Analysis of Tea Geometrid (Ectropis grisescens) Pheromone Gland Extracts Using GC-EAD and GC×GC/TOFMS

Widespread presence of gut bacterium Glutamicibacter ectropisis sp. nov. confers enhanced resistance to the pesticide bifenthrin in tea pests

The gut microbiota in Lepidopterans demonstrates variability and susceptibility to environmental influences, thereby presenting opportunities for the acquisition of novel bacterial strains. Ectropis grisescens (Warren), a notorious Lepidopteran pest, causes substantial damage to tea crops. Prolonged application usage of bifenthrin for the management of this pest has led to increased resistance. This study aims to investigate the relationship between the gut microbiota, as shaped by long-term pesticide use and the resistance of E. grisescenes. We employed high-throughput sequencing of the 16S rRNA gene to analyze the gut microbiota compositions in bifenthrin-resistant (BIF-R) and bifenthrin-sensitive (BIF-S) strains. Bifenthrin-degrading strains were isolated from the gut of BIF-R using selective media. The degradation efficiency and products of bifenthrin by the key strain were detected using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The effect of the key strain on host resistance was verified in vivo. Finally, the distribution and abundance of the degrading bacterium, in conjunction with insect's pesticide resistance, were assessed in 22 distinct E. grisescens populations. Bifenthrin resistance was diminished in BIF-R following the removal of gut bacteria, a phenomenon not observed in BIF-S. Subsequent high-throughput amplicon sequencing revealed distinct structural differences in the gut microbiota between the two groups, notably an increased abundance of Glutamicibacter in BIF-R. A newly identified bacterial strain from BIF-R larvae, Glutamicibacter ectropisis (B1), demonstrated bifenthrin degradation efficiency and the main metabolite was 2,4-di-tert-butylphenol. Inoculation of B1 into BIF-S larvae conferred increased resistance to bifenthrin. Furthermore, we confirmed the prevalence of B1 in the gut of E. grisescens across 22 tea-growing areas in China. A positive correlation was observed between the absolute abundance of B1 and bifenthrin resistance in E. grisescens. This study represents the first identification of a novel gut bacterium, G. ectropisis, which mediates host resistance through the direct degradation of bifenthrin. This mechanism has been widely validated across 22 distinct populations.

The novel function of an orphan pheromone receptor reveals the sensory specializations of two potential distinct types of sex pheromones in noctuid moth

Sex pheromones play crucial role in mating behavior of moths, involving intricate recognition mechanisms. While insect chemical biology has extensively studied type I pheromones, type II pheromones remain largely unexplored. This study focused on Helicoverpa armigera, a representative species of noctuid moth, aiming to reassess its sex pheromone composition. Our research unveiled two previously unidentified candidate type II sex pheromones-3Z,6Z,9Z-21:H and 3Z,6Z,9Z-23:H-in H. armigera. Furthermore, we identified HarmOR11 as an orphan pheromone receptor of 3Z,6Z,9Z-21:H. Through AlphaFold2 structural prediction, molecular docking, and molecular dynamics simulations, we elucidated the structural basis and key residues governing the sensory nuances of both type I and type II pheromone receptors, particularly HarmOR11 and HarmOR13. This study not only reveals the presence and recognition of candidate type II pheromones in a noctuid moth, but also establishes a comprehensive structural framework for PRs, contributing to the understanding of connections between evolutionary adaptations and the emergence of new pheromone types.

