Notes on Genus: Hordeivirus

rigid rods
rigid rods

Type member: Barley stripe mosaic virus


General Description

The genus Hordeivirus derives its name from the scientific name (Hordeum) of the host of the type member, barley stripe mosaic virus. Viruses in this genus have rigid rod shaped particles of (usually) three lengths up to 150 nm and a tripartite genome. They are transmitted through seeds.


Virions rigid rod-shaped, not enveloped, 20-25 nm in diameter and of three lengths: 150-160 nm (B), 126 nm (M) and 109 nm (T). The nucleocapsids are longitudinally striated.


Tri- (or possibly quadri-) partite, linear, single stranded, positive sense RNA distributed among the different lengths of particle.

Genus Genomic Organization

Only the type member has been fully sequenced and this has RNAs of c. 3800 (RNA1), 3300 (RNA2) and 2900-3200 (RNA3) nucleotides. A fourth RNA of 800-2000 nucleotides may be a subgenomic. The 3' terminus of each RNA has a poly(A) tract (of 8-40 nucleotides length) and a tRNA-like structure (of 236-238 nucleotides which accepts tyrosine). The 5' terminus has a methylated nucleotide cap with the sequence m7G5pppGUA. There are a total of 7 open reading frames:
  • RNA1 encodes a replication protein
  • RNA2 encodes the coat protein (at the 5'-end) followed by a triple-gene-block (probably involved in cell-to-cell movement)
  • RNA3 encodes a polymerase and a cysteine-rich protein

Type Member Genomic Organization

There are a total of 7 open reading frames:
RNA1 (alpha) has a single open reading frame:
1. 130 kDaReplication protein
RNA2 (beta) has four open reading frames:
2. 22 kDaCoat protein
3. 58 kDa       Triple gene block
        involved in
      cell-to-cell movement
4. 17 kDa
5. 14 kDa
RNA3 (gamma) has two open reading frames:
6. 87 kDaPolymerase
7. 17 kDaCysteine-rich protein, probably expressed from a subgenomic RNA