cDNA cloning and sequence determination of the pheromone biosynthesis activating neuropeptide of Mamestra brassicae: a new member of the PBAN family

Supplemental Sugar Is Required for Sex Pheromone Biosynthesis in Mythimna separata

Supplemental nutrients of adult moths maximize moth fitness and contribute to the pollination of many plants. Previous reports have revealed that sugar feeding promotes to sex pheromone biosynthesis by increasing the haemolymph trehalose concentration in mating moths. Here, Mythimna separata adults were employed as a model to investigate the effect of sugar feeding on sex pheromone biosynthesis. Results showed that in virgin females, sugar feeding markedly increased the concentrations of trehalose, pyruvic acid, and acyl-CoA in pheromone glands (PGs), which in turn led to an increase in sex pheromone titer, female ability to attract males and successfully mating frequency in sugar-fed females. Consistently, sugar-fed females laid more eggs than water-fed females. Furthermore, the refeeding of starved females also caused significantly increase in the concentrations of trehalose, pyruvic acid, and acyl-CoA in PGs, thus facilitating a significant increase in sex pheromone production. Most importantly, RNAi-mediated knockdown of trehalase (leading to PG starvation) resulted in an increase in trehalose content, and decrease in the concentrations of pyruvic acid, and acyl-CoA in PGs, which in turn led to a decrease of sex pheromone titer, female ability to attract males and successful mating efficacy. Altogether, results revealed a mechanism by which sugar feeding contributed to trehalose utilization in PGs, promoted to significantly increased sex pheromone precursor by increasing the concentrations of pyruvic acid and acyl-CoA, and facilitated to sex pheromone biosynthesis and successful mating.

Identification and functional characterization of the pheromone biosynthesis activating neuropeptide receptor isoforms from Mamestra brassicae

In most moth species, including Mamestra brassicae, pheromone biosynthesis activating neuropeptide (PBAN) regulates pheromone production. Generally, PBAN acts directly on the pheromone gland (PG) cells via its specific G protein-coupled receptor (i.e. PBANR) with Ca²⁺ as a second messenger. In this study, we identified cDNAs encoding three variants (A, B and C) of the M. brassicae PBANR (Mambr-PBANR). The full-length coding sequences were transiently expressed in cultured Trichoplusia ni cells and Sf9 cells for functional characterization. All three isoforms dose-dependently mobilized extracellular Ca²⁺ in response to PBAN analogs with Mambr-PBANR-C exhibiting the greatest sensitivity. Fluorescent confocal microscopy imaging studies demonstrated binding of a rhodamine red-labeled ligand (RR10CPBAN) to all three Mambr-PBANR isoforms. RR10CPBAN binding did not trigger ligand-induced internalization in cells expressing PBANR-A, but did in cells expressing the PBANR-B and -C isoforms. Furthermore, activation of the PBANR-B and -C isoforms with the 18 amino acid Mambr-pheromonotropin resulted in co-localization with a Drosophila melanogaster arrestin homolog (Kurtz), whereas stimulation with an unrelated peptide had no effect. PCR-based profiling of the three transcripts revealed a basal level of expression throughout development with a dramatic increase in PG transcripts from the day of adult emergence with PBANR-C being the most abundant.

Identification and expression profiling of pheromone biosynthesis activating neuropeptide in Chlumetia transversa (Walker)

Insect neuropeptides (NPs) in the pyrokinin/pheromone biosynthesis-activating neuropeptide (PBAN) family are actively involved in many essential endocrine functions. These peptides are potential targets in the search for novel insect control agents. This is the first report on the cloning and sequence determination of Chlumetia transversa (Walker) PBAN (Ct-PBAN) using rapid amplification of cDNA ends. The open reading frame of Ct-PBAN was 588bp in length and encoded 195 amino acids, which were assembled into five putative neuropeptides (diapause hormone homolog, α-neuropeptide, β-neuropeptide, PBAN, and γ-neuropeptide). These peptides were amidated at C-terminus and shared the conserved pentapeptide motif FXPR (or K) L. Moreover, Ct-PBAN had high homology to PBANs in Helicoverpa zea (84.1%), Helicoverpa armigera (83.5%), Helicoverpa assulta (83%), and Heliothis virescens (82.6%). Phylogenetic analysis showed that Ct-PBAN was closely related to its orthologs in the family Noctuidae. In addition, real-time quantitative polymerase chain reaction assays showed that the expression of Ct-PBAN peaked in the female head and was also detected at high levels in 1-d-old adults. These results suggested that Ct-PBAN is associated with sex pheromone biosynthesis in female C. transversa and could be used for developing C. transversa control systems based on molecular techniques.

Agonist-mediated activation of Bombyx mori diapause hormone receptor signals to extracellular signal-regulated kinases 1 and 2 through Gq-PLC-PKC-dependent cascade

Diapause is a developmental strategy adopted by insects to survive in challenging environments such as the low temperatures of a winter. This unique process is regulated by diapause hormone (DH), which is a neuropeptide hormone that induces egg diapause in Bombyx mori and is involved in terminating pupal diapause in heliothis moths. An G protein-coupled receptor from the silkworm, B. mori, has been identified as a specific cell surface receptor for DH. However, the detailed information on the DH-DHR system and its mechanism(s) involved in the induction of embryonic diapause remains unknown. Here, we combined functional assays with various specific inhibitors to elucidate the DHR-mediated signaling pathways. Upon activation by DH, B. mori DHR is coupled to the Gq protein, leading to a significant increase of intracellular Ca(2+) and cAMP response element-driven luciferase activity in an UBO-QIC, a specific Gq inhibitor, sensitive manner. B. mori DHR elicited ERK1/2 phosphorylation in a dose- and time-dependent manner in response to DH. This effect was almost completely inhibited by co-incubation with UBO-QIC and was also significantly suppressed by PLC inhibitor U73122, PKC inhibitors Gö6983 and the Ca(2+) chelator EGTA. Moreover, DHR-induced activation of ERK1/2 was significantly attenuated by treatment with the Gβγ specific inhibitors gallein and M119K and the PI3K specific inhibitor Wortmannin, but not by the Src specific inhibitor PP2. Our data also demonstrates that the EGFR-transactivation pathway is not involved in the DHR-mediated ERK1/2 phosphorylation. Future efforts are needed to clarify the role of the ERK1/2 signaling pathway in the DH-mediated induction of B. mori embryonic diapause.

