Hormonal regulation of the expression of two storage proteins in the larval fat body of the greater wax moth (Galleria mellonella)

During larval development of the greater wax moth, Galleria mellonella, genes of storage proteins LHP76 and LHP82 are tissue- and stage-specifically expressed. In this study, hormonal regulation of this expression has been investigated in vivo. Messenger RNAs of the juvenile hormone (JH-suppressible) Lhp82 gene are present only during the feeding period of the final larval instar, suggesting that a high level of JH during earlier stages prevents its expression and that a small rise in JH titer observed on day 8 of the final larval instar is responsible for the rapid shut-off of its transcription. Application of 1μg of JH analog (fenoxycarb) specifically inhibits expression of Lhp82, whereas Lhp76 mRNAs remain at the same level. 20-hydroxyecdysone (20HE) does not exert any inhibitory effects on transcription of Lhp genes when injected in a dose of 0.5 or 1.5 μg per individual, regardless of larval age. However, the same dose of 20HE significantly lowers the rate of LHPs synthesis within the fat body and completely blocks secretion of LHPs into the hemolymph. Therefore, we propose that 20HE inhibits the synthesis of storage proteins and their secretion without altering the level of mRNAs.