An RNA interference pathway modulates the persistent infection of <italic>Southern rice black-streaked dwarf virus</italic> in insect vector, <italic>Sogatella furcifera</italic>

Abstract

Southern rice black-streaked dwarf virus (SRBSDV) is transmitted by the white-backed planthopper (WBPH; Sogatella furcifera Horvath) in a persistent-propagative manner. The mechanism for the highly efficient propagation of SRBSDV in the WBPH vector is unknown. RNA interference (RNAi) is generally thought to be an evolutionarily conserved antiviral immunity pathway in insects. To determine whether the persistent propagation of SRBSDV in the WBPH vector is modulated by an RNAi antiviral immunity pathway, we used small-RNA deep sequencing to detect 21- and 22-nt virus-derived small RNAs in cultured cells derived from WBPH infected with SRBSDV; the presence of these small RNAs implied that an RNAi response was trigged by viral infection. In addition, knockdown of the expressions of key RNAi pathway factors Dicer2 and Argonaute2 by treatment with dsRNA synthesized from Dicer2 and Argonaute2 genes strongly increased viral infection and accumulation in the WBPH vector and its cultured cells. Furthermore, the knockdown of Dicer2 and Argonaute2 expression reduced the survival rate and lifespan of the viruliferous insects. Taken together, these results indicate that the RNAi pathway effectively modulates the persistent infection of SRBSDV in the WBPH vector. This pathway thus plays a crucial role by preventing excessive plant virus accumulation in insect vectors, thereby protecting them from the negative impact of these viruses.