''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. Viruses are found in almo ...

, in the order ''

Reovirales ''Reovirales'' is an Order (biology), order of double-stranded RNA viruses. Member viruses, called reoviruses, have a wide Host (biology), host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid Viral envelop ...

'', in the family ''

Sedoreoviridae ''Sedoreoviridae'' (''sedo'' = smooth) is a family of the ''Reovirales'' order of viruses. Viruses in this family are distinguished by the absence of a turreted protein on the inner capsid to produce a smooth surface. Taxonomy The family contain ...

''. They are non-turreted

reovirus ''Sedoreoviridae'' (''sedo'' = smooth) is a family of the ''Reovirales'' order of viruses. Viruses in this family are distinguished by the absence of a turreted protein on the inner capsid to produce a smooth surface. Taxonomy The family contain ...

es that are major agricultural pathogens, particularly in

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

Oryza sativa ''Oryza sativa'', having the common name Asian cultivated rice, is the much more common of the two rice species cultivated as a cereal, the other species being ''Oryza glaberrima, O. glaberrima'', African rice. It was History of rice cultivation ...

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, ...

for WTV, and

leafhoppers Leafhopper is the common name for any species from the family Cicadellidae: based on the type genus ''Cicadella''. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or trees. Their hind ...

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 ''Sedoreoviridae'', genus ''Phytoreovirus ''Phytoreovirus'' is a genus of viruses, in the order ''Reovirales'', in the family ''Sedoreoviridae''. They are non-turreted reoviruse ...

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

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

. 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 residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

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 m ...

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 catalyzes the chemical reactions that synthesize RNA from a DNA template. Using the e ...

, 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 respirato ...

and

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

, 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 genus contains the following species, listed by scientific name and followed by the exemplar virus of the species: * ''Phytoreovirus alphaoryzae'',

* ''Phytoreovirus betaoryzae'',

Rice gall dwarf virus Rice is a cereal grain and in its domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much less commonly, ' ...

* ''Phytoreovirus vulnustumoris'',

Wound tumor virus Wound tumor virus is an invertebrate and plant virus found in the United States of America belonging to the genus ''Phytoreovirus'' and the family ''Sedoreoviridae''. It is a type III virus under the Baltimore classification system; that is it ha ...

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