Notes on Genus: Oryzavirus

icosahedra

Type member: Rice ragged stunt virus

Contents

Members of this Genus
General Description
Morphology
Electron Micrograph
Genome
Genus Genomic Organization
Genome Map
Type Member Genomic Organization
All Known Sequences
Curated Sequences

General Description

This is one of 3 plant virus genera in the family Reoviridae. Members have 10 genome segments and are transmitted by planthoppers. They differ from Fijiviruses in the sizes of the genome segments and in having only one type of surface projection on their (slightly smaller) virions. The viruses infect only the phloem tissues of their Gramineae hosts and replicate in both the plant and the vector. All members cause tumours in infected plants. The name derives from the scientific name (Oryza sativa) of rice, the host of the type member, rice ragged stunt virus.

Morphology

Virions isometric (icosahedral), 57-65 nm in diameter, not enveloped and with obvious apparently round, regular surface structure. There are distinct surface projections, "B"-type spikes, restricted to 12 vertices. These are about 8-10 nm in length and 23-26 nm wide at the base narrowing to 14-17 nm at the top.

Genome

Linear, double stranded RNA in 10 segments. Each virion contains a single copy of the entire genome. Total genome c.27000 nucleotides long (c.3900, 3800, 3700, 3800, 2700, 2200, 1950, 1900, 1130, 1160). 3' terminus has neither a poly(A) tract nor a tRNA-like structure. All RNA segments have highly conserved nucleotide sequences at the 3'- and 5'-termini (5' GAUAAA.....GUGC 3').

Genus Genomic Organization

Each segment has one or at most two ORFs. The major coat protein is on segment 8 and the RNA-dependent RNA polymerase is on segment 4.

Type Member Genomic Organization