Analysis On Epigenetic Stability Of A Synthetic Allohexaploid Wheat

Rampant genomic instability can be elicited by nascent allopolyploidization in plants. Most previous studies however have not endeavored to define whether and to what extent the allopolyploidy-incurred rapid genomic instability represents a general response, and hence likely consequential to evolution, or merely anomalous and incidental events occurring stochastically in limited individuals. We report here that in a newly formed allohexaploid wheat line (Allo-AT6) between tetraploid wheat Triticum turgidum ssp. durum (genome BBAA) and Aegilops tauschii (genome DD), the great majority of individual plants showed chromosomal stability, and exhibiting a genomic constitution similar to that of the present-day T. aestivum (genome BBAADD). In contrast, a single individual plant was identified at S2, which exhibited chromosomal instability in both number and structure based on multicolor genomic in situ hybridization (mc-GISH) analysis. Accordingly, this plant also manifested extensive changes at the molecular level including loss and gain of DNA segments. Based on these evidences, we take the MSAP method to further analysis on the synthetic Allohexaploid wheat (Allo-AT6), as well as its consecutive progenies (S2~S8), to unveil its epigenetic stability (DNA methylation) in this experiment. The results show that the progenies are higher than their parents in terms of methylation level. Meanwhile, there is a high frequency of methylation variation among the progenies and it can be stably inherited. Our results suggest that these ephemeral and individual-specific rapid genomic changes, albeit interesting, probably have not played a major role in the speciation and evolution of common wheat, T. aestivum.