Abstract
Rising temperatures and decreasing precipitations in relation to climate change are causing intense drought episodes and forest decline. Sessile and perennial organisms as trees must adapt to survive thanks to two biological processes: individual phenotypic plasticity and adaptation, the genetic evolutionary capacity of a population. Moreover, after experiencing stress, plants have the remarkable ability to retain an ecological memory of that event. They exploit this stress memory to manage their phenotypic plasticity, to improve their resistance, resilience and recovery, to finally increase chances of survival when they encounter similar conditions again.Recent studies showed that all differents mechanisms involved an epigenetic component in trees. However, little is known about the effects of recurring drought-rewatering stress cycles in trees and notably the epigenetic memory and potential priming effects. Such research was conducted in the frame of the ANR EPITREE project, which aims at studying the impact of DNA methylation, gene expression and allelic variations in the adaptation mechanisms of trees to their environment. Here, we tested for an ecological memory effect in genotypes from European natural populations of black poplars (Populus nigra). An experimental setup was designed to evaluate the tree's recovery, after a drought-rewatering cycle of five weeks of drought and one week of re-watering. The response was evaluated one week (short-time) after recovery to a first stress cycle and one week after a second stress cycle done a one year (inter-annual) after the first one. Phenotypic measurement as well as multi-omics characterizations (transcriptome and methylome) were performed on cambium, the meristematic tissue forming the conductive vessels and enabling the production of wood. Our results support a short-time as well as an interannual memory related to epigenetic variation, in black poplar subjected to drought stress cycles.