DNA Methylation and Transgenerational Stress Memories in Arabidopsis thaliana

The long-standing proposition that plants may pass on a memory of stress events to the following generations is again gaining interest now that a plausible mechanism has been identified. Specifically, changes in DNA methylation, a dynamic epigenetic mark which regulates gene expression, can be inherited. Whilst indirect evidence indicates transgenerational stress memories may involve perturbations to the DNA methylome, we are still some way from identifying specific regions of the epigenome which can carry a memory of stress to the following generations. This research therefore sought to establish to what extent stress-induced changes in DNA methylation are inherited and what regions of the genome are epigenetically regulated in the progeny of stressed plants. A novel stress memory was observed in the progeny of Arabidopsis thaliana plants subjected zinc stress. This stress memory was observed to be stable over an untreated generation and appears to be specific to zinc. RNA-Seq analysis suggests that the progeny of zinc stressed plants display an altered transcriptome relative to control progeny in the absence of stress. Genes involved in iron uptake in the roots, which are upregulated in zinc stress, show a reduced expression in the progeny of zinc stressed plants. Biochemical analysis identified alterations in iron uptake in the zinc stress progeny. The activity of the jasmonate signalling pathways also appears to be altered in the zinc stress progeny. Wide-scale changes in DNA methylation were not observed during zinc stress or in the progeny of zinc stressed plants. Indeed, the DNA methylation profile of Arabidopsis thaliana was observed to be stable in response to a variety of stress conditions. Additionally, none of the other stressors tested resulted in a stress memory in the progeny. The results presented here suggest that transgenerational stress responses, such as the zinc stress memory identified, are rare in A.thaliana.