The effect of H2O2 pretreatment on Cd tolerance and translocation of rice seedlings were studied using two rice cultivars （N07-6 and N07-63） differing in Cd tolerance. The contents of malondialdehyde （MDA）, reduced glutathione （GSH）, non-protein thiols （NPT）, phytochelatins （PCs） and the activity of glutathione S-transferase （GST） were compared between the two cultivars exposed to various treatments. The results showed that 50 μmol/L Cd exposure significantly inhibited rice growth, enhanced the production of GSH, NPT, PCs and MDA, and increased the activity of GST, and there were significant differences between the two cultivars. More Cd was transported into the shoot of N07-6. The H2O2 pretreatment alleviated Cd toxicity by further increasing GSH, NPT and PCs contents, as well as the GST activity in roots. The increase degrees of these parameters in N07-63 were higher than those in N07-6, suggesting that the tolerance of N07-63 was enhanced more significantly than N07-6. Hydrogen peroxide reduced Cd translocation to rice shoot but affected the Cd content in root differently. From the above results, it may be speculated that there were remarkable differences in the Cd detoxification and response to the H2O2 pretreatment between the two cultivars.
BAI Xiao-JuanLiu Li-JuanZHANG Chun-huaGE YingCHENG Wang-da
A hydroponic culture experiment was done to investigate the effect of Cd stress on glutathione content （GSH） and glutathione S-transferase （GST, EC 2.5.1,18） activity in rice seedlings. The rice growth was severely inhibited when Cd level in the solution was higher than 10 mg/L. In rice shoots, GSH content and GST activity increased with the increasing Cd level, while in roots, GST was obviously inhibited by Cd treatments, Compared with shoots, the rice roots had higher GSH content and GST activity, indicating the ability of Cd detoxification was much higher in roots than in shoots. There was a significant correlation between Cd level and GSH content or GST activity, suggesting that both parameters may be used as biomarkers of Cd stress in rice.
Cadmium （Cd） contamination in paddy soils poses a serious threat to the production and quality of rice. Among various biochemical processes related to Cd detoxification in rice, glutathione S-transferase （GST） plays an important role, catalyzing Cd complexation with glutathione （GSH） and scavenging reactive oxygen species （ROS） in cells. In this study, a hydroponic experiment was conducted to investigate the response of GST isozymes in rice roots upon Cd exposure. Results showed that the GST activity in rice roots was clearly enhanced by 50 pmol/L Cd treatment for 7 d. The GST isozymes were purified by ammonium sulphate precipitation, gel filtration chromatography and affinity chromatography. After being separated by SDS-PAGE and visualized by silver staining, GSTU6 was identified by in-gel digestion, MALDI-TOF-MS analysis and peptide mass fingerprint. The results confirm the vital function of tau class rice GST in Cd detoxification.
