The Evolutionary Value of Recombination Is Constrained by Genome Modularity

Department of Molecular & Cell Biology, University of Cape Town, Kaapstad, Western Cape, South Africa
PLoS Genetics (Impact Factor: 7.53). 11/2005; 1(4):e51. DOI: 10.1371/journal.pgen.0010051
Source: PubMed



Genetic exchange between organisms, called recombination, occurs in all biological kingdoms and is also common in viruses in which it may threaten the long-term control of important human pathogens such as HIV and influenza. Although recombination can produce advantageous gene combinations, bioinformatic analyses of bacterial genomes have suggested that recombination is not well tolerated when it involves exchanges of genes that interact with a lot of other genes. Using laboratory-constructed recombinants of a small plant virus called MSV, Martin and co-workers provide the first direct experimental evidence that the evolutionary value of exchanging a genome fragment is constrained by the number of ways in which the fragment interacts with the rest of the genome. They note that fitness losses suffered by artificial MSV recombinants increase with decreasing parental relatedness. Furthermore, these losses accurately anticipate the patterns of genetic exchange detectable in natural MSV recombinants, suggesting that they accurately reflect the impact of deleterious selection on natural isolates of the virus.

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    • "Recombination not only complicates the genotyping systems of viruses, but also affects the analyses of molecular clock, and natural selection (Hon et al. 2008a, b). Natural recombinants might emerge in viral populations only if they maintain relatively good fitness, i.e. they preserve the functionality of each viral protein (Lefeuvre et al. 2007) and the functional interactions between viral proteins (Martin et al. 2005). "
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    • "Similar results were observed for tomato-infecting begomoviruses in Brazil, which are thought to have arisen from inter-species recombination between begomoviruses infecting non-cultivated hosts (Ribeiro et al., 2007; Rocha et al., 2013). Although some studies indicate that a large number of recombinants arising from events between distantly related genomes are defective and probably would be removed from the population by selection (Liu et al., 1999; Martin et al., 2005), our results continue to emphasize the importance of recombination for microevolution and macroevolution of agronomically important begomo- viruses. "
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    • "Therefore, when genome components from different parental viruses are reassembled, they must be able to function as efficiently as they did within the genomic backgrounds in which they evolved (Martin et al. 2011a). High levels of nucleotide sequence dissimilarity between parental viruses can constrain the fitness of hybrid progeny by disrupting coevolved intragenome interactions (Martin et al. 2005, 2011b; Escriu et al. 2007; Lefeuvre et al. 2007; Rokyta and Wichman 2009). Although the extent to which hybrid fitness declines with increasing genetic distance between parental strains can vary according to the genomic region which is exchanged, genetic exchange among plant viruses rarely yields viable progeny when levels of parental nucleotide sequence identity are lower than 90% (Martin et al. 2005; Escriu et al. 2007; Lefeuvre et al. 2007). "
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