Tobamovirus

Tobamovirus
Electron micrograph of Tobacco mosaic virus particles at 160,000x magnification
Virus classification
Group:	Group IV ((+)ssRNA)
Family:	Virgaviridae
Genus:	Tobamovirus
Species
Pepper mosaic virus Samsun latent strain of tobacco mosaic virus

The genus Tobamovirus contains viruses with a positive sense RNA genome that infect plants. The most common tobamovirus is probably tobacco mosaic virus, which infects tobacco and other plants including potato, tomato, and squash. The name Tobamovirus comes from the host and symptoms: Toba for Tobacco and mo for mosaic. There are four subgroups within this genus; the brassicas, cucurbits, malvaceous and solanaceous infecting tobamoviruses. The main differences between these groups are genome sequence and range of host plants.

Evolution

These viruses are thought to have codiverged with their hosts from a common ancestor.

Genome

The RNA genome encodes four polypeptides; the non-structural protein and the read through product which are involved in virus replication, the movement protein which is necessary for the virus to move between cells and the coat protein. 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.

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.

Members

Definitive members of the Tobamovirus genus:

• Tobacco mosaic virus (TMV)
• Bell pepper mosaic virus (BPeMV)
• Cactus mild mottle virus (CMMoV)
• Cucumber green mottle mosaic virus (CGMMV)
• Cucumber virus 4 (CV4)
• Frangipani virus (FV)
• Hibiscus latent Fort Pierce virus (HLFPV)
• Hibiscus latent Singapore virus (HLSV)
• Maracuja mosaic virus (MarMV)
• Odontoglossum ringspot virus (ORSV)
• Rattail cactus necrosis associated virus (RCNaV)
• Ribgrass mosaic virus (HRV)
• Sammons' opuntia virus (SOV)
• Sunn-hemp mosaic virus (SHMV)
• Tomato mosaic virus (ToMV) and U2 - tobacco mosaic virus (T2MV)
• Turnip vein-clearing virus (TVCV)
• Wasabi mottle virus (WMoV)
• Youcai mosaic virus (YoMV) aka oilseed rape mosaic virus (ORMV)

Tentative members of the Tobamovirus genus include:

• 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)

This list is incomplete; you can help by expanding it.

References

• Cactus mild mottle virus is a new cactus-infecting tobamovirus BE Min, BN Chung, MJ Kim, JH Ha, BY Lee, KH Ryu - Archives of Virology, 2006
• Subcellular localization of host and viral proteins associated with tobamovirus RNA replication - Yuka Hagiwara, Keisuke Komoda, Takuya Yamanaka, Atsushi Tamai, Tetsuo Meshi, Ryo Funada, Tomohiro Tsuchiya, Satoshi Naito and Masayuki Ishikawa

• Min-Huei Chen and Vitaly Citovsky (August 2003). "Systemic movement of a tobamovirus requires host cell pectin methylesterase". The Plant Journal 35 (3): 386–92. doi:10.1046/j.1365-313X.2003.01818.x. PMID 12887589. http://www.blackwell-synergy.com/doi/pdf/10.1046/j.1365-313X.2003.01818.x?cookieSet=1. 

External links

• Viralzone: Tobamovirus