The regulation of major haemolymph protein synthesis: Changes in mRNA content during the development of Bombyx mori larvae

Abstract

Major haemolymph proteins (MHP) correspond to a family of polypeptides synthesized by the larval fat body. Their production is regulated by juvenile hormone (JH; Plantevin et al., 1987). In vitro translation of messenger RNAs and polyribosome profiles show that JH applications decrease MHP production without any accumulation of untranslated MHP mRNAs. Three probes corresponding to three different MHP mRNAs were isolated from a cDNA library and used to determine mRNA prevalence during development and JH treatment. These profiles closely parallel the net syntheses of the corresponding proteins. In contrast to other haemolymph proteins, no translation control occurs at the end of the feeding period. The effects of JH on MHP messenger amount differ between the beginning and the end of the fifth instar feeding period, suggesting that different regulation processes are involved.