Résumé
In a context of global climate change, trees as sessile and long lifespan organisms need to develop mechanisms enablingthem to adapt and to survive. These last years, epigenetic mechanisms such as DNA methylation have been proposed as avaluable resource since they can be triggered by the environmental conditions in a reversibleway. However, evidences fortheir role in tree phenotypic plasticity are still lacking (Bräutigam et al., 2013; Plomion et al., 2016). In this context, wedevelop different complementary approaches:i) A correlative approach with simultaneous analysis of methylome and transcriptome dynamics in the shoot apicalmeristem (center of shoot morphogenesis) of poplar in various environments (Gourcilleau et al., 2010; LafonPlacette etal., 2013; Bastien et al., 2015; Le Gac, 2017; LafonPlacette et al., 2017).ii) A reverse genetic approach, using RNAi clones of Populus tremula x alba (Zhu et al., 2013; Condé et al., 2017; LeGac et al., in prep) hypo or hypermethylated and grown under environmental constraints.iii) A population approach, using natural populations from diverse geographic origins to explore microevolutiveadaptation to local environment and phenotypic plasticity (Project ‘EPITREE’ ANR 20182021, S. Maury). Our previousdata highlight a relationship between DNA methylation in the shoot apical meristem biomass productivity and a possibleconnection with phytohormone signaling in response to abiotic stress. New data will be also presented concerning thestability of the epigenetic modifications and their genetic diversity in populations. Altogether, our data provide newinsights into how trees modulate their epigenomes to ensure developmental plasticity and adaptation in a changingenvironment.