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. 2010 Nov 18;6(11):e1001210.
doi: 10.1371/journal.pgen.1001210.

Endless forms most viral

Welkin E Johnson  1
Affiliations

Endless forms most viral

Welkin E Johnson. PLoS Genet. .
No abstract available

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Conflict of interest statement

The author has declared that no competing interests exist.

Figures

Figure 1
Figure 1. Formation of a hypothetical EVE and relationship to modern viruses.
1. An ancestral virus spreads in a host population, infecting and replicating in somatic tissue(s) of infected individuals. 2. Occasionally, a virion may encounter a germline cell (or any cell in the developmental pathway leading to germline tissue); in some cases viral sequence is inserted into chromosomal DNA. For retroviruses, integration is an essential step in viral replication; for other viruses, insertion is a rare by-product of replication and must be mediated by other mechanisms, such as retrotransposition in trans or recombination. In addition, any given virus may not efficiently infect or replicate well in such cells, reducing the probability of insertion. Likewise, infections or insertions that are deleterious to the cell or tissue will reduce the probability of vertical transmission. 3. If gametes bearing the insertion are formed and the chromosome bearing the viral sequence is inherited, the insertion initially exists as a rare allele (the majority of individuals lack the insertion) and the fate of the newborn EVE is similar to any other chromosomal mutation, subject to loss or fixation by random genetic drift (if the insertion has phenotypic consequences, natural selection may also play a role). 4. More often than not, EVEs are probably lost by chance. On rare occasions, an insertion may drift towards higher frequency. Early on, speciation events and incomplete lineage sorting can lead to fixation in some lineages but not others, and chance extinction of populations with the insertion can still lead to loss (only fixation is shown). 5. In descendant species that share the insertion, the orthologous EVE loci will evolve independently. 6. The genetic distance between orthologous EVEs in the genomes of modern species reflects the time passed since the last common ancestor of these species, and provides a lower bound estimate of the time since insertion. Divergence between EVE sequences and the sequences of their modern viral relatives is the combined result of EVE evolution (as part of the nuclear genome) and exogenous viral evolution, the rates of which can differ by several orders of magnitude.
See this image and copyright information in PMC

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