AGO2 and viral infectious disease: However, recent researches might reveal the mystery of the relationship between miR403 and AGO2. As miR168 and miR403 were down-regulated when plants receive virus infection signal and both ago1 and ago2 mutations were hypersensitive to virus infection, AGO1 and AGO2 represented the first and second layer to RNA-mediated defense and counter-defense in the interaction between plants and plant-virus [19,29,48,49].