Plant stress memory: epigenetic mechanisms for abiotic stress acclimation

Plants, being sessile organisms, have to endure unfavourable environmental conditions, thus they have developed exceptionally refined molecular systems that can sense, react and even recall stress signals. Stress memory, the ability to store information about previous stress treatments for faster and stronger reactions in the case of new exposures, is an indispensable adaptive mechanism that not only increases plant survival but also their overall fitness. Over the past few years, a considerable amount of evidence has been indicating the significance of epigenetic control in both the formation and the sustainability of stress memory, especially in the case of abiotic stress. This article presents an overview of the latest development on the epigenetic origin of plant stress memory with a focus on the mechanisms that play key role in the acclimatization to abiotic stress. The various molecular layers that are involved in the formation of stress memory viz. DNA methylation, chromatin remodelling, modifications of histones at post-translational level and the regulatory activities of non-coding RNAs have been elaborated. The stress specific epigenetic reactions due to abiotic stresses have been discussed to uncover regulatory attributes. Moreover, the review discusses the merging of cutting-edge technologies such as multi-omics tactics, the CRISPR/dCas9-targeted epigenome editing and machine learning solutions, with the aim of developing stress tolerant and high yielding crops. Despite the substantial progress made in identifying key epigenetic components, the major hurdles exist such as causal relationships being unclear, transgenerational stress memory over multiple generations being stable over time and eventually converting lab results into practical use in agriculture.