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

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.

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.

Sex in the night: fatty acid-derived sex pheromones and corresponding membrane pheromone receptors in insects

The moth sex pheromone communication is one of the most striking examples of chemical communication in the animal kingdom. Investigating the molecular mechanisms of pheromone biosynthesis in the female pheromone gland and of pheromone reception in the male antennae not only defines new concepts in signalling research but also opens new perspectives for insect control. In this mini-review, we use the cotton leafworm Spodoptera littoralis as a guideline to illustrate the recent advances gained in the understanding of moth sex pheromone communication.

cDNA cloning and sequence determination of the pheromone biosynthesis activating neuropeptide from the seabuckthorn carpenterworm, Holcocerus hippophaecolus (Lepidoptera: Cossidae)

The PBAN (pheromone biosynthesis activating neuropeptide)/pyrokinin peptides comprise a major neuropeptide family characterized by a common FXPRL amide at the C-terminus. These peptides are actively involved in many essential endocrine functions. For the first time, we reported the cDNA cloning and sequence determination of the PBAN from the seabuckthorn carpenterworm, Holcocerus hippophaecolus, by using rapid amplification of cDNA ends. The full-length cDNA of Hh-DH-PBAN contained five peptides: diapause hormone (DH) homolog, α-neuropeptide (NP), β-NP, PBAN, and γ-NP. All of the peptides were amidated at their C-terminus and shared a conserved motif, FXPR (or K) L. Moreover, Hh-DH-PBAN had high homology to the other members of the PBAN peptide family: 56% with Manduca sexta, 66% with Bombyx mori, 77% with Helicoverpa zea, and 47% with Plutella xylostella. Phylogenetic analysis revealed that Hh-DH-PBAN was closely related to PBANs from Noctuidae, demonstrated by the relatively higher similarity compared with H. zea. In addition, real-time quantitative PCR (qRT-PCR) analysis showed that Hh-DH-PBAN mRNA expression peaked in the brain-subesophageal ganglion (Br-SOG) complex, and was also detected at high levels during larval and adult stages. The expression decreased significantly after pupation. These results provided information concerning molecular structure characteristics of Hh-DH-PBAN, whose expression profile suggested that the Hh-DH-PBAN gene might be correlated with larval development and sex pheromone biosynthesis in females of the H. hippophaecolus.

Circadian rhythms and endocrine functions in adult insects

Many behavioral and physiological processes in adult insects are influenced by both the endocrine and circadian systems, suggesting that these two key physiological systems interact. We reviewed the literature and found that experiments explicitly testing these interactions in adult insects have only been conducted for a few species. There is a shortage of measurements of hormone titers throughout the day under constant conditions even for the juvenile hormones (JHs) and ecdysteroids, the best studied insect hormones. Nevertheless, the available measurements of hormone titers coupled with indirect evidence for circadian modulation of hormone biosynthesis rate, and the expression of genes encoding proteins involved in hormone biosynthesis, binding or degradation are consistent with the hypothesis that the circulating levels of many insect hormones are influenced by the circadian system. Whole genome microarray studies suggest that the modulation of farnesol oxidase levels is important for the circadian regulation of JH biosynthesis in honey bees, mosquitoes, and fruit flies. Several studies have begun to address the functional significance of circadian oscillations in endocrine signaling. The best understood system is the circadian regulation of Pheromone Biosynthesis Activating Neuropeptide (PBAN) titers which is important for the temporal organization of sexual behavior in female moths. The evidence that the circadian and endocrine systems interact has important implications for studies of insect physiology and behavior. Additional studies on diverse species and physiological processes are needed for identifying basic principles underlying the interactions between the circadian and endocrine systems in insects.

Modulation of the temporal pattern of calling behavior of female Spodoptera littoralis by exposure to sex pheromone

We have examined the timing of calling behavior in the female Egyptian cotton leafworm, Spodoptera littoralis and its modification by exposure to sex pheromone. The calling rhythm of the female moth was found to be circadian, persistent for at least 4 days once it has been entrained, and could be phase shifted by altering the light:dark regime. We also found that female exposure to pheromone affected the rate and duration of calling. A brief exposure to pheromone gland extract increased the proportion of females calling in a constant dim light and this effect persisted for at least 2 days. In response to pheromone exposure, significantly more females also called late into scotophase when most unexposed control females had ceased calling. The adaptive significance of responding to conspecific sex pheromone is discussed.

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.

