Notes on Family: Mesoniviridae
enveloped spheres
Contents
General Description
This family consists of insect-infecting nidoviruses and is placed in the order
Nidovirales, together with the families
Arteriviridae,
Coronaviridae and
Roniviridae. Its name reflects the fact that the genomes in this family are intermediate (Greek,
meso = medium) in size between the small arteriviruses and the large corona- and roni-viruses.
Morphology
Virions are enveloped spheres about 60-80 nm in diameter.
Genomen
Monopartite positive sense single-stranded RNA about 20kb long and with a 3'-polyA tail. 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 at least 4 other genes, mostly or entirely encoding structural proteins, and these are probably expressed from a 3'-coterminal nested set of subgenomic RNAs.
Genera in the Family
There is currently only one genus: