Horizontal Transfer of LTR Retrotransposons Contributes to the Genome Diversity of .

While horizontally transferred transposable elements (TEs) have been reported in several groups of plants, their importance for genome evolution remains poorly understood. To understand how horizontally transferred TEs contribute to plant genome evolution, we investigated the composition and activity of horizontally transferred TEs in the genomes of four species. A total of 35 horizontal transfer (HT) events were identified between the four species and 21 other plant species belonging to 14 different families. We determined the donor and recipient species for 28 of these HTs, with the species being recipients of 15 of them. As a result of HTs, 8-10 LTR retrotransposon clusters were newly formed in the genomes of the four species. The activities of the horizontally acquired LTR retrotransposons differed among species, showing that the consequences of HTs vary during the diversification of the recipient lineage. Our study provides the first evidence that the HT of TEs contributes to the diversification of plant genomes by generating additional TE subfamilies and causing their differential proliferation in host genomes.