Abstract: Tobacco(Nicotiana tabacum),Arabidopsis thaliana,and host papaya(Carica papaya L.)of PRSV were used as model plant materials to testing whether RNAi could mediate resistance to papaya ringspot virus(PRSV).The agrobacterium was harbored with pHellsgate12-CP_IR containing structured inverted sequences of the CP gene of PRSV,where were transformed into the tobacco and Arabidopsis.We also conducted an Agrobacterium-mediated transient expression experiment by infiltration in papaya.The three transgenic plants inoculated with PRSV were tested for resistance to PRSV.After PRSV challenge-inoculation for 3 to 7 days,leaves of the wild type plants displayed symptoms of necrosis,wrinkling and/or chlorosis,and the scale of the abnormal leaves in the transgenic plants was significantly lower than that of the wild type when the PRSV were inoculated in papaya and Arabidopsis separately.However,the difference in symptoms was not significant in transgenic tobacco and the control wild plant.We carried out a RT-PCR experiment on the three kinds of plants.The expression of CP mRNA was detected in the wild type plants infected with PRSV,but not in the transgenic plants.These results suggest that the transgenic plants may induce the RNAi process to resist PRSV.