Control of EVD and other COPIA elements silencing in Arabidopsis thaliana

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Hesketh, Amy | Pélissier, Thierry | Mathieu, Olivier

Edité par CCSD -

International audience. Transposable elements (TEs) are major components of plant genomes. Their capacity to travel to distant loci not only makes them a threat to genome integrity but also a tool for evolution. Their expression is, therefore, tightly regulated by different mechanisms, one of which is DNA methylation, in particular CG methylation. A null mutation in the METHYLTRANSFERASE1 (MET1) gene causes a general loss of CG methylation associated with a reactivation of many TEs. The Evadé (EVD) retrotransposon is also reactivated but only after floral transition. It was also observed that transposition of EVD only occurs after several generations of inbreeding. These observations suggest that there are different levels of silencing that control EVD activation and transposition. To explore these different layers of silencing we are generating successive generations from a met1-7 heterozygous plant in which we are studying the reactivation and the chromatin context of EVD and other COPIA elements. In parallel, we are producing a line of backcrossed met1-7 plants in order to examine the effects of inbreeding in the control of TE transposition. Analysing the first generation of the segregating met1-7 mutant allowed us to confirm the specific reactivation pattern of EVD and, in a lesser extent, of two other COPIA elements, COPIA27 and COPIA48. Surprisingly, our results also show a reactivation of COPIA27 and COPIA48 in wild type and heterozygous plants obtained from the segregation of the met1-7 heterozygous plants.

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