Structure, Synthesis, and Bioassays of Sex Pheromone for Pyrausta machaeralis (Lepidoptera: Crambidae)

The leaf skeletonizer, Pyrausta machaeralis (Lepidoptera: Crambidae), is a serious insect pest of teak (Tectona grandis) in China. The application of insect pheromones is widely applied as an environmentally friendly technology for integrated pest management (IPM). In the present study, crude extracts of sex pheromone glands of calling P. machaeralis females were collected and then analyzed using gas chromatography/electroantennographic detection (GC/EAD) and gas chromatography-mass spectrometry (GC-MS). The combination of infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectrometry was used for structure identification. Afterward, their electrophysiological and behavioral activity was evaluated in the laboratory and field. Herein, we eventually determined two active components, E-11-tetradecenyl acetate (E11-14:Ac) and Z-11-tetradecenyl acetate (Z11-14:Ac), at a ratio of 96:4, as the sex pheromone of P. machaeralis. The identification of sex pheromones would facilitate the development of efficient strategies for monitoring and controlling the field populations of P. machaeralis.

Non-targeted metabolomics aids in sex pheromone identification: a proof-of-concept study with the triangulate cobweb spider, Steatoda triangulosa

Targeted metabolomics has been widely used in pheromone research but may miss pheromone components in study organisms that produce pheromones in trace amount and/or lack bio-detectors (e.g., antennae) to readily locate them in complex samples. Here, we used non-targeted metabolomics-together with high-performance liquid chromatography-mass spectrometry (HPLC-MS), gas chromatography-MS, and behavioral bioassays-to unravel the sex pheromone of the triangulate cobweb spider, Steatoda triangulosa. A ternary blend of three contact pheromone components [N-4-methylvaleroyl-O-isobutyroyl-L-serine (5), N-3-methylbutyryl-O-isobutyroyl-L-serine (11), and N-3-methylbutyryl-O-butyroyl-L-serine (12)] elicited courtship by S. triangulosa males as effectively as female web extract. Hydrolysis of 5, 11 and 12 at the ester bond gave rise to two mate-attractant pheromone components [butyric acid (7) and isobutyric acid (8)] which attracted S. triangulosa males as effectively as female webs. Pheromone components 11 and 12 are reported in spiders for the first time, and were discovered only through the use of non-targeted metabolomics and GC-MS. All compounds resemble pheromone components previously identified in widow spiders. Our study provides impetus to apply non-targeted metabolomics for pheromone research in a wide range of animal taxa.

Antennal transcriptomic analysis of carboxylesterases and glutathione S-transferases associated with odorant degradation in the tea gray geometrid, Ectropis grisescens (Lepidoptera, Geometridae)

Introduction: Carboxylesterases (CXEs) and glutathione S-transferases (GSTs) can terminate olfactory signals during chemosensation by rapid degradation of odorants in the vicinity of receptors. The tea grey geometrid, Ectropis grisescens (Lepidoptera, Geometridae), one of the most devastating insect herbivores of tea plants in China, relies heavily on plant volatiles to locate the host plants as well as the oviposition sites. However, CXEs and GSTs involved in signal termination and odorant clearance in E. grisescens remains unknown. Methods: In this study, identification and spatial expression profiles of CXEs and GSTs in this major tea pest were investigated by transcriptomics and qRT-PCR, respectively. Results: As a result, we identified 28 CXEs and 16 GSTs from female and male antennal transcriptomes. Phylogenetic analyses clustered these candidates into several clades, among which antennal CXEs, mitochondrial and cytosolic CXEs, and delta group GSTs contained genes commonly associated with odorants degradation. Spatial expression profiles showed that most CXEs (26) were expressed in antennae. In comparison, putative GSTs exhibited a diverse expression pattern across different tissues, with one GST expressed specifically in the male antennae. Disscussion: These combined results suggest that 12 CXEs (EgriCXE1, 2, 4, 6, 8, 18, 20-22, 24, 26, and 29) and 5 GSTs (EgriGST1 and EgriGST delta group) provide a major source of candidate genes for odorants degradation in E. grisescens.

