Rapid Chromosome Evolution in Recently Formed Polyploids in Tragopogon AsteraceaeReport as inadecuate

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Polyploidy, frequently termed -whole genome duplication-, is a major force in the evolution of many eukaryotes. Indeed, most angiosperm species have undergone at least one round of polyploidy in their evolutionary history. Despite enormous progress in our understanding of many aspects of polyploidy, we essentially have no information about the role of chromosome divergence in the establishment of young polyploid populations. Here we investigate synthetic lines and natural populations of two recently and recurrently formed allotetraploids Tragopogon mirus and T. miscellus formed within the past 80 years to assess the role of aberrant meiosis in generating chromosomal-genomic diversity. That diversity is likely important in the formation, establishment and survival of polyploid populations and species.

Methodology-Principal Findings

Applications of fluorescence in situ hybridisation FISH to natural populations of T. mirus and T. miscellus suggest that chromosomal rearrangements and other chromosomal changes are common in both allotetraploids. We detected extensive chromosomal polymorphism between individuals and populations, including i plants monosomic and trisomic for particular chromosomes perhaps indicating compensatory trisomy, ii intergenomic translocations and iii variable sizes and expression patterns of individual ribosomal DNA rDNA loci. We even observed karyotypic variation among sibling plants. Significantly, translocations, chromosome loss, and meiotic irregularities, including quadrivalent formation, were observed in synthetic S0 and S1 generations polyploid lines. Our results not only provide a mechanism for chromosomal variation in natural populations, but also indicate that chromosomal changes occur rapidly following polyploidisation.


These data shed new light on previous analyses of genome and transcriptome structures in de novo and establishing polyploid species. Crucially our results highlight the necessity of studying karyotypes in young <150 years old polyploid species and synthetic polyploids that resemble natural species. The data also provide insight into the mechanisms that perturb inheritance patterns of genetic markers in synthetic polyploids and populations of young natural polyploid species.

Author: K. Yoong Lim, Douglas E. Soltis, Pamela S. Soltis, Jennifer Tate, Roman Matyasek, Hana Srubarova, Ales Kovarik, J. Chris Pires, Z

Source: http://plos.srce.hr/


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