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    Experimental observations of rapid Maize streak virus evolution reveal a strand-specific nucleotide substitution bias

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    Author
    Martin, D.P.
    Varsani, A.
    Polston, J.E.
    Rybicki, E.P.
    van der Walt, E.
    Date
    2008
    Permanent Link
    http://hdl.handle.net/10092/2618

    Background: Recent reports have indicated that single-stranded DNA (ssDNA) viruses in the taxonomic families Geminiviridae, Parvoviridae and Anellovirus may be evolving at rates of similar to ∼10⁻⁴ substitutions per site per year (subs/site/year). These evolution rates are similar to those of RNA viruses and are surprisingly high given that ssDNA virus replication involves host DNA polymerases with fidelities approximately 10 000 times greater than those of error-prone viral RNA polymerases. Although high ssDNA virus evolution rates were first suggested in evolution experiments involving the geminivirus maize streak virus (MSV), the evolution rate of this virus has never been accurately measured. Also, questions regarding both the mechanistic basis and adaptive value of high geminivirus mutation rates remain unanswered. Results: We determined the short-term evolution rate of MSV using full genome analysis of virus populations initiated from cloned genomes. Three wild type viruses and three defective artificial chimaeric viruses were maintained in planta for up to five years and displayed evolution rates of between 7.4 x 10⁻⁴ and 7.9 x 10⁻⁴ subs/site/year. Conclusion: These MSV evolution rates are within the ranges observed for other ssDNA viruses and RNA viruses. Although no obvious evidence of positive selection was detected, the uneven distribution of mutations within the defective virus genomes suggests that some of the changes may have been adaptive. We also observed inter-strand nucleotide substitution imbalances that are consistent with a recent proposal that high mutation rates in geminiviruses (and possibly ssDNA viruses in general) may be due to mutagenic processes acting specifically on ssDNA molecules.

    Subjects
    escherichia-coli
     
    mosaic-virus
     
    rna virus
     
    phylogenetic evidence
     
    spontaneous mutation
     
    molecular evolution
     
    positive selection
     
    genetic diversity
     
    leaf-curl-virus
     
    simian kidney-cells
     
    Fields of Research::270000 Biological Sciences::270300 Microbiology::270303 Virology
     
    Fields of Research::270000 Biological Sciences::270200 Genetics::270208 Molecular evolution
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    • Science: Journal Articles [500]
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