Identification of a cis-regulatory element that directs prothoracicotropic hormone gene expression in the silkworm Bombyx mori

摘要

In the silkworm Bombyx mori and other insects, prothoracicotropic hormone (PITH) plays a central role in controlling molting and metamorphosis by stimulating the prothoracic glands to synthesize and release the molting hormone ecdysone. Using an AcNPV (Autographa californica nucleopolyhedrovirus)mediated transient gene transfer system, we identified a cis-regulatory element that participates in the decision to switch expression of PTTH on or off in PTTH-producing neurosecretory cells (PTPCs). The nucleotide sequence of this cis-regulatory element is similar to a cis-regulatory element that participates in direction of expression of diapause hormone-pheromone biosynthesis activating neuropeptide gene (DH-PBAN) (Shiomi et al., 2007). Furthermore, we found that B. mori Pitx (BmPitx), a bicoid-like homeobox transcription factor, binds the element and activates PITH expression. Therefore, we propose that the cell-specific expression of two neuropeptide hormone genes, PITH and DH-PBAN, is activated by the Pitx transcription factor, which may act as a pan-activator in the insect neuroendocrine system and in vertebrate pituitary cells