Notes on Family: Carmotetraviridae

icosahedra
icosahedra

Contents

General Description

This family consists of ssRNA viruses with 40nm isometric particles and that infect insects. The name is derived from the Greek tettares = four, because of the T=4 symmetry of the virions. All tetraviruses were formerly classified in a single family but this has now been split because of large differences in the types of RNA polymerase and other genome differences. In this family,there are unstructured genome terminal sequences, a unique readthrough signal controlling RdRp expression and a large third ORF overlapping with the replication protein that has a distant relationship to the 'carmo' supergroup of plant viruses.

Morphology

Virions isometric (icosahedral), not enveloped, about 40 nm in diameter with T=4 icosahedral shell quasi-symmetry.

Genomen

Monopartite positive sense single-stranded RNA of about 6.2 kb without a 3'-polyA tail. There are three major ORFs, one encoding a replication protein with a readthrough strategy to express the RNA polymerase and the other a coat protein precursor. The third, and largest, ORF is of unknown function.

Genera in the Family

There is currently only one genus: