Abstract: To verify whether the signal peptide sequence of fibroin H chain (fib-H) functionally possesses the activity in the middle silk gland, based on the characteristics of the strong promoter of the silk protein gene and the high level secretion of silk protein of the silkworm, Bombyx mori, we constructed the promoter ser-HS of sericin-1 gene (ser-1) with the signal peptide sequence of fib-H. Then, we constructed the transitorily secretory expression vector pSK-serHS-DsRed-polyA via driving the DsRed gene with the promoter ser-HS. We transfected pSK-serHS-DsRed-polyA into BmN cells by liposome. From the cells transfected with the vector, the red fluorescence could be detected, which verified that the expression vector could express DsRed in BmN cells transiently. Furthermore, when silkworm had been injected with the expression vector pSK-serHSDsRed-polyA, red fluorescence could be observed in the lumen of the middle silk gland of silkworm. The results indicated that DsRed was expressed transiently and was secreted into the lumen of the middle silk gland. We concluded that the cloned signal peptide sequence of fib-H possesses the biological functions of the signal peptide in the middle silk gland.

Key words: Bombyx mori, sericin promoter, fibroin H chain, signal peptide, DsRed, BmN cell, silk gland