The regulation of Δ11-desaturase gene expression in the pheromone gland of Mamestra brassicae (Lepidoptera; Noctuidae) during pheromonogenesis

Cabbage moth (Mamestra brassicae) females produce sex pheromones to attract conspecific males. In our M. brassicae colony, the pheromone blend is composed of Z11-hexadecenyl acetate (Z11-16Ac) and hexadecyl acetate (16Ac) in a 93:7 ratio. A fatty acyl Δ11-desaturase is involved in the production of the main pheromone component. The release of Pheromone Biosynthesis Activating Neuropeptide (PBAN) regulates the pheromone production in the pheromone gland (PG). We cloned a cDNA encoding the MambrΔ11-desaturase and analyzed its expression profile over time in M. brassicae tissues. Transcript levels of the Δ11-desaturase in larvae, pupal PGs, fat body, brain and muscle tissues were <0.1% of that in female PGs, whereas expression in male genitalia was 2%. In the PGs of virgin females the expression level increased continuously from eclosion to the end of the 1st day when it reached a plateau without further significant fluctuation up to the 8th day. In contrast, we recorded a characteristic daily rhythmicity in pheromone production with a maximum around 200 ng Z11-16Ac/PG. In some experiments, females were decapitated to prevent PBAN release and thereby inhibit pheromone production, which remarkably increased after treatment with Mambr-Pheromonotropin. Further experiments revealed that mating resulted in a significant suppression of pheromone production. However, expression of the Δ11-desaturase was not affected by any of these interventions, suggesting that it's not regulated by PBAN. Fluorescent microscopy was used to study the potential role of lipid droplets during pheromone production, however, no lipid droplets were identified indicating that pheromonogenesis is regulated via de novo fatty acid synthesis.

Transcription factor fork head regulates the promoter of diapause hormone gene in the cotton bollworm, Helicoverpa armigera, and the modification of SUMOylation

The transcription factor fork head (FoxA) plays important roles in development and metabolism. Here, we cloned a fork head gene in Helicoverpa armigera, and found that the fork head protein is mainly located in the nucleus. This fork head gene belongs to the FoxA subfamily of the Fox transcription factors. The diapause hormone and pheromone biosynthesis-activating neuropeptide (DH-PBAN), which are two well-documented insect neuropeptides that regulate insect development and pheromone biosynthesis, are encoded by a single mRNA. In the present study, fork head was shown to bind strongly to the promoter of H. armigera DH-PBAN gene, and regulate its promoter activity. Furthermore, the effect of SUMOylation of the FH protein on the regulation of Har-DH-PBAN gene was investigated, and we show that the SUMO can modify Har-FH protein and cause down-regulation of DH-PBAN gene expression. These results suggest that SUMOylated FH plays a key role in insect diapause in H. armigera.

RNA interference of pheromone biosynthesis-activating neuropeptide receptor suppresses mating behavior by inhibiting sex pheromone production in Plutella xylostella (L.)

Sex pheromone production is regulated by pheromone biosynthesis-activating neuropeptide (PBAN) in many lepidopteran species. We cloned a PBAN receptor (Plx-PBANr) gene from the female pheromone gland of the diamondback moth, Plutella xylostella (L.). Plx-PBANr encodes 338 amino acids and has conserved structural motifs implicating in promoting G protein coupling and tyrosine-based sorting signaling along with seven transmembrane domains, indicating a typical G protein-coupled receptor. The expression of Plx-PBANr was found only in the pheromone gland of female adults among examined tissues and developmental stages. Heterologous expression in human uterus cervical cancer cells revealed that Plx-PBANr induced significant calcium elevation when challenged with Plx-PBAN. Female P. xylostella injected with double-stranded RNA specific to Plx-PBANr showed suppression of the receptor gene expression and exhibited significant reduction in pheromone biosynthesis, which resulted in loss of male attractiveness. Taken together, the identified PBAN receptor is functional in PBAN signaling via calcium secondary messenger, which leads to activation of pheromone biosynthesis and male attraction.

Expression of pheromone biosynthesis activating neuropeptide and its receptor (PBANR) mRNA in adult female Spodoptera exigua (Lepidoptera: Noctuidae)

The full-length cDNA of pheromone biosynthesis activating neuropeptide receptor (PBANR) was cloned from the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae); it included an open reading frame of 1,053 bp encoding 350 amino acids. The PBANR of S. exigua (SePBANR) was structurally characteristic of G protein-coupled receptor and its amino acid sequence shared 98% identity with the PBANR of Spodoptera littoralis. Both pheromone biosynthesis activating neuropeptide (PBAN) and PBANR mRNA abundance were measured in the brain-subesophageal ganglion complex, pheromone gland, ventral nerve cord, and ovary of S. exigua female moths by real-time RT-PCR. The abundance of PBAN mRNA in brain-subesophageal ganglion complex and PBANR mRNA in pheromone gland was significantly greater compared to other tissues, suggesting that the ligand-receptor relationship of PBAN and PBANR exists quantitatively in S. exigua. Both PBAN and PBANR expression displayed a remarkable diurnal rhythm, for they were low and stable during the photophase (07:00-21:00) and increased markedly during the scotophase (with a maximum abundance at 23:30) in 3-day-old female moths. The abundance of PBAN and PBANR increased steadily from the 1st day to the 5th day of the adult female life. The pattern of both diurnal and daily expression of PBAN and PBANR mRNA were coincident with enhanced capacity of sex pheromone release and mating of S. exigua moths during the same period. We infer from these results that pheromone biosynthesis and release in S. exigua is regulated by PBAN via up-regulating synthesis.

Molecular diversity of PBAN family peptides from fire ants

The PBAN/Pyrokinin peptide family is a major neuropeptide family characterized with a common FXPRLamide in the C-termini. These peptides are ubiquitously distributed in the Insecta and are involved in many essential endocrinal functions, e.g., pheromone production. Previous work demonstrated the localization of PBAN in the fire ant central nervous system, and identified a new family of PBAN from the red imported fire ant, Solenopsis invicta. In this study, we identified five more PBAN/Pyrokinin genes from S. geminata, S. richteri, S. pergandii, S. carolinensis, and a hybrid of S. invicta and S. richteri. The gene sequences were used to determine the phylogenetic relationships of these species and hybrid, which compared well to the morphologically defined fire ant subgroup complexes. The putative PBAN and other peptides were determined from the amino acid sequences of the PBAN/pyrokinin genes. We summarized all known insect PBAN family neuropeptides, and for the first time constructed a phylogenetic tree based on the full amino acid sequences translated from representative PBAN cDNAs. The PBAN/pyrokinin gene is well conserved in Insecta and probably extends into the Arthropod phylum; however, translated pre-propeptides may vary and functional diversity may be retained, lost, or modified during the evolutionary process.

Cloning and expression of the gene encoding the diapause hormone and pheromone biosynthesis activating neuropeptide of the beet armyworm,Spodoptera exigua

Diapause hormone (DH) and pheromone biosynthesis activating neuropeptide (PBAN), two important insect neuropeptides, regulate insect development and sex pheromone biosynthesis, respectively. DH-like immunoreactivity has been detected in the suboesophageal ganglion (SG) of pharate adult of Spodoptera exigua (Spe) by using an antiserum against Helicoverpa armigera DH. A full-length of Spe-DH-PBAN cDNA was obtained based on reverse transcription-PCR and rapid amplification of cDNA ends strategies. The open reading frame of this cDNA encodes a 197-amino acid precursor protein that contains DH, PBAN, and three other SG neuropeptides, all of which share a conservative C-terminal pentapeptide motif FXPR/KL (X = G, T or S). Northern blot analysis demonstrates the presence of an 800 bp transcript in the SG. The Spe-DH-PBAN mRNA is detectable at high levels at larval and adult stages, suggesting that Spe-DH-PBAN gene might be correlated with larval development and sex pheromone biosynthesis in moths.

