Tobamovirus

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Tobamovirus
Electron micrograph of Tobacco mosaic virus particles at 160,000x magnification
Virus classification
Group:
Group IV ((+)ssRNA)
Family:
Virgaviridae
Genus:
Tobamovirus
Type species
Tobacco mosaic virus

Tobamovirus is a genus in the virus family Virgaviridae.[1] Many plants, including tobacco, potato, tomato, and squash, serve as natural hosts. There are currently 37 species in this genus including the type species Tobacco mosaic virus. Diseases associated with this genus include: necrotic lesions on leaves.[1][2][3] The name Tobamovirus is an acronym, coming from the host and symptoms of the first virus discovered (Tobacco mosaic virus).

There are four informal subgroups within this genus: these are the tobamoviruses that infect the brassicas, the cucurbits, and malvaceous and solanaceous plants. The main differences between these groups are genome sequences, and respective range of host plants.[citation needed]

Evolution

These viruses are thought to have codiverged with their hosts from a common ancestor.[4] There are at least 3 distinct clades of tobamoviruses, which to some extent follow their host ranges: that is, there is one infecting solanaceous species; a second infecting cucurbits and legumes and a third infecting the crucifers.[5]

Genome

The RNA genome encodes at least four polypeptides:[1] these are the non-structural protein and the read-through product which are involved in virus replication (RNA-dependent RNA polymerase, RdRp); the movement protein (MP) which is necessary for the virus to move between cells and the coat protein (CP). The read-through portion of the RdRp may be expressed as a separate protein in TMV.[6] The virus is able to replicate without the movement or coat proteins, but the other two are essential. The non-structural protein has domains suggesting it is involved in RNA capping and the read-through product has a motif for an RNA polymerase. The movement proteins are made very early in the infection cycle and localized to the plasmodesmata, they are probably involved in host specificity as they are believed to interact with some host cell factors.

Structure

Tobamoviruses are non-enveloped, with helical rod geometries, and helical symmetry. The diameter is around 18 nm, with a length of 300-310 nm. Genomes are linear and non-segmented, around 6.3-6.5kb in length.[1][2]

Genus Structure Symmetry Capsid Genomic arrangement Genomic segmentation
Tobamovirus Rod-shaped Helical Non-enveloped Linear Non-Segmented

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription is the method of transcription. Translation takes place by suppression of termination. The virus exits the host cell by monopartite non-tubule guided viral movement. Plants serve as the natural host. Transmission routes are mechanical.[1][2]

Genus Host details Tissue tropism Entry details Release details Replication site Assembly site Transmission
Tobamovirus Plants None Unknown Viral movement Cytoplasm Cytoplasm Mechanical

Routes of Infection

The infection is localized to begin with but if the virus remains unchallenged it will spread via the vascular system into a systemic infection. The exact mechanism the virus uses to move throughout the plant is unknown but the interaction of pectin methylesterase, a cellular enzyme important for cell wall metabolism and plant development, with the movement protein has been implicated.[7]

Classification

Taxonomy

Group: ssRNA(+)

Order: Unassigned

[3]

Species Details

[9]

Proposed members

  • Beet necrotic yellow vein virus (BNYVV)
  • Chara corallina virus (CCV)
  • Nicotiana velutina mosaic virus (NVMV)
  • Peanut clump virus (PCV)
  • Potato mop-top virus (PMTV)
  • Soil-borne wheat mosaic virus (SBWMV)
  • Streptocarpus flower break virus (SFBV)
  • cucumber green mottle mosaic virus (CGMMV)
  • cucumber fruit mottle mosaic virus (CFMMV)

[9]

References

  1. ^ a b c d e "ICTV Online Report Virgaviridae".
  2. ^ a b c "Viral Zone". ExPASy. Retrieved 15 June 2015.
  3. ^ a b ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
  4. ^ Stobbe, A. H.; Melcher, U.; Palmer, M. W.; Roossinck, M. J.; Shen, G. (2011). "Co-divergence and host-switching in the evolution of tobamoviruses". Journal of General Virology. 93 (2): 408–418. doi:10.1099/vir.0.034280-0. PMID 22049092.
  5. ^ Lartey, R. T.; Voss, T. C.; Melcher, U. (1996). "Tobamovirus evolution: Gene overlaps, recombination, and taxonomic implications" (PDF). Molecular Biology and Evolution. 13 (10): 1327–1338. doi:10.1093/oxfordjournals.molbev.a025579. PMID 8952077.
  6. ^ Creager, Angela. "Dr". The Plant Cell. Retrieved 24 September 2016.
  7. ^ Chen, M. H.; Citovsky, V. (2003). "Systemic movement of a tobamovirus requires host cell pectin methylesterase". The Plant Journal. 35 (3): 386–392. doi:10.1046/j.1365-313X.2003.01818.x. PMID 12887589.
  8. ^ Min, B. E.; Chung, B. N.; Kim, M. J.; Ha, J. H.; Lee, B. Y.; Ryu, K. H. (2005). "Cactus mild mottle virus is a new cactus-infecting tobamovirus". Archives of Virology. 151 (1): 13–21. doi:10.1007/s00705-005-0617-7. PMID 16132178.
  9. ^ a b "Descriptions of Plant Viruses: Tobamovirus Group". The Association of Applied Biologists (AAB).

External links

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