Acyl-CoA Z9- and Z10-desaturase genes from a New Zealand leafroller moth species,Planotortrix octo

Two cDNAs encoding acyl-CoA Z9-desaturase from the fat body and Z10-desaturase from the pheromone gland of the greenhead leafroller moth, Planotortrix octo, were obtained by RACE PCR. The Z9-desaturase (Pocto-Z9) cDNA spans 2291 nt with an ORF encoding a 352 amino-acid protein, which has 65% identity to Trichoplusia ni Delta 9 desaturase (Tni-Z9). The Z10-desaturase (Pocto-Z10) cDNA spans 2777 nt with an ORF encoding a protein with 356 amino acids. Pocto-Z10 shows lower identity to Pocto-Z9 and Tni-Z9 (48 and 46%, respectively) and relatively higher identity to the Delta 11 desaturases of T. ni and Helicoverpa zea (57 and 56%, respectively). The ORFs of these two P. octo cDNAs were constructed into an expression vector, YEpOLEX, that complemented the unsaturated fatty acid (UFA) auxotrophy of a desaturase-deficient ole1 strain of Saccharomyces cerevisiae. Expression of Pocto-Z9 produced a 5:2 ratio of Z9-16 and Z9-18 acids, with minor amounts (<4%) of Z9-14, Z9-15, and Z9-17 acids. Pocto-Z10 was successfully expressed in the YEpOLEX system when complemented with Z11-18:Me, and the major desaturase product proved to be Z10-16:Acid. The results confirm the regio- and stereo-selectivity of this unusual Delta 10 desaturase.     

Moth desaturase characterized that produces both Z and E isomers of delta 11-tetradecenoic acids

The redbanded leafroller moth, Argyrotaenia velutinana (Lepidoptera: Tortricidae) uses a 92:8 mixture of (Z)-11- and (E)-11-tetradecenyl acetate in its pheromone blend. These are produced in the abdominal pheromone gland from the corresponding acids, which are biosynthesized in the gland in a 3:2 Z/E ratio by desaturation of myristoyl CoA. The delta 11 desaturase involved in this reaction exhibits unusual substrate and stereospecificities in specifically producing Z11 and E11 isomers of tetradecenoic acid, and exhibiting no activity with C16 and C18 precursor acids. This report describes the cloning and expression of the redbanded leafroller moth delta 11 desaturase, and compares its amino-acid sequence to those of other known insect Z9, Z10, Z11, and E11 desaturases. The metabolic Z9 desaturase from fat body tissue also was cloned and expressed, and found mainly to produce Z9-16:Acid and Z9-18:Acid. The open reading frame of the delta 11 desaturase encodes a protein with 329 amino acids, whereas the open reading frame of the Z9 desaturase encodes a protein with 351 amino acids. Addition of this new delta 11 desaturase with its different substrate and regiospecificites to the databank of characterized integral-membrane desaturases will be key in efforts to determine amino-acid mutations responsible for the wide array of unsaturated fatty-acid products.     

The effects of topical application of various fatty acids on pheromone and glandular lipid biosynthesis in the moth Heliothis virescens

Binary mixtures of deuterium-labeled palmitic acid and an excess of different fatty acids were applied to the sex pheromone gland of female Heliothis virescens and the effects on the terminal steps of pheromone biosynthesis, including incorporation of fatty acids into the glandular lipids, observed. Relative to labeled palmitic acid applied alone, application of all the binary mixtures resulted in decreased levels of the labeled pheromone component, (Z)-11-hexadecenyl acetate (Z11-16:OAc), but there was generally no decrease in the amounts of labeled pheromone precursor, (Z)-11-hexadecenoate, nor labeled palmitate in the glandular lipids. These data suggest that the excess of fatty acid in the gland inhibits Delta11-desaturation. However, in the case of excess myristoleic acid, the amount of labeled (Z)-11-hexadecenoate increased significantly, suggesting that this acid inhibited fatty acid reduction. Dose-response tests with certain of the fatty acids were consistent with the above interpretations and further indicated that the gland had a high capacity for rapidly activating and incorporating excess fatty acids into the glandular lipids. Finally, application of the various fatty acids resulted in increased levels of these acids in the gland and, in the cases of myristoleic, palmitoleic and myristic acids, it also resulted in increased levels of the corresponding aldehydes, which had previously been detected in the gland of female H. virescens. This suggests that the fatty acid reductase in H. virescens is not highly specific for the major component, and that the final ratio of pheromone components is determined in part by the availability of their corresponding fatty acids in the gland.     

