Résumé
Because of their detrimental influence on plant genome structure and gene expression, Transposable Elements (TEs) are maintained in a transcriptionally inactive state through powerful and specific epigenetic mechanisms involving DNA methylation. However, these silencing processes can be alleviated under stress conditions, leading to the more or less transient reactivation of TEs and, in some cases, to the emergence of variant phenotypes. The mantled somaclonal variation resulting from the in vitro propagation of oil palm (Elaeis guineensis Jacq.) has been correlated with the occurrence of a genome-wide hypomethylation in both in vitro- cultivated and adult tissues, as well as with alterations in gene expression. The time-dependent increase of DNA methylation in long-term in vitro cultures retaining their embryogenic ability has also been demonstrated. In order to assess the contribution of TEs to a possible loss of genomic stability during long-term in vitro propagation of embryogenic suspensions, we evaluated the background genetic instability of the cultures using AFLP and used the retrotransposon-based S-SAP technique to detect evidence of retroelement mobility. Cultures derived from normal and mantled oil palms from two different genotypes were compared in the aim of identifying phenotype-associated TE insertions. (Texte intégral)