Pheromone biosynthesis activating neuropeptide (PBAN): regulatory role and mode of action

This review focuses on the endocrine regulation of reproductive behavior in moth species with particular emphasis on Helicoverpa spp. Reproductive behavior in most adult moths is dependent on the release of a unique blend of sex pheromones by the females to attract conspecific males. Mating, on the other hand, results in a loss of sexual receptivity due to the transfer of secretions from the male accessory glands, which renders females unattractive to ensuing mates. Synchronization of sexual behavior is attained by the timely release of Pheromone-Biosynthesis-Activating Neuropeptide (PBAN), a member of the PBAN/Pyrokinin neuropeptide family, characterized by a common amino acid sequence FXPRLamide motif in the C-terminus. PBAN is released into the hemolymph of females during the scotophase and is drastically reduced after mating, contributing to the loss in female receptivity. Pheromone production is age-dependent and Juvenile Hormone is involved in its regulation. PBAN activates pheromone production through its binding to a PBAN-Receptor (PBAN-R) and subsequent up-regulation of key enzymes in the biosynthetic pathway. The PBAN-R gene was identified as a member of the G-protein coupled receptor family (GPCRs), classified with the vertebrate subfamily of neuromedin U receptors. Using both biochemical and in silico mutagenesis studies, putative binding sites are predicted. Differential expression studies reveal its localization in pheromone glands, neural tissues and the male aedeagus. In the latter tissue, no activity and/or receptor-binding can be detected in response to PBAN. These results raise many questions concerning the evolutionary role of the PBAN/Pyrokinin receptors belonging to the GPCR family.

Identification of a new member of the PBAN family of neuropeptides from the fire ant, Solenopsis invicta

Neuropeptide hormones produced by neurosecretory cells in the central or peripheral nervous systems regulate various physiological and behavioral events during insect development and reproduction. PBAN/Pyrokinin is a major neuropeptide family, characterized by a 5-amino-acid C-terminal sequence, FXPRLamide. This family of peptides has been implicated in regulating various physiological functions including, pheromone biosynthesis, muscle contraction, diapause induction or termination, melanization, and puparium formation in different insect species. In the present study, we report a new member of the PBAN family from the red imported fire ant, Solenopsis invicta, Soi-PBAN, composed of 26-AA (GSGEDLSYGDAYEVDEDDHPLFVPRL). Three additional peptides were deduced from Soi-PBAN cDNA: 15-AA (TSQDIASGMWFGPRL), 8-AA (QPQFTPRL) and 9-AA (LPWIPSPRL), that correspond to diapause hormone (DH), beta-neuropeptide (NP), and gamma-NP, which are found in many lepidopteran moths. Five peptides, DH, alpha, beta, gamma NPs, and PBAN are encoded from PBAN genes of lepidopteran moths, but in the fire ant the alpha-NP is missing. Each of the four synthetic peptides from the fire ant Soi-PBAN cDNA showed significant pheromonotropic activity in a moth model, indicating that these peptides are cross-reactive. Soi-beta-NP induced the highest amount of pheromone production of the four peptides evaluated. The Soi-DH homologue had the lowest pheromonotropic activity, but was still significantly greater than control values. When the deduced amino acid sequences (entire ORF domains) from Soi-PBAN cDNA were compared with other known sequences, the fire ant was most similar to the honey bee, but phylogenetically distant from moth and beetle species. Soi-PBAN (26-AA) unlike the other three peptides shows a low degree of sequence identity with honeybee PBAN (33-AA). Based on the amino acid sequences encoded from insect PBAN genes identified to date, neuropeptide diversity is correlated with the taxonomic or phylogenetic classification of Insecta. From the present study we report the first neuropeptide identified and characterized from the central nervous system of Formicidae.

Biological activity and identification of neuropeptides in the neurosecretory complexes of the cabbage pest insect, Mamestra brassicae (Noctuidae; Lepidoptera)

The need for more environmentally sound strategies of plant protection has become a driving force in physiological entomology to combat insect pests more efficiently. Since neuropeptides regulate key biological processes, these "special agents" or their synthetic analogues, mimetics, agonists or antagonists may be useful tools. We examined brain-suboesophageal ganglia and corpora cardiaca-corpora allata complexes of the cabbage moth, Mamestra brassicae, in order to obtain clues about possible peptide candidates which may be appropriate for the biological control of this pest. With the aid of bioassays, reversed phase high performance liquid chromatography, and mass spectrometry, five neuropeptides were unequivocally identified and the presence of a further three were inferred solely by comparing mass spectra with known peptides. Only one neuropeptide with adipokinetic capability was identified in M. brassicae. Data from the established homologous bioassay indicated that the cabbage moths rely on a lipid-based metabolism which is aided by an adipokinetic hormone (viz. Manse-AKH) that had previously been isolated in many different lepidopterans. Other groups of neuropeptides identified in this study are: FLRFamides, corazonin, allatostatin and pheromonotropic peptide.

Predicted versus expressed adipokinetic hormones, and other small peptides from the corpus cardiacum-corpus allatum: a case study with beetles and moths

This mass spectrometric study confines itself to peptide masses in the range of 500-1500Da. Adipokinetic hormones (AKHs) that are predicted from the genome of the red flour beetle, Tribolium castaneum, and the silk moth, Bombyx mori, are shown to exist as expressed peptides in the corpora cardiaca (CC) of the respective species as evidenced by various mass spectrometric methods. Additionally, some related species were included in this study, such as the tenebrionid beetles Tribolium brevicornis and Tenebrio molitor, as well as the moths Spodoptera frugiperda, Spodoptera littoralis, Mamestra brassicae and Lacanobia oleracea, to investigate whether AKH peptides are structurally conserved in the same genus or family. Interestingly, the AKH peptide of T. brevicornis is identical to that of T. molitor but not to the ones of its close relative T. castaneum. Moreover, other peptides in T. brevicornis, such as various FXPRL amides (=pyrokinins), also match the complement in T. molitor but differ from those in T. castaneum. All the CC of beetles lacked the signal for the mass of the peptide corazonin. All moths have the nonapeptide Manse-AKH expressed in their CC. In addition, whereas the silk moth has the decapeptide Bommo-AKH as a second peptide, all other moths (all noctuids) express the decapeptide Helze-HrTH. In M. brassicae and L. oleracea a novel amidated Gly-extended Manse-AKH is found as a possible third AKH. The noctuid moth species also all express the same FLRF amide-I, corazonin, and a group-specific isoform of a gamma-PGN-(=gamma-SGNP) peptide. In L. oleracea, however, the latter peptide has a novel sequence which is reported for the first time, and the peptide is code-named Lacol-PK.

