)

Background

A large number of insect chemosensory genes from different gene subfamilies have been identified and annotated, but their functional diversity and complexity are largely unknown. A systemic examination of expression patterns in chemosensory organs could provide important information.

Methodology/Principal Findings

We identified 92 putative chemosensory genes by analysing the transcriptome of the antennae and female sex pheromone gland of the purple stem borer Sesamia inferens, among them 87 are novel in this species, including 24 transcripts encoding for odorant binding proteins (OBPs), 24 for chemosensory proteins (CSPs), 2 for sensory neuron membrane proteins (SNMPs), 39 for odorant receptors (ORs) and 3 for ionotropic receptors (IRs). The transcriptome analyses were validated and quantified with a detailed global expression profiling by Reverse Transcription-PCR for all 92 transcripts and by Quantitative Real Time RT-PCR for selected 16 ones. Among the chemosensory gene subfamilies, CSP transcripts are most widely and evenly expressed in different tissues and stages, OBP transcripts showed a clear antenna bias and most of OR transcripts are only detected in adult antennae. Our results also revealed that some OR transcripts, such as the transcripts of SNMP2 and 2 IRs were expressed in non-chemosensory tissues, and some CSP transcripts were antenna-biased expression. Furthermore, no chemosensory transcript is specific to female sex pheromone gland and very few are found in the heads.

Conclusion

Our study revealed that there are a large number of chemosensory genes expressed in S. inferens, and some of them displayed unusual expression profile in non-chemosensory tissues. The identification of a large set of putative chemosensory genes of each subfamily from a single insect species, together with their different expression profiles provide further information in understanding the functions of these chemosensory genes in S. inferens as well as other insects.

Identification and tissue distribution of odorant binding protein genes in the beet armyworm, Spodoptera exigua

Odorant binding proteins (OBPs) contribute to the remarkable sensitivity of the insect's olfactory system and play an important role in insect chemical communication. In this study, we identified 11 putative cDNAs encoding OBPs (namely SexiOBP1-11) from the antennal full length cDNA library of the beet armyworm Spodoptera exigua (Lepidoptera: Noctuidae) and examined their expression profiles in different adult body tissues (antennae, heads, thoraxes, abdomens, legs and wings) by real-time quantitative PCR (qPCR). All SexiOBPs had the characteristic typical features of the OBP family, with the exception of SexiOBP11, which lacked the predicted signal peptide sequence at the N-terminus. qPCR revealed that all of these genes were highly transcribed in the antennae. SexiOBP1-4 and SexiOBP10 were dominantly restricted to antennae. Within antennae, SexiOBP2-4 and SexiOBP10 exhibited female-biased expression patterns, while the expression of SexiOBP7 was male-biased, indicating that they might be involved in interacting with sex pheromones. In general, these OBPs were mainly expressed in chemosensory-specific tissues, although some displayed non-chemosensory or ubiquitous tissue expression. The data is helpful for further determining the potential physiological functions of S. exigua OBPs, and paves the way towards a better understanding of the chemosensory perception of this pest, which may help to uncover new targets for behavioral interference used as a control strategy.

Sex pheromone recognition and immunolocalization of three pheromone binding proteins in the black cutworm moth Agrotis ipsilon

Insect pheromone binding proteins (PBPs) are believed to solubilize and transport hydrophobic sex pheromones across sensillum lymph to membrane-associated pheromone receptors. To address the molecular mechanisms of PBPs in insect pheromone perception, we undertook a systemic study on the PBPs of the black cutworm Agrotis ipsilon at transcript as well as protein level from tissue distribution and cellular localization to pheromone binding affinity. We cloned three full-length PBP genes AipsPBP1-3 from A. ipsilon antennae, and demonstrated that AipsPBP1-3 transcripts were highly expressed in male antennae. The electron microscopic examinations revealed at least six types of olfactory sensilla on male and female antenna: trichodea, chaetica, basiconica, coeloconica, squamiformia and Böhm bristles. The immunocytochemistry results demonstrated that AipsPBP1-3 proteins were strongly expressed in the sensillum lymph of the trichoid sensilla of male moth. The binding assays showed that AipsPBP1 had high binding affinities with the major sex pheromone components Z7-12:Ac and Z9-14:Ac among five related chemicals and was clustered together with the long trichoid sensilla-expressing LdisPBPs of Lymantria dispar. AipsPBP2 showed high binding affinities also with Z11-16:Ac. AipsPBP3 displayed a high affinity only with Z11-16:Ac. Our studies provide further detail evidences for the involvement of moth PBPs in pheromone discrimination and selective recognition of specific components of the female sex pheromone blends.

