Polyene hydrocarbons and epoxides: a second major class of lepidopteran sex attractant pheromones

Tandemly expanded OR17b in Himalaya ghost moth facilitates larval food allocation via olfactory reception of plant-derived tricosane

Herbivorous insects utilize intricate olfactory mechanisms to locate food plants. The chemical communication of insect-plant in primitive lineage offers insights into evolutionary milestones of divergent olfactory modalities. Here, we focus on a system endemic to the Qinghai-Tibetan Plateau to unravel the chemical and molecular basis of food preference in ancestral Lepidoptera. We conducted volatile profiling, neural electrophysiology, and chemotaxis assays with a panel of host plant organs to identify attractants for Himalaya ghost moth Thitarodes xiaojinensis larvae, the primitive host of medicinal Ophiocordyceps sinensis fungus. Using a DREAM approach based on odorant induced transcriptomes and subsequent deorphanization tests, we elucidated the odorant receptors responsible for coding bioactive volatiles. Contrary to allocation signals in most plant-feeding insects, T. xiaojinensis larvae utilize tricosane from the bulbil as the main attractant for locating native host plant. We deorphanized a TxiaOR17b, an indispensable odorant receptor resulting from tandem duplication of OR17, for transducing olfactory signals in response to tricosane. The discovery of this ligand-receptor pair suggests a survival strategy based on food location via olfaction in ancestral Lepidoptera, which synchronizes both plant asexual reproduction and peak hatch periods of insect larvae.

Identification of Candidate Genes Associated with Type-II Sex Pheromone Biosynthesis in the Tea Geometrid (Ectropis obliqua) (Lepidoptera: Geometridae)

Ectropis obliqua, a notorious tea pest, produces a Type-II sex pheromone blend for mate communication. This blend contains (Z,Z,Z)-3,6,9-octadecatriene, (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene, and (Z,Z)-3,9-cis-6,7-epoxy-nonadecadiene. To elucidate the genes related to the biosynthesis of these sex pheromone components, transcriptome sequencing of the female E. obliqua pheromone gland and the abdomen without pheromone gland was performed. Comparative RNAseq analyses identified 52 putative genes, including 7 fatty acyl-CoA elongases (ELOs), 9 fatty acyl-CoA reductases (FARs), 1 decarbonylase (DEC), 3 lipophorins (LIPs), and 32 cytochrome P450 enzymes (CYPs). Tissue expression profiles revealed that two ELOs (ELO3 and ELO5), two FARs (FAR2 and FAR9), one DEC (CYP4G173), and one LIP (LIP1) displayed either abdomen-centric or -specific expression, suggesting potential roles in sex pheromone biosynthesis within the oenocytes of E. obliqua. Furthermore, the tissue expression patterns, combined with phylogenetic analysis, showed that CYP340BD1, which was expressed specifically and predominantly only in the pheromone gland, was clustered with the previously reported epoxidases, highlighting its potential role in the epoxidation of the unsaturated polytriene sex pheromone components. Collectively, our research provides valuable insights into the genes linked to sex pheromone biosynthesis.

Functional disparity of four pheromone-binding proteins from the plum fruit moth Grapholita funebrana Treitscheke in detection of sex pheromone components

Grapholita funebrana, also known as the plum fruit moth, is an oligophagous pest species that causes enormous economic losses of the fruits of Rosaceae. An eco-friendly method for the control of G. funebrana besides chemical control has not yet been developed. The sex pheromone communication system plays an important role in moth courtship and mating, in which pheromone-binding proteins (PBPs) are critical. In this research, we identified four PBPs, namely, GfunPBP1.1, GfunPBP1.2, GfunPBP2, and GfunPBP3, from the antennae of G. funebrana. The results of real-time quantitative PCR (RT-qPCR) showed that all four GfunPBPs were overwhelmingly expressed in the antennae and that GfunPBP1.2 and GfunPBP2 showed male-biased expression patterns, whereas GfunPBP1.1 and GfunPBP3 were equally expressed between sexes. The results of ligand-binding assays illustrated that although all four recombinant GfunPBPs (rGfunPBPs) had binding activity with the tested sex pheromone compounds, their preferred ligands were significantly different. rGfunPBP2 had the strongest binding affinity to Z8-12:Ac and Z8-12:OH; rGfunPBP1.1 preferred to bind Z8-14:Ac, Z10-14:Ac, and 12:OH more than to the other three GfunPBPs; and rGfunPBP1.2 exhibited stronger binding affinity to E8-12:Ac than to the other rGfunPBPs. Molecular docking results demonstrated that hydrophobic forces, especially van der Waals forces and hydrogen bonds, were the most important forces that maintained GfunPBP-pheromone ligand complexes. This study will improve our understanding of the sex pheromone recognition mechanisms of G. funebrana and promote the development of novel strategies for controlling G. funebrana.

Identification of the Sex Pheromone of the Pink Grass Worm, Tmetolophota atristriga, Reveals Possible Population Differences in Male Response to Sex Pheromone

The pink grass worm, Tmetolophota atristriga (Walker), is an endemic New Zealand noctuid moth species that is abundant throughout the North and South Islands. The larvae are minor defoliators of agricultural pasture. We investigated the sex pheromone of this species. Analysis of extract of the female sex pheromone gland identified six compounds: two monounsaturated compounds, (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-11-hexadecenyl acetate (Z11-16:Ac), three saturated compounds, hexadecanal (16:Ald), hexadecyl acetate (16:Ac) and octadecan-1-ol (18:OH), and a triene hydrocarbon, (3Z,6Z,9Z)-tricosatriene (Z3Z6Z9-23:Hy). Several field-trapping experiments testing combinations of the six compounds were conducted. Results suggested that males of two different populations of T. atristriga responded differently to different blends of the compounds. Males of one population responded equally to a two-component blend as to other blends, including the one with all six compounds. By contrast, males of the second population responded only to the six-component blend or a ternary blend of Z11-16:Ald, Z11-16:Ac and Z3Z6Z9-23:Hy. In experiments testing different doses of Z11-16:Ald and Z11-16:Ac in a binary or a six-component blend, a 1 mg dose of the binary blend gave the greatest male catch for both populations. This is the second sex pheromone identification of a New Zealand species of Noctuidae and is the first reported occurrence of Z3Z6Z9-23:Hy as a sex pheromone component of any noctuid species.

Identification of a unique three-component sex pheromone produced by the tea black tussock moth, Dasychira baibarana (Lepidoptera: Erebidae: Lymantriinae)

BACKGROUND

The tea black tussock moth Dasychira baibarana Matsumura is a devastating pest in tea plantations that causes substantial economic losses. Presently, there is no effective method to control this pest other than pesticide application. The identified sex pheromone of D. baibarana could be used for detecting and monitoring this pest.

