Whatwe have learned from studies of the differential movement mechanism of cymbidium mosaic virus

Cymbidium mosaic virus (CymMV) is one of the most important viruses that infect orchids. Previous observations indicated that although CymMV was mostly restricted to infecting the Orchidaceae, experimental inoculation indicated that CymMV can infect several families of plant hosts. In addition, CymMV has never been isolated from wild orchids. We found two CymMV isolates that can move differentially between hosts. Both can infect Phalaenopsis orchids, but only one can systemically infect Nicotiana benthamiana (the model plant used by plant virologists). Genetic studies revealed two control modes involved in CymMV movement, with the coat protein (CP) playing a dominant role. Biochemistry studies revealed that the movement ability of CymMV is associated with the binding affinity of the CP and viral RNA, and the important amino acids for CymMV movement in N. benthamiana were identified. Sequence analysis of worldwide CymMV CPs suggests that CymMV may have once had a broader host range, and only some isolates evolved to infect orchids only. A remaining issue is identifying the natural host of CymMV, so important for disease management in the orchid industry.