Lipid analysis of the sex pheromone gland of the moth Heliothis virescens

The sex pheromone gland of female Heliothis virescens was analyzed for fatty acid and lipid content. Base methanolysis of the gland showed a large amount of methyl (Z)-11-hexadecenoate (Z11-16:Acyl), the fatty acyl analog of the major pheromone component, (Z)-11-hexadecenal, as well as a small amount of methyl (Z)-11-octadecenoate. Methyl esters of various common fatty acids were also observed. HPTLC analysis of the glandular lipids revealed large quantities of triacylglycerols (TGs), and lesser amounts of 1,2-diacylglycerols (1,2-DGs), 2-monoacylglycerols (2-MGs), phosphatidyl ethanolamines, and phosphatidyl cholines. The greatest amount of Z11-16:Acyl in these lipids was in the TGs, with lesser amounts in the two phospholipid classes and only trace amounts in the other neutral lipids. The glands of females at various ages and photoperiodic times were extracted, fractionated into neutral and polar fractions by silica SPE, and fatty acid titers in these fractions determined. All fatty acids, but notably Z11-16:Acyl, showed significant total and neutral lipid fraction peaks at mid scotophase for 2-day-old females; a less dramatic, but significant, Z11-16:Acyl peak in the polar fraction was also observed. However, only a relatively small proportion (<50%) of this acid was recovered from the silica at all times. This "non-recoverable" Z11-16:Acyl showed a dramatic and significant peak at mid scotophase for 2-day females, corresponding roughly with maximal pheromone titer. All other acids in the gland were recovered in high proportions, and their respective "non-recoverable" titers were not different at any of the times analyzed. Based on previous work, this non-recoverable Z11-16:Acyl is likely the CoA ester. Therefore, it appears that the pheromone gland of H. virescens maintains pools of Z11-16:Acyl in both CoA ester and TG forms, which are available for biosynthesis of pheromone. These pools are greatest during maximal pheromone production when the biosynthetic enzymes, possibly the fatty acid reductase, are unable to utilize rapidly enough the quantities of Z11-16:Acyl biosynthesized.     

Effect of the pheromone biosynthesis activating neuropeptide on sex pheromone biosynthesis in Spodoptera littoralis isolated glands

The control of Spodoptera littoralis sex pheromone biosynthesis has been investigated with synthetic pheromone biosynthesis activating neuropeptide (PBAN) and different labeled tracers using an in vitro isolated gland system. Responsiveness of the glands to PBAN stimulation was impaired by careless tissue manipulation. The fact that PBAN is active in the isolated gland system suggests that this might be a target organ for this peptide in S. littoralis. As reported previously with Br-SOG extracts and intact females, label incorporation into the pheromone increased in glands treated with PBAN from all the precursors tested. However, the formation of labeled intermediates from d₅E11–14:Acid also occurred in glands incubated in the absence of the peptide, but the amounts of d₅Z9, E11–14:Acid were lower in PBAN treated glands than in controls. These results indicate that PBAN controls pheromone biosynthesis in S. littoralis by regulating the reduction of acyl moieties. © 1994 Wiley-Liss, Inc.     

