Involvement of DNA methylation in regulating the growth of Arabidopsis thaliana seedling exposed to lanthanum(III) at environmental relevant levels

Rare earth elements (REEs) are excessively enriched in the environment. Epigenetic changes at the level of DNA methylation is often rapidly established in plant’s response to environmental factors. However, how the level of DNA methylation changes and then regulates plant growth in REE exposure at environmental relevant levels is still a mystery. Here, this mystery was initially revealed in Arabidopsis thaliana exposed to lanthanum [La(III), a widespread REE] at environmental relevant levels (0, 30 and 80 µM). The results showed that the DNA methylation levels, biomarker of one-carbon metabolism providing methyl for DNA methylation (S-adenosylmethionine content, S-adenosyl homocysteine content, the ratio of S-adenosylmethionine to S-adenosyl homocysteine] and plant growth did not change under a short-term La(III) exposure; with increased exposure time, the DNA methylation levels increased, along with the reduced one-carbon metabolism and improved growth (plant height, leaf number, leaf area, primary root length, lateral root number, and root hair number). However, the opposite changes were observed in the DNA methylation levels, one-carbon metabolism and growth under high-dose La(III) exposure. After adding DNA methylation inhibitor, La(III)-induced changes in plant growth were relieved, indicating that plant growth can be regulated by DNA methylation in the response to environmental REEs. Our study would provide references for revealing the mechanism of REEs acting on plants, scientifically assessing the environmental risk of REEs and alleviating the negative effects of REEs pollution.