RESULTS

Gas chromatography-electroantennogram detection showed that D. baibarana male moth antennae responded strongly to three components in the female sex pheromone gland, which were identified as: (3Z,6Z)-cis-9,10-epoxyhenicosa-3,6-diene (Z3,Z6,epo9-21:H) (I), (3Z,6Z,11E)-cis-9,10-epoxyhenicosa-3,6,11-triene (Z3,Z6,epo9,E11-21:H) (II) and (3Z,6Z)-henicosa-3,6-dien-11-one (Z3,Z6-21:11-one) (III). Dasychira baibarana uses a unique composition of an epoxydiene, epoxytriene, and dienone with the same 3,6-dienyl motif as its sex pheromone. The epoxytriene and dienone were not previously characterized as insect pheromone components. Electroantennogram analysis showed that each synthetic compound strongly stimulated male antennae, and compounds II and III elicited stronger responses than compound I. A wind tunnel bioassay and field trapping experiments proved that, ternary blends of compounds I-III attracted D. baibarana. Efficient attraction was achieved with a rubber septum baited with 500 μg of a mixture of compounds I-III at the ratio 25:20:55.

CONCLUSION

The three identified compounds elicited an electroantennogram response in D. baibarana male moth antennae, and a mixture of the three components at the ratio 25:20:55 attracted D. baibarana male moths in a wind tunnel assay and field trapping experiments. This blend could be used for integrated management of D. baibarana in tea plantations. © 2022 Society of Chemical Industry.

Pyruvate Kinase Is Required for Sex Pheromone Biosynthesis in Helicoverpa armigera

Pyruvate kinase (PYK) is a speed-limited enzyme of glycolysis that catalyzes the formation of pyruvate, and plays an important role in acetyl-CoA synthesis. The acetyl-CoA is the precursor of sex pheromone biosynthesis in Helicoverpa armigera. However, the role of PYK in sex pheromone biosynthesis remains elusive. Here, PYK in H. armigera (HaPYK) was found to be highly expressed in the pheromone glands (PGs). The developmental expression profile of HaPYK was consistent with the fluctuation of sex pheromone release. Function analysis revealed that the knockdown of HaPYK led to a decrease in the levels of pyruvic acid and acetyl-CoA in PGs, which in turn caused a significant decrease in cis-11-hexadecenal (Z11-16: Ald) production, female capability to attract males, and mating frequency. Further study demonstrated that sugar feeding (5% sugar) increased the transcription and enzyme activity of HaPYK, thereby facilitating sex pheromone biosynthesis. Moreover, pheromone biosynthesis activating neuropeptide (PBAN) upregulated HaPYK activity through protein kinase C (PKC), as shown by PKC-specific inhibitor analysis. Altogether, our results revealed that PBAN activated HaPYK by Ca²⁺/PKC, thereby regulating the synthesis of pyruvate and subsequent acetyl-CoA, ensuring the supply of sex pheromone precursor, and finally facilitating sex pheromone biosynthesis and mating behavior.

An Overview of Antennal Esterases in Lepidoptera

Lepidoptera are used as a model for the study of insect olfactory proteins. Among them, odorant degrading enzymes (ODEs), that degrade odorant molecules to maintain the sensitivity of antennae, have received less attention. In particular, antennal esterases (AEs; responsible for ester degradation) are crucial for intraspecific communication in Lepidoptera. Currently, transcriptomic and genomic studies have provided AEs in several species. However, efforts in gene annotation, classification, and functional assignment are still lacking. Therefore, we propose to combine evidence at evolutionary, structural, and functional level to update ODEs as well as key information into an easier classification, particularly of AEs. Finally, the kinetic parameters for putative inhibition of ODEs are discussed in terms of its role in future integrated pest management (IPM) strategies.

Putative carboxylesterase gene identification and their expression patterns in Hyphantria cunea (Drury)

The olfactory system of insects is important for behavioral activities as it recognizes internal and external volatile stimuli in the environment. Insect odorant degrading enzymes (ODEs), including antennal-specific carboxylesterases (CXEs), are known to degrade redundant odorant molecules or to hydrolyze important olfactory sex pheromone components and plant volatiles. Compared to many well-studied Type-I sex pheromone-producing lepidopteran species, the molecular mechanisms of the olfactory system of Type-II sex pheromone-producing Hyphantria cunea (Drury) remain poorly understood. In the current study, we first identified a total of ten CXE genes based on our previous H. unea antennal transcriptomic data. We constructed a phylogenetic tree to evaluate the relationship of HcunCXEs with other insects’ CXEs, and used quantitative PCR to investigate the gene expression of H. cunea CXEs (HcunCXEs). Our results indicate that HcunCXEs are highly expressed in antennae, legs and wings, suggesting a potential function in degrading sex pheromone components, host plant volatiles, and other xenobiotics. This study not only provides a theoretical basis for subsequent olfactory mechanism studies on H. cunea, but also offers some new insights into functions and evolutionary characteristics of CXEs in lepidopteran insects. From a practical point of view, these HcunCXEs might represent meaningful targets for developing behavioral interference control strategies against H. cunea.

Functional Disparity of Three Pheromone-Binding Proteins to Different Sex Pheromone Components in Hyphantria cunea (Drury)

Hyphantria cunea (Drury) is a destructive invasive pest species in China that uses type II sex pheromone components. To date, however, the binding mechanisms of its sex pheromone components to their respective pheromone-binding proteins (HcunPBPs 1/2/3) have not been explored. In the current study, all three HcunPBPs were expressed in the antennae of both sexes. The prokaryotic expression and ligand binding assays were employed to study the binding of the moth's four sex pheromone components, including two aldehydes and two epoxides, and 24 plant volatiles to the HcunPBPs. Our results showed that the abilities of these HcunPBPs to bind to the aldehydes were significantly different from binding to the epoxides. These three HcunPBPs also selectively bind to some of the plant volatiles tested. Our molecular docking results indicated that some crucial hydrophobic residues might play a role in the binding of HcunPBPs to their sex pheromone components. Three HcunPBPs have different selectivities for pheromone components with both major and minor structural differences. Our study provides a fundamental insight into the olfactory mechanism of moths at the molecular level, especially for moth species that use various type II pheromone components.

