The 126- and/or 183-kDa replicases or their coding regions are responsible both for inefficient local and for systemic movements of Paprika mild mottle virus Japanese strain in tomato plants.

Paprika mild mottle virus Japanese strain (PaMMV-J), a member of the genus Tobamovirus, was originally isolated from sweet pepper plants (Capsicum annuum L.). In experimental conditions, PaMMV-J spread more slowly in inoculated leaves of tomato plants and moved to uninoculated upper leaves at a lower frequency than Tomato mosaic virus (ToMV). In this study, we aimed to identify the viral factors responsible for the low efficiency of local and systemic movement of PaMMV-J in tomato plants. Using several viruses formed as chimeras between PaMMV-J and ToMV, we observed that a chimeric virus (Pa-RepL) having the 126- and 183-kDa replicase genes of ToMV could move systemically in tomato plants, similar to ToMV. Furthermore, analysis of a PaMMV-J mutant (PaMMV-1483C) showed that a single nucleotide substitution in 126- and 183-kDa replicase genes of PaMMV-J enhanced the efficiency of local movement of the virus in inoculated leaves to an extent similar to that of ToMV. However, PaMMV-1483C did not spread over the uninoculated upper leaves. In addition, viral RNA accumulation levels in tomato protoplasts inoculated with Pa-RepL and PaMMV-1483C were lower and similar to those of parental PaMMV-J. These results suggest that the 126- and/or 183-kDa replicases or their coding regions are responsible both for inefficient local and for systemic movements of PaMMV-J in tomato plants.

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