Notes on Genus: Okavirus

enveloped bacilliform
enveloped bacilliform

Type member: Gill-associated virus


General Description

This is currently the only genus in the family Roniviridae (rod-shaped nidoviruses) and is named after the crustacean lymphoid organ (oka) in which the viruses are commonly found.


Virions enveloped and bacilliform, 150-200 nm x 40-60 nm.


Monopartite positive sense single-stranded RNA of size about 26kb and with a 3'-polyA tail.

Genus Genomic Organization

Two large, overlapping ORFs at the 5'-end of the genome encode the major non-structural proteins and are expressed as a fusion protein by ribosomal frameshift. Downstream are about 4 other genes, encoding structural proteins, and these are expressed from a 3'-coterminal nested set of subgenomic RNAs.

Type Member Genomic Organization

The RNA of 26.2kb is translated into the following products:
  • Replication protein 1a of 460 kDa
  • Polymerase 1b of 302 kDa expressed as a fusion protein with 1a by ribosomal frameshift
  • Coat protein ORF2 of 16 kDa
  • Structural protein precursor ORF3 of 182 kDa processed into two glycoproteins (gp116 and gp64) and a putative transmembrane protein of 25 kDa
  • Putative ORF4 of 9 kDa