Identification of cytochrome P450, odorant-binding protein, and chemosensory protein genes involved in Type II sex pheromone biosynthesis and transportation in the tea pest, Scopula subpunctaria

Sex pheromone-based pest management technology has been widely used to monitor and control insect pests in the agricultural, forestry, and public health sectors. Scopula subpunctaria is a widespread tea pest in China with Type II sex pheromone components. However, limited information is available on the biosynthesis and transportation of Type II sex pheromone components. In this study, we constructed an S. subpunctaria sex pheromone gland (PG) transcriptome and obtained 85,246 transcripts. Cytochrome P450 monooxygenases (CYPs) thought to epoxidize dienes and trienes to epoxides in the PG and odorant-binding proteins (OBPs) and chemosensory genes (CSPs) thought to be responsible for the binding and transportation of sex pheromone components. In present study, a total of 79 CYPs, 29 OBPs and 17 CSPs were identified. We found that SsubCYP341A and SsubCYP341B_ortholog1 belonged to the CYP341 family and were more highly expressed in the PG than in the female body. Of these, SsubCYP341A was the seventh-most PG-enriched CYP in the PG transcriptome. Two CYP4 members, CYP340BD_ortholog2 and CYP4G, were the top two most PG-enriched CYPs. Tissue expression and phylogenetic tree analysis showed that SsubOBP25, 27, and 28 belonged to the moth pheromone-binding protein family; they were distinctly expressed in the antennae and were more abundant in male antennae than in female antennae. SsubCSP16 was distributed into the same clade as CSPs from other moths that showed high binding affinities to sex pheromone components. It indicated that all the above-mentioned genes could be involved in sex pheromone biosynthesis or transportation. Our study provides large-scale PG sequence information that can be used to identify potential targets for the biological control of S. subpunctaria by disrupting its sex pheromone biosynthesis and transportation pathways.

Identification of the Female-Produced Sex Pheromone of the Dotted White Geometrid Naxa seriaria (Lepidoptera: Geometridae)

The dotted white geometrid moth, Naxa seriaria Motschulsky (Lepidoptera: Geometridae), is a pest of Oleaceae in Korea, Japan, and China. In this study, we identified (3Z,6Z,9Z,12Z,15Z)-heneicosapentaene (C-21 pentaene) as the only compound in extracts of the pheromone glands of female N. seriaria causing a response from receptors on the antennae of males in analyses by gas chromatography with electroantennographic detection. The synthetic sex pheromone elicited dose-dependent electrophysiological responses from antennae of male N. seriaria. In field tests, more male moths were captured in traps baited with synthetic C-21 pentaene than in unbaited traps, and increasing the loading of C-21 pentaene in the lure increased catches of male moths. Significantly more male N. seriaria moths were caught in delta traps than in bucket traps. Based on these results, C-21 pentaene is proposed to be the major, if not the only, component of the sex pheromone of N. seriaria.

Synthesis of disparlure and monachalure enantiomers from 2,3-butanediacetals

2,3-Butanediacetal derivatives were used for the stereoselective synthesis of unsymmetrically substituted cis-epoxides. The procedure was applied for the preparation of both enantiomers of disparlure and monachalure, the components of the sex pheromones of the gypsy moth (Lymantria dispar) and the nun moth (Lymantria monacha) using methyl (2S,3R,5R,6R)-3-ethylsulfanylcarbonyl-5,6-dimethoxy-5,6-dimethyl-1,4-dioxane-2-carboxylate as the starting material.

Environmental decomposition of olefinic cuticular hydrocarbons of Periplaneta americana generates a volatile pheromone that guides social behaviour

Once emitted, semiochemicals are exposed to reactive environmental factors that may alter them, thus disrupting chemical communication. Some species, however, might have adapted to detect environmentally mediated breakdown products of their natural chemicals as semiochemicals. We demonstrate that air, water vapour and ultraviolet (UV) radiation break down unsaturated cuticular hydrocarbons (CHCs) of Periplaneta americana (American cockroach), resulting in the emission of volatile organic compounds (VOCs). In behavioural assays, nymphs strongly avoided aggregating in shelters exposed to the breakdown VOCs from cuticular alkenes. The three treatments (air, water vapour, UV) produced the same VOCs, but at different time-courses and ratios. Fourteen VOCs from UV-exposed CHCs elicited electrophysiological responses in nymph antennae; 10 were identified as 2-nonanone, 1-pentanol, 1-octanol, 1-nonanol, tetradecanal, acetic acid, propanoic acid, butanoic acid, pentanoic acid and hexanoic acid. When short-chain fatty acids were tested as a mix and a blend of the alcohols and aldehyde was tested as a second mix, nymphs exhibited no preference for control or treated shelters. However, nymphs avoided shelters that were exposed to VOCs from the complete 10-compound mix. Conditioned shelters (occupied by cockroaches with faeces and CHCs deposited on the shelters), which are normally highly attractive to nymphs, were also avoided after UV exposure, confirming that breakdown products from deposited metabolites, including CHCs, mediate this behaviour. Our results demonstrate that common environmental agents degrade CHCs into behaviourally active volatile compounds that potentially may serve as necromones or epideictic pheromones, mediating group dissolution.

The sensilla trichodea-biased EoblPBP1 binds sex pheromones and green leaf volatiles in Ectropis obliqua Prout, a geometrid moth pest that uses Type-II sex pheromones

Pheromone-binding proteins (PBPs) are considered to play critical roles in sex pheromone detection. Lepidopteran moths can be divided into two taxa, those that use Type-I sex pheromones, such as C10-C18 unsaturated aldehydes, alcohols and acetates, and those that use Type-II pheromones, which are C17-C23 polyunsaturated hydrocarbons and their epoxide derivatives. To date, nearly all the characterized PBPs have been reported in moths with Type-I sex pheromones, and the physiological functions of PBPs in moths that use Type-II sex pheromones remains unclear. In the present study we functionally examine EoblPBP1 in Ectropis obliqua Prout, an important geometrid moth pest that uses Type-II sex pheromones. The phylogenetic analysis of the sequence indicated that EoblPBP1 clustered together with ScerPBP1, a geometrid PBP for detecting Type-II sex pheromones. Scanning electron microscopy showed that E. obliqua moths of both sexes mainly had six types of antennal sensilla, including two types of sensilla trichodea, Str-I and Str-II, sensilla basiconica (Sba), sensilla styloconica (Sst), sensilla chaetica (Sch) and sensilla auricillica (Sau). Of these, Str-I was confirmed to be male moth-specific and had five different subtypes. Fluorescence in situ hybridization revealed that EoblPBP1 was primarily expressed at the base of Str-I. A comparative binding assay showed that recombinant EoblPBP1 bound three sex pheromone components of E. obliqua, demonstrating its involvement in the detection of Type-II sex pheromones. Besides, EoblPBP1 also highly bound unsaturated acetates pheromones and the green leaf volatiles. These results indicate that PBP1 is associated with detecting Type-II sex pheromones in E. obliqua but cannot differentiate Type-II sex pheromones from Type-I sex pheromones or green leaf volatiles. Our findings provide a foundation for further study on molecular basis of Type-II sex pheromone recognition in lepidopteran moths.

