Modified baculovirus system for high expression of Bombyx mori bidensovirus NS1 in silkworm / 生物工程学报

To improve the expression of heterologous genes using baculovirus expression system, we constructed a novel shuttle vector based on the Bm-Bacmid. In the Bm-Bacmid, partial sequences of Chitinase and Cystein Protease were replaced with a tandem cassette of Cm and egfp through homologous recombination. Bombyx mori bidensovirus (BmBDV) ns1 under the control of polyhedrin promoter was inserted into the modified Bm-bacmid by transposition. For comparison, BmBDV ns1 under the control of polyhedrin promoter was also cloned in the wild type Bm-bacmid. The resulting Bm-bacmids were transfected into the cultured BmN cells to prepare recombinant virus to infect silkworms for expression of BmBDV ns1. Total proteins of hemocyte from infected silkworms were subjected to Western blotting and ELISA analysis. The yield of BmBDV NS1 1 with the modified vector was three times as much as that with the unmodified vector. The method to improve the yield of BmBDV NS1 in silkworms will facilitate the function and three-dimensional structure study of BmBDV NS1.

Expression of ns1 gene from Bombyx mori bidensovirus by a novel baculovirus expression system / 生物工程学报

Baculovirus gene expression is the most popular method to make target protein in cultured insect cells. To fast determine the generation of recombinant virus in cultured cells, donor plasmid of pFastBacI was modified by introducing egfp cassette. In the modified vector, egfp cassette was under the control of ie1 promoter, and target gene cassette was under the control of polyhedron promoter. To evaluate the convenience of the genetically modified donor plasmid used in eukaryotic expression, ns1 gene from Bombyx mori bidensovirus was ligated into the donor plasmid to generate recombinant plasmid pFastBacI-[P(ie1)-egfp-sv40]-[P(polh)-ns1-sv40]. Then the plasmid was transformed into DH10B competent cells containing Bm-Bacmid vector to produce the final recombinant Bm-Bacmid with the help of transposase. The resulting recombinant Bm-Bacmid was transfected into BmN cells to generate recombinant virus, which was easily and rapidly judged by green fluorescent signal observed in BmN cells. After infection for 96 h, the BmN cells were harvested and the total protein extracted from the infected BmN cells was subjected to Western blotting analysis. The result showed that a specific protein band about 36 kDa was detected, indicating that NS1 protein was successfully expressed in the BmN cells. In conclusion, the expression of NS1 protein with the modified expression system is useful for further research on the function of NS1 protein.