AGO4 and infection: Mutation in V2 does not affect viral replication (Wartig et al., 1997), and therefore viral accumulation in local infections in N. benthamiana (leaf patch agroinfiltration assays; see Figure 3—figure supplement 1) was not different between the wild-type virus and the V2 null mutant virus (Figure 3E); in both cases, AGO4 silencing led to a not statistically significant but reproducible trend to higher viral accumulation, suggesting an antiviral role for AGO4 (Figure 3E).