Characterization of three pheromone-binding proteins (PBPs) of Helicoverpa armigera (Hübner) and their binding properties

Three pheromone-binding proteins of Helicoverpa armigera were cloned and expressed in Escherichia coli. In order to characterize their physiological properties, ligand-binding experiments were performed using five biologically relevant substances including sex pheromones and interspecific signals. The results showed that one of the pheromone-binding proteins, HarmPBP1, binds strongly to each of the two principal pheromone components of H. armigera, (Z)-11-tetradecenal and (Z)-9-hexadecenal, but not to the interspecific signal (Z)-9-tetracecenal. The two remaining pheromone-binding proteins, HarmPBP2 and HarmPBP3, showed only weak affinities with the ligands tested. The 3-D structure of HarmPBP1 was predicted and the docking experiments indicate that the key binding site of (Z)-9-hexadecenal to HarmPBP1 includes Thr112, Lys111, and Phe119 whereas that of (Z)-11-tetradecenal includes Ser9, Trp37, Phe36, and Phe119.

Identification and characterization of two general odorant binding protein genes from the oriental fruit moth, Grapholita molesta (busck)

Two novel general odorant-binding protein (GOBP) cDNAs (GmolGOBP1 and GmolGOBP2) were cloned and characterized from female antennal tissue of the oriental fruit moth, Grapholita molesta. We focused our investigation on this olfactory protein family by using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends-PCR (RACE-PCR). The full-length open reading frames of GmolGOBP1 and GmolGOBP2 were 492 and 483 nucleotides long, which encode 164 and 161 amino acid residue peptides, respectively. Protein signature analyses revealed that they each contained six conserved cysteines with an N-terminal signal sequence of 20 amino acids. The alignment of the two deduced protein sequences with other Lepidoptera GOBPs showed high sequence similarity (70-80%) with other full-length sequences from GenBank. Sequence similarity between the two GOBPs was only 48%, suggesting that the two proteins belong to different classes of lepidopteran GOBPs. RT-PCR analysis revealed that the two GOBP genes were expressed only in antennae of both sexes. Real-time PCR analysis further indicated that the transcript level of GmolGOBP1 was higher in males than in females, whereas the transcript level of GmolGOBP2 was higher in females than in males. Temporally, the two GOBP genes were expressed during the complete photoperiod (15L:9D). The highest transcript levels of GmolGOBP1 in both sexes and GmolGOBP2 in females were detected at the end of photophase and during scotophase. The expression of GmolGOBP2 in males remained at similar levels during the complete photoperiod. Based on these results, the possible physiological functions of GmolGOBPs are discussed.

Binding properties of pheromone-binding protein 1 from the common cutworm Spodoptera litura

Pheromone-binding proteins (PBPs) were formerly thought to act as passive pheromone carriers. However, recent studies, particularly in Drosophila melanogaster, suggest that PBPs are involved in the recognition of semiochemicals, thus making ligand-binding studies more meaningful. Previously, we cloned three PBPs from Spodoptera litura (Slit), and showed that SlitPBP1 is much more abundant than the other two, particularly in male antennae. To investigate the ligand specificity of SlitPBP1, we expressed the protein in a bacterial system and performed binding experiments with the three components of the specific sex pheromones (Z9-14:Ac, Z9,E11-14:Ac and Z9,E12-14:Ac), as well as with 26 volatile ligands. The results indicated that SlitPBP1 bound all three sex pheromone components with dissociation constants between 0.6 and 1.1 μM. The same protein also bound with comparable affinities several pheromone analogs, but not plant volatiles. The presence of a double bond was the most important element for a strong binding, while its position and configuration also affected the affinity. Finally, the binding of pheromone components is strongly affected by pH, showing a critical pH value corresponding to isoelectric point of the protein. This suggests that a pH-dependent conformational mechanism might exist in SlitPBP1 for pheromone binding and release.

Ultrastructural characterization of olfactory sensilla and immunolocalization of odorant binding and chemosensory proteins from an ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae)

The three-dimensional structures of two odorant binding proteins (OBPs) and one chemosensory protein (CSP) from a polyphagous ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) were resolved bioinformatically. The results show that both SguaOBP1 and OBP2 are classic OBPs, whereas SguaCSP1 belongs to non-classic CSPs which are considered as the “Plus-C” CSP in this report. The structural differences between the two OBPs and between OBP and CSP are thoroughly described, and the structural and functional significance of the divergent C-terminal regions (e.g., the prolonged C-terminal region in SguaOBP2 and the additional pair of cysteines in SguaCSP1) are discussed. The immunoblot analyses with antisera raised against recombinant SguaOBP1, OBP2, and CSP1, respectively, indicate that two SguaOBPs are specific to antennae, whereas SguaCSP1, which are more abundant than OBPs and detected in both male and female wasps, expresses ubiquitously across different tissues.

