rRNA degradation in Bombyx mori and Bombyx mandarina cells infected witv veterologous nucleopolyvedroviruses

We previously found that rRNA of BM-N cells derived from the silkworm Bombyx mori undergoes rapid and extensive degradation through site-specific cleavage during abortive infection with nucleopolyhedroviruses (NPVs) of Autographa californica (AcMNPV), Hyphantria cunea (HycuMNPV), Spodoptera exigua and S. litura. Here, we demonstrated that rRNA degradation also occurs in Bme21 and Bm-aff3 cells, which are derived from B. mori embryo and fat body, respectively, during infection with AcMNPV. rRNA degradation in Bme21 cells was also observed following HycuMNPV infection, but was not detected in Bm-aff3 cells. We further showed that rRNA in a cell line derived from B. mandarina, an ancestor of B. mori, underwent degradation in response to cellular infection with AcMNPV and HycuMNPV. In contrast, no rRNA degradation was observed in a cell line derived from Antheraea pernyi. Taken together, these results indicate that NPV-triggered rRNA degradation represents a mechanism of innate antiviral immunity that is unique to B. mori and B. mandarina cells.