GSE121150
Excess light priming in Arabidopsis thaliana genotypes with altered DNA methylomes
Plants must continuously react to the ever-fluctuating nature of their environment. Repeated exposure to stressful conditions can lead to priming, whereby prior encounters heighten a plant's ability to respond to future events. A clear example of priming is provided by the model plant species Arabidopsis thaliana (Arabidopsis), in which photosynthetic and photoprotective responses are enhanced following recurring light stress. While there are various post-translational mechanisms underpinning photoprotection, an unresolved question is the relative importance of transcriptional changes towards stress priming and, consequently, the potential contribution from DNA methylation – a heritable chemical modification of DNA capable of influencing gene expression. Here, we systematically investigate the potential molecular underpinnings of physiological priming against recurring excess light (EL), specifically DNA methylation and transcriptional regulation: the latter having not been examined with respect to EL priming. The capacity for physiological priming of photosynthetic and photoprotective parameters following a recurring EL treatment was not impaired in Arabidopsis mutants with perturbed establishment, maintenance and removal of DNA methylation, nor was the transmission of this priming into naive tissues developed in the absence of excess light. Importantly, no differences in developmental or basal photoprotective capacity were identified in the mutants that may confound the above result. Little evidence for a causal transcriptional component of physiological priming was identified; in fact, most alterations in primed plants presented as a transcriptional 'dampening' in response to an additional EL exposure, likely a consequential of physiological priming. However, a set of transcripts uniquely regulated in primed plants provide preliminary evidence for a novel transcriptional component of recurring EL priming, independent of physiological changes. Thus, we propose that physiological priming of recurring EL in Arabidopsis occurs independently of DNA methylation; and that the majority of the associated transcriptional alterations are a consequence, not cause, of this physiological priming. Overall design: Experiments were performed using recurring excess-light treatments on Arabidopsis thaliana. MethylC-seq was performed on 3 replicates of unstressed Col-0 and strs2  plants. RNA-seq was performed on 3 replicates of naïve, naïve-triggered, primed, and primed-triggered plants.