We also describe the ultrastructure of the antennal sensilla types in S. guani and compare them to 19 species of parasitic Hymenoptera. There are 11 types of sensilla in the flagellum and pedicel segments of antennae in both male and female wasps. Seven of them, including sensilla placodea (SP), long sensilla basiconica (LSB), sensilla coeloconica (SC), two types of double-walled wall pore sensilla (DWPS-I and DWPS-II), and two types of sensilla trichodea (ST-I and ST-II), are multiporous chemosensilla. The ultralsturctures of these sensilla are morphologically characterized. In comparison to monophagous specialists, the highly polyphagous generalist ectoparasitoids such as S. guani possess more diverse sensilla types which are likely related to their broad host ranges and complex life styles. Our immunocytochemistry study demonstrated that each of the seven sensilla immunoreacts with at least one antiserum against SguaOBP1, OBP2, and CSP1, respectively. Anti-OBP2 is specifically labeled in DWPS-II, whereas the anti-OBP1 shows a broad spectrum of immunoactivity toward four different sensilla (LSB, SP, ST-I and ST-II). On the other hand, anti-CSP1 is immunoactive toward SP, DWPS-I and SC. Interestingly, a cross co-localization pattern between SguaOBP1 and CSP1 is documented for the first time. Given that the numbers of OBPs and CSPs in many insect species greatly outnumber their antennal sensilla types, it is germane to suggest such phenomenon could be the rule rather than the exception.

Odorant-binding proteins in insects

Our understanding of the molecular and biochemical mechanisms that mediate chemoreception in insects has been greatly improved after the discovery of olfactory and taste receptor proteins. However, after 50 years of the discovery of first insect sex pheromone from the silkmoth Bombyx mori, it is still unclear how hydrophobic compounds reach the dendrites of sensory neurons in vivo across aqueous space and interact with the sensory receptors. The presence of soluble polypeptides in high concentration in the lymph of chemosensilla still poses unanswered questions. More than two decades after their discovery and despite the wealth of structural and biochemical information available, the physiological function of odorant-binding proteins (OBPs) is not well understood. Here, I review the structural properties of different subclasses of insect OBPs and their binding to pheromones and other small ligands. Finally, I discuss current ideas and models on the role of such proteins in insect chemoreception.

Large-scale identification of odorant-binding proteins and chemosensory proteins from expressed sequence tags in insects

Background

Insect odorant binding proteins (OBPs) and chemosensory proteins (CSPs) play an important role in chemical communication of insects. Gene discovery of these proteins is a time-consuming task. In recent years, expressed sequence tags (ESTs) of many insect species have accumulated, thus providing a useful resource for gene discovery.

Results

We have developed a computational pipeline to identify OBP and CSP genes from insect ESTs. In total, 752,841 insect ESTs were examined from 54 species covering eight Orders of Insecta. From these ESTs, 142 OBPs and 177 CSPs were identified, of which 117 OBPs and 129 CSPs are new. The complete open reading frames (ORFs) of 88 OBPs and 123 CSPs were obtained by electronic elongation. We randomly chose 26 OBPs from eight species of insects, and 21 CSPs from four species for RT-PCR validation. Twenty two OBPs and 16 CSPs were confirmed by RT-PCR, proving the efficiency and reliability of the algorithm. Together with all family members obtained from the NCBI (OBPs) or the UniProtKB (CSPs), 850 OBPs and 237 CSPs were analyzed for their structural characteristics and evolutionary relationship.

Conclusions

A large number of new OBPs and CSPs were found, providing the basis for deeper understanding of these proteins. In addition, the conserved motif and evolutionary analysis provide some new insights into the evolution of insect OBPs and CSPs. Motif pattern fine-tune the functions of OBPs and CSPs, leading to the minor difference in binding sex pheromone or plant volatiles in different insect Orders.

