Tobamovirus

A Viral Biorealm page on the genus 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

Tobamoviruses are one of the most studied plant viruses. Tobamoviruses are classified into two subgroups, defined by different genomic locations of their origin of virion assembly. (sources: Chen and Citovsky, Lartey et al.)

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)

Viral Ecology & Pathology

Tobamoviruses are extremely stable. According to Castello et al., "For example, infectivity was reduced only 12-fold when purified tobacco mosaic tobamovirus (TMV) was exposed on the surface of a rocket to solar radiation for several minutes at an altitude of up to 149 km. The tobamoviruses survive over long periods of time under conditions favoring preservation." Tobamoviruses also have a wide host range, and have been detected in plants, soil, water, and clouds. There is no known insect vector, but it is known that tobamoviruses are transmitted through the sap of infected plants by plant to plant contact, handling by workers, on glasshouse structures and utensils, and by plant propagation. (source: Castello et al., Spence et al.)

References

Castello et al. "Detection of tomato mosaic tobamovirus RNA in ancient glacial ice." Polar Biology 22.3 (1999): 207-212.

Chen, Min-Huei and Vitaly Citovsky. "Systemic movement of a tobamovirus requires host cell pectin methylesterase." The Plant Journal 35.3 (2003): 386-392.

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

Lartey et al. "Tobamovirus Evolution: Gene Overlaps, Recombination, and Taxonomic Implications." Molecular Biology and Evolution 13.10 (1996): 1327-1338.

Spence et al. "Characterisation of a Tobamovirus from Trailing Petunias." European Journal of Plant Pathology 107.6 (2001): 633-638.