Hyperosmotic stress memory in Arabidopsis is mediated by a limited set of epigenetically labile DNA sequences and is restricted by DNA glycosylase activity in the male germline. DNA methylation upon hyperosmotic stress in dr1drm2 Arabidopsis mutants

Inducible epigenetic changes are believed to enable rapid adaptation to environmental fluctuations in eukaryotes. We have found a limited set of regions of the Arabidopsis genome that are specifically targeted for DNA (de)methylation in response to hyperosmotic stress. The stress-induced epigenetic changes are associated with conditionally heritable adaptive phenotypic stress responses, which are extensively reset in absence of stress. These stress responses are not transmitted equally from the two parents due to widespread DNA glycosylase activity in the male germline. Molecular analyses of the CNI1/ATL31 stress-response regulator further revealed that epigenetically targeted sequences function as distantly-acting control elements of antisense long non-coding RNAs that in turn regulate CNI1 expression in response to stress. Collectively, our findings reveal that plants have a highly dynamic ‘short-term stress memory’ with which to respond to adverse external conditions. This short-memory relies on discrete DNA methylation and associated transcriptional changes that extend the phenotypic space accessible to the immediate offspring.