Virus Resistant Papaya Plants Derived from Tissues Bombarded with the Coat Protein Gene for Management of Papaya Ringspot Virus Disease

Abstract

Papaya (Carica papaya) gets damaged by the papaya ringspot virus (PRSV). Transgenic papaya was generated using the coat protein gene isolated from the Papaya ringspot virus Thai isolate. A vector that contains the coat protein gene under the supervision of a 35S promoter has been developed and transformed by microprojectile bombardment into somatic embryos of Khak Dum papaya cultivar. Eight transgenic lines of papaya somatic embryos bombarded by kanamycin were reported from 1980. PCR amplification of the protein gene, GUS research and Southern blot hybridization has checked the incorporation of the transferred genes into kanamycin-resistant papaya calli. Although the coat protein gene was found to be highly resistant to virus in all transgenic lines, out of which only line G2 was found to be resistant. The resistant line showed the inserted coat protein expression cassette to a high level of rearrangement while the coat protein gene itself was removed by 166 bp at the 3 ' end of the series. While RT-PCR was detected in every transgenic line in the transcription of the coat protein gene, only two transgenic papayas were expressing the intact coat protein. In addition, the volume of the truncated protein mRNA in the resistant line G2 has been significantly reduced. These results suggest that the RNA mediated process, which is presumably formed in post-transcriptional gene silencing, is a protein mediated resistance in papaya.