Study On Resistence To BmNPV Of RNAi-transgenic Silkworm

Nowadays, some studies suggest that the use of RNAi technology could inhibit BmNPV proliferation by interfering the viral genes essential for viral DNA replication, such as ie-1, lef-1 and gp64. But another problem is that even targeting the same gene the silent efficiency will be much different when focusing different regions of the gene. In order to verify the effect that transgenic silkworms expressing different dsRNA restrain proliferation of Bombyx mori nucleopolyhedrovirus virus(BmNPV), the transgenic vector pigA3-LEF-Neo containing lef-1 dsRNA and neo gene expression cassette was transferred into the eggs of silkworm(Haoyue stain)by sperm-mediated gene transferring methods. Screened with GFP and antibiotics G418, combined identification of PCR and Dot hybridization, transformed silkworms were obtained. The mortality of G6-generation second-instar transgenic silkworms infected with BmNPV decreased 10% to 30% compared with normal ones, suggesting that the resistance to BmNPV on the transgenic silkworms has improved. Real-time PCR demonstrated that after being infected the lef-1 mRNA from G6-generation fifth-instar declined 72 folds and 26.5 folds on average, at most 104 folds, compared with normal silkworms. The results further confirmed that the transcribed lef-1 dsRNA in transgenic silkworms inhibited the expression of the lef-1 gene.Meanwhile, we transferred the transgenic vector pigA3-IE-Neo containing ie-1 dsRNA and neo gene expression cassette into the eggs of silkworm(Jingsong Varieties)by sperm-mediated gene transferring methods. G1-generation second-instar transgenic silkworms infected with BmNPV suggesting that the transgenic silkworms can depressed BmNPV.In addition, the resistence to BmNPV of five different strains of two-instar silkworms, respectively, Jingsong, Haoyue, Suju (A, B series), Ming Hu (A, B series) and gao bai×Haoyue, infectd with BmNPV has been confirmed. Also their resistence compared with the transgenic silkworms. The results showd that different strains of silkworms had different resistence to the BmNPV, but the transgenic silkworms had high resistence to the virus on the whole. The results further confirmed that the transgenic silkworm can enhance the resistance to the BmNPV.