Molecular characterization and expression pattern of two general odorant binding proteins from the diamondback moth, Plutella xylostella

In the Lepidoptera, odorant signals are thought to be mediated by general odorant binding proteins (GOBPs) in the sensillar lymph surrounding the olfactory receptors. We describe the identification and characterization of two new cDNAs encoding GOBPs from the antennae of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), a species for which no GOBPs have been identified to date. We focused our investigation on this olfactory protein family by using reverse transcription-polymerase chain reaction strategies. The deduced amino acid sequences of PxylGOBP1 and PxylGOBP2 revealed open reading frames of 168 and 163 amino acids, respectively, with six cysteine residues in conserved positions relative to other known GOBPs. The alignment of the mature PxylGOBPs with other Lepidoptera GOBPs showed high sequence identity (70-80%) with other full-length sequences from GenBank. Sequence identity between PxylGOBP1and PxylGOBP2 was only 50%, suggesting that the two proteins belong to different classes of lepidopteran GOBPs. The expression patterns of the two PxylGOBP genes, with respect to tissue distribution and sex, were further investigated by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. Although the two GOBP genes were expressed only in the antennae of both sexes, reflecting the antennal specificity of GOBPs, the transcription levels of these genes depended on the sex, the age, the mating status, and the genes.

Molecular characterization and expression pattern of two pheromone-binding proteins from Spodoptera litura (Fabricius)

Pheromone perception is thought to be mediated by pheromone-binding proteins (PBPs) in the lymph surrounding the olfactory receptors. We cloned and characterized two PBP genes (SlitPBP1 and SlitPBP2) from the common cutworm, Spodoptera litura (F.; Lepidoptera: Noctuidae), which encode PBPs belonging to two different PBP groups. Western blot analysis of the crude antennal extracts with SexigPBP1 antibody revealed a single immunoreactive band (much stronger in male than in female) of approximately 16 kDa, in agreement with the calculated values for SlitPBPs. From genomic DNA, two introns and a similar exon/intron structural pattern were identified in each PBP genes, but the introns differed in length within and between PBP genes. The expression patterns of two SlitPBP genes, with respect to tissue distribution and sex, were further investigated by reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time PCR. Although the two PBP genes were expressed only in the antennae of both sexes, reflecting the antennal specificity of PBPs, the transcription levels of PBP genes differed between the sexes and the genes. The transcription levels of SlitPBP1 and SlitPBP2 in females were only 2.1% and 7.0%, respectively, relative to those in males, and the levels of PBP2 compared with PBP1 were 31.4% and 95.3% in males and females, respectively. These differential expression levels might suggest different roles played by the two SlitPBPs in the perception of sex pheromone both in males and females.

Identification and molecular cloning of putative odorant-binding proteins and chemosensory protein from the bethylid wasp, Scleroderma guani Xiao et Wu

Two putative odorant-binding proteins (OBPs) and one putative chemosensory protein (CSP) from females of the ant-like bethylid wasp, Scleroderma guani Xiao et Wu (Hymenoptera: Bethylidae), were identified and cloned. The putative OBPs and CSP were identified by nondenaturing polyacrylamide gel electrophoresis (native-PAGE). 3' rapid amplification of cDNA ends (3'RACE) was performed to obtain the sequences of the mature proteins by using degenerate primers designed from N-terminal sequences. Gene-specific primers for 5' rapid amplification of cDNA ends (5'RACE) were designed according to 3'RACE results and used in polymerase chain reaction (PCR) to obtain full-length sequences. The proteins (Sgua-OBP1, Sgua-OBP2, and Sgua-CSP1) encode 133, 142, and 129 amino acid-deduced sequences, respectively. Prediction of signal peptide sequences matches the N-terminal amino acid sequence of the isolated proteins. Database searches suggest that the Sgua-OBP1 and Sgua-OBP2 are homologs of OBPs from other insects, and Sgua-CSP1 shares a high level of identity with previously described CSPs.

Molecular characterization of two pheromone binding proteins and quantitative analysis of their expression in the beet armyworm, Spodoptera exigua Hübner

Pheromone binding proteins (PBP) play an important role in insect pheromone communication. However, the PBP for the beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae), an important agricultural pest worldwide, remains unaddressed. We report the cloning of two PBP genes, SexigPBP1 and SexigPBP2, from the antennal cDNA of S. exigua by reverse transcriptase-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends-PCR (RACE-PCR). The deduced PBP amino acid sequences are characteristic of the odorant binding protein (OBP) family, although the two PBPs are only 44% identical. From an analysis of the genomic DNA, two introns and a similar intron/extron structural pattern were identified in each of the two PBP genes. RT-PCR analysis revealed that the two PBP genes are only expressed in antennae. Real-time PCR further indicated that the expression of SexigPBP1 is much higher than that of SexigPBP2, regardless of sex. However, the female expression levels for SexigPBP1 and SexigPBP2 are about 39% and 73%, respectively, relative to male levels. Finally, phylogenetic analysis suggested that PBPs from the Noctuidae are divided into three distinct groups based on the primary sequences.

