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On the road to diploidization? Homoeolog loss in independently formed populations of the allopolyploid Tragopogon miscellus (Asteraceae)

DOI: 10.1186/1471-2229-9-80

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Of the 13 loci analyzed in 84 T. miscellus individuals, 11 showed loss of at least one parental homoeolog in the young allopolyploids. Two loci were retained in duplicate for all polyploid individuals included in this study. Nearly half (48%) of the individuals examined lost a homoeolog of at least one locus, with several individuals showing loss at more than one locus. Patterns of loss were stochastic among individuals from the independently formed populations, except that the T. dubius copy was lost twice as often as T. pratensis.This study represents the most extensive survey of the fate of genes duplicated by allopolyploidy in individuals from natural populations. Our results indicate that the road to genome downsizing and ultimate genetic diploidization may occur quickly through homoeolog loss, but with some genes consistently maintained as duplicates. Other genes consistently show evidence of homoeolog loss, suggesting repetitive aspects to polyploid genome evolution.Allopolyploidy combines the processes of hybridization with genome doubling, and together, these provide a potential avenue for instantaneous speciation [1-3]. Whole-genome sequencing efforts have revolutionized our thinking about the significance of polyploidy, as it is clear that paleopolyploidy is a common phenomenon. Ancient whole-genome duplications have been detected in many eukaryotic lineages, including angiosperms, vertebrates, and yeast [4-12]. Polyploidy has been particularly prevalent in flowering plants, where previous estimates indicated that 30–70% of angiosperm species had polyploidy in their ancestry [reviewed in [13]]. In the last decade, the view of polyploidy in angiosperms has changed, and it is now appreciated that perhaps all angiosperm lineages have experienced at least one round of polyploidy, with many lineages undergoing two or more such episodes [14-18]. On more recent timescales, molecular data have also revealed that most extant polyploid plant species have formed rec


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