CYPs in different families are involved in the divergent regio-specific epoxidation of alkenyl sex pheromone precursors in moths

In moth species that utilize alkenyl sex pheromones, the epoxidation of alkenes confers further diversity on the chemical structures of pheromone components. Hc_epo1 (CYP341B14), the first pheromone gland (PG)-specific epoxidase identified from the fall webworm Hyphantria cunea (Erebidae), specifically epoxidizes the Z9 double bond in the triene precursor, (3Z,6Z,9Z)-3,6,9-henicosatriene (Z3,Z6,Z9-21:H). In the present study, we identified a novel PG-specific epoxidase, As_epo1, from the Japanese giant looper Ascotis selenaria (Geometridae), which secretes cis-3,4-epoxy-(6Z,9Z)-6,9-nonadecadiene (epo3,Z6,Z9-19:H) as the main sex pheromone component. A functional assay using the Sf9 insect cell line-baculovirus expression system showed that As_epo1 specifically epoxidizes the Z3 double bond in the pheromone precursor triene, (3Z,6Z,9Z)-3,6,9-nonadecatriene (Z3,Z6,Z9-19:H). As_epo1 also Z3-specifically epoxidized a triene with a longer carbon chain, Z3,Z6,Z9-21:H, which does not occur in this species. A phylogenetic analysis indicated that As_epo1 belonged to the CYP340 family, not the CYP341 family to which Hc_epo1 belongs. These results suggest that moth PG-specific epoxidases with divergent regio-specificities have evolved independently.

Linoleic acid and stearic acid are biosynthetic precursors of (7Z,10Z)-7,10-hexadecadienal, the major component of the sex pheromone of Chilecomadia valdiviana (Lepidoptera: Cossidae)

The main pheromone compound of Chilecomadia valdiviana (Lepidoptera: Cossidae) has been recently identified as (7Z,10Z)-7,10-hexadecadienal. The biosynthesis of this pheromone compound showing attributes of both Type I and Type II lepidopteran pheromones was studied by the topical application of isotope-labeled fatty acids to the pheromone gland and subsequent analysis of the gland contents (pheromone compounds and fatty acyl compounds) by gas chromatography-mass spectrometry. The deuterium label of D₁₁-linoleic acid was incorporated into the pheromone compound and its putative acyl precursor (7Z,10Z)-7,10-hexadecadienoate, demonstrating that the pheromone compound is biosynthesized from linoleic acid by chain-shortening and further functional group transformation. Furthermore, the deuterium label of D₃-stearic acid was also incorporated into the pheromone compound, which indicates that the pheromone can be synthesized de novo by C. valdiviana, as is the case for Type I lepidopteran pheromone compounds.

Functional characterization of the epoxidase gene, Li_epo1 (CYP341B14), involved in generation of epoxyalkene pheromones in the mulberry tiger moth Lemyra imparilis

Epoxidation of alkenes derived from essential fatty acids is a key step in the biosynthesis of sex pheromones in moth species that utilize alkenyl sex pheromones. The position of the epoxy ring in the pheromone molecule differs depending on the species, thereby conferring diversities on sex pheromones. To date, only one pheromone gland (PG)-specific epoxidase, Hc_epo1 (CYP341B14), has been reported. Hc_epo1, which was identified from an arctiid moth Hyphantria cunea, catalyzes the epoxidation of a double bond at position 9 of the triene, Z3,Z6,Z9-21:H. In the present study, we investigated the PG-specific epoxidase from another arctiid, the mulberry tiger moth Lemyra imparilis, in order to verify whether cytochrome P450 in the CYP341B subfamily, to which Hc_epo1 belongs to, is responsible for the epoxidation of pheromone precursors at position 9 in moths other than H. cunea. A fragment of the Hc_epo1 homolog was amplified from cDNA prepared from the PG of L. imparilis by PCR with degenerate primers. The deduced amino acid sequence of the subsequently cloned homolog, Li_epo1, showed 88.5% identity to Hc_epo1. A functional assay using the Sf9 insect cell line-baculovirus expression system showed that Li_epo1 exhibited epoxidase activity with high selectivity to the double bond at position 9 of two trienes, Z3,Z6,Z9-21:H and Z3,Z6,Z9-23:H, precursors of epoxy diene sex pheromone components in L. imparilis.

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.

From Acetoin to ( Z)-3-Hexen-1-ol: The Diversity of Volatile Organic Compounds that Induce Plant Responses

Evidence that plants can respond to volatile organic compounds (VOCs) was first presented 35 years ago. Since then, over 40 VOCs have been found to induce plant responses. These include VOCs that are produced not only by plants but also by microbes and insects. Here, we summarize what is known about how these VOCs are produced and how plants detect and respond to them. In doing so, we highlight notable observations we believe are worth greater consideration. For example, the VOCs that induce plant responses appear to have little in common. They are derived from many different biosynthetic pathways and have few distinguishing chemical or structural features. Likewise, plants appear to use several mechanisms to detect VOCs rather than a single dedicated "olfactory" system. Considering these observations, we advocate for more discovery-oriented experiments and propose that future research take a fresh look at the ways plants detect and respond to VOCs.

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.

Key genes of the sex pheromone biosynthesis pathway in female moths are required for pheromone quality and possibly mediate olfactory plasticity in conspecific male moths in Spodoptera litura

Ninety sex pheromone biosynthesis genes in Spodoptera litura were identified in transcriptome data and were investigated and classified into the following five groups: fatty acid synthase, beta oxidase, fatty acyl-coenzyme A (CoA) reductase, desaturase and acetyl-CoA acetyltransferase. Fourteen female-specific genes were identified through semi-quantitative PCR, and 15 additional genes had expression levels that were 3- to 10-fold higher in females than in males. The majority of the genes had higher expression levels in the sex pheromone glands. Injection of double-stranded RNA (dsRNA) against nine selected genes showed that down-regulation of Desaturase 3 (Des3), Des5 or fatty acyl coenzyme A reductase 17 (FAR17) significantly changed the ratio of the four sex pheromone components (Z,E) -9,11-tetradecadienyl acetate (Z9E11-14:Ac), (Z,E)-9,12-Tetradecadienyl acetate(Z9E12-14:Ac), (Z)-9-tetradecenyl acetate (Z9-14:Ac), (E)-11-Tetradecenyl acetate(E11-14:Ac). These key genes were differentially expressed in female moths collected from different geographical regions. Furthermore, field bioassays demonstrated geographical variation in the olfactory profile of male moths in response to the different sex pheromone mixtures, which therefore indicates that a significant variation in the sex pheromone components exists in the natural population. Our results suggest that a change in the expression of these key genes, Des3, Des5 and FAR17, in the sex pheromone biosynthesis pathway could change the ratio of the sex pheromone components. We surmise that the differential expression levels of the key genes of the sex pheromone biosynthesis pathway may lead to differential ratios of the sex pheromones in the field. Our field trapping experiment suggested that the change of the ratio of the sex pheromone components may have been adapted by the olfactory system and possibly mediate olfactory plasticity in conspecific male moths.

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.

