The profiles of mRNA 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 dehydrogenase (SDH) gene contains nucleotide sequences that might be recognized and bound by steroid hormone receptors such as Drosophila hormone receptor 39 (DHR39) and Fushi tarazu transcription factor 1 (FTZ-F1). As a first trial to find out regulator(s) involved in gene expression for SDH in Bombyx eggs, we have cloned a cDNA encoding a Bombyx homolog (BHR39) of DHR39, and examined levels of mRNA expressions for BHR39 and Bombyx FTZ-F1 (BmFTZ-F1) during the entire embryonic development and diapause. During embryonic development of non-diapause eggs, mRNA 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.