Abstract: To study the regulation mechanism of silk genes in the silkworm, Bombyx mori, the upstream 1 233 bp promoter sequence of fibroin P25 gene and its regulatory elements were analyzed by using Bac-to-Bac expression system and real-time quantitative PCR technique. The results showed that there existed positive regulatory elements at position  -423 to -1 233 and -127 to -238 in P25 promoter region, and negative regulatory elements at position -238 to -423. PSGF and BMFA regulatory elements played a negative regulation role in P25 expression. PSGF element had a certain degree of enhancement to A3 promoter’s activity in posterior silk glands, which further validates the function of PSGF regulatory element. Analysis of P25 promoter activity, especially functional analysis of PSGF and BMFA regulatory elements, could be helpful in further understanding the mechanism of P25 expression and fine regulation.

Key words: Bombyx mori, fibroin P25, promoter; cis-acting element, Bac-to-Bac, real-time PCR