Background: Polyploidy (whole-genome duplication) is an important speciation mechanism,
particularly in plants. Gene loss, silencing, and the formation of novel gene complexes are some of
the consequences that the new polyploid genome may experience. Despite the recurrent nature
of polyploidy, little is known about the genomic outcome of independent polyploidization events.
Here, we analyze the fate of genes duplicated by polyploidy (homoeologs) in multiple individuals
from ten natural populations of Tragopogon miscellus (Asteraceae), all of which formed
independently from T. dubius and T. pratensis less than 80 years ago.
Results: 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.
Conclusion: 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.
Tate, J. A., Joshi, P., Soltis, K. A., Soltis, P. S., & Soltis, D. E. (2009). On the road to diploidization? Homoeolog loss in independently formed populations of the allopolyploid Tragopogon miscellus (Asteraceae). Bmc Plant Biology, 9(80). doi: 10.1186/1471-2229-9-80
2009 Tate et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.