Pheromone biosynthetic pathways in the moths Helicoverpa zea and Helicoverpa assulta

Sex pheromones of many Lepidopteran species have relatively simple structures consisting of a hydrocarbon chain with a functional group and usually one to several double bonds. The sex pheromones are usually derived from fatty acids through a specific biosynthetic pathway. We investigated the incorporation of deuterium-labeled palmitic and stearic acid precursors into pheromone components of Helicoverpa zea and Helicoverpa assulta. The major pheromone component for H. zea is (Z)11-hexadecenal (Z11-16:Ald) while H. assulta utilizes (Z)9-hexadecenal (Z9-16:Ald). We found that H. zea uses palmitic acid to form Z11-16:Ald via delta 11 desaturation and reduction, but also requires stearic acid to biosynthesize the minor pheromone components Z9-16:Ald and Z7-16:Ald. The Z9-16:Ald is produced by delta 11 desaturation of stearic acid followed by one round of chain-shortening and reduction to the aldehyde. The Z7-16:Ald is produced by delta 9 desaturation of stearic acid followed by one round of chain-shortening and reduction to the aldehyde. H. assulta uses palmitic acid as a substrate to form Z9-16:Ald, Z11-16:Ald and 16:Ald. The amount of labeling indicated that the delta 9 desaturase is the major desaturase present in the pheromone gland cells of H. assulta; whereas, the delta 11 desaturase is the major desaturase in pheromone glands of H. zea. It also appears that H. assulta lacks chain-shortening enzymes since stearic acid did not label any of the 16-carbon aldehydes.     

The fate of topically applied fatty acids in the sex pheromone gland of the moth Heliothis virescens

Deuterium-labeled hexadecanoic acid (D4-16:COOH), a sex pheromone biosynthetic intermediate, and heptadecanoic acid (D3-17:COOH), an acid that cannot be converted to sex pheromone, were topically applied to the pheromone gland of female Heliothis virescens, and the fate of the label determined. Both acids were incorporated similarly into the glycerolipids, with by far the greatest amount found in the triacylglycerols (TGs), and relatively small amounts found in other neutral and polar classes. For D4-16:COOH, the labeled pheromone precursor, (Z)-11-hexadecenoate, was also found predominantly in the TGs but relatively (compared to labeled hexadecanoate) high amounts were also found in the phospholipids. Within the TGs, both acids, as well as the pheromone precursor, were found almost exclusively on the sn-3 position of the glycerol backbone. This demonstrates that the major fate, in the glycerolipids, of free fatty acids is addition to 1,2-diacylglycerols. A relatively large amount of the applied acid was also found in the gland in the form of the acyl-CoA thioester. In a 24-h time-course study, this form remained at a relatively high level for the duration of the assay, and decreased at a rate comparable to the titer of this acid in the TGs, suggesting that titers of fatty acids in the glycerolipids and acyl-CoA thioesters may be in equilibrium. A time-course assay with D4-16:COOH demonstrated that peak pheromone titer after application was reached before peak titers of both total hexadecanoate and hexadecanoyl-CoA. Combined with a dose-response experiment, which showed that labeled pheromone titer did not increase above an applied concentration of 20 mg/ml, these data suggest that the final step in pheromone biosynthesis, reduction of Z11-16:Acyl-CoA, may be inhibited by increased acyl-CoA titers in the gland. Overall, our data are consistent with the glycerolipids modulating acyl-CoA concentrations in the pheromone gland.     

Moth sex pheromones affect interspecific competition among sympatric species and possibly population distribution by modulating pre-mating behavior

