Notes on Genus: Phytoreovirus
Type member: Wound tumor virus
This is one of 3 plant virus genera in the family Reoviridae
. The distinctive feature of this genus are its 12 (rather than 10) genome segments and its transmission by cicadellid leafhoppers. The viruses replicate in both the plant and the vector. The name indicates they are plant (Greek phyton
Virions isometric (icosahedral), 65-70 nm in diameter, not enveloped and with obvious apparently angular, regular surface structure. There are distinct surface projections (spikes) restricted to 12 vertices. Shell of virion has three layers (an outer amorphous layer, a layer of distinct capsomeres, and a smooth core having a diameter of about 50 nm).
Virions composed of 22 % nucleic acid and 78 % protein.
Linear, double stranded RNA in 12 segments. Each virion contains a single copy of the entire genome. Total genome 25000-30000 nucleotides long. The 3' terminus has neither a poly(A) tract nor a tRNA-like structure. Conserved nucleotide sequences occur at the 3'-terminus (56-495 nucleotides long) and at the 5'-terminus (14-63 nucleotides long) of each gene segment.
Genus Genomic Organization
Each ds RNA encodes a single product, except for S12 which (in the type member) may be bicistronic. Seven structural proteins are present in the virions and (for the type member) five of these have been mapped to their respective RNA segment, together with five non-structural proteins whose function is unknown.
Type Member Genomic Organization
The products encoded are as follows:
|Segment || Size (bp)|| Protein || Size (kDa) || Function (location)|
|1. ||P1||c. 155||(core)|
|2. ||P2||c. 130 ||(outer coat)|
|3. || P3||c. 108||(core)|
|4. ||2565||Pns4||81||unknown |
|5. ||2613||P5||91 ||(outer coat)|
|6. ||1700 ||Pns7||59||(unknown)|
|8. ||1472||P8||48 ||(capsid)|
|9. ||1182 ||Pns10||<39||(unknown)|
|10. ||1172||Pns11||39||(unknown) |
|11. ||1128||P9||36 ||(capsid)|
|12. ||851 ||Pns12||19||(unknown) |