Ecdysone-responsive transcription factors determine the expression region of target cuticular protein genes in the epidermis of Bombyx mori.

In the present study, we found that different ecdysone-responsive transcription factors were expressed differentially in different regions of the epidermis at around pupation. βFTZ-F1 transcripts were strongly but E74A transcripts were barely observed in the thoracic region of the epidermis, and vice versa in the abdominal region. Transcripts of all the examined transcription factors were observed in wing disc. Transcript of a cuticular protein gene, BMWCP4, which does not have a βFTZ-F1 binding site in the 2-kb upstream region, was not observed in the thoracic region of the epidermis. Transcript of BMWCP9, which does not have an E74 binding site in the 2-kb upstream region, was not observed in the abdominal region of the epidermis. BMWCP2 has all the transcription factor binding sites examined and was expressed in the thoracic and abdominal region of the epidermis. Thus, it is suggested that ecdysone-responsive transcription factors determined the space where the cuticular protein genes were expressed, which, in turn, determined the character of the cuticle that was characterized by the combination of cuticular proteins.