Effects of heat shock protein Hsp25.4 of Bombyx mori on BmNPV proliferation

【Objective】To explore the expression changes of silkworm heat shock protein(Hsp25.4) gene after infection by Bombyx mori nuclear polyhedrovirus(BmNPV), and clarify the effect of knocking down of gene expression on the proliferation and replication of BmNPV, which could provide a reference for further analysis of the role of Bm Hsp25.4 protein in the infection of silkworm by BmNPV. 【Method】The 5^th instar larvae of silkworm were used as material, and fed with 10 µL prepared BmNPV polyhedra suspension(5×10⁸ insect/mL),control group fed with equal amounf of sterile water. The real-time fluorescence quantitative PCR was applied to analyze the expression of BmHsp25.4'gene in various tissues of silkworm larvae infected with BmNPV for 6 h, and 3 tissues with relatively high expression levels were selected to analyze the spatiotemporal expression map of BmHsp25.4' gene. Then, the interference effect of BmHsp25.4' gene in vivo was detected by injection of the double-stranded RNA(dsRNA), and the effect of BmHsp25.4'gene interference on the proliferation and replication of BmNPV was detected by real-time fluorescence quantitative PCR.【Result】The BmHsp25.4' gene was up-regulated in the midgut,hemolymph and fat body of silkworm larvae at 6 h after the BmNPV infection and the expression profile of BmHsp25.4' gene in those three tissues showed a trend of rising fist and then decreasing. The relative expression in hemolymph and midgut reached the highest peak at 6 h,while the expression of fat body reached the highest at 12 h after BmNPV infection. After interference with dsRNA injection,the relative expression of BmHsp25.4' gene in experimental group decreasing by 61.81% compared with the control group,the difference was extremely significant(P<0.01,the same below),indicating that the expression of BmHsp25.4' gene was successfully interfered. After BmHsp25.4' gene interference, the relative expression of gp41 gene of ds BmHsp25.4' was extremely significantly higher than control ds GFD, and the difference was significant at 48 h after infection(P<0.05). 【Conclusion】The results indicate that BmNPV infection can induce the expression of BmHsp25.4' gene,and knockdown of BmHsp25.4' gene can promote the early proliferation of BmNPV in the silkworm,suggesting that Hsp25.4 protein may play a related role in the antiviral immunity of silkworm.