Notes on Family: Birnaviridae

icosahedra

Contents

• Members of this Family
• General Description
• Morphology
• Genome
• Genera in the Family
• All Known Sequences
• Curated Sequences

General Description

This family consists of viruses that infect animals (vertebrates, insects, molluscs and crustaceans) and which have double stranded RNA genomes in two components (bi-RNA-viruses). The isometric virions (60 nm) are much larger than those in the family Partitiviridae, whose members infect plants or fungi.

Morphology

Virions isometric (icosahedral), not enveloped, 60 nm in diameter, made of 260 units trimeric subunits.

Genomen

Bipartite double-stranded RNA totalling 5.8-6.5 kb with a genome-linked protein (VPg) at the 5'-termini. There is no 3'-polyA tail. Each segment encodes a large polyprotein that it is subsequently processed into the functional products and there is an additional, smaller ORF on the larger (A) segment. The capsid proteins are encoded on segment A and an RNA-dependent RNA polymerase on segment B.

Genera in the Family

• Aquabirnavirus: infecting fish, molluscs and crustaceans
• Avibirnavirus: infecting birds
• Blosnavirus: infecting fish; additional mature protein on segment A and low percentage identity to other birnaviruses
• Entomobirnavirus: infecting insects