Effects of overexpression and inhibited expression of thymosin, an actin-interacting protein from Bombyx mori, on BmNPV proliferation and replication.

Previous study showed that exogenously applied recombinant thymosin from Bombyx mori (BmTHY) reduces B. mori nucleopolyhedrovirus (BmNPV) proliferation in silkworm. Which stands to reason that BmTHY in B. mori is crucial for the defense against BmNPV. However, little is known about the effect of endogenously overexpressed or repressed BmTHY on B. mori resistance to virus infection. To study this issue, we constructed an overexpression and inhibited expression systems of BmTHY in BmN cells. The viral titer and the analysis from the quantitative real-time polymerase chain reaction (PCR) revealed that overexpression of BmTHY decreased the copies of BmNPV gene gp41, which goes over to inhibit the proliferation of BmNPV in BmN cells, while the inhibited expression of BmTHY significantly enhanced viral proliferation in infected BmN cells. These results indicated that endogenous BmTHY can inhibit BmNPV proliferation and replication in infected BmN cells. Furthermore, Co-IP showed that BmTHY could bind to actin in BmN cells. Also, the overexpression or inhibited expression of BmTHY shifted the ratio of F/G-actin in infected BmN cells. Lastly, the BmTHY, an actin-interacting protein, might be one of the key host factors against BmNPV, which inhibits viral proliferation and replication in BmN cells.