Identification and molecular characterization of LTR and LINE retrotransposable elements in Fagus sylvatica L.

Retrotransposable elements are important and peculiar genetic components derived from ancient retrovirus insertion inside plants genome. Their ability to move and/or replicate inside the genome is an important evolutionary force, responsible for the increase of genome size and the regulation of gene expression. Retrotransposable elements are well characterized in model or crop species like Arabidopsis thaliana and Oryza sativa, but are poorly known in forest tree species. In this paper the molecular identification of retrotransposable elements in Fagus sylvatica L. is reported. Two retrotransposons, belonging to the two major classes of LTR and non-LTR elements, were characterized trough a SCAR (Sequence Characterized Amplified Region) strategy. The analysis demonstrated the presence of multiple copies of retrotransposable elements inside the genome of beech, in accordance with the viral quasi-species theory of retrotransposon evolution. The cloning and sequencing of amplification products and a Cleaved Amplified Polymorphisms (CAPs) approach on the identified retrotransposons, showed a high level of diversity among the multiple copies of both elements. The identification of retrotransposable elements in forest trees represents an important step toward the understanding of mechanisms of genome evolution. Furthermore, the high polymorphism of retrotransposable elements can represent a starting point for the development of new genetic variability markers.