MOLECULAR CHARACTERIZATION OF OVARY TREHALASE OF THE SILKWORM, BOMBYX-MORI AND ITS TRANSCRIPTIONAL ACTIVATION BY DIAPAUSE HORMONE

We have isolated a cDNA encoding ovary trehalase of the silkworm, Bomb yx mori. Sequence analyses revealed that the isolated cDNA contains 31 43 nucleotides and comprises 579 amino acids, including a cleavable si gnal sequence and five potential N-glycosylation sites. Northern blot analysis showed a 3.0 kb transcript in developing ovaries carrying mem brane-bound trehalase. A single copy of trehalase gene was present in the haploid genome of the silkworm. The effect of diapause hormone on the accumulation of trehalase mRNA was examined on developing ovaries in in vivo and in vitro conditions. The synthetic diapause hormone bro ught about a 6-fold increase in trehalase mRNA content in ovaries 4 h after injection. The similar increase was found in ovaries which were incubated in vitro with diapause hormone. Coincubation of ovaries with diapause hormone and actinomycin D could not increase the mRNA level in ovaries, and maintained a basal level which was found in ovaries in cubated without diapause hormone. These results indicate that diapause hormone stimulates transcription of the trehalase gene in developing ovaries of the silkworm.