The nonstructural protein pC6 of rice grassy stunt virus trans-complements the cell-to-cell spread of a movement-defective tomato mosaic virus

The nonstructural protein pC6 encoded by rice grassy stunt virus is thought to correspond functionally to the nonstructural protein pC4 of rice stripe virus, which can support viral cell-to-cell movement. In a trans-complementation experiment with a movement-defective tomato mosaic virus, pC6 and pC4 facilitated intercellular transport of the virus. Transient expression of pC6, fused with green fluorescent protein, in epidermal cells was predominantly observed close to the cell wall as well as in a few punctate structures, presumably associated with plasmodesmata. These results suggest that pC6 has a role similar to that of pC4 in viral cell-to-cell movement.