Tobamovirus

EM of Tobacco Mosaic virus. From ICTVdb Picture Gallery, Courtesy Dr. RG Milne

Baltimore Classification

Higher order taxa

Viruses; ssRNA positive-strand viruses, no DNA stage; (no assigned family); Tobamovirus

Species

Tobacco mosaic virus, Cucumber green mottle mosaic virus, Frangipani mosaic virus, Turnip vein-clearing virus (examples)

Description and Significance

A strain of tomato mosaic tobamovirus causes single virus streak which produces brown streaks on the stems and pertioles or sunken brown rings on fruit. A strain of tomato mosaic tobamovirus also causes double virus streak.

Genome Structure

The Tobamovirus genome is either monomeric or polymeric, non-segmented, and contains a single molecule of linear, positive-sense, single-stranded RNA. Minor species of non-genomic nucleic acid may also be found in virions. The encapsidated nucleic acid is mainly of genomic origin but virions may also contain nucleic acid of host origin and subgenomic mRNA including host rRNA found in the short particles of some species. The complete genome sequence is about 6450 nucleotides long. The 5'-end of the genome has a methylated nucleotide cap. The 3'-terminus has a tRNA-like structure that accepts histidine. (source: ICTVdB)

Virion Structure of a Tobamovirus

Tobamovirus virions consist of a non-enveloped capsid. The capsid is elongated, rod shaped, straight, and exhibits helical symmetry. Virons are 70-100 nm in length and 15-17.26-18.2 nm in width. The capsid has a herring-bone pattern with a low percentage in population clear predominate lengths. The axial canal could be distinct with a diameter of 2-3.257-4 nm. The basic helix can either be be obvious or obscure, and has a pitch of 2.3-2.314-2.4 nm. (source: ICTVdB)

References

ICTVdB - The Universal Virus Database, version 4. http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/