Premating behaviors mediated by pheromones play pivotal roles in animal mating choices. In natural populations of the striped stem borer Chilo suppressalis and the rice leaf roller Cnaphalocrocis medinalis in the rice field habitat, we discovered that Z11-16:Ald, a major component of the C. suppressalis pheromone, modulated the premating behavior of C. medinalis. Z11-16:Ald evoked a strong olfactory response in male antennae and strongly inhibited the sex pheromone trapping of male C. medinalis in the field. The functions of three C. medinalis sex pheromone receptor genes (CmedPR1–3) were verified through heterologous expression in Xenopus oocytes. CmedPR1 responded to Z11-18:OH and Z11-18:Ald, as well as the interspecific pheromone compound Z11-16:Ac of sympatric species; CmedPR2 responded to Z13-18:OH and Z13-18:Ald, as well as the sex pheromone compounds Z11-16:Ald and Z9-16:Ald of sympatric species; and CmedPR3 responded to Z11-18:OH and Z13-18:OH, as well as the interspecific pheromones Z11-16:OH, Z9-16:Ald, Z11-16:Ac, and Z11-16:Ald of sympatric species. Thus, CmedPR2 and CmedPR3 share the ligand Z11-16:Ald, which is not a component of the C. medinalis sex pheromone. Therefore, the sex pheromones of interspecific species affected the input of neural signals by stimulating the sex pheromone receptors on the antennae of male C. medinalis moths, thereby inhibiting the olfactory responses of the male moths to the sex pheromones. Our results demonstrate chemical communication among sympatric species in the rice field habitat, the recognition of intra- and interspecific sex pheromones by olfactory receptors, and how insect premating behaviors are modulated to possibly affect resource partitioning.     

cDNA cloning and in situ hybridization of Delta11-desaturase, a key enzyme of pheromone biosynthesis in Ostrinia scapulalis (Lepidoptera: Crambidae)

Female sex pheromones are considered to be produced in a "pheromone gland" located in the terminal abdominal segments (8th-10th, TAS) of a moth; however, in many moth species, the cells that produce pheromones have not actually been specified. We investigated cells in the TAS that synthesize pheromones in the adzuki bean borer Ostrinia scapulalis, by locating pheromones and their precursors, and mRNA for Delta11-desaturase, a key enzyme in pheromone biosynthesis. We demonstrated that the pheromone components, (E)-11- and (Z)-11-tetradecenyl acetates, and their fatty acyl precursors were specifically contained in the dorsal part of the TAS. A cDNA (OscaZ/E11) that encodes a Delta11-desaturase was cloned from the TAS. RT-PCR and in situ hybridization unequivocally showed that OscaZ/E11 is specifically expressed in the modified epidermal cells located at the dorsal end of the 8th-9th intersegmental membrane.     

Communication interference in sympatrically occurring moth species

In moth species, females emit a species‐specific sex pheromone that is perceived over long distance by conspecific males. The species‐specificity in the chemical communication channel is achieved by a combination of unique components in specific ratios and sometimes also by interspecific behavioural antagonists to deter sympatrically occurring heterospecific males. In this study, we determined possible antagonistic effects in Helicoverpa gelotopoeon Dyar (Lepidoptera: Noctuidae) males to the major sex pheromone component of sympatrically occurring heliothine moths, Z11‐16:Ald, as well as to the sex pheromone of the sympatrically occurring Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) (Z11‐16:Ald and Z9‐14:Ald). We also explored whether other co‐occurring species are attracted to these pheromone blends. Our field experiments showed that the addition of Z11‐16:Ald alone or in combination with Z9‐14:Ald inhibited trap catches of H. gelotopoeon males and that this inhibition depended on the concentration of these compounds. In addition, other moth species were attracted to the blends. Together, our results confirm the antagonistic effect of heterospecific sex pheromone compounds of H. virescens to H. gelotopoeon.     

Sex pheromone precursors in the processionary moth Thaumetopoea pityocampa (Lepidoptera: Thaumetopoeae)

The fatty acid composition of Thaumetopoea pityocampa female sex pheromone gland was determined. In addition to the common C16 and C18 fatty acids, the glandular tissue contains large amounts of (Z)-11-hexadecenoate, (Z,Z)-11,13-hexadecadienoate, (Z)-13-hexadecen-11-ynoate and 11-hexadecynoate, as well as some unusual C18 fatty acids, such as (Z)-11 and (Z)-13-octadecenoic acids. From these results, different biosynthetic pathways are discussed for the formation of (Z)-13-hexadecen-11-ynyl acetate, the main component of the sex pheromone of the processionary moth.     

Thiafatty acids as tracers to investigate biosynthetic pathways of lepidopteran sex pheromones

In order to investigate the potential utility of thiafatty acids as tracers for biosynthetic studies of moth sex pheromones, a series of thiatetradecanoic acids, namely 8-, 9-, 10-, 11-, 12- and 13-thiatetradecanoic, were prepared and their metabolism was investigated in pheromone glands of Spodoptera littoralis. Analysis by gas chromatography coupled to mass spectrometry of extracts from pheromone glands treated with the above acids showed that only 8-thiatetradecanoic acid and 13-thiatetradecanoic acid were metabolized by desaturation and were incorporated into the sex pheromone biosynthetic pathway. 13-Thiatetradecanoic acid was converted into (E)- and (Z)-13-thiatetradec-11-enoic acids, (Z,E)-13-thiatetradeca-9,11-dienoic acid, 11-thiadodecanoic acid, (E)- and (Z)-11-thiadodec-9-enoic acids and 15-thiahexadecanoic acid. 8-Thiatetradecanoic acid gave rise to two monoenoic thiafatty acids and two dienoic thiafatty acids, which were assigned to (Z)- and (E)-8-thiatetradec-11-enoic acids, (Z,E)-8-thiatetradeca-9,11-dienoic acid and (E,E)-8-thiatetradeca-10,12-dienoic acid. The other thiafatty acids tested, 9-, 10-, 11- and 12-thiatetradecanoic acids, were not metabolized by desaturation, although the corresponding products of beta-oxidation and chain elongation were detected. The occurrence of sulfoxides was not detected in this case, in disagreement with results on the metabolism of some thiaacids previously reported by other authors in yeast, Saccharomyces cerevisiae.     

Key biosynthetic gene subfamily recruited for pheromone production prior to the extensive radiation of Lepidoptera

Background  

Moths have evolved highly successful mating systems, relying on species-specific mixtures of sex pheromone components for long-distance mate communication. Acyl-CoA desaturases are key enzymes in the biosynthesis of these compounds and to a large extent they account for the great diversity of pheromone structures in Lepidoptera. A novel desaturase gene subfamily that displays Δ11 catalytic activities has been highlighted to account for most of the unique pheromone signatures of the taxonomically advanced ditrysian species. To assess the mechanisms driving pheromone evolution, information is needed about the signalling machinery of primitive moths. The currant shoot borer, Lampronia capitella, is the sole reported primitive non-ditrysian moth known to use unsaturated fatty-acid derivatives as sex-pheromone. By combining biochemical and molecular approaches we elucidated the biosynthesis paths of its main pheromone component, the (Z,Z)-9,11-tetradecadien-1-ol and bring new insights into the time point of the recruitment of the key Δ11-desaturase gene subfamily in moth pheromone biosynthesis.     

Sex pheromone biosynthesis in the tortricid moth Planotortrix excessana (Walker) involves chain-shortening of palmitoleate and oleate