Origin, structure and functional transition of sex pheromone components in a false widow spider

Female web-building spiders disseminate pheromone from their webs that attracts mate-seeking males and deposit contact pheromone on their webs that induces courtship by males upon arrival. The source of contact and mate attractant pheromone components, and the potential ability of females to adjust their web’s attractiveness, have remained elusive. Here, we report three new contact pheromone components produced by female false black widow spiders, Steatoda grossa: N-4-methylvaleroyl-O-butyroyl-L-serine, N-4-methylvaleroyl-O-isobutyroyl-L-serine and N-4-methylvaleroyl-O-hexanoyl-L-serine. The compounds originate from the posterior aggregate silk gland, induce courtship by males, and web pH-dependently hydrolyse at the carboxylic-ester bond, giving rise to three corresponding carboxylic acids that attract males. A carboxyl ester hydrolase (CEH) is present on webs and likely mediates the functional transition of contact sex pheromone components to the carboxylic acid mate attractant pheromone components. As CEH activity is pH-dependent, and female spiders can manipulate their silk’s pH, they might also actively adjust their webs’ attractiveness.

The Potential of Parapanteles hyposidrae and Protapanteles immunis (Hymenoptera: Braconidae) as Biocontrol Agents for the Tea Grey Geometrid Ectropis grisescens (Lepidoptera)

The tea grey geometrid Ectropis grisescens has long been a significant insect pest of tea plants in China. Two parasitoids, Parapanteles hyposidrae and Protapanteles immunis (Hymenoptera: Braconidae: Microgastrinae), are the most important parasitoids in the larval stage of E. grisescens. Yet, the potential of these two parasitoids for controlling the tea grey geometrid is not known. Here, we studied the parasitism performance of these two parasitoid species on different host densities under different temperatures as well as the interference effect of parasitoid density. The results showed that both parasitoid species, Pa. hyposidrae and Pr. immunis, exhibited a Type II functional response towards the tea grey geometrid E. grisescens at four tested temperatures. With increasing the density of E. grisescens larvae, the number of parasitized larvae increased until a maximum was reached. The highest number of hosts parasitized by Pa. hyposidrae or Pr. immunis reached 14.5 or 14.75 hosts d^-1 at 22 °C, respectively. The estimated values of instantaneous searching efficiency (a) and handling time (h) for Pa. hyposidrae or Pr. immunis were 1.420 or 3.621 and 0.04 or 0.053 at 22 °C, respectively. Pr. immunis performed better than Pa. hyposidrae under higher temperatures. The parasitism rate by a single female parasitoid decreased with increasing parasitoid density at different temperatures, resulting in a reduction of searching efficiency. The findings of this study showed that Pr.immunis could be a better effective biocontrol agent than Pa. hyposidrae against the tea grey geometrid.

Development and Evaluation of Sex Pheromone Mass Trapping Technology for Ectropis grisescens: A Potential Integrated Pest Management Strategy

Since the identification of the Ectropis grisescens sex pheromone, no effective control technology based on this pheromone has yet been developed and evaluated. In this study, pheromone proportion and dosage, sustained-release dispensers, and pheromone lure-matched traps were optimized. The mass trapping technology developed with the above optimized parameters was tested in a field trial. The results show that two compounds, (Z,Z,Z)-3,6,9-octadecatriene and (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene, at a ratio of 30:70 and impregnated into rubber septa at 1 mg, were the most attractive to male moths. These compounds provided the best performance when combined with a sticky wing trap. Adult male moth monitoring data showed that there was a lower population density in the trapping plot compared with the control plot, and there was a clear difference during the peak adult occurrence of the first five insect generations in 2017. The effect of mass trapping on the larva population was investigated in 2018; the control efficiency reached 49.27% after trapping of one generation of adults and was further reduced to 67.16% after two successive adult moth generations, compared with the control plot. The results of the present study provide a scientific basis for the establishment of sex pheromone-based integrated pest management strategies.

Transcriptomic Analysis Reveals Insect Hormone Biosynthesis Pathway Involved in Desynchronized Development Phenomenon in Hybridized Sibling Species of Tea Geometrids (Ectropis grisescens and Ectropis obliqua)

Ectropis grisescens and Ectropis obliqua are sibling species of tea-chewing pests. An investigation of the distribution of tea geometrids was implemented for enhancing controlling efficiency. E. grisescens is distributed across a wider range of tea-producing areas than Ectropis obliqua in China with sympatric distribution found in some areas. In order to explore reproductive isolation mechanisms in co-occurrence areas, hybridization experiments were carried out. Results showed they can mate but produce infertile hybrids. During experiments, the desynchronized development phenomenon was found in the hybridized generation of sibling tea geometrids. Furthermore, transcriptome analysis of those individuals of fast-growing and slow-growing morphs revealed that the insect hormone biosynthesis pathway was enriched in two unsynchronized development groups of hybrid offspring. More importantly, some genes regulating the synthesis of moulting hormone showed significantly up-regulated expression in fast-growing groups. Above all, metabolism of the juvenile hormone and synthesis of the ecdysone pathway were found to be crucially involved in the desynchronized development phenomenon. This research finding contributes to a better understanding of the mechanisms of insect development and reproductive isolation of two sibling species.

Comparison of male antennal morphology and sensilla physiology for sex pheromone olfactory sensing between sibling moth species: Ectropis grisescens and Ectropis obliqua (Geometridae)

Ectropis grisescens and Ectropis obliqua (Lepidoptera: Geometridae) are sibling pest species that co-occur on tea plants. The sex pheromone components of both species contain (Z,Z,Z)-3,6,9-octadecatriene and (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene. E. obliqua has (Z,Z)-3,9-cis-6,7-epoxy-nonadecadiene as an additional sex pheromone component, which ensures reproductive segregation between the two species. To ascertain the detection mechanism of olfactory organs for sex pheromone components of E. grisescens and E. obliqua, we applied scanning electron microscopy and single sensillum recording to compare antennal morphology and sensillum physiology in the two species. There was no apparent morphological difference between the antennae of the two species. Both species responded similarly to all three sex pheromone components, including, E. obliqua specific component. The distribution patterns of antennal sensilla trichodea differed between the two species. Sex pheromone olfactory sensing in these sibling species appears to be determined by the density of different types of olfactory sensing neurons. Dose-dependent responses of sensilla trichodea type 1 to (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene, the most abundant component, showed an "all or none" pattern and the other two components showed sigmoidal dose-response curves with a half threshold of 10^-4 (dilution equal to the concentration of 10 μg/μl). These results suggest that the major sex pheromone component functions as an on-off controller while secondary components function as modulators during olfactory transmission to the primary olfactory center.

Identification of Sex Pheromone of Miltochrista striata (Lepidoptera: Arctiidae)

A species of lichen moth, Miltochrista striata (Bremer & Grey, 1852), feeds on lichens in Chinese tea plantations (Camellia sinensis (L.) O. Kuntze (Ericales:Theaceae)). A previous sex attractant screening test showed that male moths of M. striata were attracted by a mixture of (Z,Z,Z)-3,6,9-octadecatriene (Z3,Z6,Z9-18:H), (Z,Z,Z)-3,6,9-nonadecatriene (Z3,Z6,Z9-19:H), and their monoepoxy derivatives. To determine which of the component is an effective sex attractant for M. striata, the sex pheromone glands of female moths were excised and extracted with n-hexane. By comparison with the retention time and mass spectra of synthetic chemicals, two compounds in the crude extracts were identified as Z3,Z6,Z9-18:H and (Z,Z)-3,6-cis-9,10-epoxy-octadecadiene (Z3,Z6,epo9-18:H) using gas chromatography-mass spectrometry. The results of electroantennographic tests showed that the electrophysiological activities of Z3,Z6,Z9-18:H and Z3,Z6,epo9-18:H were distinctly higher than those of (Z,Z)-6,9-cis-3,4-epoxy-octadecadiene, (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene, (Z,Z,Z)-3,6,9-nonadecatriene, (Z,Z)-6,9-cis-3,4-epoxy-nonadecatriene, (Z,Z)-3,9-cis-6,7-epoxy-nonadecatriene, and (Z,Z)-3,6-cis-9,10-epoxy-nonadecatriene. Field trapping showed that only a mixture of Z3,Z6,Z9-18:H and Z3,Z6,epo9-18:H attracted male moths, and the optimal mixture of these compounds was the ratio of 4:6 at 1.0-mg dosage. The results represent the first determination of the sex pheromone of a lichen moth in a tea plantation and provide a scientific basis to develop an effective protocol using sex pheromone to monitor populations of M. striata.

