Abstract: A Hairpin RNA coding structure of the 824 bp region（from 2 274 to 3 097）of PRSV HC-Pro gene was constructed by the OZ-LIC method. After inserted into the plasmid pSP73，the structure was transformed into M-Jm109LacY of the RNaseⅢ-deficient strain and induced with IPTG. The recombinant E. coli strain could express H824-dsRNA that remained stable in the presence of DNase I enzyme and RNase A enzyme. We carry out a protective resistance assay and a therapeutic resistance assay. In the protective resistance assay，dsRNA was used to spray onto the plant surface before inoculation of papaya leaves with PRSV. Protective treatment experimental results showed dsRNA derived from the functional gene of PRSV could protect papaya plants from virus infection. ELISA analysis and Real-time RT-PCR results confirmed that the virus accumulation could be inhibited by dsRNA. In the therapeutic resistance assay，dsRNA was used to spray onto the plant surfaces 25 days after inoculation of papaya leaves with PRSV. ELISA analysis and Real-time RT-PCR results showed that the virus accumulation declined slightly after spraying dsRNA for 3 days.

Key words: Papaya ringspot virus（PRSV）, HC-Pro, dsRNA, prokaryotic expression system, RNA silencing