Marks that persist: DNA methylation in plant transgenerational memory and inheritance

Although the term "plant memory" remains somewhat controversial, its effects have played a fundamental role in shaping plant evolution. As plants evolved under dynamic and often unpredictable environmental conditions, they developed a variety of adaptive strategies to ensure survival and reproductive success. The ability to modulate responses based on prior experiences suggests that plants can retain short- and long-term memories to optimize future stress responses. While genetic mutations are undeniably involved in evolutionary adaptation, more dynamic mechanisms of stress recall and response are largely mediated by epigenetic regulation. This review focuses on the most recent advances in epigenetically mediated plant memory, particularly the role of DNA methylation in transgenerational inheritance. We explore examples of memory formation induced by abiotic and biotic factors, as well as molecular mechanisms that may promote the persistence or reversibility of memory across generations. Studies include the repression of defense genes in modern maize cultivars, memory transmission through volatile organic compounds, contrasting results in Arabidopsis plants regarding DNA methylation and heritable stress memory, and experiments conducted in extreme environments such as outer space and the Chernobyl zone. Finally, we highlight practical applications, such as seed priming and hardening, and outline major future challenges related to plant species variability and the development of molecular tools for memory detection and manipulation.