Characterization of a novel retrotransposon TriRe‒1 using nullisomic-tetrasomic lines of hexaploid wheat

　Retrotransposons constitute the large fraction (～80%) of the wheat genome where numerous and diverse retrotransposon families exist, where especially the long terminal repeat (LTR) retrotransposon family is known to be predominant. Thus, they have been considered to contribute to the genome expansion, sequence diversification and the genome structure alternation in the wheat genome. In addition, the insertion polymorphism of the LTR retrotransposon family among the cultivars has been known to be quite useful for the genetic analysis such as the linkage mapping and the phylogenetic studies. Here, we report the characteristics of a novel active LTR retrotransposon family TriRe‒1, which belongs to the Ty1‒copia group in the hexaploid wheat (Triticum aestivum L.) genome. This retroelement appears to encode all proteins required for the transposition and showed high insertion polymorphism among the hexaploid wheat cultivars, suggesting its potential of transpositional activity with at least recent transposition during wheat evolution. We studied the chromosomal localization of the TriRe‒1 insertion site based on the genome-wide comparative analysis using the nullisomic-tetrasomic lines of the cultivar Chinese Spring. The results showed that although the majority of the TriRe‒1 insertion sites exist across the homoeologous chromosomes of A, B or D genomes, a higher number of insertions in the B genome was detected compared to A or D genome, suggesting a specific amplification in the history of B genome progenitors. In conclusion, a novel LTR retrotransposon TriRe‒1 should be valuable for the development of molecular markers based on insertion polymorphism among the cultivars, and also the genome-specific TriRe‒1 insertion site can be utilized to study evolutional history of wheat genomes.

原著論文 (Original paper)