Developmental regulation of the pheromone biosynthesis activating neuropeptide-receptor (PBAN-R): re-evaluating the role of juvenile hormone

Sex pheromone production in Helicoverpa armigera is regulated by pheromone-biosynthesis-activating neuropeptide (PBAN), which binds to a G-protein coupled receptor at the pheromone gland. We demonstrate the temporal differential expression levels of the PBAN receptor (PBAN-R) gene, reaching peak levels at a critical period of 5 h post-eclosion. Previous studies implied a possible regulatory role for juvenile hormone (JH). We herein demonstrate that PBAN-R expression levels increase normally when females are decapitated or head-ligated, removing the source of JH, before peak transcript levels are reached. Similarly, sex pheromone production can be induced by PBAN in such decapitated females. These results indicate that up-regulation, at this critical time, is not dependent on JH originating from the head. Conversely, JH injected in vivo at this critical period significantly inhibits PBAN-R transcript levels.

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.

The release of a pheromonotropic neuropeptide, PBAN, in the turnip moth Agrotis segetum, exhibits a circadian rhythm

In the female turnip moth, Agrotis segetum, a pheromone biosynthesis activating neuropeptide (PBAN) stimulates sex pheromone biosynthesis which exhibits a daily rhythm. Here we show data supporting a circadian rhythm in PBAN release from the corpora cardiaca, which we propose regulates the endogenous rhythm in sex pheromone biosynthesis. This conclusion is drawn as the observed daily rhythm in PBAN-like immunoreactivity in the hemolymph is persistent in constant darkness and is phase-shifted by an advanced light:dark cycle. PBAN-like immunoreactivity was found in the brain, the optic lobe, the suboesophageal ganglion and in the retrocerebral complex. In each hemisphere ca. 10 immunopositive neurons were observed in the pars intercerebralis and a pair of stained somata in the dorso-lateral protocerebrum. A cluster of cells containing PBAN-like immunoreactive material was found in the tritocerebrum and three clusters of such cells were found in the SOG. Their processes reach the corpora cardiaca via nervi corporis cardiaci and the dorsal surface of the corpora allata via the nervi corporis allati.

Morph-associated JH titer diel rhythm in Gryllus firmus: Experimental verification of its circadian basis and cycle characterization in artificially selected lines raised in the field

Previous studies demonstrated a high-amplitude, diel cycle for the hemolymph JH titer in the wing-polymorphic cricket, Gryllus firmus. The JH titer rose and fell in the flight-capable morph (long-winged, LW(f)) above and below the relatively temporally invariant JH titer in the flightless (short-winged, SW) morph. The morph-specific JH titer cycle appeared to be primarily driven by a morph-specific diel cycle in the rate of JH biosynthesis. In the present study, cycles of the JH titer and rate of JH biosynthesis in the LW(f) morph persisted in the laboratory under constant darkness with an approximate 24h periodicity. The JH titer cycle also shifted in concert with a shift in the onset of the scotophase, was temperature compensated in constant darkness, and became arrhythmic under constant light. These results provide strong support for the circadian basis of the morph-specific diel rhythm of the JH titer and JH biosynthetic rate. Persistence of the JH titer cycle under constant darkness in multiple LW-selected and SW-selected stocks also provides support for the genetic basis of the morph-associated circadian rhythm. The morph-specific JH titer cycle was observed in these stocks raised in the field, in both males and females, in each of 3 years studied. The onset of the cycle in the LW(f) morph, a few hours before sunset, correlated well with the onset of the cycle, a few hours before lights-off, in the laboratory. The morph-specific JH titer cycle is a general feature of G. firmus, under a variety of environmental conditions, and is not an artifact of specific laboratory conditions or specific genetic stocks. It is a powerful experimental model to investigate the mechanisms underlying endocrine circadian rhythms, their evolution, and their impact on life history evolution.

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.

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.

Molecular modeling of the binding of pheromone biosynthesis activating neuropeptide to its receptor

Moth sex-pheromone biosynthesis follows a circadian cycle, which is cued by the release of the neurohormone pheromone biosynthesis activating neuropeptide (PBAN) to the hemolymph. PBAN binds to a G protein-coupled receptor (GPCR), in pheromone glands, (PG) initially identified by us in Helicoverpa zea moths (HezPBAN-R). In this study, the sequences of the seven transmembrane helices of HezPBAN-R were identified, built, packed and oriented correctly after multiple sequence alignment of the HezPBAN-R and several other GPCRs using the X-ray structure of rhodopsin as a template. Molecular dynamics simulations were run on three different beta-turn types of the C-terminal hexapeptide of PBAN and the results clustered into 12 structurally distinct groups. The lowest energy conformation from each group was used for computer-simulated docking with the model of the HezPBAN-R. Highest scoring complexes were examined and putative binding sites were identified. Experimental studies, using in vitro PG, revealed lower levels of pheromonotropic activity when challenged with pyrokinin-like peptides than with HezPBAN as ligand. Thus, the Drosophila melanogaster pyrokinin-1 receptor (CG9918) was chosen to create chimera receptors by exchanging between the three extracellular loops of the HezPBAN-R and the CG9918 for in silico mutagenesis experiments. The predicted docking model was validated with experimental data obtained from expressed chimera receptors in Sf9 cells.