Identification of the pheromone biosynthesis genes from the sex pheromone gland transcriptome of the diamondback moth, Plutella xylostella

The diamondback moth was estimated to increase costs to the global agricultural economy as the global area increase of Brassica vegetable crops and oilseed rape. Sex pheromones traps are outstanding tools available in Integrated Pest Management for many years and provides an effective approach for DBM population monitoring and control. The ratio of two major sex pheromone compounds shows geographical variations. However, the limitation of our information in the DBM pheromone biosynthesis dampens our understanding of the ratio diversity of pheromone compounds. Here, we constructed a transcriptomic library from the DBM pheromone gland and identified genes putatively involved in the fatty acid biosynthesis, pheromones functional group transfer, and β-oxidation enzymes. In addition, odorant binding protein, chemosensory protein and pheromone binding protein genes encoded in the pheromone gland transcriptome, suggest that female DBM moths may receive odors or pheromone compounds via their pheromone gland and ovipositor system. Tissue expression profiles further revealed that two ALR, three DES and one FAR5 genes were pheromone gland tissue biased, while some chemoreception genes expressed extensively in PG, pupa, antenna and legs tissues. Finally, the candidate genes from large-scale transcriptome information may be useful for characterizing a presumed biosynthetic pathway of the DBM sex pheromone.

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.

An Evolutionary Perspective on Linoleic Acid Synthesis in Animals

The diet of organisms generally provides a sufficient supply of energy and building materials for healthy growth and development, but should also contain essential nutrients. Species differ in their exogenous requirements, but it is not clear why some species are able to synthesize essential nutrients, while others are not. The unsaturated fatty acid, linoleic acid (LA; 18:2n-6) plays an important role in functions such as cell physiology, immunity, and reproduction, and is an essential nutrient in diverse organisms. LA is readily synthesized in bacteria, protozoa and plants, but it was long thought that all animals lacked the ability to synthesize LA de novo and thus required a dietary source of this fatty acid. Over the years, however, an increasing number of studies have shown active LA synthesis in animals, including insects, nematodes and pulmonates. Despite continued interest in LA metabolism, it has remained unclear why some organisms can synthesize LA while others cannot. Here, we review the mechanisms by which LA is synthesized and which biological functions LA supports in different organisms to answer the question why LA synthesis was lost and repeatedly gained during the evolution of distinct invertebrate groups. We propose several hypotheses and compile data from the available literature to identify which factors promote LA synthesis within a phylogenetic framework. We have not found a clear link between our proposed hypotheses and LA synthesis; therefore we suggest that LA synthesis may be facilitated through bifunctionality of desaturase enzymes or evolved through a combination of different selective pressures.

Unsaturated Cuticular Hydrocarbons Enhance Responses to Sex Pheromone in Spruce Budworm, Choristoneura fumiferana

The primary sex pheromone components of the female spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), are (E)- and (Z)-11-tetradecenal, produced in 95:5 ratio. However, male flight responses to calling females in a wind tunnel were faster and maintained longer than responses to any synthetic aldehyde blend. Analyses of cuticular extracts from spruce budworm adults revealed series of n-alkanes and n-monoalkenes with predominantly odd numbers of carbon atoms from C₂₃- C₂₉ in both sexes. (Z,Z,Z)-3,6,9-tricosatriene and (Z,Z,Z)-3,6,9-pentacosatriene were identified only in cuticular extracts from females. Pheromonally naïve males showed wing fanning and circling responses to forewing scales from females but not to scales from males. Males also exhibited the same strong responses to scales excised from pharate females, indicating that the pheromone components are produced by females prior to emergence. (Z)-11-hexadecenal and (Z)-5-tricosene enhanced male responses to the primary sex pheromone aldehydes in wind tunnel bioassays, including higher proportions of in-flight and copulatory responses by males and increased time on the source. Addition of (Z,Z,Z)-3,6,9-tricosatriene to the 95/5 blend of (E)- and (Z)-11-tetradecenal released close-range copulatory responses including abdomen curling on treated septa. We propose that the sex pheromone blend of C. fumiferana is composed of the 95/5 blend of (E)- and (Z)-11-tetradecenal as primary components, with (Z)-11-hexadecenal, (Z)-5-tricosene and (Z,Z,Z)-3,6,9-tricosatriene fulfilling secondary roles in orientation and close-range courtship.

Antennal transcriptome analysis of the piercing moth Oraesia emarginata (Lepidoptera: Noctuidae)

The piercing fruit moth Oraesia emarginata is an economically significant pest; however, our understanding of its olfactory mechanisms in infestation is limited. The present study conducted antennal transcriptome analysis of olfactory genes using real-time quantitative reverse transcription PCR analysis (RT-qPCR). We identified a total of 104 candidate chemosensory genes from several gene families, including 35 olfactory receptors (ORs), 41 odorant-binding proteins, 20 chemosensory proteins, 6 ionotropic receptors, and 2 sensory neuron membrane proteins. Seven candidate pheromone receptors (PRs) and 3 candidate pheromone-binding proteins (PBPs) for sex pheromone recognition were found. OemaOR29 and OemaPBP1 had the highest fragments per kb per million fragments (FPKM) values in all ORs and OBPs, respectively. Eighteen olfactory genes were upregulated in females, including 5 candidate PRs, and 20 olfactory genes were upregulated in males, including 2 candidate PRs (OemaOR29 and 4) and 2 PBPs (OemaPBP1 and 3). These genes may have roles in mediating sex-specific behaviors. Most candidate olfactory genes of sex pheromone recognition (except OemaOR29 and OemaPBP3) in O. emarginata were not clustered with those of studied noctuid species (type I pheromone). In addition, OemaOR29 was belonged to cluster PRIII, which comprise proteins that recognize type II pheromones instead of type I pheromones. The structure and function of olfactory genes that encode sex pheromones in O. emarginata might thus differ from those of other studied noctuids. The findings of the present study may help explain the molecular mechanism underlying olfaction and the evolution of olfactory genes encoding sex pheromones in O. emarginata.

The relationship between epicuticular long-chained hydrocarbons and surface area - volume ratios in insects (Diptera, Hymenoptera, Lepidoptera)

Long-chain cuticular hydrocarbons (CHCs) are common components of the epicuticle of terrestrial arthropods. CHC serve as a protective barrier against environmental influences but also act as semiochemicals in animal communication. Regarding the latter aspect, species- or intra-functional group specific CHCs composition and variation are relatively well studied. However, comparative knowledge about the relationship of CHC quantity and their relation to surface area—volume ratios in the context of water loss and protection is fragmentary. Hence, we aim to study the taxon-specific relationship of the CHC amount and surface-area to volume ratio related to their functional role (e.g. in water loss). We focused on flower visiting insects and analyzed the CHC amounts of three insect orders (Hymenoptera, Lepidoptera and Diptera) using gas chromatography—mass spectrometry (GC-MS). We included 113 species from two grassland plots, quantified their CHCs, and measured their body mass and surface area. We found differences in the surface area, CHCs per body mass and the CHC density (= amount of CHCs per surface area) across the three insect taxa. Especially the Hymenoptera had a higher CHC density compared to Diptera and Lepidoptera. CHC density could be explained by surface area-volume ratios in Hymenoptera but not in Diptera and Lepidoptera. Unexpectedly, CHC density decreased with increasing surface area—volume ratios.

