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Nucleo-cytoplasmic Large DNA Viruses (NCLDV) of Eukaryotes

  1. Eugene V Koonin,
  2. Natalya Yutin

Published Online: 15 MAY 2012

DOI: 10.1002/9780470015902.a0023268

eLS

eLS

How to Cite

Koonin, E. V. and Yutin, N. 2012. Nucleo-cytoplasmic Large DNA Viruses (NCLDV) of Eukaryotes. eLS. .

Author Information

  1. National Institutes of Health, Bethesda, Maryland, USA

Publication History

  1. Published Online: 15 MAY 2012

Abstract

A group of diverse viruses with large deoxyribonucleic acid (DNA) genomes that replicate in the cytoplasm and in some cases partly in the nucleus of eukaryotic cells share a set of conserved genes and probably have evolved from a common ancestral virus. Known as nucleo-cytoplasmic large DNA viruses (NCLDV), this class of viruses encompasses seven families: Poxviridae, Asfarviridae, Iridoviridae, Ascoviridae, Phycodnaviridae, Mimiviridae, and a probable new family represented by Marseillevirus and Lausannevirus. The family Mimiviridae includes giant viruses that possess genomes of a million or more basepairs that are comparable in size and complexity with some bacterial genomes. Phylogenetic analysis of the conserved genes of the NCLDV and mapping of the resulting phylogeny of the NCLDV onto the phylogeny of their eukaryotic hosts suggest an early origin and primary radiation of the NCLDV, possibly concomitant with the primary radiation of eukaryotes.

Key Concepts:

  • Seven families of viruses with large double-stranded DNA genomes together constitute a monophyletic class of viruses known as Nucleo-Cytoplasmic Large DNA Viruses (NCLDV).

  • All NCLDV share several genes that encode essential proteins involved in viral genome replication and virion formation.

  • An evolutionary reconstruction using a maximum-likelihood model assigns approximately 50 genes coding for most of the key virus functions to the common ancestor of all extant NCLDV.

  • Some of the NCLDV families infect many diverse eukaryotes whereas many groups of eukaryotes are infected by diverse NCLDV suggesting that the major radiation of the NCLDV occurred at an early stage of evolution, perhaps concomitantly with eukaryogenesis.

  • The NCLDV includes the largest known viruses: Mimiviruses which encode over 1000 genes and are comparable to bacteria in size and complexity.

Keywords:

  • giant viruses;
  • evolution of viruses;
  • virus families;
  • evolutionary reconstruction;
  • phylogenetic analysis