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.

Female sex pheromone suppression and the fate of sex-peptide-like peptides in mated moths of Helicoverpa armigera

Insect males produce accessory gland (MAG) factors that are transferred in the seminal fluid to females during copulation, and elicit changes in the mated female's behavior and physiology. Our previous studies showed that the injection of synthetic Drosophila melanogaster sex-peptide (DrmSP) into virgin females of the moth Helicoverpa armigera causes a significant inhibition of pheromone production. In this and other moth species, pheromone production, correlated with female receptivity, is under neuroendocrine control due to the circadian release of the neuropeptide PBAN. In this study, we show that PBAN, present in the hemolymph during the scotophase in females, is drastically reduced after mating. We also identify 4 DrmSP-like HPLC peaks (Peaks A, S1, S2, and B) in MAGs, with increasing levels of DrmSP immunoreactivity during the scotophase, when compared to their levels observed during the photophase. In H. armigera MAGs, a significant reduction in the pheromonostatic peak (Peak B) was already evident after 15 min of copulation, and depletion of an additional peak (Peak S2) was evident after complete mating. Peak A is also detected in female brains, increasing significantly 1 h after mating, at which time inhibition of pheromone biosynthesis also occurs. However, changes corresponding to the other MAG peaks were not detected in mated female tissues.

SPODOBASE: an EST database for the lepidopteran crop pest Spodoptera

Background

The Lepidoptera Spodoptera frugiperda is a pest which causes widespread economic damage on a variety of crop plants. It is also well known through its famous Sf9 cell line which is used for numerous heterologous protein productions. Species of the Spodoptera genus are used as model for pesticide resistance and to study virus host interactions. A genomic approach is now a critical step for further new developments in biology and pathology of these insects, and the results of ESTs sequencing efforts need to be structured into databases providing an integrated set of tools and informations.

Description

The ESTs from five independent cDNA libraries, prepared from three different S. frugiperda tissues (hemocytes, midgut and fat body) and from the Sf9 cell line, are deposited in the database. These tissues were chosen because of their importance in biological processes such as immune response, development and plant/insect interaction. So far, the SPODOBASE contains 29,325 ESTs, which are cleaned and clustered into non-redundant sets (2294 clusters and 6103 singletons). The SPODOBASE is constructed in such a way that other ESTs from S. frugiperda or other species may be added. User can retrieve information using text searches, pre-formatted queries, query assistant or blast searches. Annotation is provided against NCBI, UNIPROT or Bombyx mori ESTs databases, and with GO-Slim vocabulary.

Conclusion

The SPODOBASE database provides integrated access to expressed sequence tags (EST) from the lepidopteran insect Spodoptera frugiperda. It is a publicly available structured database with insect pest sequences which will allow identification of a number of genes and comprehensive cloning of gene families of interest for scientific community. SPODOBASE is available from URL:

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.

Sequence and expression of the CAPA/CAP2b gene in the tobacco hawkmoth, Manduca sexta

The gene coding for cardioacceleratory peptide 2b (CAP2b; pELYAFPRV) has been isolated and sequenced from the moth Manduca sexta (GenBank accession #AY649544). Because of its significant homology to the CAPA gene in Drosophila melanogaster, this gene is called the Manduca CAPA gene. The Manduca CAPA gene is 958 nucleotides long with 29 untranslated nucleotides from the beginning of the sequence to the putative start initiation site. The CAPA gene has a single open reading frame, 441 nucleotides long, that codes for a predicted precursor protein of 147 amino acids. The predicted prepropeptide encodes a single copy of each of three deduced propeptides, a CAP2b propeptide, with a Q substituted for an E at the N-terminus (QLYAFPRVa), and two novel CAP2b-related propeptides (DGVLNLYPFPRVa and TEGPGMWFGPRLa). To reduce confusion and to adopt a more standardized nomenclature, we rename pELYAFPRVa as Mas-CAPA-1 and assign the names of Mas-CAPA-2 to DGVLNLYPFPRVa and Mas-PK-1 (Pyrokinin-1) to TEGPGMWFGPRLa. The spatial and temporal expression pattern of the CAPA gene in the Manduca central nervous system (CNS) was determined in all major post-embryonic stages using in situ hybridization techniques. The CAPA gene is expressed in a total of 27 pairs of neurons in the post-embryonic Manduca CNS. A total of 16 pairs of cells is observed in the brain, two pairs in the sub-esophageal ganglion (SEG), one pair in the third thoracic ganglion (T3), one pair in each unfused abdominal ganglion (A1-A6) and two pairs in the fused terminal ganglion. The mRNA from the CAPA gene is present in nearly every ganglion in each post-embryonic stage. The number of cells expressing the CAPA gene varies during post-embryonic life, starting at 54 cells in first-instar larvae and declining to a minimum of 14 cells midway through adult 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.