Prediction of neuropeptide cleavage sites in insects

MOTIVATION

The production of neuropeptides from their precursor proteins is the result of a complex series of enzymatic processing steps. Often, the annotation of new neuropeptide genes from sequence information outstrips biochemical assays and so bioinformatics tools can provide rapid information on the most likely peptides produced by a gene. Predicting the final bioactive neuropeptides from precursor proteins requires accurate algorithms to determine which locations in the protein are cleaved.

RESULTS

Predictive models were trained on Apis mellifera and Drosophila melanogaster precursors using binary logistic regression, multi-layer perceptron and k-nearest neighbor models. The final predictive models included specific amino acids at locations relative to the cleavage sites. Correct classification rates ranged from 78 to 100% indicating that the models adequately predicted cleaved and non-cleaved positions across a wide range of neuropeptide families and insect species. The model trained on D.melanogaster data had better generalization properties than the model trained on A. mellifera for the data sets considered. The reliable and consistent performance of the models in the test data sets suggests that the bioinformatics strategies proposed here can accurately predict neuropeptides in insects with sequence information based on neuropeptides with biochemical and sequence information in well-studied species.

Identification of a unique pheromonotropic neuropeptide including double FXPRL motifs from a geometrid species, Ascotis selenaria cretacea, which produces an epoxyalkenyl sex pheromone

Virgin females of the Japanese giant looper (Ascotis selenaria cretacea, Assc) in the family of Geometridae secrete an epoxyalkenyl sex pheromone to attract males. To regulate its biosynthesis in the pheromone gland, Assc females produce a pheromone biosynthesis-activating neuropeptide (PBAN) in the suboesophageal ganglion (SG), as do females in many lepidopteran species. We have isolated Assc-PBAN cDNA, which encodes 181 amino acids, including a PBAN homologue and four other putative peptides: a diapause hormone (DH) homologue, alpha-SG neuropeptide (SGNP), beta-SGNP, and gamma-SGNP, all of which shared an FXPR(K)L motif on their C-termini. Although PBANs with 30-35 amino acids have been characterized from 15 other species, the Assc-PBAN homologue consisted of 28 amino acids and showed low homology (<46%) compared with the others. Assc-beta-SGNP with eight amino acids was also shorter than the other beta-SGNPs (16-22 amino acids). Furthermore, all of the known PBAN cDNAs have a GRR sequence between beta-SGNP and PBAN as a cleavage site, but the Assc-PBAN cDNA showed an unusual GR sequence at the corresponding position, indicating the possibility of non-cleavage between the beta-SGNP and PBAN. When the GR sequence was a cleavage site, the question arose of whether or not the glutamine residue at the N-terminus of the Assc-PBAN homologue was cyclized. To identify the sequence of the Assc-PBAN, the brain-SG extract was fractionated by HPLC referring to three synthetic peptides with the predicted sequences. The chromatographic behavior of the natural pheromonotropic peptide revealed the unique structure of Assc-PBAN including beta-SGNP, i.e., SVDFTPRLGRQLVDDVPQRQQIEEDRLGSRTRFFSPRL-NH(2), as the first determination of PBAN from the insects producing an epoxyalkenyl sex pheromone.

Protein–DNA interactions in the promoter region of the gene encoding diapause hormone and pheromone biosynthesis activating neuropeptide of the cotton bollworm, Helicoverpa armigera

Diapause hormone (DH) and pheromone biosynthesis activating neuropeptide (PBAN) are two crucial neuropeptides which regulate insect development and sex pheromone biosynthesis respectively. These peptides are encoded by a single gene, termed DH-PBAN gene. In this study, we characterized the promoter of the DH-PBAN gene in Helicoverpa armigera (Har). Transient transfection assays using a series of stepwise deletion fragments linked to the luciferase reporter gene indicate that the promoter contains multiple regulator domains that can activate and repress reporter gene expression. The fragment spanning -467 to -371 bp of the DH-PBAN promoter is an activator domain of transcription, whereas the region from -965 to -534 bp represses the promoter activity in the insect cell line BmN. Electrophoretic mobility shift assays demonstrate that at least two nuclear protein factors from the nuclear protein extracts of H. armigera suboesophageal ganglion, Har-DHMBP-1 and-2 (DH-modulator-binding protein) can specifically bind to the activating region. Furthermore, we characterized in detail that the nuclear protein factor Har-DHMBP-3 can specifically bind to a classical E-box, CAGCTG localized at positions -360 to -355 bp, a potential site for interaction with basic helix-loop-helix transcription factors. Mutation of this E-box results in a significant reduction of the promoter activity, suggesting it can modulate the previously identified activator domain. Taken together, multipartite cis-elements and transcription factors in the DH-PBAN promoter are involved in regulation of the gene expression.

Molecular characterization of pheromone biosynthesis activating neuropeptide from the diamondback moth, Plutella xylostella (L.)

Pheromone biosynthesis activating neuropeptide (PBAN) produced in the subesophageal ganglion stimulates pheromone production in the pheromone gland. A cDNA isolated from female adult heads of the diamondback moth (Plutella xylostella (L.)) encodes 193 amino acids including PBAN, designated as Plx-PBAN, and four other neuropeptides (NPs): diapause hormone (DH) homologue, alpha-NP, beta-NP and gamma-NP. All of the peptides are amidated in their C-termini and shared a conserved motif, FXPR(or K)L structure, as reported from other PBAN cDNAs. Plx-PBAN consists of 30 amino acids, the shortest PBAN so far reported. Plx-PBAN exhibited below 50% homology, compared with other known PBANs. The Plx-DH homologue is structurally different from DH of Bombyx mori. The length of Plx-beta-NP (16 amino acids) was the shortest and showed relatively low similarity, whereas gamma-NP (10 amino acids in length) was the longest among examined gamma-NPs. When female adults were injected with synthetic Plx-PBAN, pheromone production showed a maximal increase 1h post-injection. RT-PCR screening revealed that Plx-PBAN cDNA was expressed in all examined body parts, with the highest expression level in the head of female adults. Analysis of RT-PCR products indicated the Plx-PBAN sequence was identical in all examined body parts of both sexes. Phylogenetic analysis revealed that the Plx-PBAN gene is distantly related to other PBANs, demonstrated by the relatively low similarity.

Structural characterization and transcriptional regulation of the gene encoding diapause hormone and pheromone biosynthesis activating neuropeptide in the cotton bollworm, Helicoverpa armigera

We have cloned the gene encoding the diapause hormone and the pheromone biosynthesis activating neuropeptide in Helicoverpa armigera (Har-DH-PBAN). The Har-DH-PBAN gene contains six exons and five introns that fall in the same positions as in the Bombyx mori DH-PBAN gene (Bom-DH-PBAN). The transcription initiation site lays 29 bp upstream of the translation initiation site. Southern blot analysis suggests that a single copy of this gene is present per haploid genome. A structural comparison of DH-PBAN promoters between H. armigera and B. mori show similarities in the TATA box and in a potential binding site for a POU family transcription factor, POU-M2. However, testing of these DNA regions for factor binding in vitro and transcription assays in cell culture highlight significant differences in their regulation particularly in reference to the POU-M2 sites. Our results uncover common and different regulatory mechanisms at work in the control of DH-PBAN gene expression in H. armigera and B. mori.