Physicochemical Basis and Comparison of Two Type II Sex Pheromone Components Binding with Pheromone-Binding Protein 2 from Tea Geometrid, Ectropis obliqua

Lepidopteran geometrid moth can produce complex Type II sex pheromone components to attract males and trigger mating behavior. Although several sex pheromone components have been identified, it remains unclear whether their physicochemical roles in sex pheromone sensing are the same. Therefore, we utilized tea geometrid ( Ectropis obliqua) as an example model to investigate and compare the physicochemical basis of two key Type II sex pheromone components, cis-6,7-epoxy-(3Z,9Z)-3,9-octadecadiene ( Z3 Z9-6,7-epo-18:Hy) and ( Z, Z, Z)-3,6,9-octadecatriene (Z3Z6Z9-18:Hy), interacting with pheromone-binding protein 2 ( EoblPBP2) from E. obliqua. Multispectral, thermodynamic, docking, and site-directed mutagenesis indicated that the major sex pheromone component Z3Z9-6,7-epo-18:Hy is more susceptible to pH-tuned than the minor component Z3Z6Z9-18:Hy, whereas Z3Z6Z9-18:Hy seems to be more susceptible to temperature and amino acid mutations than Z3Z9-6,7-epo-18:Hy. Our study suggests that different components of Type II sex pheromone play different binding characters under specific conditions in the physicochemical behavior. This deeply supplements the theoretical knowledge of Type II pheromones involved in the recognition and discrimination in the Lepidopteran sex pheromones family.

Comparison of Olfactory Genes in Two Ectropis Species: Emphasis on Candidates Involved in the Detection of Type-II Sex Pheromones

The sibling species Ectropis grisescens and E. obliqua are the major chewing tea pests in China. A difference in sex pheromone components plays a central role in premating isolation in these two species. To investigate the mechanism of premating isolation in these two Ectropis species, we sequenced the transcriptomes of the antennae of female and male E. obliqua individuals and performed phylogenetic analyses, abundance analyses, and tissue expression profile analyses to compare the olfactory genes involved in the detection of sex pheromones. A total of 36 odorant-binding proteins (OBPs) and 52 olfactory receptors (ORs) were identified in E. obliqua. Phylogenetic analyses showed that EoblOBP2, 3, and 25 were grouped in the pheromone-binding protein clade with EgriOBP2, 3, 25, and another lepidopteran PBP. EoblOR25 and 28 were grouped with EgriOR25, 28, and pheromone receptors for the detection of Type-I sex pheromone components. EoblOR24, 31, 37, and 44 were grouped with EgriOR24, 31, 37, and 44. All of these 4 EoblORs and 4 EgriORs showed higher abundance in male antennae than in female ones. Therefore, OBP2, 3, 25 and OR24, 31, 37, 44 of E. grisescens and E. obliqua might be responsible for sex pheromone component detection. However, the sequences of these genes in E. grisescens and E. obliqua were more than 90% identical. This indicates that these orthologous genes might play similar roles in the detection of sex pheromones. In contrast, the observed OBPs and ORs differed in abundance between the antennae of the two Ectropis species. Therefore, we speculate that these two Ectropis species use the different transcript levels of PRs to differentiate sex pheromone components. The results of the present study might contribute in deciphering the mechanism for premating isolation in these species and may be of use in devising strategies for their management.