Phylogeny and Evolution of Lepidoptera

Until recently, deep-level phylogeny in Lepidoptera, the largest single radiation of plant-feeding insects, was very poorly understood. Over the past two decades, building on a preceding era of morphological cladistic studies, molecular data have yielded robust initial estimates of relationships both within and among the ∼43 superfamilies, with unsolved problems now yielding to much larger data sets from high-throughput sequencing. Here we summarize progress on lepidopteran phylogeny since 1975, emphasizing the superfamily level, and discuss some resulting advances in our understanding of lepidopteran evolution.

Analysis of the Antennal Transcriptome and Insights into Olfactory Genes in Hyphantria cunea (Drury)

Hyphantria cunea (Drury) (Lepidoptera: Arctiidae) is an invasive insect pest which, in China, causes unprecedented damage and economic losses due to its extreme fecundity and wide host range, including forest and shade trees, and even crops. Compared to the better known lepidopteran species which use Type-I pheromones, little is known at the molecular level about the olfactory mechanisms of host location and mate choice in H. cunea, a species using Type-II lepidopteran pheromones. In the present study, the H. cunea antennal transcriptome was constructed by Illumina Hiseq 2500^TM sequencing, with the aim of discovering olfaction-related genes. We obtained 64,020,776 clean reads, and 59,243 unigenes from the analysis of the transcriptome, and the putative gene functions were annotated using gene ontology (GO) annotation. We further identified 124 putative chemosensory unigenes based on homology searches and phylogenetic analysis, including 30 odorant binding proteins (OBPs), 17 chemosensory proteins (CSPs), 52 odorant receptors (ORs), 14 ionotropic receptors (IRs), nine gustatory receptors (GRs) and two sensory neuron membrane proteins (SNMPs). We also found many conserved motif patterns of OBPs and CSPs using a MEME system. Moreover, we systematically analyzed expression patterns of OBPs and CSPs based on reverse transcription PCR and quantitative real time PCR (RT-qPCR) with RNA extracted from different tissues and life stages of both sexes in H. cunea. The antennae-biased expression may provide a deeper further understanding of olfactory processing in H. cunea. The first ever identification of olfactory genes in H. cunea may provide new leads for control of this major pest.

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

The tea geometrid, Ectropis grisescens Warren, is one of the most severe defoliator insect pests in tea plantations, China. The use of insecticides, etc., is forbidden on organic tea plantations. No female-produced sex pheromones of E. grisescens had been previously identified. In the present study, female gland extracts were analyzed by gas chromatography coupled with electroantennographic detection (GC-EAD) and two-dimensional gas chromatography (GC×GC) using a time-of-flight mass spectrometric detector (TOFMS). Two components, (Z,Z,Z)-3,6,9-octadecatriene (Z3Z6Z9-18:Hy) and (Z,Z)-3,9-6,7-epoxyoctadecadiene (Z3Z9-6,7-epo-18:Hy), were identified from pheromone gland extracts, and their electrophysiological and behavioral activity evaluated. Under laboratory conditions, Z3Z9-6,7-epo-18:Hy elicited a stronger electrophysiological response than Z3Z6Z9-18:Hy. In the field, traps baited with Z3Z9-6,7-epo-18:Hy alone showed better results than traps baited with Z3Z6Z9-18:Hy, and the binary mixture of Z3Z9-6,7-epo-18:Hy and Z3Z6Z9-18:Hy in a ratio of 4:1 (approximate ratio of females emitting pheromone) caught more males than the single components or any other blends. This study showed that Z3Z6Z9-18:Hy and Z3Z9-6,7-epo-18:Hy are the sex pheromone components of E. grisescens and that they prove useful in developing alternative management tools for the pest.

Receptor for detection of a Type II sex pheromone in the winter moth Operophtera brumata

How signal diversity evolves under stabilizing selection in a pheromone-based mate recognition system is a conundrum. Female moths produce two major types of sex pheromones, i.e., long-chain acetates, alcohols and aldehydes (Type I) and polyenic hydrocarbons and epoxides (Type II), along different biosynthetic pathways. Little is known on how male pheromone receptor (PR) genes evolved to perceive the different pheromones. We report the identification of the first PR tuned to Type II pheromones, namely ObruOR1 from the winter moth, Operophtera brumata (Geometridae). ObruOR1 clusters together with previously ligand-unknown orthologues in the PR subfamily for the ancestral Type I pheromones, suggesting that O. brumata did not evolve a new type of PR to match the novel Type II signal but recruited receptors within an existing PR subfamily. AsegOR3, the ObruOR1 orthologue previously cloned from the noctuid Agrotis segetum that has Type I acetate pheromone components, responded significantly to another Type II hydrocarbon, suggesting that a common ancestor with Type I pheromones had receptors for both types of pheromones, a preadaptation for detection of Type II sex pheromone.

Characterisation of the chemical profiles of Brazilian and Andean morphotypes belonging to the Anastrepha fraterculus complex (Diptera, Tephritidae)

Fruit fly sexual behaviour is directly influenced by chemical and non-chemical cues that play important roles in reproductive isolation. The chemical profiles of pheromones and cuticular hydrocarbons (CHs) of eight fruit fly populations of the Andean, Brazilian-1 and Brazilian-3 morphotypes of the Anastrephafraterculus cryptic species complex originating from Colombia (four populations) and Brazil (four populations) were analysed using two-dimensional gas chromatography with mass spectrometric detection. The resulting chemical diversity data were studied using principal component analyses. Andean morphotypes could be discriminated from the Brazilian-1 and Brazilian-3 morphotypes by means of male-borne pheromones and/or male and female CH profiles. The Brazilian-1 and Brazilian-3 morphotypes were found to be monophyletic. The use of chemical profiles as species- and sex-specific signatures for cryptic species separations is discussed.

Alkenyl sex pheromone analogs in the hemolymph of an arctiid Eilema japonica and several non-arctiid moths

The majority of moth species utilize compounds derived from de novo synthesized fatty acids as their sex pheromones (type I). In contrast, species belonging to two recently diverged moth families, Arctiidae and Geometridae, utilize alkenes and their epoxides, which are derived from dietary essential fatty acids (EFAs), as their sex pheromones (type II). In the latter species, EFAs are considered to be converted into alkenes, often after chain elongation, in specialized cells called oenocytes. These alkenes are transported through the hemolymph to the pheromone gland, from which they are secreted with or without further modifications. We confirmed that the appearance of EFA-derived alkenes in the hemolymph was closely associated with the completion of pheromone gland formation in an arctiid moth Eilema japonica. Analyses of the hemolymph of several moth species utilizing type-I sex pheromones demonstrated the occurrence of (Z,Z,Z)-3,6,9-tricosatriene (T23), a typical type-II component, in the hemolymph of a noctuid Mamestra brassicae and two crambids Ostrinia furnacalis and Ostrinia scapulalis. Our results demonstrated that moths utilizing type-I pheromones have the ability to synthesize type-II sex pheromones, and suggested that recently diverged groups of moths may have secondarily exploited EFA-derived alkenes as sex pheromones.

