Cloning and subcellular localization of silkworm suppressor of cytokine signaling 6 and its expressional changes in response to the infection of Bombyx mori nucleopolyhedrovirus

Abstract

The role of suppressor of cytokine signaling (SOCS) 6 in the silkworm growth and development and in the immune response to Bombyx mori nucleopolyhedrovirus (BmNPV) infection remains largely unclear. In this study, we cloned the ORF of silkworm SOCS6, named as BmSOCS6. We found that BmSOCS6 locates mainly in cytoplasmic space, and expresses at the highest level in embryogenesis. BmSOCS6 expresses relatively highly in the fat body of BmNPV-susceptible silkworm 306 but lowly in BmNPV-resistant silkworm NB and BC8, and BmNPV inoculation further reduces its expression with more pronounced effect in NB and BC8 than 306. However, BmSOCS6 expression in the midgut and hemolymph decreases without BmNPV inoculation but recovers with BmNPV inoculation, both of which are more pronounced in NB and BC8 than 306. BmNPV inoculation also induces a general down-regulation of BmSOCS6 expression in BmN cells. SOCS6 has previously been shown to positively regulate apoptosis and negatively regulate the production of antimicrobial peptides (AMPs). Therefore, compared to susceptible silkworms, BmSOCS6 may promote apoptosis in the midgut and hemolymph with increased expression and enhance the production of AMPs in the fat body with decreased expression, contributing to the resistance to BmNPV infection in resistant silkworms.