Disruption of diapause induction by TALEN-based gene mutagenesis in relation to a unique neuropeptide signaling pathway in Bombyx.

Kunihiro Shiomi,Yoko Takasu,Masatoshi Ichida Takahama,Masayo Kunii,Hideki Sezutsu,Ryoma Tsuchiya,Moeka Mukaida,Masakazu Kobayashi,Akira Mizoguchi

doi:10.1038/srep15566

Abstract

The insect neuropeptide family FXPRLa, which carries the Phe-Xaa-Pro-Arg-Leu-NH2 sequence at the C-terminus, is involved in many physiological processes. Although ligand–receptor interactions in FXPRLa signaling have been examined using in vitro assays, the correlation between these interactions and in vivo physiological function is unclear. Diapause in the silkworm, Bombyx mori, is thought to be elicited by diapause hormone (DH, an FXPRLa) signaling, which consists of interactions between DH and DH receptor (DHR). Here, we performed transcription activator-like effector nuclease (TALEN)-based mutagenesis of the Bombyx DH-PBAN and DHR genes and isolated the null mutants of these genes in a bivoltine strain. All mutant silkworms were fully viable and showed no abnormalities in the developmental timing of ecdysis or metamorphosis. However, female adults oviposited non-diapause eggs despite diapause-inducing temperature and photoperiod conditions. Therefore, we conclude that DH signaling is essential for diapause induction and consists of highly sensitive and specific interactions between DH and DHR selected during ligand–receptor coevolution in Bombyx mori.

Highlights

The insect neuropeptide family FXPRLa, which carries the Phe-Xaa-Pro-Arg-Leu-NH2 sequence at the C-terminus, is involved in many physiological processes
We clearly showed in this study that in vivo disruption of diapause hormone (DH)-pheromone biosynthesis activating neuropeptide (PBAN) and DH receptor (DHR) blocked diapause induction in progeny embryos
An in vivo bioassay showed that synthetic DH was more effective than other FXPRLa at inducing diapause, with threshold levels less than 1/100 that of PBAN and other peptides encoded by DH-PBAN (Fig. 3E)[10]

Summary

Introduction

The insect neuropeptide family FXPRLa, which carries the Phe-Xaa-Pro-Arg-Leu-NH2 sequence at the C-terminus, is involved in many physiological processes. Bombyx mori, is thought to be elicited by diapause hormone (DH, an FXPRLa) signaling, which consists of interactions between DH and DH receptor (DHR). Insect FXPRLa-family neuropeptides, which carry the Phe-Xaa-Pro-Arg-Leu-NH2 sequence at the C-terminus, play a role in many physiological processes, including diapause induction, pheromone biosynthesis, cuticular tanning, myostimulation, pupariation behavior, and termination of pupal diapause[3]. These FXPRLa neuropeptides are evolutionarily related to the vertebrate peptide neuromedin U (NMU), and G-protein coupled receptors (GPCRs) in the NMU receptor clade are activated by FXPRLa peptides[4]. Some of the molecular mechanisms in the pathway leading from reception of environmental signals to expression of the diapause phenotype have been revealed

Methods

Results

Conclusion