Identification of a New Sprouty Protein Responsible for the Inhibition of the <i>Bombyx mori</i> Nucleopolyhedrovirus Reproduction

<div><p>The rat sarcoma-extracellular signal regulated kinase mitogen-activated protein kinases pathway, one of the most ancient signaling pathways, is crucial for the defense against <i>Bombyx mori</i> nucleopolyhedrovirus (BmNPV) infection. Sprouty (Spry) proteins can inhibit the activity of this pathway by receptor tyrosine kinases. We cloned and identified a new <i>B. mori</i> gene with a Spry domain similar to the Spry proteins of other organisms, such as fruitfly, mouse, human, chicken, Xenopus and zebrafish, and named it <i>BmSpry</i>. The gene expression analysis showed that <i>BmSpry</i> was transcribed in all of the examined tissues and in all developmental stages from embryo to adult. <i>BmSpry</i> also induced expression of BmNPV in the cells. Our results indicated: (1) the knock-down of <i>BmSpry</i> led to increased BmNPV replication and silkworm larvae mortality; (2) over-expression of <i>BmSpry</i> led to reduced BmNPV replication; and (3) <i>BmSpry</i> regulated the activation of ERK and inhibited BmNPV replication. These results showed that <i>BmSpry</i> plays a crucial role in the antiviral defense of the silkworm both <i>in vitro</i> and <i>in vivo</i>.</p></div>