Type-A allatostatins from the fall armyworm, Spodoptera frugiperda: molecular cloning, expression and tissue-specific localization

The gene encoding the Spodoptera frugiperda allatostatin type-A peptide family (Y/FXFGL-amides) was isolated from S. frugiperda brain cDNA. The gene encodes a precursor of 231 amino acids containing nine (or ten) Y/FXFGL-a peptides that are tandemly arranged in three blocks. The comparison of the Spofr-AST A precursor with the respective precursor genes from two other lepidopteran species, Helicoverpa armigera and Bombyx mori, shows high homology in size, sequence (84 and 57%, respectively), and organisation of the allatostatins. One-step RT-PCR analysis using a Spofr-AST A-6 to A-9 probe shows that the gene is not only expressed as one transcript in the brain and midgut of larvae and adults in a time- and tissue-specific manner, but also in the reproductive tissues of adult S. frugiperda. Data confirm the nature of the allatostatin type-A peptides as brain/gut myoregulatory hormones, whereas their function(s) in ovaries, oviduct, and testes still have to be resolved. The cell-specific localization of the preprohormone expression, as demonstrated by whole mount in situ hybridization, confirms the overall distribution of the Spofr-AST A preprohormone as shown by RT-PCR and supports the pleiotropic functions of the 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.

Functional analysis of the SGNP I in the pupal diapause of the oriental tobacco budworm, Helicoverpa assulta (Lepidoptera: Noctuidae)

Helicoverpa assulta suboesophageal ganglion neuropeptide I (Has-SGNP I) is a 24-amino acids peptide amide, which shows 62.5% similarity with the diapause hormone of Bombyx mori (Bom-DH). It has been demonstrated that embryonic diapause is induced by DH in B. mori. Injection of synthetic amidated Has-SGNP I terminated pupal diapause in a dose-dependent manner. Therefore, Has-SGNP I might be referred to a "diapause termination hormone" in H. assulta (Has-DTH). The maximal dose of Has-DTH for diapause termination was 1.0 microg and the half-maximal dose 0.4 microg. The time required for diapause termination of Has-DTH was 2-3 days longer than that of 20-hydroxyecdysone. During the pupal stage, DTH mRNA content in the SGs of nondiapausing pupae was always higher than in diapausing pupae using the combined method of quantitative RT-PCR and Southern blot. DTH gene also expressed at a low level while diapausing pupae were chilled at 4 degrees C, but increased rapidly and largely after being transferred to 25 degrees C. Using a competitive ELISA, Has-DTH-like immunoreactivity in the haemolymph showed the same pattern as that of Has-DTH gene expression. Those results indicated that Has-DTH gene expression was related to diapause development and could be activated by low temperature. Has-DTH might be useful to elucidate the mechanism of diapause termination in pupal diapause species.

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.

Molecular characterization of prothoracicotropic hormone and diapause hormone in Heliothis virescens during diapause, and a new role for diapause hormone

cDNAs encoding prothoracicotropic hormone (PTTH) and diapause hormone (DH) were isolated from the tobacco budworm, Heliothis virescens (Hvi). Hvi-PTTH cDNA reveals key structural features known from other PTTHs, yet there is a > 30% amino acid difference between the PTTH sequences found in this noctuid when compared with the PTTHs known from Bombycoidea. Hvi-DH-PBAN cDNA encodes a precursor protein including a DH-like peptide, pheromone biosynthesis-activating neuropeptide (PBAN) and three additional neuropeptides with an FXPRL sequence at the C terminus. PTTH and DH-PBAN transcripts are most highly expressed in the brain and subesophageal ganglion (SG), respectively. Expression of both the PTTH and the DH-PBAN transcripts is high in larvae and remains high in nondiapausing pupae, but in larvae programmed for pupal diapause, expression declines sharply at the onset of larval wandering behaviour and remains low during pupal diapause. This pattern implies that both of these genes are shut down during diapause. These results are not consistent with a role for DH in promoting the entry into diapause as noted in Bombyx mori. Instead, the higher expression of DH in nondiapausing pupae suggests a possible role for DH in promoting continuous development. The injection of DH into diapausing pupae did indeed successfully terminate diapause, thus suggesting a possible new role for this neuropeptide.