ICTV Virus Taxonomy Profile: Marnaviridae 2021

Abstract

The family Marnaviridae comprises small non-enveloped viruses with positive-sense RNA genomes of 8.6-9.6 kb. Isolates infect marine single-celled eukaryotes (protists) that come from diverse lineages. Some members are known from metagenomic studies of ocean virioplankton, with additional unclassified viruses described from metagenomic datasets derived from marine and freshwater environments. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Marnaviridae, which is available at ictv.global/report/marnaviridae.

Keywords: ICTV Report; Marnaviridae; taxonomy.

Fig. 1.

Marnaviridae virion structure. (a) Negatively stained transmission electron micrograph of Heterosigma akashiwo RNA virus virions (scale bar=50 nm). (b) Cryo-electron microscopy reconstructed capsid structure at 3.1 Å resolution of Chaetoceros tenuissimus RNA virus type II (species Chaetenuissarnavirus II, genus Sogarnavirus) (PDB structure 6SHL viewed in NGL-WebGL). The three major capsid proteins are represented in dark blue (VP1), light blue (VP2) and yellow (VP3).

Fig. 2.

Genome architectures of viruses in the family Marnaviridae. IRES, internal ribosome entry site. RdRP, RNA-directed RNA polymerase. There is a putative IRES in the intergenic region (IGR) of the di-cistronic genomes.