Biosynthesis of the sex pheromone components, (Z)-5-tetradecenyl acetate (Z5-14:OAc) and (Z)-7-tetradecenyl acetate (Z7-14:OAc), was investigated in the New Zealand tortricid moth Planotortrix excessana (Walker) by fatty acid methyl ester (FAME) analysis of base-methanolyzed extracts of lipids in the sex pheromone gland and through application of various labelled fatty acids. Analysis of the base-methanolyzed gland extracts revealed common FAMEs, including methyl oleate and methyl palmitoleate, as well as the FAMEs of the putative precursors, methyl (Z)-5-tetradecenoate and methyl (Z)-7-tetradecenoate. Application of labelled, saturated fatty acids, myristic, palmitic, and stearic did not result in any significant incorporation of label into either of the unsaturated pheromone components, although label was incorporated into tetradecyl acetate (14:OAc). In contrast, application of labelled oleic acid resulted in incorporation of label into Z5-14:OAc but not into Z7-14:OAc or into 14:OAc, whereas application of labelled palmitoleic acid resulted in incorporation of label into Z7-14:OAc but not into Z5-14:OAc or 14:OAc. These data support a route for biosynthesis of Z5-14:OAc and Z7-14:OAc in this species by limited β-oxidation of the common fatty acyl moieties, respectively, oleate (involving two cycles of 2-carbon chain-shortening) and palmitoleate (involving only one cycle of 2-carbon chain-shortening), and apparently involving no desaturase (other than the common Δ9) specific to sex pheromone biosynthesis. Interestingly, P. excessana females biosynthesize the same component (Z5-14:OAc) from an entirely different route from that of the related species Ctenopseustis obliquana (which biosynthesizes Z5-14:OAc by Δ5-desaturation of myristate). Additionally, the pheromone biosynthesis activating neuropeptide (PBAN) stimulates pheromone biosynthesis in this species. Arch. Insect Biochem. Physiol. 37:158–167, 1998. © 1998 Wiley-Liss, Inc.     

Pheromone biosynthetic pathways in the moths Heliothis subflexa and Heliothis virescens

Sex pheromones of many moth species have relatively simple structures consisting of a hydrocarbon chain with a functional group and one to several double bonds. These sex pheromones are derived from fatty acids through specific biosynthetic pathways. We investigated the incorporation of deuterium-labeled tetradecanoic, hexadecanoic, and octadecanoic acid precursors into pheromone components of Heliothis subflexa and Heliothis virescens. The two species utilize (Z)11-hexadecenal as the major pheromone component, which is produced by Delta11 desaturation of hexadecanoic acid. H. subflexa also produced (Z)11-hexadecanol and (Z)-11-hexadecenyl acetate via Delta11 desaturation. In H. subflexa, octadecanoic acid was used to biosynthesize the minor pheromone components (Z)9-hexadecenal, (Z)9-hexadecenol, and (Z)9-hexadecenyl acetate. These minor components are produced by Delta11 desaturation of octadecanoic acid followed by one round of chain-shortening. In contrast, H. virescens used hexadecanoic acid as a substrate to form (Z)11-hexadecenal and (Z)11-hexadecenol and hexadecenal. H. virescens also produced (Z)9-tetradecenal by Delta11 desaturation of the hexadecanoic acid followed by one round of chain-shortening and reduction. Tetradecanoic acid was not utilized as a precursor to form Z9-14:Ald in H. virescens. This labeling pattern indicates that the Delta11 desaturase is the only active desaturase present in the pheromone gland cells of both species.     

Functional characterization of a desaturase from the tobacco hornworm moth (Manduca sexta) with bifunctional Z11- and 10,12-desaturase activity

The pheromone blend produced by the tobacco hornworm moth (Manduca sexta) (L.) female is unusually complex and contains two conjugated dienals and trienals together with two monounsaturated alkenals. Here, we describe the identification and construction of two genes encoding MsexKPSE and MsexAPTQ desaturases from a cDNA library prepared from the total RNA of the M. sexta pheromone gland. The MsexKPSE desaturase shares a high degree of similarity with Delta(9)-desaturases from different moth species. The functional expression of MsexAPTQ desaturase in Saccharomyces cerevisiae followed by a detailed GC-MS analysis of fatty acid methyl esters (FAME) and their derivatized products and gas-phase Fourier transform infrared (FTIR) spectroscopy of the extracted FAME confirms that this enzyme is a bifunctional Z-Delta(11)-desaturase. MsexAPTQ desaturase catalyses the production of Z11-hexadecenoate (Z11-16) and Z10E12- and E10E12-hexadecadienoates (Z10E12-16) via 1,4-desaturation of the Z11-16 substrate. The stereochemistry of 1,4-desaturation and formation of isomers is discussed.     

