Tungrovirus

Tungrovirus is a genus of viruses, in the family Caulimoviridae order Ortervirales. Monocots and family Poaceae serve as natural hosts. There is currently only one species in this genus: the type species Rice tungro bacilliform virus. Diseases associated with this genus include: stunting, yellow to orange leaf discoloration with fewer tillers.[1][2] Tungro means 'degenerated growth' and the virus was first observed in the Philippines 1975.

Tungrovirus
Virus classification
(unranked): Virus
Realm: Riboviria
Kingdom: Pararnavirae
Phylum: Artverviricota
Class: Revtraviricetes
Order: Ortervirales
Family: Caulimoviridae
Genus: Tungrovirus
Type species
Rice tungro bacilliform virus

Taxonomy

Group: ssRNA-RT

[2]

Structure

Viruses in Tungrovirus are non-enveloped, with icosahedral and bacilliform geometries, and T=3 symmetry. Genomes are circular.[1] The virus withstands temperatures below 63-degree Celsius for 10 minutes. The tungro virus is known to have at least two strains - S and M. The 'S' strain in these varieties produces conspicuous interveinal chlorosis, giving an appearance of yellow stripe and sometimes irregular chlorotic specks on younger leaves. On the other hand, the 'M'strain produces only mottling.

GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
TungrovirusBacilliformT=3Non-envelopedCircularMonopartite

Life cycle

Viral replication is nuclear/cytoplasmic. Replication follows the dsDNA(RT) replication model. The method of transcription is dsDNA(RT) transcription. Translation takes place by leaky scanning, and ribosomal shunting. The virus exits the host cell by nuclear pore export, and tubule-guided viral movement. Monocots and family poaceae serve as the natural host. The virus is transmitted via vectors such as aphids and leafhoppers (e.g. Nephotettix spp.).[1]

GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
TungrovirusPlantsNoneViral movement; mechanical inoculationViral movementNucleusCytoplasmMechanical inoculation: aphids

Clinical

Tungro affected rice plants are stunted and have reduced number of tillers. The young emerging leaves develop interveinal chlorosis leading to discoloration of the leaves, starting from tip downwards. Often whole leaf is discolored, plants infected at an early stage generally die prematurely. Infected plants take more time for maturity because of delayed flowering. The panicles are often poorly developed and the grains are also often covered with dark brown blotches and are lighter than those of healthy plants.

References
  1. "Viral Zone". ExPASy. Retrieved 15 June 2015.
  2. ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
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