Nucleotide sequence analysis of the 3' terminal region of a wasabi strain of crucifer tobamovirus genomic RNA: subgrouping of crucifer tobamoviruses

Abstract

The 3' terminal 2378 nucleotides of a wasabi strain of crucifer tobamovirus (CTMV-W) infectious to crucifer plants was determined. This includes the 3' non-coding region of 235 nucleotides, coat protein (CP) gene (468 nucleotides), movement protein (MP) gene (798 nucleotides) and C-terminal partial readthrough portion of 180 K protein gene (940 nucleotides). Comparison of the sequence with homologous regions of thirteen other tobamovirus genomes showed that it had much higher identity to those of four other crucifer tobamoviruses, 85.2% to cr-TMV and turnip vein-clearing virus (TVCV), 87.4% to oilseed rape mosaic virus (ORMV) and 87.1% to TMV-Cg, than to those of other tobamoviruses. Thus CTMV-W was most similar to ORMV and TMV-Cg in sequence, but only marginally so, whereas the location and size of its MP gene was the same as cr-TMV amd TVCV. These results, together with other analyses, show that CTMV-W is a new crucifer tobamovirus, that the five crucifer tobamoviruses can be classified into two subgroups based on MP gene organization, and that the rate of sequence change is not the same in all lineages.