Transposed Genes in Arabidopsis Are Often Associated with Flanking Repeats

摘要

Much of the eukaryotic genome is known to be mobile, largely due to the movement of transposons and other parasitic elements. Recent work in plants and Drosophila suggests that mobility is also a feature of many nontransposon genes and gene families. Indeed, analysis of the Arabidopsis genome suggested that as many as half of all genes had moved to unlinked positions since Arabidopsis diverged from papaya roughly 72 million years ago, and that these mobile genes tend to fall into distinct gene families. However, the mechanism by which single gene transposition occurred was not deduced. By comparing two closely related species, Arabidopsis thaliana and Arabidopsis lyrata , we sought to determine the nature of gene transposition in Arabidopsis. We found that certain categories of genes are much more likely to have transposed than others, and that many of these transposed genes are flanked by direct repeat sequence that was homologous to sequence within the orthologous target site in A. lyrata and which was predominantly genic in identity. We suggest that intrachromosomal recombination between tandemly duplicated sequences, and subsequent insertion of the circular product, is the predominant mechanism of gene transposition. Author Summary Repetitive DNA, such as satellite repeats and transposons, is ubiquitous throughout the genome. Such repeats have been associated with DNA loss, circle formation, and gene transposition in plants and Drosophila. In this work we suggest that, in plants, one mechanism of gene mobility is intrachromosomal recombination via tandem repeats. In addition, we have demonstrated that the classes of genes that tend to form tandem duplications are more likely to have transposed than other gene classes. We conclude that tandem duplications may particularly facilitate gene excision and may also provide targets for gene insertion.