Abstract: In this study, the changes of DNA methylation levels and patterns in Arabidopsis thaliana seedlings under 0-3.0 mg·L^-1 Cu²⁺ stress were studied using methylationsensitive amplified polymorphism (MSAP) technique, and the sensitivity of the fresh weight and root growth of seedlings to Cu stress were compared. The results showed that: (1) Under Cu stress (0.25, 1.0 mg·L^-1) for 15 days, no significant changes were observed in root growth and fresh weight of A. thaliana seedlings compared with the control group, but the genomic MSAP rate first increased and then decreased with the increase of Cu²⁺ concentration. The MSAP rates were 15.93%, 16.28% and 15.83% at 0, 0.25, 1.0 mg·L^-1 Cu²⁺, respectively; (2) At the high concentration of Cu²⁺ (3.0 mg·L^-1), the root length was shortened, the fresh weight was significantly decreased and the MSAP rate was reduced to 14.26%; (3) Under Cu stress (0.25-3.0 mg·L^-1), the number of methylation (M) type and demethylation (D) type sites increased significantly, and Msp I was more sensitive to stress response compared to Hpa II. Therefore, the MSAP of A. thaliana was sensitive to low concentration Cu²⁺ stress, which could be used for early diagnosis and ecological risk assessment of Cu pollution.

Key words: sensing signal molecule, wastewater treatment, quorum sensing, regulation behavior