THE PROFILES OF MESSENGER-RNA LEVELS FOR BHR39, A BOMBYX HOMOLOG OF DROSOPHILA HORMONE-RECEPTOR-39, AND BOMBYX FTZ-F1 IN THE COURSE OF EMBRYONIC-DEVELOPMENT AND DIAPAUSE

In the silkworm. Bombyx mori, the 5'-upstream region of the sorbitol d ehydrogenase (SDH) gene contains nucleotide sequences that might be re cognized and bound by steroid hormone receptors such as Drosophila hor mone receptor 39 (DHR39) and Fushi tarazu transcription factor 1 (FTZ- F1). As a first trial to find out regulator(s) involved in gene expres sion for SDH in Bombyx eggs, we have cloned a cDNA encoding a Bombyx h omolog (BHR39) of DHR39, and examined levels of mRNA expressions for B HR39 and Bombyx FTZ-F1 (BmFTZ-F1) during the entire embryonic developm ent and diapause. During embryonic development of non-diapause eggs, m RNA expression for BmFTZ-F1, but not for BHR39, was shown to occur in parallel with that for SDH, although such a parallelism was not found at the termination of diapause, when SDH mRNA was expressed.