Transcriptional regulation of the PTTH receptor in prothoracic glands of the silkworm, Bombyx mori

The present study investigated transcriptional regulation of the prothoracicotropic hormone (PTTH) receptor (Torso) gene in prothoracic glands (PGs) of the silkworm, Bombyx mori. The results showed that PTTH treatment in vitro time-dependently affected Torso mRNA levels, with an inhibitory effect being detected after 1- and 2-h periods of incubation. When methoprene, a juvenile hormone analogue (JHA), was applied to newly ecdysed last instar larvae, a decline in Torso mRNA levels during the early last larval instar was delayed compared to those treated with acetone. Injection of 20-hydroxyecdysone appeared to have a stimulatory effect on Torso mRNA levels. Torso mRNA levels were also shown to be nutrition-sensitive. From these results, it was suggested that Torso mRNA levels of the PGs appear to be hormonally regulated and nutrition-sensitive, and the endogenous precisely coordinated regulation of Torso mRNA levels may play a role in regulating ecdysteroidogenesis by PGs during development.