<i>BmWARS</i> inhibits BmNPV infection via the PI3K-Akt pathway

<i>Bombyx mori</i> Tryptophanyl-tRNA synthetase (<i>BmWARS</i>) belongs to the family of Ic-like aminoacyl-tRNA synthetases (aaRSs), whose specific recognition of the substrate Trp, tRNA, maintains the fidelity of protein synthesis. In this study, <i>BmWARS</i> was cloned and characterized from the midgut of the silkworm, <i>Bombyx mori</i>, resulting in an open reading frame (ORF) with a full length of 1,149 bp, which can encode 382 Aa. BmWARS is localized in the cytoplasm, and is expressed in all tissues of the silkworm, with higher expression in the testis, ovary, silk gland and malpighian tubule. The expression of <i>BmWARS</i> was significantly up-regulated in the midgut and silk gland after infection with <i>Bombyx mori</i> nuclear polyhedrosis virus (BmNPV). In addition, overexpression of <i>BmWARS</i> inhibited BmNPV infection and replication extremely significantly, while interference with <i>BmWARS</i> expression promoted BmNPV infection and replication. Analysis of the immune pathways in which <i>BmWARS</i> may be involved revealed that the expression of the key genes of the PI3K-Akt pathway, <i>BmPI3K, BmAkt, BmPDK1, BmeIF4E, BmS6</i>, and p-Akt protein was significantly reduced, whereas the expression of <i>BmPTEN, BmFoxO</i>, and <i>BmCaspase9</i> was significantly increased in the cells that overexpressed <i>BmWARS</i> and were infected with BmNPV. Meanwhile, the results of the study interfering with the expression of <i>BmWARS</i> were completely opposite to those of the study overexpressing <i>BmWARS</i>. This is the first report that <i>BmWARS</i> has antiviral effects in <i>Bombyx mori</i>. Moreover, <i>BmWARS</i> inhibits BmNPV infection and replication in <i>Bombyx mori</i> cells by promoting apoptosis and inhibiting cell proliferation.