DNA methylation contributes to plant acclimation to naturally fluctuating light

Plants in the natural environment experience continuous dynamic changes in light intensity. Here, we exposed Arabidopsis thaliana plants to naturally fluctuating light regimes alongside traditional square light regimes such as those often found in control environment growth chambers. The physiological response was highly consistent across experiments in sibling plants, indicating the possibility of an epigenetic mechanism, leading us to investigated differences in DNA methylation. Our results identified a large number of changes in DNA methylation patterns between fluctuating light acclimated plants and square light acclimated plants, demonstrating natural fluctuations in light impacts plant epigenetic mechanisms. Most importantly, there are more differences in DNA methylation patterns between different light pattern regimes than between different light intensities. These differences in DNA methylation were accompanied by significant changes in gene expression, some of which correlated with altered DNA methylation. One of these genes, MCCA, was found to significantly impact photosynthetic efficiency when knocked out. Thousands of transposable elements copies were differentially methylated between light regimes. Interestingly, up to 30% of these TEs are linked to nearby differentially expressed genes. Our data suggests DNA methylation plays a role in acclimation to natural light which may directly regulate gene expression and impact transposable element activation. WGBS: 4 samples (1 replicate per light regime) consisting of a pool of 6 leaves from individual plants RNAseq: 12 samples (3 per light regime), each is an independent replicate