Tissue localization and partial characterization of pheromone biosynthesis activating neuropeptide in Achaea janata

Female sex pheromone production in certain moth species have been shown to be regulated by a cephalic endocrine peptidic factor: pheromone biosynthesis activating neuropeptide (PBAN), having 33 amino acid residues. Antisera against synthetic Heliothis zea-PBAN were developed. Using these polyclonals, immunoreactivity was mapped in the nervous system of Achaea janata. Three distinct groups of immunopositive secretory neurons were identified in the suboesophageal ganglion; and immunoreactivity was observed in the corpora cardiaca, thoracic and in the abdominal ganglia. From about 6000 brain sub-oesophageal ganglion complexes, the neuropeptide was isolated; and purified sequentially by Sep-pak and reversed phase high performance liquid chromatographic methods. Identity of purified PBAN fraction was confirmed with polyclonal antibody by immunoblotting. Molecular mass of the isolated peptide was determined by matrix-assisted laser desorption/ionization mass spectrometry, and was found to be 3900 Da, same as that of known H. zea-PBAN. Radiochemical bioassay confirmed the pheromonotropic effect of the isolated neuropeptide in this insect.

Developmental expression of FXPRLamide neuropeptides in peptidergic neurosecretory cells of diapause- and nondiapause-destined individuals of the cotton bollworm, Helicoverpa armigera

The diapause hormone (DH)-pheromone biosynthesis activating neuropeptide (PBAN) gene encodes five neuropeptides, DH, PBAN, alpha-SGNP, beta-SGNP, and gamma-SGNP (subesophageal ganglion neuropeptide). All share the C-terminal pentapeptide FXPRLamide sequence and are produced in the subesophageal ganglion (SG). Expression of the DH-PBAN gene in the central nervous system of embryonic, larval, pupal, and adult Helicoverpa armigera (Har) was studied using in situ hybridization, whole-mount immunocytochemistry, and competitive ELISA. Both Har-DH-PBAN mRNA and protein are localized in the mandibular, maxillary, and labial cell clusters of the SG and a pair of ventral midline neurons of each thoracic ganglion. The FXPRLamide titers in hemolymph are significantly higher in diapause-destined larvae during the fifth and sixth instar than in similar nondiapause-destined individuals. In contrast, the FXPRLamide titers in diapause-destined pupae are significantly lower than in nondiapause-destined pupae. The results from immunocytochemistry and in situ hybridization are consistent with changes of FXPRLamide titers as measured by ELISA. These data suggest that the expression of DH-PBAN might be correlated with diapause induction at the larval stage of diapause-destined individuals and continuous development at pupal stage of nondiapause-destined individuals. Thus, the DH-PBAN gene may play an important regulatory role in aspects of insect development besides diapause termination and pheromone biosynthesis. The transport pathways of FXPRLamide neuropeptides suggest that humoral route is involved in their regulation of development.

Molecular cloning, developmental expression, and tissue distribution of the gene encoding DH, PBAN and other FXPRL neuropeptides in Samia cynthia ricini

We obtained a full-length cDNA encoding diapause hormone (DH) and pheromone biosynthesis activating neuropeptide (PBAN) in Samia cynthia ricini based on both reverse transciptase-PCR (RT-PCR) and rapid amplification of cDNA ends (RACE) strategies. The open reading frame (ORF) of this cDNA encodes a 198-amino acid precursor protein that contains a 33-aa PBAN, a 24-aa DH-like peptide, and three other neuropeptides, all of which share a common C-terminal pentapeptide motif FXPR/KL (X = G, T, S). Samia DH-like and PBAN show high homology to their counterpart in other Lepidoptera. Northern blots demonstrate the presence of a 0.8-kb transcript in the suboesophageal ganglion (SG). The DH-PBAN mRNA was detectable at much lower levels in other neural tissues, such as brain and thoracic ganglia (TG), but not in non-neural tissue, such as the midgut, silk gland, fat body or epidermis. The DH-PBAN mRNA content in the SG was measured using the combined method of quantitative RT-PCR and Southern blotting and was shown to vary with developmental stage. Using an antiserum against Helicoverpa armigera PBAN, PBAN-like immunoreactivity was detected in the SG, TG and terminal abdomen ganglion of S. cynthia ricini by whole-mount immunocytochemistry. The changes of PBAN-like immunoreactivity in the hemolymph are consistent with PBAN transcripts in the SG during pupal development. PBAN increases quickly at adult eclosion, an observation that is consistent with PBAN's key role in pheromone biosynthesis, and synthetic PBAN or brain-SG extracts successfully stimulates pheromone biosynthesis in decapitated moths.

Identification of a POU factor involved in regulating the neuron-specific expression of the gene encoding diapause hormone and pheromone biosynthesis-activating neuropeptide in Bombyx mori

Diapause hormone (DH) and PBAN (pheromone biosynthesis-activating neuropeptide) are two important insect neuropeptides regulating development and reproduction respectively. In the present study, we report two Bombyx mori transcription factors interacting specifically with the promoter of Bom-DH-PBAN (where Bom-DH stands for B. mori DH); we named them DHMBP-1 and -2 (DH-modulator-binding proteins 1 and 2). The developmental changes of DHMBP-1/-2 are closely correlated with that of Bom-DH-PBAN mRNA throughout the pupal stage. Competition assays indicate that DHMBP-1 from Chinese B. mori possesses binding characteristics similar to those of the POU-M1 protein from Japanese B. mori. POU-M1 cDNAs were cloned from various tissues of Chinese B. mori and were found to be distinct from the previously published POU-M1 in amino acid residues 108-136 because of insertion mutations. Owing to this difference in amino acid residues, we named this cDNA POU-M2. Even though POU-M2 differs from POU-M1 at the N-terminal, the POU domain and the binding properties of both POU-M1 and -M2 are the same. Functional analysis showed that overexpression of POU-M2 in the Bombyx cell line BmN activated the promoter of Bom-DH-PBAN, but failed to activate a promoter in which the POU-binding element was mutated. The transcriptional activity of POU-M2 is probably regulated by other factors binding to the upstream of the promoter sequence. We show that the POU-M2-binding site was able to activate the transcription of a heterologous promoter of the gene encoding B. mori larval serum protein. POU-M1 was found to exhibit the same transcriptional activities as POU-M2. Taken together, these results demonstrate that POU-M2 plays an important role in the transcriptional regulation of the Bom-DH-PBAN gene.

