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Review
. 2005;6(3):212.
doi: 10.1186/gb-2005-6-3-212. Epub 2005 Mar 2.

New evolutionary frontiers from unusual virus genomes

Christopher Desjardins  1 , Jonathan A Eisen, Vishvanath Nene
Affiliations
Review

New evolutionary frontiers from unusual virus genomes

Christopher Desjardins et al. Genome Biol. 2005.

Abstract

The sequences of two giant viral genomes, Mimivirus and a polydnavirus, have recently been published. Mimivirus has the largest known viral genome and encodes an unprecedented number of proteins, whereas the polydnavirus genome has an extremely low coding density and does not encode DNA-replication proteins. These and other unusual features challenge the way we view the evolution and definition of viruses.

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Figures

Figure 1
Figure 1
The transmission and replication cycles of Mimivirus and CcBV. (a) Mimivirus. At the beginning of the life cycle, 1, the virus enters the amoeba; 2, the viral genome is released; 3, viral proteins are expressed and whole virus genomes are replicated; 4, viral genomes are packaged into capsids; 5, viral particles are released from the amoeba. The grey circle represents the nucleus. (b) CcBV. Steps 1-3 take place in specialized ovarian cells of the wasp: 1, the provirus integrated in the wasp genome is amplified; 2, amplified viral DNA is packaged into capsids; 3, several capsids are enveloped by membrane(s); 4, the wasp oviposits eggs (only one is shown) and virions into a caterpillar; 5, viral gene expression promotes survival of the wasp progeny (such as the larva shown), but virions do not replicate; 6, the wasp larva (oval) emerges from the caterpillar and metamorphoses into an adult, and the caterpillar dies.
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