Abstract: In order to find a strong promoter that can be used to promote expression of piggyBac transposase and thereby increase genetic transformation efficiency in cells of the silkworm, Bombyx mori, the transcriptional activities of eight promoters were compared in the BmN cells of B. mori, including hsp70, hsp82, actin3 （A3）, polyubiquitin （PUB）, α-tubulin, fibroin-L, artificial promoter 3×P3 and immediately early 1 gene promoter flanked by the hr5 enhancer element （hr5-IE1）. The results showed that hr5-IE1 displayed the highest transcriptional activity, followed by A3, while the activities of the other six promoters were relatively low. When transfected with an EGFP vector and a piggyBac helper plasmid, in which the expression of piggyBac transposase was driven by hr5-IE1, the EGFP cassette was successfully integrated into the genome of BmN cells. Therefore, hr5-IE1 has the potential of serving as a sound element in future piggyBac-based transgenic research of B. mori with the capability of increasing transformation efficiency.

Key words: Bombyx mori, hr5-IE1, luciferase assay, piggyBac, promoter, genetic transformation