Hormonal regulation of protein synthesis in the silk gland of Galleria mellonella

Synthesis of the low molecular mass silk proteins of 24 and 30 kDa in the last larval instar of Galleria mellonella starts between 24 and 48 h; synthesis of the former protein significantly preceding that of the latter. Posterior silk glands (PSG) from day-1 last instar larvae are transiently sensitive in vitro to exogenous 20-hydroxyecdysone (20-HE), which stimulates transcription of the 24 kDa protein gene and induces transcription of the gene for the 30 kDa protein. The glands from the day -3 last instar larvae are insensitive to this hormone. The brain extract acts directly on RNA synthesis in silk gland in vitro at the concentration of 0.1 brain equivalent per gland. This factor is protease sensitive and thermostable.