Important roles played by TGF-β member of Bmdpp and Bmdaw in BmNPV infection.

Transforming growth factor (TGF)-β superfamily members inhibit Bombyx mori nucleohedrovirus (BmNPV) multiplication in silkworm are not determined. In this study, we first found that BmNPV RNA transcription and protein expression level were regulated by TGF-β members, Decapentaplegic (Bmdpp) and Dawdle (Bmdaw) in the domesticated silkworm, B. mori and silkworm ovary-derived cells. Furthermore, subcellular localization showed that Bmdpp and Bmdaw were mainly presented in cytomembrane of the cultured BmN cells. Tissues expression pattern analysis found that the highest expression levels of Bmdpp and Bmdaw genes were in the hemocyte of fifth instar larvae. During the immune response, the expression level of Bmdpp gene was elevated and Bmdaw gene was declined in BmNPV infected BmN cells and silkworm. The multiplication of BmNPV was inhibited by overexpression of Bmdpp and Bmdaw genes in BmN cells. RNA interference experiments found that the multiplication of BmNPV was raised with specific siRNAs of Bmdpp and Bmdaw genes in BmN cells. The antiviral immune pathways were not significantly regulated by the TGF-β superfamily members. Taken together, these findings provided a clue to understand the function of Bmdpp and Bmdaw gene in response to the BmNPV infection in silkworm.