Polyploidization-induced genome variation in triticale

Abstract

Polyploidization-induced genome variation in triticale (x Triticosecale Wittmack) was investigated using both AFLP and RFLP analyses. The AFLP analyses were implemented with both EcoRI-MseI (E-M) and PstI-MseI (P-M) primer combinations, which, because of their relative differences in sensitivity to cytosine methylation, primarily amplify repetitive and low-copy sequences, respectively. The results showed that the genomic sequences in triticale involved a great degree of variation including both repetitive and low-copy sequences. The frequency of losing parental bands was much higher than the frequency of gaining novel bands, suggesting that sequence elimination might be a major force causing genome variation in triticale. In all cases, variation in E-M primer-amplified parental bands was more frequent in triticale than that using P-M primers, suggesting that repetitive sequences were more involved in variation than low-copy sequences. The data also showed that the wheat (Triticum spp.) genomes were relatively highly conserved in triticales, especially in octoploid triticales, whereas the rye (Secale cereale L.) genome consistently demonstrated a very high level of genomic sequence variation (68%-72%) regardless of the triticale ploidy levels or primers used. In addition, when a parental AFLP band was present in both wheat and rye, the tendency of the AFLP band to be present in triticale was much higher than when it was present in only one of the progenitors. Furthermore, the cDNA-probed RFLP analyses showed that over 97% of the wheat coding sequences were maintained in triticale, whereas only about 61.6% of the rye coding sequences were maintained, suggesting that the rye genome variation in triticale also involved a high degree of rye coding sequence changes. The data also suggested that concerted evolution might occur in the genomic sequences of triticale. In addition, the observed genome variation in wheat-rye addition lines was similar to that in triticale, suggesting that wheat-rye addition lines can be used to thoroughly study the genome evolution of polyploid triticale.

Extensive and Heritable Epigenetic Remodeling and Genetic Stability Accompany Allohexaploidization of Wheat

“…Among these, the most striking are rapid genetic, epigenetic, and gene expression dynamics associated with nascent allopolyploidy, which are proposed to have played important roles in the immediate stabilization and longer-term establishment of newly formed allopolyploids as new species (Wendel 2000;Liu and Wendel 2003;Levy and Feldman 2004;Ma et al 2004;Pontes et al 2004;Adams and Wendel 2005b;Feldman and Levy 2005;Chen and Ni 2006;Adams 2007;Chen 2007;Otto 2007;Hegarty and Hiscock 2008;Feldman and Levy 2009;Jones and Hegarty 2009). Paradoxically, not all newly formed plant allopolyploids are associated with rapid genomic changes, albeit they all represent established species (Hufton and Panopoulou 2009;Jackson and Chen 2009).…”

Genomic Changes in ResynthesizedBrassica napusand Their Effect on Gene Expression and Phenotype

“…Importantly, we observed large variation among independent lines for both the extent and direction of genomic change (Figure 1), highlighting the importance of analyzing many polyploid events to accurately assess the dynamics of genome change. Genomic changes directed toward one parental genome have been observed in Brassica juncea, in which the direction was dependent on the lineage analyzed (Song et al, 1995), and in Triticale polyploids, in which the rye (Secale cereale) subgenome tended to be preferentially modified (Ma et al, 2004;Ma and Gustafson, 2006). The cause of variation in number of rearrangements observed among our S5 lines is not known; however, it appears to be unrelated to variation in methylation changes in the S0 or S5 generations since these parameters were not correlated (r ¼ 0.09 and 0.05, respectively).…”

Developmental Timing of DNA Elimination Following Allopolyploidization in Wheat

“…Newly synthesized allopolyploids (amphiploids) can induce a variety of rapid and reproducible genomic changes, including the elimination of DNA sequences (Liu et al 1998a;Ozkan et al 2001;Shaked et al 2001;Ma et al 2004;Pires et al 2004;Adams and Wendel 2005a;Skalicka et al 2005;Lukens et al 2006;Gaeta et al 2007). Yet, nothing is known about the biological significance, the mechanism, or the precise developmental timing of this phenomenon.…”