Ashok K. Raina

Identification of a neuropeptide hormone that regulates sex pheromone production in female moths

A pheromone biosynthesis activating neuropeptide (PBAN) hormone that controls sex pheromone production in female moths was identified from the brain-subesophageal ganglion complexes of the adult corn earworm, Heliothis zea. PBAN has 33 amino acid residues and a molecular weight of 3900. Its amino acid sequence has no significant homology with any of the fully characterized peptide hormones. The synthetic peptide, at a dose of between 2 and 4 picomoles, induced production of a normal quantity of sex pheromone in ligated H. zea females. The peptide also induced pheromone production in six other species of moths, thus indicating that this or similar peptides may be responsible for the regulation of pheromone production in moths.

A pentapeptide of the C-terminal sequence of PBAN with pheromonotropic activity.

Abstract Peptides ranging in length from 4 to 18 amino acid residues representing various sequence fragments of Helicoverpa (Heliothis) zea -pheromone biosynthesis activating neuropeptide (Hez-PBAN) were synthesized and tested for pheromonotropic activity. Biological activity resides in the C-terminus and the C-terminal pentapeptide (Phe-Ser-Pro-Arg-Leu-NH 2 ) represents the minimum sequence essential for induction of pheromone production. The C-terminal hexapeptide (Tyr-Phe-Ser-Pro-Arg-Leu-NH 2 ) had significantly higher activity at the lower doses of 100 and 10 pmol and may represent a tryptic cleavage product of PBAN.

Insect peptide nomenclature

Abstract A system of nomenclature is proposed for insect peptides based on their source and biological activity. Under this sytem the Locust-AKH (Stone et al., Nature, Lond. 263 , 207–211, 1976) will be represented as Lom-AKH-I.

The identification of two myoinhibitory peptides, with sequence similarities to the galanins, isolated from the ventral nerve cord of Manduca sexta.

Two new myoinhibitory peptides, Mas-MIP I and Mas-MIP II, were identified from the ventral nerve cord of the adult tobacco hornworm, Manduca sexta. Sequences obtained by a combination of automated Edman degradation and electrospray mass spectrometry were, respectively, AWQDLNSAW and GWQDLNSAW. The native peptides were found to co-elute with synthetic C-terminal amides on a reverse phase HPLC system. When applied to isolated ilea (anterior hindgut) of adult M. sexta, both peptides were found to significantly reduce the rate of peristalsis, or abolish peristalsis entirely, at concentrations of 1 x 10(-9) M. Both peptides share sequence similarities with Lom-MIP, a previously identified myoinhibitory peptide from Locusta migratoria, and with the N-terminal portion of vertebrate peptides in the galanin family.

Isolation and identification of a pheromonotropic neuropeptide from the brain-suboesophageal ganglion complex of Lymantria dispar: A new member of the PBAN family

A pheromonotropic peptide was isolated from brain-suboesophageal ganglion complexes of the adult female gypsy moth, Lymantria dispar, using a 5-step HPLC purification protocol and an in vivo bioassay in Helicoverpa zea. The intact peptide was sequenced by automated Edman degradation. The L. dispar pheromone biosynthesis activating neuropeptide (Lyd-PBAN) is a C-terminally amidated 33-amino acid peptide with a molecular weight of 3881. The peptide was synthesized using Fmoc procedures. Lyd-PBAN has sequence homology with Hez-PBAN (81.8%) and Bom-PBAN-I (66.7%). All three PBANs share the C-terminal hexapeptide sequence, Tyr-Phe-Ser-Pro-Arg-Leu-NH2. In addition, the C-terminal pentapeptide sequences of Pseudaletia pheromonotropin (Pss-PT), Bombyx diapause hormone (Bom-DH), the locustamyotropins (Lom-MT) and leucopyrokinin (Lem-PK) are identical or have a high degree of homology to the C-terminus of PBANs.

Isolation and identification of a new diuretic peptide from the tobacco hornworm, Manduca sexta

A 30-amino acid diuretic peptide was isolated from the corpora cardiaca-corpora allata complexes and, separately, from medial neurosecretory cells of the Sphingid moth, Manduca sexta. The peptide was found to have the following sequence, determined by automated Edman degradation and mass spectrometry: SFSVNPAVDILQHRYMEKV AQNNRNFLNRV-NH2. We have named the peptide Mas-DP II. The peptide was synthesized and shown to possess diuretic activity in decapitated moths. Mas-DP II is related by sequence homology to a 41-amino acid diuretic peptide identified previously from M. sexta, and it belongs to the family of corticotropin releasing factor-like peptides.

Circadian system controlling release of sperm in the insect testes.

Release of mature sperm from the testis into seminal ducts of the gypsy moth exhibits a circadian rhythm. The rhythm of sperm release was shown to persist in vitro, in isolated complexes of testis and seminal ducts cultured in light-dark cycles or in constant darkness. The phase of the rhythm was also reset in vitro by exposure to shifted light-dark cycles. Therefore, the testis—seminal ducts complex from the gypsy moth is photosensitive and contains a circadian pacemaker, which controls the rhythm of sperm movement. This finding extends the range of structures in multicellular organisms that are known to contain circadian oscillators and provides a new model system in which circadian mechanisms may be studied.

Chemical Signals from Host Plant and Sexual Behavior in a Moth

In the phytophagous corn earworm, Helicoverpa (Heliothis) zea, females delay their reproductive behaviors until they find a suitable host on which to deposit their eggs. Perception of volatile chemical signals from corn silk triggers the production of sex pheromone followed by its release, which leads to mating. Several natural corn silk volatiles, including the plant hormone ethylene, induced pheromone production in H. zea females. Because H. zea larvae feed on the fruiting parts of a wide variety of hosts, ethylene, which is associated with fruit ripening, could act as a common cue.

Action of pheromone biosynthesis activating neuropeptide on In vitro pheromone glands of Heliothis armigera females

Abstract Pheromone glands of Heliothis armigera were stimulated in vitro to incorporate 14C from the radioactive precursor sodium acetate, in the presence of synthetic pheromone biosynthesis activating neuropeptide (PBAN). When hexane extracts of the radioactive products were analysed by TLC and HPLC the radioactivity corresponded in retention time to the main pheromone component (Z)-11-hexadecenal. Maximal stimulation, as depicted by TLC analysis, was observed after 4 h of incubation. The PBAN response was shown to be dose dependent, maximal levels, as analysed by TLC, were obtained at a concentration of 5 pmol/gland. This response was shown to be mediated by cAMP.

Characteristics of a neurohormone that controls sex pheromone production in Heliothis zea

Abstract A neuropeptide hormone that controls production of the sex pheromone in Heliothis zea females, originates in the sub-oesophageal ganglion. Because of the difficulty in separating brain from sub-oesophageal ganglion, the entire complex was used in all the experiments unless otherwise stated. Pheromonotropic activity was maximal in brain + sub-oesophageal ganglion extracts from 1–2-day old adults. This age corresponds to normal peak pheromone production in the females. The hormone caused significant pheromonotropic activity within 15 min after injection of the brain + sub-oesophageal ganglion homogenate into ligated females, and reached the peak in 4 h. Activity was detected with a crude preparation of the hormone at 1 8th brain + sub-oesophageal ganglion equivalent. High-performance size-exclusion chromatography of the extracts of brain + sub-oesophageal ganglion indicated that the pheromone-biosynthesis activating neuropeptide may occur in more than one active form. The hormonal activity was destroyed by carboxypeptidase Y and TPCK trypsin, but activity was not destroyed by treatment with aminopeptidase M. These results indicate that the hormonal substance is proteinaceous and may have a blocked NH2-terminus. Occurrence of pheromonotropic activity in brain + sub-oesophageal ganglion homogenates from other moth species and a species of cockroach indicates the wide distribution of hormones with similar activity.