''Phytoreovirus'' is a genus of

viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

, in the family ''

Reoviridae ''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...

'', in the subfamily ''

Sedoreovirinae ''Sedoreovirinae'' (''sedo'' = smooth) is a subfamily of the ''Reoviridae'' family of viruses. Viruses in this subfamily are distinguished by the absence of a turreted protein on the inner capsid to produce a smooth surface. Characteristics Like ...

''. They are non-turreted

reovirus ''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layered ...

es that are major agricultural pathogens, particularly in

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

Oryza sativa ''Oryza sativa'', commonly known as Asian rice or indica rice, is the plant species most commonly referred to in English as ''rice''. It is the type of farmed rice whose cultivars are most common globally, and was first domesticated in the Yan ...

for RDV and RGDV,

dicotyledonous The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...

for WTV, and

leafhoppers A leafhopper is the common name for any species from the family Cicadellidae. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or trees. Their hind legs are modified for jumping, and a ...

serve as natural hosts. There are three species in this genus. Diseases associated with this genus include: WTV: galls (tumor). RDV: dwarf (or stunt) disease of rice. RGDV: dwarfing, stunting, and galls.

Classification

One member of this family,

Rice Dwarf Virus Rice dwarf virus (RDV) is a plant pathogenic virus of the family Reoviridae ''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. T ...

(RDV), has been extensively studied by electron cryomicroscopy and

x-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

. From these analyses, atomic models of the capsid proteins and a plausible model for capsid assembly have been derived. While the structural

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

s of RDV share no sequence similarity to other proteins, their folds and the overall

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...

structure are similar to those of other reoviruses. Phytoreoviruses are unique among reoviruses in that there are 12 dsRNA segments in each virus. Like all other reoviruses, they contain their own RNA-dependent

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...

, allowing for endogenous synthesis of viral mRNA within the virus. Although less well studied than

orthoreovirus ''Orthoreovirus'' is a genus of viruses, in the family ''Reoviridae'', in the subfamily '' Spinareovirinae''. Vertebrates serve as natural hosts. There are ten species in this genus. Diseases associated with this genus include mild upper respirat ...

and

orbivirus ''Orbivirus'' is a genus of double-stranded RNA viruses in the family ''Reoviridae'' and subfamily '' Sedoreovirinae''. Unlike other reoviruses, orbiviruses are arboviruses. They can infect and replicate within a wide range of arthropod and ver ...

, considerable structural and biochemical studies have been undertaken to characterize phytoreoviruses, which in general infect plants. There are three recognized phytoreoviruses: ''Wound tumour virus'' (WTV), ''Rice dwarf virus'' (RDV) and ''Rice gall dwarf virus'' (RGDV). Possible additional family members include tobacco leaf enation virus (TLEF), rice bunchy stunt virus and sweet potato virus (ICTV, VIDE). There are also several RDV isolates, all of which share over 90% sequence identity. Of these phytoreoviruses, RDV has been extensively studied and is the best characterized member. Most of our knowledge about phytoreovirus assembly and structure is based on structural data accumulated in RDV studies.

Taxonomy

The following three species are assigned to the genus: *''

Rice dwarf virus Rice dwarf virus (RDV) is a plant pathogenic virus of the family Reoviridae ''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. T ...

'' *'' Rice gall dwarf virus'' *'' Wound tumor virus''

Structure

Viruses in ''Phytoreovirus'' are non-enveloped, with icosahedral geometries, and T=13, T=2 symmetry. The diameter is around 70 nm. Genomes are linear and segmented. Segments range in size from 1066 to 4423 base pairs, resulting in a total genome length of around 26kb. The genome codes for 15 proteins and has 4 open reading frames.

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. The virus exits the host cell by monopartite non-tubule guided viral movement.

for rdv and rgdv and

for wtv serve as the natural host. The virus is transmitted via a vector (insect mechanical inoculation in plant by leafhoppers). Transmission routes are vector and mechanical.

References

External links