''Naldaviricetes'' is a

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

es, which infect

arthropods Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

. Members of ''Naldaviricetes'' are characterized by large enveloped rod-shaped virions, circular double-stranded DNA genomes, and replication in the nucleus of the host cell. All of them (including the unassigned ''

Polydnaviridae A polydnavirus (PDV) is a member of the family ''Polydnaviridae'' of insect viruses. There are two genera in the family: '' Bracovirus'' and ''Ichnovirus''. Polydnaviruses form a symbiotic relationship with parasitoid wasps; (ichnoviruses (IV) ...

'' family) share a set of unique

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

s not found in other viruses, which include the presence of multiple interspersed direct repeats, various subunits of

DNA polymerase A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create ...

and

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...

, four late expression factor genes, and infectivity factor genes suggesting a common host entry mechanism.Henry M. Kariithi, Just M. Vlak, Johannes A. Jehle, Max Bergoin, Drion G. Boucias y Adly MM Abd-Alla. (2019)
Hytrosaviridae Profile
ICTV.

Phylogenetics

These viruses encompass several genes that are distantly related to core genes of the ''

Nucleocytoviricota ''Nucleocytoviricota'' is a phylum of viruses. Members of the phylum are also known as the nucleocytoplasmic large DNA viruses (NCLDV), which serves as the basis of the name of the phylum with the suffix - for virus phylum. These viruses are refe ...

'' and thus could be highly derived members of the DJR-MCP viruses (kingdom ''

Bamfordvirae ''Bamfordvirae'' is a kingdom of viruses. This kingdom is recognized for its use of double jelly roll major capsid proteins. It was formerly known as the PRD1- adenovirus lineage. The kingdom is named after Dennis H. Bamford who first promoted ...

'' of the realm ''

Varidnaviria ''Varidnaviria'' is a realm of viruses that includes all DNA viruses that encode major capsid proteins that contain a vertical jelly roll fold. The major capsid proteins (MCP) form into pseudohexameric subunits of the viral capsid, which stores t ...

''), despite the absence of the DJR-MCP and formation of odd-shaped virions. Preliminary phylogenetic analysis of several essential genes that are shared by all these arthoropod viruses and the ''Nucleocytoviricota'', such as PolB, RNAP subunits, helicase-primase and thiol oxidoreductase, has suggested that this group of viruses might be a highly derived offshoot of the ''Nucleocytoviricota''.Eugene V. Koonin, Valerian V. Dolja, Mart Krupovic, Arvind Varsani, Yuri I. Wolf, Natalya Yutin, F. Murilo Zerbini, Jens H. Kuhn (2020)
Global Organization and Proposed Megataxonomy of the Virus World
American Society for Microbiology.Eugene V. Koonin, Valerian V. Dolja, Mart Krupovic (2015).
Origins and evolution of viruses of eukaryotes: The ultimate modularity
Sciences Direct.

Classification

''Naldaviricetes'' contains one order and a family unassigned to an order. This taxonomy is shown hereafter: * Class: ''Naldaviricetes'' ** Order: '' Lefavirales'' ** Unassigned family: '' Nimaviridae'' The unassigned family ''

'' is a potential member of the group because they share the characteristic genes of ''Naldaviricetes'' and appear to have evolved from nudiviruses of the order ''Lefavirales''.

References

Viruses Virus classes {{Virus-stub