Responses of Cerambycidae and Other Insects to Traps Baited With Ethanol, 2,3-Hexanediol, and 3,2-Hydroxyketone Lures in North-Central Georgia

In north-central Georgia, 13 species of woodboring beetles (Coleoptera: Cerambycidae: Cerambycinae) were attracted to multiple-funnel traps baited with ethanol and one of the following pheromones: (1) racemic 3-hydroxyhexan-2-one; (2) racemic 3-hydroxyoctan-2-one; and (3) syn-2,3-hexanediol. The following species were attracted to traps baited with ethanol and 3-hydroxyhexan-2-one: Anelaphus pumilus (Newman), Eburia quadrigeminata (Say), Euderces pini (Olivier), Knulliana cincta (Drury), Neoclytus mucronatus (F.), Neoclytus scutellaris (Olivier), and Xylotrechus colonus (F.). Clytus marginicollis Castelnau & Gory, and Anelaphus parallelus (Newman) were attracted to traps baited with ethanol and 3-hydroxyoctan-2-one, whereas traps baited with ethanol and syn-2,3-hexanediol were attractive to Anelaphus villosus (F.), A. parallelus, Neoclytus acuminatus (F.), Neoclytus jouteli jouteli Davis, and Megacyllene caryae (Gahan). Ethanol enhanced catches of seven cerambycid species in traps baited with syn-2,3-hexanediol and 3,2-hydroxyketones. Catches of bark and ambrosia beetles (Curculionidae: Scolytinae) in ethanol-baited traps were largely unaffected by the addition of syn-2,3-hexanediol and 3,2-hydroxyketone lures, except for two species. The mean catches of Hypothenemus rotundicollis Wood & Bright and Dryoxylon onoharaensum (Murayama) in ethanol-baited traps increased and decreased, respectively, with the addition of racemic 3-hydroxyoctan-2-one. Traps baited with ethanol and syn-2,3-hexanediol were attractive to Xylobiops basilaris (Say) (Bostrichidae) and Chariessa pilosa (Forster) (Cleridae), whereas Temnoscheila virescens (F.) (Trogossitidae) were attracted to traps baited with ethanol and 3-hydroxyhexan-2-one. The assassin bug, Apiomerus crassipes (F.) (Hemiptera: Reduviidae), was attracted to traps baited with ethanol and 3,2-hydroxyketones.

Identification of the Female-Produced Sex Pheromone of the Leafminer Holocacista capensis Infesting Grapevine in South Africa

We report the first identification of a sex pheromone in a heliozelid moth, Holocacista capensis van Nieukerken & Geertsema. This leafminer recently infested grapevine in South Africa. Compared to solvent extraction of pheromone glands, solid phase microextraction (SPME) proved to be highly effective for collection of the pheromone from calling females. The volatiles collected by SPME were analyzed by gas chromatography with electroantennographic detection (GC/EAD). Three compounds eliciting electrophysiological activity from the male antenna were identified as (Z)-5-tetradecenal, (Z)-7-tetradecenal, and (Z)-9-hexadecenal by coupled gas chromatography-mass spectrometry (GC/MS). GC/MS analysis of dimethyldisulphide (DMDS) derivatives of fatty acyl moieties in pheromone gland extracts confirmed the presence of the corresponding putative pheromone precursors with double bonds in the same position and with Z geometry. Field trapping experiments in a South African vineyard confirmed that both (Z)-5-tetradecenal and (Z)-7-tetradecenal are essential for the attraction of male H. capensis, whereas addition of (Z)-9-hexadecenal to the blend did not affect the attractiveness. The composition of the pheromone is discussed in relation to the phylogeny of this family of moths.

The effect of dietary fatty acids on the cuticular hydrocarbon phenotype of an herbivorous insect and consequences for mate recognition

The cuticular hydrocarbon (CHC) profile of the mustard leaf beetle Phaedon cochleariae is known to mediate mate recognition and is dependent on food plant species; beetles previously were shown to prefer mates that fed on the same plant species and which have a similar CHC pattern. In order to elucidate whether the pattern of ingested fatty acids affects the CHC pattern of P. cochleariae adults, we fed beetles: (a) with two different host plant species differing in fatty acid profile; and (b) artificial diets differing mainly in their composition of mono-, di-, and triunsaturated fatty acids. Analyses of the beetles' CHCs revealed that ingestion of different fatty acid blends results in quantitative effects on the beetle's straight-chain and methyl-branched CHCs. Interestingly, CHC patterns of males and females were affected differently by ingestion of fatty acids. In contrast to the effect on mating caused by feeding on different host plant species, beetles that were fed with different artificial diets, leading to different beetle CHC profiles, did not exhibit mating preference. We suggest that the occurrence of CHC-dependent assortative mating in P. cochleariae does not depend on the dietary fatty acids offered to the beetles in this study, but on other food constituents that affect CHC biosynthesis.

CYP341B14: a cytochrome P450 involved in the specific epoxidation of pheromone precursors in the fall webworm Hyphantria cunea

Two of the four sex pheromone components in the fall webworm Hyphantria cunea (Lepidoptera: Arctiidae), cis-9,10-epoxy-(3Z,6Z)-3,6-henicosadiene and cis-9,10-epoxy-(3Z,6Z)-1,3,6-henicosatriene, possess an epoxy ring within their molecules. These compounds have been suggested to be biosynthesized from dietary linolenic acid via the following enzymatic reactions; chain elongation, terminal desaturation (in the case of the latter component), decarboxylation, and epoxidation. The last step of this biosynthesis, epoxidation, is known to occur specifically in the sex pheromone gland of females. We identified the enzyme involved in the epoxidation of pheromone precursors by focusing on cytochromes P450, which are known to catalyze the oxidation of various compounds. Three P450-like sequences (Hc_epo1, Hc_epo2, and Hc_epo3) were identified in the cDNA library prepared from the sex pheromone gland of H. cunea. Among these clones, only Hc_epo1 was specifically expressed in the pheromone gland. The full-length sequence of Hc_epo1 contained an ORF of 1527 bp, which encoded a protein of 509 amino acids with a predicted molecular weight of 57.9 kDa. The deduced Hc_epo1 amino acid sequence possessed the characteristics of P450. A phylogenetic analysis of the sequence indicated that Hc_epo1 belonged to the CYP341B clade in the CYP341 family. Therefore, it was named CYP341B14. A subsequent functional assay using Sf-9 cells transiently expressing CYP341B14 demonstrated that this P450 protein was able to specifically epoxidize a (Z)-double bond at the 9th position in the pheromone precursor, (3Z,6Z,9Z)-3,6,9-henicosatriene.

Putative pathway of sex pheromone biosynthesis and degradation by expression patterns of genes identified from female pheromone gland and adult antenna of Sesamia inferens (Walker)

The general pathway of biosynthesis and degradation for Type-I sex pheromones in moths is well established, but some genes involved in this pathway remain to be characterized. The purple stem borer, Sesamia inferens, employs a pheromone blend containing components with three different terminal functional groups (Z11-16:OAc, Z11-16:OH, and Z11-16:Ald) of Type-I sex pheromones. Thus, it provides a good model to study the diversity of genes involved in pheromone biosynthesis and degradation pathways. By analyzing previously obtained transcriptomic data of the sex pheromone glands and antennae, we identified 73 novel genes that are possibly related to pheromone biosynthesis (46 genes) or degradation (27 genes). Gene expression patterns and phylogenetic analysis revealed that one desaturase (SinfDes4), one fatty acid reductase (SinfFAR2), and one fatty acid xtransport protein (SinfFATP1) genes were predominantly expressed in pheromone glands, and clustered with genes involved in pheromone synthesis in other moth species. Ten genes including five carboxylesterases (SinfCXE10, 13, 14, 18, and 20), three aldehyde oxidases (SinfAOX1, 2 and 3), and two alcohol dehydrogenases (SinfAD1 and 3) were expressed specifically or predominantly in antennae, and could be candidate genes involved in pheromone degradation. SinfAD1 and 3 are the first reported alcohol dehydrogenase genes with antennae-biased expression. Based on these results we propose a pathway involving these potential enzyme-encoding gene candidates in sex pheromone biosynthesis and degradation in S. inferens. This study provides robust background information for further elucidation of the genetic basis of sex pheromone biosynthesis and degradation, and ultimately provides potential targets to disrupt sexual communication in S. inferens for control purposes.

Discovery of a disused desaturase gene from the pheromone gland of the moth Ascotis selenaria, which secretes an epoxyalkenyl sex pheromone

Female Ascotis selenaria (Geometridae) moths use 3,4-epoxy-(Z,Z)-6,9-nonadecadiene, which is synthesized from linolenic acid, as the main component of their sex pheromone. While the use of dietary linolenic or linoleic fatty acid derivatives as sex pheromone components has been observed in moth species belonging to a few families including Geometridae, the majority of moths use derivatives of a common saturated fatty acid, palmitic acid, as their sex pheromone components. We attempted to gain insight into the differentiation of pheromone biosynthetic pathways in geometrids by analyzing the desaturase genes expressed in the pheromone gland of A. selenaria. We demonstrated that a Δ11-desaturase-like gene (Asdesat1) was specifically expressed in the pheromone gland of A. selenaria in spite of the absence of a desaturation step in the pheromone biosynthetic pathway in this species. Further analysis revealed that the presumed transmembrane domains were degenerated in Asdesat1. Phylogenetic analysis demonstrated that Asdesat1 anciently diverged from the lineage of Δ11-desaturases, which are currently widely used in the biosynthesis of sex pheromones by moths. These results suggest that an ancestral Δ11-desaturase became dysfunctional in A. selenaria after a shift in pheromone biosynthetic pathways.

Identification of sex pheromone components of blueberry spanworm Itame argillacearia (Lepidoptera: Geometridae)

Blueberry spanworm, Itame argillacearia (Packard), is an important defoliator of lowbush (syn. 'wild') blueberry, Vaccinium angustifolium Aiton, in north-eastern North America. The goal of the present study was to identify the female I. argillacearia sex pheromone, which could be used in traps for monitoring or mass-trapping this pest. Gas chromatography/mass spectrometry (GC/MS) and electroantennogram (EAG) recordings of sex pheromone gland extracts, in combination with chemical synthesis, a Y-tube olfactometer study and field experiments confirmed (2R,3S)-2-ethyl-3-((Z,Z)-tridecadi-2,5-enyl) oxirane (hereafter (Z,Z)-(3R,4S)-3,4-epoxy-6,9-heptadecadiene) and (Z,Z,Z)-3,6,9-heptadecatriene as female-produced sex pheromone components. (Z,Z)-(3R,4S)-3,4-Epoxy-6,9-heptadecadiene elicited a response from male I. argillacearia antennae during EAG recording, and in the Y-tube olfactometer tests males did not discriminate between a live female and (Z,Z)-(3R,4S)-3,4-epoxy-6,9-heptadecadiene. Field-trapping experiments showed that a blend of (Z,Z)-(3R,4S)-3,4-epoxy-6,9-heptadecadiene and (Z,Z,Z)-3,6,9-heptadecatriene was more attractive to male moths than (Z,Z)-(3R,4S)-3,4-epoxy-6,9-heptadecadiene alone.

Characterization of posticlure and the structure-related sex pheromone candidates prepared by epoxidation of (6Z,9Z,11E)-6,9,11-trienes and (3Z,6Z,9Z,11E)-3,6,9,11-tetraenes

trans-11,12-Epoxy-(6Z,9Z)-6,9-henicosadiene (posticlure) has been identified from a pheromone gland of the lymantriid species, Orgyia postica. Since the diversity of Lepidoptera suggests that some species utilize the structure-related epoxy compound as a sex pheromone component, epoxydienes and epoxytrienes derived from (6Z,9Z,11E)-6,9,11-trienes and (3Z,6Z,9Z,11E)-3,6,9,11-tetraenes with a C19-C21 chain were systematically synthesized and the chemical data were accumulated in order to contribute to a new pheromone research. Peracid oxidation of each triene and each tetraene produced, respectively, a mixture of three epoxydienes (cis-6,7-epoxy-9,11-diene; cis-9,10-epoxy-6,11-diene; and trans-11,12-epoxy-6,9-diene) and four epoxytrienes (cis-3,4-epoxy-6,9,11-triene; cis-6,7-epoxy-3,9,11-triene; cis-9,10-epoxy-3,6,11-triene; and trans-11,12-epoxy-3,6,9-triene). While the 9,10-epoxy compounds were unstable and, interestingly, converted into 9-ketone derivatives after chromatography over SiO2, each positional isomer was isolated by HPLC equipped with an ODS column, and the chemical structure was determined by NMR analysis. On the GC-MS analysis with a DB-23 column, the positional isomers were also eluted separately and characteristic mass spectra were proposed. By comparing the spectral data of the epoxy compounds with a different carbon chain, diagnostic fragment ions reflecting the chemical structure were determined as follows: m/z 79, 109, 113, and M-114 for the 6,7-epoxydienes; m/z 69, 97, 111, 139, and M-111 for the 9,10-epoxydienes; m/z 57, 79, 109, 136, M-151, and M-111 for the 11,12-epoxydienes; m/z 79, 91, 105, and 119 for the 3,4-epoxytrienes; m/z 79, 124, M-124, M-96, and M-69 for the 6,7-epoxytrienes; m/z 79, 95, 109, 137, and M-108 for the 9,10-epoxytrienes; and m/z 79, 134, M-149, M-109, and M-95 for the 11,12-epoxytrienes.