''Lenarviricota'' is a phylum of

RNA virus An RNA virus is a virus characterized by a ribonucleic acid (RNA) based genome. The genome can be single-stranded RNA (ssRNA) or double-stranded (Double-stranded RNA, dsRNA). Notable human diseases caused by RNA viruses include influenza, SARS, ...

es that includes all

positive-strand RNA virus Positive-strand RNA viruses (+ssRNA viruses) are a group of related viruses that have Sense (molecular biology), positive-sense, single-stranded genomes made of ribonucleic acid. The positive-sense genome can act as messenger RNA (mRNA) and can ...

es that infect

prokaryote A prokaryote (; less commonly spelled procaryote) is a unicellular organism, single-celled organism whose cell (biology), cell lacks a cell nucleus, nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Gree ...

s. Some members also infect

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s. Most of these viruses do not have

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or m ...

s, except for the genus '' Ourmiavirus''. The name of the group is a

syllabic abbreviation An abbreviation () is a shortened form of a word or phrase, by any method including shortening, contraction, initialism (which includes acronym), or crasis. An abbreviation may be a shortened form of a word, usually ended with a trailing per ...

of the names of founding member families " ''Le''viviridae and ''Nar''naviridae" with the suffix ''-viricota'', denoting a virus phylum.

Phylogenetics

''Lenarviricota'' is the first branch of RNA viruses to emerge, since they are the most basal branch. Most of its members, the leviviruses (class ''

Leviviricetes ''Leviviricetes'' is a class of viruses, which infect prokaryotes. Most of these bacteriophages were discovered by metagenomics Metagenomics is the study of all genetics, genetic material from all organisms in a particular environment, prov ...

''), only infect prokaryotes, and their known level of diversity has grown dramatically in recent years, which suggests that the RNA viruses may be more widespread in prokaryotes than previously believed. It has been suggested that the origin of ''Lenarviricota'' may predate that of the

last universal common ancestor The last universal common ancestor (LUCA) is the hypothesized common ancestral cell from which the three domains of life, the Bacteria, the Archaea, and the Eukarya originated. The cell had a lipid bilayer; it possessed the genetic code a ...

(LUCA). ''Lenarviricota'' viruses appear to have arisen from a primordial RdRP of the RNA-protein world that gave rise to leviviruses (class ''

''). It has also been suggested that the retroelements of cellular life (

group II intron Group II introns are a large class of self-catalytic ribozymes and mobile genetic elements found within the genes of all three domains of life. Ribozyme activity (e.g., self- splicing) can occur under high-salt conditions ''in vitro''. However, ...

s and

retrotransposon Retrotransposons (also called Class I transposable elements) are mobile elements which move in the host genome by converting their transcribed RNA into DNA through reverse transcription. Thus, they differ from Class II transposable elements, or ...

s) evolved from a shared ancestor with ''Lenarviricota''. The eukaryotic RNA viruses without capsids, '' Mitoviridae'', '' Narnaviridae'' and '' Botourmiaviridae'', arose from the leviviruses with the loss of the

during the time that

eukaryogenesis Eukaryogenesis, the process which created the eukaryotic cell and lineage, is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The process is widely agreed to have involved ...

occurred, when the bacterial

endosymbiont An endosymbiont or endobiont is an organism that lives within the body or cells of another organism. Typically the two organisms are in a mutualism (biology), mutualistic relationship. Examples are nitrogen-fixing bacteria (called rhizobia), whi ...

became the

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

. The genus '' Ourmiavirus'' arose by recombination between a non-capsid botourmiavirus and a virus from the family ''

Tombusviridae ''Tombusviridae'' is a family of single-stranded positive sense RNA plant viruses. The family contains 18 genera in 3 subfamilies. The name is derived from Tomato bushy stunt virus (TBSV). Genome All viruses in the family have a non-segmente ...

'', which inherited its capsid proteins.

Taxonomy

The following classes are recognized: * '' Amabiliviricetes'' * '' Howeltoviricetes'' * ''

'' * '' Miaviricetes''

References

{{Taxonbar, from=Q92194739 Viruses