Abstract
Ecdysone is the key hormone regulating insect growth and development. Ecdysone synthesis occurs in the prothoracic glands (PGs) and is regulated by several neuropeptides. Four prothoracicotropic and three prothoracicostatic factors have been identified to date, suggesting that ecdysone biosynthesis is intricately regulated. Here, we demonstrate that the neuropeptide pigment dispersing factor (PDF) stimulates ecdysone biosynthesis and that this novel signaling pathway partially overlaps with the prothoracicotropic hormone (PTTH) signaling pathway. We performed transcriptome analysis and focused on receptors predominantly expressed in the PGs. From this screen, we identified a candidate orphan G protein coupled receptor (GPCR), Bombyx neuropeptide GPCR-B2 (BNGR-B2). BNGR-B2 was predominantly expressed in ecdysteroidogenic tissues, and the expression pattern in the PGs corresponded to the ecdysteroid titer in the hemolymph. Furthermore, we identified PDF as a ligand for BNGR-B2. PDF stimulated ecdysone biosynthesis in the PGs, but the stimulation was only observed in the PGs during a specific larval stage. PDF did not affect the transcript level of known ecdysone biosynthetic enzymes, and inhibiting transcription did not suppress ecdysone biosynthesis, suggesting that the effects of PDF might be mediated by translational regulation and/or post-translational modification. In addition, the participation of protein kinase A (PKA), phosphatidylinositol 3-kinase (PI3K), target of rapamycin (TOR) and eukaryotic translation initiation factor 4E (eIF4E)-binding protein (4E-BP) in the PDF signaling pathway was discovered.
Highlights
Ecdysone is the key regulator of insect growth and development
Because torso is a known prothoracicotropic hormone (PTTH) receptor gene and the expression of BNGR-A34 was not confirmed in prothoracic glands (PGs), these were excluded as candidate genes
pigment dispersing factor (PDF) is primarily considered an important component for regulating circadian rhythms in insects, but here we showed that PDF has a novel function in the stimulation of ecdysone biosynthesis
Summary
Ecdysone is synthesized in the PGs and the biosynthesis is intricately regulated by several neuropeptides. The participation of four cytochrome P450 (CYP) enzymes (CYP307A1, Spook (Spo); CYP306A1, Phantom (Phm); CYP302A1, Disembodied (Dib); CYP315A1, Shadow (Sad)); an oxygenase-like protein, Neverland (Nvd); and a shortchain dehydrogenase/reductase, Non-molting glossy/Shroud (Nm-g/Sro), have been reported in the ecdysone biosynthetic pathway [2,3,4,5,6,7]. The transcript levels of spo, dib and phm are upregulated by PTTH and suppressed by Bommo-FMRFamides [8]. All the regulatory mechanisms identified to date were initiated by the discovery of the ligand, after which the receptor and corresponding signaling pathway were investigated. To identify a novel regulatory pathway regulating ecdysone biosynthesis, we focused on the receptors expressed predominantly in the PGs of B
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