Identification of a new member of PBAN family and immunoreactivity in the central nervous system from Adoxophyes sp. (Lepidoptera: Tortricidae)

Production of sex pheromones, Z9-14:OAc and Z11-14:OAc, of the smaller tea tortrix, Adoxophyes sp. was stimulated by injection of the female or male head extracts as well as synthetic pheromone biosynthesis activating neuropeptide (PBAN) into decapitated females. The amount of pheromone produced reached a maximum level 3 h after injection of synthetic PBAN into females. A cDNA isolated from brain-suboesophageal ganglion complex (Br-SEG) of A. sp. females contained an ORF of 576 nucleotides encoding 192 amino acids. Based on endoproteolytic sites, it can be predicted to be cleaved into five putative peptide domains including PBAN and four other neuropeptides. Ado-PBAN consisting of 31-amino acids is the shortest PBAN so far reported. Four other putative PBAN-encoding gene neuropeptides (PGN) are predicted with PGN-24, PGN-7, PGN-20, and PGN-8 amino acids. All of the peptides are amidated in their C-termini with a FXPR(or I, K)L structure, except for PGN-8 (TVKLTPRLamide). PBAN-like immunoreactive material was observed in Br, SEG and ventral nerve cord (VNC) of the female adult. In the brain, 5-7 pairs of neurons containing PBAN-like immunoreactivity were found in each protocerebral hemisphere. Three groups of cell clusters found in the SEG corresponded to the mandibular, maxillary and labial neurons as in other moths. PBAN-like immunoreactive neurons in the VNC were found in thoracic (three pairs) and abdominal ganglia (two pairs). As compared to other moths, a relatively low similarity of peptide sequences deduced from Ado-PBAN gene and a different expression pattern of PBAN-like immunoreactivity could indicate phylogenetical distance from the other species.

Role of neuropeptides in sex pheromone production in moths

Sex pheromone biosynthesis in many moth species is controlled by a cerebral neuropeptide, termed pheromone biosynthesis activating neuropeptide (PBAN). PBAN is a 33 amino acid C-terminally amidated neuropeptide that is produced by neuroendocrine cells of the subesophageal ganglion (SEG). Studies of the regulation of sex pheromone biosynthesis in moths have revealed that this function can be elicited by additional neuropeptides all of which share the common C-terminal pentapeptide FXPRL-amide (X = S, T, G, V). In the past two decades extensive studies were carried out on the chemical, cellular and molecular aspects of PBAN and the other peptides (termed the pyrokinin (PK)/PBAN family) aiming to understand the mode of their action on sex pheromone biosynthesis. In the present review we focus on a few of these aspects, specifically on the: (i) structure-activity relationship (SAR) of the PK/PBAN family, (ii) characterization of the PK/PBAN receptor and (iii) development of a novel strategy for the generation of PK/PBAN antagonists and their employment in studying the mode of action of the PK/PBAN peptides.

Identification of a cDNA encoding DH, PBAN and other FXPRL neuropeptides from the tobacco hornworm, Manduca sexta, and expression associated with pupal diapause

We have cloned the diapause hormone (DH)-pheromone biosynthesis activating neuropeptide (PBAN) cDNA from the suboesophageal ganglion (SG) of Manduca sexta pupae using rapid amplification of cDNA ends. The Mas-DH-PBAN cDNA encodes a preprohormone of 194 amino acids that contains five peptides (PBAN, DH-like, and alpha-, beta-, gamma-SGNP), all of which share a common FXPRL sequence at the C-terminus. Yet, the sequences are rather distinct from those reported from other species: Mas-alpha-SGNP has a unique C-terminal FXPEL (the arginine or lysine at FXPR(or K)L is replaced by glutamic acid), Mas-gamma-SGNP is one amino acid shorter than its counterpart in other species, and Mas-PBAN contains two extra residues not seen in other species. Mas-DH-like peptide has the highest homology (83%) to Bombyx mori DH. Northern blot analysis shows a single mRNA corresponding in size to the Mas-DH-PBAN cDNA detected in brain-SG samples of pupae and adults, suggesting that these peptides are derived from a precursor through posttranslational processing. Using the more sensitive method of RT-PCR, DH-PBAN mRNA is also detectable in thoracic ganglia, although the expression is much lower than in the SG. Developmental profiles of DH-PBAN transcripts in the early pupal stage reveal different patterns in diapause and nondiapause individuals. While a conspicuous drop in expression of the DH-PBAN gene is noted in diapausing pupae 9 days after pupation, high expression persists in nondiapausing individuals. At earlier stages (wandering larva and day 3 pupae) expression is high in diapausing individuals but low in nondiapausing individuals. These observations suggest a possible contribution of the DH-like peptide to the induction phase of diapause in M. sexta.

The diapause hormone-pheromone biosynthesis activating neuropeptide gene of Helicoverpa armigera encodes multiple peptides that break, rather than induce, diapause

FXPRLamide peptides encoded by the DH-PBAN (diapause hormone-pheromone biosynthesis activating neuropeptide) gene induce embryonic diapause in Bombyx mori, but terminate pupal diapause in Helicoverpa armigera (Har). Here, we explore the mechanisms of terminating pupal diapause by the FXPRLamide peptides. Using quantitative RT-PCR, we observed that expression of Har-DH-PBAN mRNA in the SG of nondiapause-type pupae was significantly higher than in diapause-type pupae. Immunocytochemical results indicated that the level of FXPRLamide peptides and axonal release are related to the diapause decision. Ecdysteroidogenesis in prothoracic glands (PGs) was stimulated by synthetic Har-DH in vivo and in vitro, and labeled Har-DH bound to the membrane of the PG, thus suggesting that DH breaks diapause by activating the PG to synthesize ecdysone. Furthermore, the response of DH in terminating diapause was temperature dependent. Decerebration experiments showed that the brain can control pupal development through the regulation of DH, and DH can terminate diapause and promote development without the brain. This result suggests a possible mechanism of response for the signals of DH and other FXPRLamide peptides in H. armigera.

Cloning and expression of the cDNA encoding the FXPRL family of peptides and a functional analysis of their effect on breaking pupal diapause in Helicoverpa armigera

Diapause hormone (DH) and pheromone biosynthesis activating neuropeptide (PBAN) are encoded by a single mRNA in the suboesophegeal ganglion (SG) and are responsible for induction of embryonic diapause in Bombyx mori and sex pheromone biosynthesis in lepidopteran insects. PBAN cDNA analyses revealed that the DH-like peptide is present in several species that have a pupal diapause. However, the function of the DH-like peptide remains unknown. In the present study, we cloned the cDNA encoding DH-PBAN in Helicoverpa armigera utilizing the rapid amplification of the cDNA ends method. The nucleotide se quence analysis revealed that the longest open reading frame of this cDNA encodes a 194-amino acid precursor protein that con tains a 33-aa PBAN, a 24-aa DH-like peptide, and three other neuropeptides, all of which have a common C-terminal pentapeptide motif FXPR/KL ( X=G, T, S). A homology search showed that H. armigera DH-like and PBAN are highly homologous to those from other insects. Northern blot analysis demonstrated a single message RNA corresponding to the size of Har-DH-PBAN cDNA from pupal SG with significantly higher expression in the SG of nondiapause pupae than diapausing pupae. Western blot analysis showed DH-like peptide expression from SG of both males and females. When DH-like peptide was injected into nondiapause larvae and pupae, it did not induce diapause, but rather efficiently broke pupal diapause in H. armigera. The ED(50) of DH to terminate pupal diapause is 20 pmol/pupae. The other four FXPRLamide neuropeptides from the DH-PBAN polyprotein precursor have cross activity for diapause termination. These observations therefore suggest a potential role for these FXPRL family peptides in promoting continuous development in several noctuid species. The high expression of this gene in pharate adults and adults indicates that the FXPRL family peptides may have multiple physiological functions.

