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- Articles by Hazzouri, K. M.
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- Articles by Hazzouri, K. M.
- Articles by Wright, S. I.
Genetics, Vol. 179, 581-592, May 2008, Copyright © 2008
doi:10.1534/genetics.107.085761
Contrasting Patterns of Transposable-Element Insertion Polymorphism and Nucleotide Diversity in Autotetraploid and Allotetraploid Arabidopsis Species
Khaled M. Hazzouri*,
Arezou Mohajer*,
Steven I. Dejak
,
Sarah P. Otto
and
Stephen I. Wright*,1
* Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada, Department of Mathematics, University of Toronto, Toronto, Ontario M5S 2E4, Canada and Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
1 Corresponding author: Department of Biology, York University, 4700 Keele St., Toronto, ON M3J 1P3, Canada.
E-mail: stephenw{at}yorku.ca
It has been hypothesized that polyploidy permits the proliferation of transposable elements, due to both the masking of deleterious recessive mutations and the breakdown of host silencing mechanisms. We investigated the patterns of insertion polymorphism of an Ac-like transposable element and nucleotide diversity at 18 gene fragments in the allotetraploid Arabidopsis suecica and the autotetraploid A. arenosa. All identified insertions were fixed in A. suecica, and many were clearly inherited from the parental species A. thaliana or A. arenosa. These results are inconsistent with a rapid increase in transposition associated with hybrid breakdown but support the evidence from nucleotide polymorphism patterns of a recent single origin of this species leading to genomewide fixations of transposable elements. In contrast, most insertions were segregating at very low frequencies in A. arenosa samples, showing a significant departure from neutrality in favor of purifying selection, even when we account for population subdivision inferred from sequence variation. Patterns of nucleotide variation at reference genes are consistent with the TE results, showing evidence for higher effective population sizes in A. arenosa than in related diploid taxa but a near complete population bottleneck associated with the origins of A. suecica.