Summary auto-generated
This study classifies tobamoviruses by comparing their 126K proteins, which are part of the viral replication machinery. Researchers isolated RNA from eight tobamovirus species, translated them in vitro, and digested the resulting 126K proteins with five different proteases to generate characteristic peptide maps. These peptide patterns were then used to construct phylogenetic trees using maximum parsimony analysis. The analysis grouped tobamoviruses into two main clusters: Cluster I containing tobacco mosaic virus (TMV), tomato mosaic virus (ToMV), tobacco mild green mosaic virus (TMGMV), and pepper mild mottle virus (PMMV); and Cluster II containing sunn-hemp mosaic virus (SHMV), kyuri green mottle mosaic virus (KGMMV), and cucumber green mottle mosaic virus (CGMMV), with ribgrass mosaic virus (RMV) in an intermediate position. This classification pattern matched previous groupings based on coat protein comparisons, suggesting that different genomic regions have diverged at similar evolutionary rates and that recombination has not played a major role in tobamovirus evolution.
Key findings
- Tobamovirus 126K proteins cluster into two main groups with similar relationships as coat protein-based classifications
- Different genome regions (126K protein encoding ~3400 nucleotides and coat protein ~480 nucleotides) show parallel evolutionary divergence patterns
- Phylogenetic analysis of partial proteolysis peptide maps provides reliable complementary data to coat protein comparisons for viral classification
- Evidence suggests recombination has not been a major mechanism in tobamovirus evolution, as genome segments diverged at similar rates
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Abstract
The products of partial proteolysis of the Mr 126000 in vitro translation products of the RNA of eight tobamoviruses were separated by SDS-polyacrylamide gel electrophoresis. The peptide patterns obtained were compared using a computer program designed to establish phylogenetic relationships. The resulting most-parsimonious phylogenetic trees grouped the tobamoviruses into clusters I (tobacco mosaic virus, tomato mosaic virus, tobacco mild green mosaic virus, pepper mild mottle virus) and II (sunn-hemp mosaic virus, cucumber green mottle mosaic virus, kyuri green mottle mosaic virus), with ribgrass mosaic virus in an intermediate position. This clustering resembles that obtained when the coat proteins of these viruses are compared. If the tobamoviruses have arisen by divergence from an ancestral type, the results suggest that different parts of the genome have diverged similarly and that recombination has not played a major role in the evolution of the group.