Insect neuropeptide antagonists

The development of a new integrated approach to the generation of a novel type of insect neuropeptide (Np) antagonists and putative insect control agents based on backbone cyclic compounds is described. The approach, termed the backbone cyclic neuropeptide-based antagonist (BBC-NBA), was applied to the insect pyrokinin (PK)/pheromone biosynthesis activating neuropeptide (PBAN) family as a model, and led to the discovery of a potent linear lead antagonist and several highly potent, metabolically stable BBC antagonists, devoid of agonistic activity, which inhibited PBAN-mediated activities in moths in vivo. This review briefly summarizes our knowledge of insect Nps, describes the PK/PBAN Np family, presents the basic concepts behind the BBC-NBA approach, and introduces the advantages of this method for generation of Np agonists, antagonists and insecticide prototype molecules.

Neuropeptides in the nervous system of Drosophila and other insects: multiple roles as neuromodulators and neurohormones

Neuropeptides in insects act as neuromodulators in the central and peripheral nervous system and as regulatory hormones released into the circulation. The functional roles of insect neuropeptides encompass regulation of homeostasis, organization of behaviors, initiation and coordination of developmental processes and modulation of neuronal and muscular activity. With the completion of the sequencing of the Drosophila genome we have obtained a fairly good estimate of the total number of genes encoding neuropeptide precursors and thus the total number of neuropeptides in an insect. At present there are 23 identified genes that encode predicted neuropeptides and an additional seven encoding insulin-like peptides in Drosophila. Since the number of G-protein-coupled neuropeptide receptors in Drosophila is estimated to be around 40, the total number of neuropeptide genes in this insect will probably not exceed three dozen. The neuropeptides can be grouped into families, and it is suggested here that related peptides encoded on a Drosophila gene constitute a family and that peptides from related genes (orthologs) in other species belong to the same family. Some peptides are encoded as multiple related isoforms on a precursor and it is possible that many of these isoforms are functionally redundant. The distribution and possible functions of members of the 23 neuropeptide families and the insulin-like peptides are discussed. It is clear that each of the distinct neuropeptides are present in specific small sets of neurons and/or neurosecretory cells and in some cases in cells of the intestine or certain peripheral sites. The distribution patterns vary extensively between types of neuropeptides. Another feature emerging for many insect neuropeptides is that they appear to be multifunctional. One and the same peptide may act both in the CNS and as a circulating hormone and play different functional roles at different central and peripheral targets. A neuropeptide can, for instance, act as a coreleased signal that modulates the action of a classical transmitter and the peptide action depends on the cotransmitter and the specific circuit where it is released. Some peptides, however, may work as molecular switches and trigger specific global responses at a given time. Drosophila, in spite of its small size, is now emerging as a very favorable organism for the studies of neuropeptide function due to the arsenal of molecular genetics methods available.

A new member of the PBAN family in Spodoptera littoralis: molecular cloning and immunovisualisation in scotophase hemolymph

In this article, we report evidence suggesting that the immunoreactive factor previously detected in Spodoptera littoralis scotophase hemolymph is PBAN, which supports a humoral route of the hormone to the pheromone gland. Western blot after native-PAGE of prepurified scotophase hemolymph extracts yielded an immunoreactive band with the same mobility as S. littoralis Br-SOG factor and the expected mobility for a noctuid PBAN. This band was not detected in photophase hemolymph extract. The identity of S. littoralis Br-SOG factor as PBAN was obtained from cDNA cloning using RT-PCR strategy. This allowed us to deduce the amino acid sequence of Spl-PBAN, which is highly homologous to other known PBANs. Moreover, we found that the PBAN encoding cDNA also encoded four other putative amidated peptides (Spl-DH homologue, Spl-alpha-NP, Spl-beta-NP and Spl-gamma-NP) that are identical or highly conserved among noctuids, and two non amidated peptides of unknown function. This cDNA organization is common to all known cDNAs encoding PBANs, leading to the release of different peptides after putative enzymatic cleavage of the preprohormone.

Neuroendocrine control of pheromone biosynthesis in moths

Prevalent among the Lepidoptera, as in many other insect orders, species-specific pheromones are synchronously produced and released for mate finding. Pheromone biosynthesis activating neuropeptide (PBAN) is a neuropeptide widespread throughout the class Insecta. Although its role in the several different orders of insects has not been fully elucidated, its regulatory role in Lepidopteran pheromone biosynthesis has been strongly implicated. The biosynthesis, gene expression, distribution, and release of PBAN have been studied in several moth species. This review discusses PBAN's mode of action as a pheromonotropic neurohormone at the organism, tissue, and cellular levels. The discussion includes an overview on PBAN structure-activity relationships, its target tissue identification, its putative receptor proteins, and the second messengers involved in signal transduction and the key regulatory enzymes in the pheromone biosynthetic pathway that may be influenced by PBAN. Finally, the review includes a discussion of various mediators and inhibitors of the pheromonotropic action due to PBAN.

Insect neuropeptide antagonist. Part II. Synthesis and biological activity of backbone cyclic and precyclic PBAN antagonists

A new approach for the design and synthesis of pheromone biosynthesis activating neuropeptide (PBAN) agonists and antagonists using the backbone cyclization and cycloscan concepts is described. Two backbone cyclic (BBC) libraries were synthesized: library I (Ser library) was based on the active C-terminal hexapeptide sequence Tyr-Phe-Ser-Pro-Arg-Leu-NH2 of PBAN1-33NH2; whereas library II (D-Phe library) was based on the sequence of the PBAN lead linear antagonist Arg-Tyr-Phe-d-Phe-Pro-Arg-Leu-NH2. In both libraries the Pro residue was replaced by the BBC building unit Nalpha-(omega-aminoalkyl) Gly having various lengths of alkyl chain. The peptides of the two libraries were tested for agonistic and antagonistic activity. Four precyclic peptides based on two of the BBC antagonists were also synthesized; their activity revealed that a negative charge at the N-terminus of the peptide abolished antagonistic activity. We also describe the use of the reagent SiCl3I for selective deprotection of the Boc group from the building unit prior to on-resin amino-end to backbone-nitrogen (AE-BN) cyclization, during solid-phase synthesis with Fmoc chemistry.

