Characterization of cymbidium mosaic virus coat protein gene and its expression in transgenic tobacco plants.
Cymbidium mosaic potexvirus (CyMV) is the most prevalent virus infecting orchids. With a view to increasing resistance by overexpression of the coat protein (CP), partial cDNA clones encoding the genomic RNA of CyMV were isolated and sequenced (EMBL accession no. X62133). Like most of the polyadenylated monopartite positive-strand RNA viruses, the open reading frame (ORF) coding for the CP is located at the 3′ end. The ORF predicts a polypeptide chain of 220 amino acids with a molecular weight of 23 600. Sequence comparison of this ORF to the CP sequences of potato X potexvirus (PVX) and white clover mosaic potexvirus (WC1MV) revealed a strong amino acid homology in the mid-portion of the CP, but the overall homology was low. The CyMV CP gene was placed downstream of a cauliflower mosaic caulimovirus 35S promoter and the chimaeric gene was transferred into Nicotiana benthamiana. Transgenic plants expressing the CyMV CP were protected against CyMV infection.