The epigenetic basis of responses to climate change. Insights from the model plant Arabidopsis thaliana

Abstract

Plants are highly vulnerable to rising atmospheric carbon dioxide, one of the primary drivers of anthropogenic climate change. Changes in carbon availability have been shown to alter gene expression, physiology, morphology, and evolutionary fitness of plants. In the short-term, the most important response mechanism to elevated carbon dioxide will be phenotypic plasticity. While plasticity does not, by definition, involve changes in DNA, it may be induced via changes in the epigenome. Thus, exploring the epigenetic basis of phenotypic plasticity of plants to elevated carbon dioxide (eCO2) is an important step toward predicting their short-term responses to climate change. I used azacitidine (Aza), a non-selective demethylating agent, to investigate the effects of genome-wide demethylation on phenotypic plasticity to eCO2 and the effect of eCO2 on the methylome using three ecotypes of the model flowering plant Arabidopsis thaliana. Seeds were germinated inside petri dishes on filter paper saturated with either autoclaved water or either 50, 75, 100 or 200 Aza, and then transferred to either low or high carbon dioxide treatments and grown to maturity. Studies have shown that these concentrations of Aza induce measurable changes in patterns of genome-wide methylation. For each ecotype, I measured the effects of Aza on the expression and plasticity of ecologically relevant traits. I also used 420ppm and 840ppm CO2 levels to explore its effects on the methylome. Our results show that experimental demethylation of the genome with azacitidine alters both patterns of trait expression and phenotypic plasticity to eCO2 in a dose-dependent fashion. However, trait sensitivity to demethylation varied among the three ecotypes. I also found that eCO2 can lead to significant changes in methylation levels in specific regions of the genome. I conclude that, in the face of rapid climate change, epigenetic variation may be a vital source of adaptive potential in Arabidopsis.