Mapping of the exchangeable and dispensable domains of the RNA 2-encoded 2A(HP) protein of arabis mosaic nepovirus.

The N-terminal domains of the RNA 2-encoded 2A(HP) proteins of the arabis mosaic (ArMV) and grapevine fanleaf (GFLV) nepoviruses were shown to be highly variable and a hotspot for intra- and inter-species recombination events. Chimeric ArMV-NW clones in which the N-terminal domain of 2A(HP) or the entire 2A(HP) of GFLV isolates replaced the corresponding domains of ArMV retained their infectivity, showing that the 2A(HP) proteins of ArMV-NW and GFLV are exchangeable. ArMN-NW clones with deletions of the N-terminal, core, or C-terminal domains of the ArMV-NW 2A(HP) were infectious in Chenopodium quinoa although viral RNA (especially RNA 2) accumulated at reduced levels. In contrast, deletion of the entire 2A(HP) protein or of the C-terminal two thirds of the protein abolished infectivity of the ArMV-NW clones. These results suggest that multiple functional domains are distributed throughout the 2A(HP) protein and are essential for the accumulation of viral RNA 2.