Both Protein- and RNA-mediated Mechanisms Involved in the Resistance of Phalaenopsis Transformed with Viral Coat Protein Against Cymbidium Mosaic Virus

The role of recombinant CF in transgenic orchid plants against CymMV infection has not been elucidated though the involvement of RNA-mediated mechanism was proved previously. In the present study, an expression cassette harboring a maize ubiquitin promoter driven Cymbidium mosaic virus coat protein cDNA was transformed into protocorm-like bodies (PLB5) of Phalaenopsis orchid via particle bombardment and molecular characterization (Southern, northern and western analyses) of the transgenic lines revealed stable integration and expression of the transgene. Resistance in transgenic lines, challenge inoculated with CymMV, was further confirmed by RT-PCR and ELISA. Three transgenic lines with highly expressed CP were either characterized as partial resistance or resistance to CymMV infection, while other transgenic lines without any accumulation of CF also display resistance. The results suggest that except post-transcriptional gene silencing mechanism, recombinant CP also plays an important role in CymMV resistance of transgenic orchid plants. Results presented in this paper portray the attractive attributes of using CP gene for enhancing tolerance to CymMV in Phalaenopsis orchid.