Analysis of the activity of virus internal ribosome entry site in silkworm Bombyx mori

Internal ribosome entry site (IRES) has been widely used in genetic engineering; however, the application in silkworm (Bombyx mori) has hardly been reported. In this study, the bio-logical activity of partial sequence of Encephalomyocarditis virus (EMCV) IRES, Rhopalosiphum padi virus (RhPV) IRES, and the hybrid of IRES of EMCV and RhPV were investigated in Spodoptera frugiperda (Sf9) cell line and silkworm tissues. The hybrid IRES of EMCV and RhPV showed more effective than EMCV IRES or RhPV IRES in promoting downstream gene expression in insect and silk-worm. The activities of all IRESs in middle silk gland of silkworm were higher than those in the fat body and pos-terior silk gland. The hybrid IRES of EMCV and RhPV was integrated into silkworm genome by transgenic tech-nology to test biological activity of IRES. Each of the posi-tive transgenic individuals had significant expression of report gene EGFP. These results suggested that IRES has a potential to be used in the genetic engineering research of silkworm