Stimulation of pheromone biosynthesis in the moth Helicoverpa zea: action of a brain hormone on pheromone glands involves Ca2+ and cAMP as second messengers.

Abstract

Isolated abdomen and pheromone gland bioassays were utilized to determine the physiological action of the pheromone-biosynthesis-activating neuropeptide (PBAN) in the corn earworm moth Helicoverpa (= Heliothis) zea. An isolated pheromone gland bioassay showed that synthetic PBAN was active at 0.02 pmol, with maximal activity occurring at 0.5 pmol and 60 min of incubation. Second-messenger studies demonstrated that extracellular Ca2+ is necessary for PBAN activity on isolated pheromone glands. The Ca2+ ionophore A23187 stimulated pheromone biosynthesis alone, whereas the Ca2+ channel blockers La3' and Mn2+ inhibited PBAN activity. However, the organic Ca2+ channel blockers verapamil and nifedipine did not inhibit PBAN activity. Both forskolin and two cAMP analogues stimulated pheromone biosynthesis in the absence of extracellular Ca2+, indicating that Ca2+ may activate an adenylate cyclase. The biogenic amine octopamine did not elicit pheromone production in isolated gland or abdomen bioassays or when in ected into intact female moths. Removal of the ventral nerve chord, including the terminal abdominal ganglia in isolated abdomens, did not affect PBAN stimulation of pheromone production. Similar levels of stimulation were found when isolated abdomens were treated with PBAN in scotophase or photophase.Sex pheromone titers in most moths, including the corn earworm moth Helicoverpa (= Heliothis) zea, fluctuate diurnally with little or no pheromone present during the day and with peak pheromone titers occurring during midscotophase (1). This fluctuation is caused by the release and/or degradation of existing pheromone and the biosynthesis of new pheromone at precise times of the photoperiod. The biosynthesis of pheromone in H. zea is regulated by a peptide produced in the subesophageal ganglion (SEG) portion of the brain complex of female moths (2). This peptide, termed pheromone-biosynthesis-activating neuropeptide (PBAN), has been isolated and sequenced from brains of H. zea (3).Two other pheromonotropic peptides, each with about 80%o sequence identity with H. zea PBAN, have been isolated from the brains of the silkworm, Bombyx mori (4, 5). These peptides have been synthesized and the synthetic peptides retain biological activity, with cross-reactivity occurring in other species of moths (3, 4, 6, 7). These reports and others indicate that a variety of moths utilize PBAN or PBAN-like peptides in controlling pheromone biosynthesis.Although PBAN or PBAN-like activity has been identified in several different moth species, the physiological mode of action of PBAN has not been determined conclusively for any one species. In fact, there are two apparently conflicting hypotheses on how PBAN activates pheromone biosynthesis, and both are based on studies utilizing Heliothis moths as experimental animals. One hypothesis suggests that PBAN is synthesized in the SEG, transported to the corpora cardiaca, and then released into the hemolymph, where it can act on the pheromone gland to induce pheromone biosynthesis (8)....

Sex Pheromone Production in the Silkworm,Bombyx mori, Is Mediated by Store-Operated Ca2+Channels

“…Neither the molecular nature of the channel activated by PBAN nor the way the PBAN signal is communicated from PBANR to the channel has been determined. Early studies in heliothine species suggested the involvement of RACCs, 9,10) but were unable to differentiate the type of RACC (SOC or DAG-dependent) activated, and given the species differences observed in sex pheromone biosynthetic pathways, may not be applicable to other lepidopterans.…”

“…4,8) Further studies designed to characterize the PBAN-activated Ca 2þ channel have suggested that, at least in heliothine species, a receptoractivated Ca 2þ channel is involved. 9,10) The mechanism of activation and the molecular nature of the PBANactivated Ca 2þ channel, however, remain to be resolved. While extracellular Ca 2þ is an absolute requirement for pheromonotropic activity, accumulating evidence suggests that the biochemical processes under PBAN control are species-dependent.…”

Bombyx mori Homologs of STIM1 and Orai1 Are Essential Components of the Signal Transduction Cascade That Regulates Sex Pheromone Production

“…For most female moths, sex pheromone production is dependent on an influx of extracellular Ca 2ϩ (2,4), presumably via ROCs (5,6). We have recently shown in B. mori that PBAN binding triggers the opening of SOCs (4), suggesting the possible involvement of STIM1 and Orai1; two proteins that have been identified as essential components of SOC pathways (12)(13)(14)(15).…”

“…It has been well established that regardless of species, pheromonotropic activity is dependent on extracellular Ca 2ϩ (2), suggesting that PBAN signaling is associated with the influx of extracellular Ca 2ϩ ; we directly demonstrated this crucial event in Bombyx mori using fluorescent Ca 2ϩ imaging techniques (4). Early pharmacological studies in heliothine species suggested that PBAN triggers the opening of receptor-operated Ca 2ϩ channels (ROCs) (5,6). The involvement of ROCs was strengthened when the PBAN receptor (PBANR) was identified as a G protein-coupled receptor that could function upstream of Ca 2ϩ influx when heterologously expressed in cultured insect cells (7,8).…”

The pheromone biosynthesis activating neuropeptide (PBAN) receptor of Heliothis virescens: Identification, functional expression, and structure–activity relationships of ligand analogs

“…The first PBANs identified from brain and subesophageal ganglia contain 33 or 34 amino acids, amidated at the C-terminus [5,14,16,24,27]. Despite significant advances over the last decades [4,10], many questions regarding the precise functional roles of PBANs remain. Recent efforts have focused on identification and tissue-specific expression of PBAN receptors.…”