Comparative study of sex pheromone composition and biosynthesis in Helicoverpa armigera, H. assulta and their hybrid

Two Helicoverpa species, H. armigera and H. assulta use (Z)-11-hexadecenal and (Z)-9-hexadecenal as their sex attractant pheromone components but in opposite ratios. Since both female and male interspecific hybrids produced by female H. assulta and male H. armigera have been obtained in our laboratory, we can make a comparative study of sex pheromone composition and biosynthesis in the two species and their hybrid. With GC and GC-MS analyses using single gland extracts, the ratio of (Z)-9-hexadecenal to (Z)-11-hexadecenal was determined as 2.1:100 in H. armigera, and 1739:100 in H. assulta. The hybrid has a ratio of 4.0: 100, which is closer to that of H. armigera, but significantly different from H. armigera. We investigated pheromone biosynthesis with labeling experiments, using various fatty acid precursors in H. armigera, H. assulta and the hybrid. In H. armigera, (Z)-11-hexadecenal is produced by delta11 desaturation of palmitic acid, followed by reduction and terminal oxidation; (Z)-9-hexadecenal results from delta11 desaturation of stearic acid, followed by one cycle of chain shortening, reduction and terminal oxidation. delta11 desaturase is the unique desaturase for the production of the two pheromone components. In our Chinese strain of H. assulta, palmitic acid is used as the substrate to form both the major pheromone component, (Z)-9-hexadecenal and the minor one, (Z)-11-hexadecenal. Our data suggest that delta9 desaturase is the major desaturase, and delta11 desaturase is responsible for the minor component in H. assulta, which is consistent with previous work. However, the weak chain shortening acting on (Z)-9 and (Z)-11-octadecenoic acid, which is present in the pheromone glands, does occur in this species to produce (Z)-7 and (Z)-9-hexadecenoic acid. In the hybrid, the major pheromone component, (Z)-11-hexadecenal is produced by delta11 desaturation of palmitic acid, followed by reduction and terminal oxidation. The direct fatty acid precursor of the minor component, (Z)-9-hexadecenoic acid is mainly produced by delta9 desaturation of palmitic acid, but also by delta11 desaturation of stearic acid and one cycle of chain shortening. The greater relative amounts of (Z)-9-hexadecenal in the hybrid are due to the fact that both palmitic and stearic acids are used as substrates, whereas only stearic acid is used as substrate in H. armigera. The evolutionary relationships between the desaturases in several Helicoverpa species are also discussed in this paper.     

Chromosome-level genomes of two armyworms,Mythimna separata and Mythimna loreyi,provide insights into the biosynthesis and reception of sex pheromones

Mythimna separata and Mythimna loreyi are global pests of gramineous cereals, heavily controlled with synthetic insecticides. Here, we generated two high-quality chromosome-level genome assemblies for M. separata (688 Mb) and M. loreyi (683 Mb). Our analysis identified Z and W chromosomes, with few genes and abundant transposable elements (TEs) found on the W chromosome. We also observed a recent explosion of long interspersed nuclear elements (LINEs), which contributed to the larger genomes of Mythimna. The two armyworms diverged ~10.5 MYA, with only three chromosomes have intrachromosomal rearrangements. Additionally, we observed a tandem repeat expansion of α-amylase genes in Mythimna, which may promote the digestion of carbohydrates and exacerbate their damage to crops. Furthermore, we inferred the sex pheromone biosynthesis pathway for M. separata, M. loreyi and Spodoptera frugiperda. We discovered that M. loreyi and S. frugiperda synthesized the same major constituents of sex pheromones through different pathways. Specifically, the double bonds in the dominant sex pheromone components of S. frugiperda were generated by Δ9- and Δ11-desaturase, while they were generated by Δ11-desaturase and chain-shortening reactions in M. loreyi. We also identified pheromone receptor (PR) genes and inferred their corresponding components. These findings provide a better understanding of sex pheromone communication and promote the development of a new pest control strategy involving pheromone traps, which are more effective and environmentally friendly than current strategies.