Pyrokinin/PBAN radio-receptor assay: development and application for the characterization of a putative receptor from the pheromone gland of Heliothis peltigera

A radio-receptor assay (RRA) for the insect pyrokinin/PBAN family has been developed. The development involved examination of the ligand (3H-tyrosyl-PBAN28-33NH2)-receptor interaction under various incubation conditions and variations on sex pheromone gland membrane preparation. Application of the RRA for a partial characterization of the putative pyrokinin/PBAN receptor in the pheromone gland of H. peltigera revealed age-dependence of its expression. Pharmacological characterization revealed a high correlation between the binding-affinity to the receptor of various PBAN-derived peptides and their in vivo pheromonotropic bioactivity, and shed light on the interaction of backbone cyclic and linear ([Arg27,D-Phe30]PBAN28-33NH2) PBAN antagonists with the receptor.

Discovery of a linear lead antagonist to the insect pheromone biosynthesis activating neuropeptide (PBAN)

We report the discovery of a linear lead antagonist for the insect pheromone biosynthesis activating neuropeptide (PBAN) which inhibits sex pheromone biosynthesis in the female moth Heliothis peltigera. Two approaches have been used in attempting to convert PBAN agonists into antagonists. The first involved omission of the C-terminal amide and reduction of the sequence from the N-terminus in a linear library based on PBAN 1-33NH(2.) The second involved replacement of L amino-acids by the D hydrophobic amino acid D-Phe in a linear library based on PBAN28-33NH(2.) Screening of the two libraries for pheromonotropic antagonists resulted in the disclosure of one compound out of the D-Phe library (Arg-Tyr-Phe-D-Phe-Pro-Arg-Leu-NH(2)) which inhibited sex pheromone production by 79 and 64% at 100 pmol in two moth colonies and exhibited low agonistic activity. Omission of the C-terminal amide in PBAN 1-33NH(2) and its shorter analogs did not lead to the discovery of an antagonistic compound.

Control of the biosynthetic pathway of Sesamia nonagrioides sex pheromone by the pheromone biosynthesis activating neuropeptide

(Z)-11-Hexadecenyl acetate, the main pheromone component of Sesamia nonagrioides sex pheromone, is biosynthesized from palmitic acid by Delta(11)-desaturation followed by reduction and acetylation. Production of (Z)-11-hexadecenyl acetate is regulated by the Pheromone Biosynthesis Activating Neuropeptide (PBAN). Transformation of (Z)-11-hexadecen-1-ol into the corresponding acetate is a target step for PBAN in the regulation of this biosynthetic sequence, thus being the first example of a PBAN-activated acetylation. The production of the minor component (Z)-11-hexadecenal is also stimulated by PBAN. The usefulness of pentafluorobenzyloxime-derivatives for the analysis of aldehyde pheromone constituents by gas chromatography coupled to mass spectrometry is also reported.

Pheromone-producing cells in the silkmoth, Bombyx mori: identification and their morphological changes in response to pheromonotropic stimuli

A method to isolate functional clusters of viable pheromone gland cells of Bombyx mori was developed. The 8th-9th intersegmental invaginated membrane corresponding to the pheromone gland was dissected, trimmed and separated into two distinct layers, the outer and inner layers, by enzymatic digestion with papain. The outer layer mainly consists of cuticle, while the inner layer consists of homogeneous cells with many refractile granules. The solubilized microsome fraction prepared from the inner layer retained the ability to produce bombykol in vitro, whereas the outer layer fraction did not produce bombykol. Moreover, in tissue incubations, the inner layer - but not the outer layer - produced bombykol in response to the pheromonotropic peptide TKYFSPRLamide, ionomycin and calcium ionophore A23187. These results indicate that the inner-layer cells are indeed the pheromone-producing cells, which retain their functional integrity after separation with papain. These cells could be cultured successfully in Grace's medium for at least 5days.The presence or absence of pheromonotropic stimuli prior to dissection greatly influenced the size, number and distribution of refractile granules in the cytoplasm of the pheromone-producing cells. Staining with Nile Red proved that these refractile granules were lipid droplets. When pheromone production was studied under normal conditions or stimulated in decapitated females with pheromone-biosynthesis-activating neuorpeptide (PBAN) charge, the size of lipid droplets observed in the pheromone-producing cells reduced prominently and their number increased dramatically with time. By contrast, when pheromone production was suppressed by decapitation, the size and number of the lipid droplets remained constant. Lipid droplets observed in the pheromone-producing cells could be carriers of pheromone precursors and/or the pheromone bombykol. The present results suggest that the isolated cell preparation can be used for quantitative visualization of the cellular dynamics during pheromone production in B. mori.

Involvement of calcineurin in the signal transduction of PBAN in the silkworm, Bombyx mori (Lepidoptera)

In several moth species sex pheromone production in the pheromone gland is regulated by a neurohormone, pheromone biosynthesis activating neuropeptide (PBAN). In Bombyx mori it is suggested that PBAN, after binding to the cell-surface receptor, primarily activates a plasma membrane receptor-activated Ca2+ channel to increase cytosolic levels of Ca2+, and Ca2+/calmodulin complex directly or indirectly activates a phosphoprotein phosphatase, which in turn elicits activation of acyl CoA reductase (the key enzyme under PBAN control) through dephosphorylation, resulting in pheromone (bombykol) production. The effect of cyclosporin A (CsA) and FK 506, specific inhibitors of calcineurin (phosphoprotein phosphatase 2B) was studied on the sex pheromone production, in B. mori. The in vitro experiments showed that both chemicals exerted a dose-dependent inhibitory action when they were co-incubated with TKYFSPRL amide (Hez-PBAN fragment peptide). Practically, no difference was detected between the two chemicals in the tested doses (0.025-1250 microM). When effects of CsA or FK 506 were studied on cell-free production of bombykol by using microsomal fraction no inhibition was detected. Since microsomal fraction contains the acyl CoA synthetase, the rate-limiting acyl CoA reductase and the precursor, bombykol is produced if supplied with CoA, ATP and NADPH. Thus, the inhibitory action of CsA and FK506 under in vitro conditions should occur before the step of acyl group reduction and the effect is likely to be attributable to the inhibition of calcineurin in the signal transduction cascade mechanism of PBAN, in B. mori. The existence of calcineurin in the pheromone gland by using Western blot analysis is also demonstrated.

A cDNA, from Agrotis ipsilon, that encodes the pheromone biosynthesis activating neuropeptide (PBAN) and other FXPRL peptides

A cDNA encoding the prohormone of the pheromone biosynthesis activating neuropeptide (PBAN) in the moth Agrotis ipsilon was isolated. The cDNA contains 834 nucleotides, coding for a 193-amino acid protein that exhibits 89% identity with PBAN prohormones of other moths. The prohormone contains five potential peptides belonging to the FXPRL family. The peptide corresponding to the Bombyx mori diapause hormone exhibits an extra residue, and the C-terminal leucine is replaced by an isoleucine, introducing a new type of variability in this family of peptides. Northern blot analysis revealed expression in suboesophagal ganglion complexes. Constitutive heterologous expression of Agi-PBAN cDNA in yeast, using three different antibodies, did not produce PBAN-immunoreactive material.