Abstract: As a selective stress, heavy metal plays an important role during biological evolution. This study aims to explore the expression profiles of superoxide dismutase (SOD) and acetylcholine (AchE) gene in Sitobion avenae under the long-term exposure of cadmium (Cd). In the simulative natural environment, the soil for growing wheat was irrigated with CdCl2 solution. S. avenae was treated with Cd for 20 generations through the system of soil-wheat-aphids. The SOD and AchE genes in S. avenae were cloned with PCR technique. Real-time PCR was adopted to estimate the transcript levels of SOD and AchE genes in S. avenae at the 5th, 10th, 15th and 20th generations, respectively. The results showed that the expression levels of the two genes were affected by both concentration of Cd and the number of generations. Compared to control, the two genes were over-expressed in the contaminated aphids at the 10th generation, but their expression was inhibited in the 20th generation. At the concentration of Cd higher than 40 mg/kg, the gene expression levels declined, suggesting that 40 mg/kg is the crucial concentration. These results suggest that the expression of SOD and AchE is promoted by the toxicity of low-dose and short-term pollutions, and the detoxification of superoxide dismutase and hydrolysis of acetylcholine, however, is inhibited under the high-dose and long-term stress.

Key words: Sitobion avenae, heavy metal, cadmium (Cd), superoxide dismutase (SOD), acetylcholine (AchE), expression level