Gene Identification of Pheromone Gland Genes Involved in Type II Sex Pheromone Biosynthesis and Transportation in Female Tea Pest Ectropis grisescens

Moths can biosynthesize sex pheromones in the female sex pheromone glands (PGs) and can distinguish species-specific sex pheromones using their antennae. However, the biosynthesis and transportation mechanism for Type II sex pheromone components has rarely been documented in moths. In this study, we constructed a massive PG transcriptome database (14.72 Gb) from a moth species, Ectropis grisescens, which uses type II sex pheromones and is a major tea pest in China. We further identified putative sex pheromone biosynthesis and transportation-related unigenes: 111 cytochrome P450 monooxygenases (CYPs), 25 odorant-binding proteins (OBPs), and 20 chemosensory proteins (CSPs). Tissue expression and phylogenetic tree analyses showed that one CYP (EgriCYP341-fragment3), one OBP (EgriOBP4), and one CSP (EgriCSP10) gene displayed an enriched expression in the PGs, and that EgriOBP2, 3, and 25 are clustered in the moth pheromone-binding protein clade. We considered these our candidate genes. Our results yielded large-scale PG sequence information for further functional studies.

Pupation Behaviors and Emergence Successes of Ectropis grisescens (Lepidoptera: Geometridae) in Response to Different Substrate Types and Moisture Contents

Ectropis grisescens Warren (Lepidoptera: Geometridae) is one of the most severe pests of tea plants in China. This species commonly pupates in soil; however, little is known about its pupation ecology. In the present study, choice and no-choice tests were conducted to investigate the pupation behaviors and emergence success of E. grisescens in response to different substrates (sand, sandy loam 1, sandy loam 2, and silt loam) and moisture contents (5, 20, 35, 50, 65, and 80%). Moisture-choice bioassays showed that significantly more E. grisescens individuals pupated in or on soil (sandy loam 1 and 2 and silt loam) that was at the intermediate moisture levels, whereas 5%- and 35%-moisture sand was significantly more preferred over 80%-moisture sand for pupating. Substrate-choice bioassays showed that sand was most preferred by E. grisescens individuals at 20%- and 80%-moisture levels, but no preference was detected among the four substrates at 50%-moisture content. No-choice tests showed that the percentage of burrowed E. grisescens individuals and pupation depth were significantly lower when soil was dry (20% moisture) or wet (80% moisture). In addition, 20%-moisture sandy loam 2 and silt loam significantly decreased the body water content of pupae and emergence success of adults compared to 50%-moisture content. However, each measurement (percentage of burrowed individuals, pupation depth, body water content, or emergence success) was similar when compared among different moisture levels of sand. Interestingly, pupae buried with 80%-moisture soil exhibited significantly lower emergence success than that were unburied.

Evidence of Premating Isolation Between Two Sibling Moths: Ectropis grisescens and Ectropis obliqua (Lepidoptera: Geometridae)

The sex pheromones of Ectropis grisescens Warren and Ectropis obliqua Prout were both reported to contain (Z,Z,Z)-3,6,9-octadecatriene (Z3,Z6,Z9-18:H) and (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene (Z3,epo6,Z9-18:H). To clarify how these two sibling geometrids maintain premating isolation, the female sex pheromones of the two species were reexamined. Gas chromatography-electroantennographic detection (GC-EAD) and gas chromatography-mass spectrometry revealed two GC-EAD-active compounds, Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H, in E. grisescens female pheromone glands as well as an additional GC-EAD-active compound, (Z,Z)-3,9-cis-6,7-epoxy-nonadecadiene (Z3,epo6,Z9-19:H), in E. obliqua female pheromone glands. Synthesized Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H elicited dose-dependent electroantennogram (EAG) responses from male antennae of both E. grisescens and E. obliqua. However, Z3,epo6,Z9-19:H only elicited dose-dependent EAG responses from E. obliqua and limited EAG responses from E. grisescens at all doses. In wind-tunnel studies, lures that contained Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H attracted E. grisescens males and had no effect on E. obliqua males. The addition of Z3,epo6,Z9-19:H to the blend of Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H strongly attracted E. obliqua males but had a limited attraction for E. grisescens males. Thus, Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H were sex pheromone components of E. grisescens, whereas Z3,Z6,Z9-18:H, Z3,epo6,Z9-18:H and Z3,epo6,Z9-19:H were sex pheromone components of E. obliqua. The presence or absence of Z3,epo6,Z9-19:H played a central role in the premating isolation of these two sibling species.

