A recent burst of gene duplications in Triticeae

Gene duplication provides raw genetic materials for evolution and potentially novel genes for crop improvement. The two seminal genomic studies of Aegilops tauschii both mentioned the large number of genes independently duplicated in recent years, but the duplication mechanism and the evolutionary significance of these gene duplicates have not yet been investigated. Here, we found that a recent burst of gene duplications (hereafter abbreviated as the RBGD) has probably occurred in all sequenced Triticeae species. Further investigations of the characteristics of the gene duplicates and their flanking sequences suggested that transposable element (TE) activity may have been involved in generating the RBGD. We also characterized the duplication timing, retention pattern, diversification, and expression of the duplicates following the evolution of Triticeae. Multiple subgenome-specific comparisons of the duplicated gene pairs clearly supported extensive differential regulation and related functional diversity among such pairs in the three subgenomes of bread wheat. Moreover, several duplicated genes from the RBGD have evolved into key factors that influence important agronomic traits of wheat. Our results provide insights into a unique source of gene duplicates in Triticeae species, which has increased the gene dosage together with the two polyploidization events in the evolutionary history of wheat.