Identification and functional analysis of the cathepsin D gene promoter of Bombyx mori

The gene encoding cathepsin D of silkworm, Bombyx mori (BmCatD) is specifically expressed in the larval fat body and pupal gut, and plays an important role in the programmed cell death during metamorphosis. To identify element involved in this transcription-dependent spatial restriction, truncation and deletion of the 5' terminal from the BmCatD promoter were conducted in vivo. The recombinant AcMNPV vector (Autographa californica multiple nucleopolyhedrovirus) with a dual-luciferase quantitative assay system was used as the transfer. A 289 bp DNA sequence (-1,214 to -925) upstream of the transcriptional start site is found to be responsible for promoting tissue-specific transcription. Further analysis of a series of deletion within the 289 bp region of overlapping deletion showed that a 33 bp region (-1,071 to -1,038) sequence suppresses the ectopic expression of the BmCatD promoter. These results suggest that this 33 bp region could function as a promoter element in the tissue-specificity expression.