Candidate pheromone binding proteins of the silkmoth Bombyx mori

Pheromone reception is thought to be mediated by pheromone binding proteins (PBPs) in the aqueous lymph of the antennal sensilla. Recent studies have shown that the only known PBP of Bombyx mori (BmorPBP1) appears to be specifically tuned to bombykol but not to bombykal, raising the question of whether additional subtypes may exist. We have identified two novel genes, which encode candidate PBPs (BmorPBP2, BmorPBP3). Comparison with PBPs from various moth species have revealed a high degree of sequence identity and the three BmorPBP-subtypes can be assigned to distinct groups within the moth PBP family. In situ hybridization revealed that BmorPBP2 and BmorPBP3 are expressed only in relatively few cells compared to the number of cells expressing BmorPBP1. Double-labeling experiments have shown that the two novel BmorPBPs are expressed in the same cells but are not co-expressed with BmorPBP1. Furthermore, unlike BmorPBP1, cells expressing the newly identified PBPs did not surround neurons containing the BmOR-1 receptor. The results indicate that BmorPBP2 and BmorPBP3 are located in sensilla types, which are different from the long sensilla trichodea.

Molecular cloning and in Situ expression patterns of two new pheromone-binding proteins from the corn stemborer Sesamia nonagrioides

We describe the identification and characterization of two new cDNAs encoding pheromone-binding proteins (PBPs) from the male antennae of Sesamia nonagrioides, a species where no PBPs have been identified to date. Because PBPs are thought to participate in the first step of odor detection in a specific manner, we focused our investigation on this olfactory protein family using reverse transcription-polymerase chain reaction strategies. The deduced amino acid sequences of SnonPBP1 and SnonPBP2 revealed mature proteins of 142 and 143 amino acids, respectively, with six cysteine residues in conserved positions relative to other known PBPs. The alignment of the two mature S. nonagrioides PBPs with other noctuid PBPs showed high sequence identity (70-80%) with other full-length sequences from GenBank. Sequence identity between SnonPBP1 and SnonPBP2 was only 46%, suggesting that the two proteins belong to different classes of PBPs already described from the Noctuidae. Furthermore, analyses of expression patterns of SnonPBP1 and SnonPBP2 were performed by in situ hybridization on antennae of both sexes, and these studies revealed the expression of the two PBPs at the bases of olfactory sensilla (basiconica or trichodea) from both sexes. The possible binding properties of these two new PBPs are discussed according to their homologies with other known PBPs and S. nonagrioides pheromone components.

Molecular characterization and evolution of pheromone binding protein genes in Agrotis moths

Pheromone-binding proteins (PBPs) are soluble transporter proteins that increase the capture and the solubilization of pheromone molecules in the lymph surrounding the olfactory receptors. A polymerase chain reaction-based method was used to identify PBP genes in Agrotis species for an evolutionary genomic study of noctuid moth PBPs. From genomic DNA we determined the structure of different PBP genes in the two closely related species, Agrotis ipsilon and A. segetum. In all, we clearly identified four genes (Aips-1, Aips-2, Aseg-1 and Aseg-2) that represent two distinct PBP orthology groups. We found that the four genes have the same exon-intron structure and that they comprise three exons and two introns but differ in length mainly in the second intron. The three exons of Aseg-2 and Aips-2 have the same lengths but both intron 1 and intron 2 differ in length between the genes. In contrast, Aips-1 and Aseg-1 show dissimilarity only in the length of intron 2. Interestingly, introns 1 and 2 are inserted in the same positions in the Aips-1, Aips-2, Aseg-1 and Aseg-2 genes. These findings show that the Agrotis PBP genes have common ancestry and probably originate from gene duplication before the speciation of ipsilon and segetum. We found that expression of Aips-1/Aseg-1 and Aips-2/Aseg-2 is antennal-specific, but expression is not restricted to the male antennae.

Three-dimensional antennal lobe atlas of the male moth,Agrotis ipsilon: A tool to study structure-function correlation

The glomerular structure of the primary olfactory neuropil has long been thought to play an important role in odour coding. In insects, the number of glomeruli in the antennal lobe is limited in most species to fewer than 100 compared with more than 1,000 in vertebrates, making it possible to identify individual glomeruli. A complete three-dimensional atlas of the glomeruli within the antennal lobe of the male noctuid moth Agrotis ipsilon was constructed. All 66 glomeruli were singly identifiable in both antennal lobes of the three brains investigated. Further, six antennal lobes containing intracellularly stained projection neurones were reconstructed. By using the atlas, the respective target glomerulus of each projection neurone could be identified. The importance of the glomerular atlas as a tool to study central olfactory processing and its plasticity is discussed.