Bombyx mori C-Type Lectin (BmIML-2) Inhibits the Proliferation of B. mori Nucleopolyhedrovirus (BmNPV) through Involvement in Apoptosis

Abstract

C-type lectins (CTLs) are widely distributed in mammals, insects, and plants, which act as pattern recognition receptors (PRRs) to recognize pathogens and initiate immune responses. In this study, we identified a C-type lectin gene called <i>BmIML-2</i> from the silkworm <i>Bombyx mori</i>. Its open reading frame (ORF) encodes 314 amino acids, which contain dual tandem C-type lectin-like domain (CTLD). <i>BmIML-2</i> is highly expressed in the fat body and is significantly induced at 24 h after BmNPV infection. Moreover, overexpression of <i>BmIML-2</i> dramatically inhibited the proliferation of BmNPV, and knockdown assay via siRNA further validated the inhibition of <i>BmIML-2</i> on viral proliferation. In addition, transcript level detection of apoptosis-related genes and observation of apoptosis bodies implied that overexpression of <i>BmIML-2</i> promoted BmNPV-induced apoptosis. Immunofluorescence analysis indicated that BmIML-2 distributed throughout the cytoplasm and was slightly concentrated in the cell membrane. Taken together, our results suggest that BmIML-2 could inhibit in the proliferation of BmNPV by facilitating cell apoptosis.