Chemosensory Gene Families in Ectropis grisescens and Candidates for Detection of Type-II Sex Pheromones

Tea grey geometrid (Ectropis grisescens), a devastating chewing pest in tea plantations throughout China, produces Type-II pheromone components. Little is known about the genes encoding proteins involved in the perception of Type-II sex pheromone components. To investigate the olfaction genes involved in E. grisescens sex pheromones and plant volatiles perception, we sequenced female and male antennae transcriptomes of E. grisescens. After assembly and annotation, we identified 153 candidate chemoreception genes in E. grisescens, including 40 odorant-binding proteins (OBPs), 30 chemosensory proteins (CSPs), 59 odorant receptors (ORs), and 24 ionotropic receptors (IRs). The results of phylogenetic, qPCR, and mRNA abundance analyses suggested that three candidate pheromone-binding proteins (EgriOBP2, 3, and 25), two candidate general odorant-binding proteins (EgriOBP1 and 29), six pheromone receptors (EgriOR24, 25, 28, 31, 37, and 44), and EgriCSP8 may be involved in the detection of Type-II sex pheromone components. Functional investigation by heterologous expression in Xenopus oocytes revealed that EgriOR31 was robustly tuned to the E. grisescens sex pheromone component (Z,Z,Z)-3,6,9-octadecatriene and weakly to the other sex pheromone component (Z,Z)-3,9-6,7-epoxyoctadecadiene. Our results represent a systematic functional analysis of the molecular mechanism of olfaction perception in E. grisescens with an emphasis on gene encoding proteins involved in perception of Type-II sex pheromones, and provide information that will be relevant to other Lepidoptera species.

Production, identification, and field evaluation of sex pheromone from calling females in Diaphania angustalis (Lepidoptera: Crambidae)

Insect sex pheromones play a crucial role in the mate finding and calling behavior of Lepidoptera pests. Currently, little is known about the chemical ecology of Diaphania angustalis Snellen (Lepidoptera: Crambidae), a severe and important defoliator attacking the medicinal plant, Alstonia scholaris. In the present study, the pheromone components of D. angustalis females were investigated using electrophysiological and behavioral methods. Distilled hexane extracts of female pheromone glands were analyzed through electroantennogram (EAG) and gas chromatography-electroantennogram detector (GC-EAD), and the active compounds were identified through gas chromatography-mass spectrometry (GC-MS). Production peak of female sex pheromone occurred on the third day of age at 5 h into the scotophase with the EAG test, and the hexane extracts were attractive to males in the wind tunnel test. GC-EAD analysis of virgin males to gland extracts that were subsequently evaluated showed two active compounds, (E,E)-10,12-hexadecadienal (E10E12-16:Ald) and (E,E)-10,12-hexadecadien-1-ol (E10E12-16:OH), based on comparison of retention time and mass spectrum, with suitable synthetic compounds. Under laboratory conditions, the blend of E10E12-16:Ald and E10E12-16:OH in a ratio of 9:1 elicited a stronger EAG response than other treatments or a single component. In the field, more male moths were captured by traps baited with the mixture of E10E2-16:Ald and E10E2-16:OH in a ratio of 9:1, whereas a mixture of 8:1 and 10:1 also caught males. Accordingly, E10E2-16:Ald and E10E2-16:OH were regarded as the major sex pheromone components in D. angustalis females.