Genomic drive: uma poderosa máquina evolutiva?

Genomic Drive: A Powerful Engine of Evolution

Keith R. Oliver 1* and Wayne K. Greene 2

1. School of Biological Sciences and Biotechnology, Murdoch University, Western Australia.

2. School of Veterinary and Biomedical Sciences, Murdoch University, Western Australia.

e-mail: w.greene@murdoch.edu.au

There is much evidence that Transposable Elements (TEs) create what we are terming ‘Genomic Drive.’ This term recognizes that TEs render germ line genomes flexible and dynamic, making them efficient drivers of evolution. Much of evolution is driven by natural selection acting on the progeny of organisms with TE generated genomic changes (1). TEs often create genetic changes consisting of more orderly re-arrangements of the genome, than the genomic corruptions of some other mutagens. The cellular mechanisms to control TEs are important in both Genomic Drive and epigenetics. Genomic Drive complements all known mechanisms of evolution. It acts in several ways: active (transposition of TEs) and passive (ectopic recombinations of TEs). TE sequences can also be co-opted for other functions, and can alter gene regulation (2). If in a lineage the proliferation of TEs in the germ line is not adequately controlled, the lineage could become extinct, due to genomic chaos resulting in unviable progeny phenotypes. However, if effective TEs are very scarce then lineages are likely to become static, rare, or extinct, due to inability to adapt to change. Where there is a balance between TE activity and TE control, the level of variation is optimal for evolution and lineages are adaptable, fecund, and
taxonate readily. In the short term TEs may lower the fitness of some individuals, but in the long term Genomic Drive raises the fitness of lineages. Often, successive waves of modified, or novel, endogenous or exogenous TEs infiltrate germ line
genomes of some lineages, increasing Genomic Drive and taxonation. Cellular controls and degradation of the TEs impede the function of Genomic Drive over time. The result is periods of rapid taxonation alternating with periods of slow taxonation or stasis, i.e. punctuated equilibrium (3). Prolonged stasis can result in relict taxa or “living fossils.”

References

1. Kazazian, H.H., Jr. (2004) Mobile elements: drivers of genome evolution. Science 303: 1626-1632.

2. Feschotte, C. (2008) Transposable elements and the evolution of regulatory networks. Nature Reviews Genetics 9: 397-405

3. Gould, S.J. and N. Eldridge (1977) Punctuated equilibria: the tempo and mode of evolution reconsidered. Paleobiology 3: 115-151.

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