Functional analysis of BmTsp.C in modulating infection of BmNPV through apoptosis pathways in domestic silkworm (Bombyx mori)

The silkworm, <i>Bombyx mori</i>, is a crucial model insect in agriculture and biological research. Tetraspanins, known for their effects in regulating cellular functions like cell signalling, adhesion, migration and diffusion, take on a crucial role in viral dynamics, influencing both viral spread and entry into host cells. In this study, a tetraspanin gene called <i>BmTsp.C</i> from the silkworm genome was identified and investigated. Tissue profiles showed that <i>BmTsp.C</i> has the highest transcription level in midgut, with a marked increase following viral infection. The immunofluorescence localization suggested that BmTsp.C is primarily distributed on the cell membrane. Additionally, overexpression of <i>BmTsp.C</i> in BmN cells facilitated the proliferation of BmNPV. Meanwhile, siRNA-mediated knockdown of <i>BmTsp.C</i> could inhibit viral proliferation. In addition, knockdown of <i>BmTsp</i>.C at the individual level further validated the remarkable effect of <i>BmTsp.C</i> during viral infestation. Furthermore, overexpression of <i>BmTsp.C</i> could regulate the expression of apoptosis-related genes. Results from flow cytometry indicated a decrease in the number of apoptotic cells after overexpression of <i>BmTsp.C</i>. Taken together, our results demonstrated that <i>BmTsp.C</i>, as an important factor in the Tetraspanin-enriched microdomains, exerts a significant influence on the proliferation of BmNPV, most likely through the cellular apoptosis pathway.