Yeast Saccharomyces cerevisiae is a good eukaryotic model for studying the molecular mechanism of toxic metal ion stress. Numerous studies have been performed on the signal transduction induced by toxic metal ion stress. The physiological process of eukaryotic cells has been studied and various stress factors have been elucidated by constructing gene deletion library. Until now, the sensitivity and tolerance mechanism of yeast under metal ion stress have been widely studied. The sensitive genes induced by metal ion stress will provide a key foundation for studying the gene function of eukaryotic organisms. In addition, the functions of genes in response to metal ion stress mainly participate in regulating ion homeostasis, high glycerin pathway, vacuole protein separation pathway, cell wall integrity pathway, and cell autophagy. However, the interaction of these signal pathways and the detailed response mechanism need to be further studied in future. In addition, the technique of genomics and proteomics will be helpful for studying the detailed molecular mechanism induced by toxic metal ion stress. Thus, the sensitive genes related to various signal pathways under toxic metal ion stress will be reviewed in the yeast S. cerevisiae.

In the current study, the effect of trivalent cerium (Ce 3+ ) on the production of reactive oxygen species (ROS) was investigated in the root of Arabidopsis thaliana by an in vitro study. The roots of A. thaliana were exposed with 0, 1, and 5 μmol/L Ce 3+ for 12 h in vitro. It was found that the level of H 2 O 2 , O 2 .À , and ÁOH was enhanced by 5 μmol/L Ce 3+ , but reduced by 1 μmol/L Ce 3+ . The activities of peroxidase (POD), catalase (CAT), and superoxidase dismutase (SOD) were enhanced by 1 μmol/L Ce 3+ , but reduced by 5 μmol/L Ce 3+ . Moreover, we used a laser-scanning confocal microscopy to detect the changes of ROS in the root cells of A. thaliana by using a fluorochrome 2 0 ,7 0dichlorofluorescein diacetate (H 2 DCF-DA). It showed that the level of ROS was declined in the root cells treated by 1 μmol/L Ce 3+ , but the oscillation of ROS was found in the root cells treated with 5 μmol/L Ce 3+ . In addition, REEs affect the uptake of mineral elements, which may be related to the oxidative stress in the cells of roots. In all, the data of our study indicated that the appropriate concentration of Ce 3+ exhibited an antioxidation property and improved the defense system in the root cells of A. thaliana.