Ancient hybridizations among the ancestral genomes of bread wheat
In a second edition of TGAC-with-original-authors, we'll discuss Marcussen et al. (2014), a recent Science paper on ancient hybridization of polyploid wheat genomes. The first author Thomas Marcussen will join our discussion, and since Kjetill Jakobsen was involved in the study, we may even have two authors present to answer all our questions. We're switching back to the old meeting time, starting at 1 pm.
Abstract: The allohexaploid bread wheat genome consists of three closely related subgenomes (A, B, and D), but a clear understanding of their phylogenetic history has been lacking. We used genome assemblies of bread wheat and five diploid relatives to analyze genome-wide samples of gene trees, as well as to estimate evolutionary relatedness and divergence times. We show that the A and B genomes diverged from a common ancestor ~7 million years ago and that these genomes gave rise to the D genome through homoploid hybrid speciation 1 to 2 million years later. Our findings imply that the present-day bread wheat genome is a product of multiple rounds of hybrid speciation (homoploid and polyploid) and lay the foundation for a new framework for understanding the wheat genome as a multilevel phylogenetic mosaic.