​To better understand the role of epigenetics in the drought tolerance of trees, a research consortium including the Epigenetic and Environment Laboratory (LEE; CNRGH) decided to study the poplar.

That species, both sensitive to drought and a model for the study of trees, also holds economic interest in France as the third most-frequently cultivated deciduous tree for its wood.

In a first, the researchers used poplar lines in which DNA methylation regulation was modified to permit a better understanding of epigenetic mechanisms in trees.

They compared the drought response of the modified poplars to that of wild-type poplars, used as controls. The team reported that the drought tolerance of the modified poplars was better than that of the controls. The researchers went on to compare genome-wide DNA methylation in the modified and control trees. They observed in the trees exposed to drought approximately 5,000 DNA regions with methylation changes or epimutations. The genes associated with those regions were involved most notably with hormone-related environmental stress responses.

In contrast to the genetic mutations that occur randomly in evolution, the results of this study show that the epigenetic modifications brought on by environmental stress are targeted specifically to the genes directly involved in the response to it. Thus, DNA methylation is a part of a tree's ability to acclimatize to water deprivation.

With its description of the epigenetic mechanisms that occur during drought and the gene mutations they may provoke, this study brings a better understanding of the adaptive mechanisms available to trees as they confront the consequences of climate change.