Diverse RNA viral effectors converge on facilitation of AGO4 degradation to promote infection

ARGONAUTE4 (AGO4)-mediated RNA-directed DNA methylation (RdDM) defends against DNA viruses by methylating their genomes. However, there is limited information available regarding RNA viruses. Here, we show that OsAGO4 has antiviral immunity against two different types of RNA viruses, rice stripe virus (RSV, Tenuivirus) and Southern rice black streaked dwarf virus (SRBSDV, Fijivirus). To facilitate infection, the evolutionarily distinct viral effectors RSV P2 and SRBSDV SP8 both targeted OsAGO4 for degradation. These unrelated viral proteins both recruited the F-box protein OsFBX68 to promote their association with OsAGO4, resulting in enhanced OsAGO4 degradation. In summary, our findings elucidated OsAGO4-mediated antiviral defense and reveal new mechanisms by which diverse RNA viral effectors exploit OsAGO4 to promote infection using a common counter-defense strategy.