| In recent years, as the heavy metal ions in the industrial waste water is discharged into the water environment, the resulting environmental risk has attracted widely attention. Cadmium (Cadmium, Cd) is one of the important pollution of heavy metals and has been listed as the current one of the most important agricultural environmental pollutants by the United States agriculture committee. It is also recognized as the carcinogenic heavy metals and greatly harmful to organisms. Its way of invading organisms is through the digestive tract, respiratory tract, skin, and so on. It can greatly accumulate in plants through the effect of enrichment after the waste gas, waste water and waste residue is discharged into the environment and soil. Then it will enter human body and endanger the human body health through the food chain..Numerous studies have shown that cadmium can inhibite the activity of antioxidant enzymes (SOD, CAT), causing the accumulation of free radicals in the body. Then the oxygen free radicals (ROS) produced by the body and the imbalance of antioxidant system will lead to many physiological or pathological changes of the body. The toxic effect of cadmium is also reflected in the disorders of gene expression induced and genomic instability epigenetic changes induced by the biological epigenetic changes. Relevant studies involve the genomic DNA methylation level, specific gene promoter region methylation status and the chang of expression of methyltransferase activity, etc. In recent years many evidences shows the environmental factor induced epigenetic changes induced by the environmental factor have the character of heritability.The study uses the Drosophila melanogaster (Canton-S strain) as the research object and uses cadmium (26.0 mg/L) to process treatment of the male, female, male and female. The study coerces the offsprings or procees in the same way. Then we continuously cultivative and process five generations (F0?F4). Every generation is tested different treatment group drosophila longevity and fertility change at the physiological level. After cadmium coercion, the study uses the Real-time PCR method to detect the change of every generation different treatment group of the Drosophila melanogaster DNA methylation modification system related gene (dDnmt2, dMBD2/3) and cell apoptosis related gene (p53, Caspase-3) at the molecular level. The experimental results are as follows:1. Cadmium has more obvious inhibitory effect on the life of Drosophila melanogaster. After cadmium treatment parental generation, the average life, middle life and the highest life of the offspring (male and female) are significantly reduced (p< 0.05) compared with control group. In shortened life-span under cadmium stress between different treatment groups, male and female treatment group compared with the treatment group of male or female groups have significant difference. After cadmium coercion, the life of inhibition by can pass at least two generations. The study shows that heavy metal cadmium can induce premature senescence and this effect can be passed to the offspring, so its toxic effects may have a certain genetic risk.2. Cadmium coercion has a more obvious inhibitory effect on Drosophila melanogaster fertility. After five consecutive generation experiment, the study finds that the heavy metal cadmium can weak Drosophila melanogaster fertility. The study also finds that the more treatment generations, the more significant effects on the Drosophila melanogaster fertility. The degree of the inhibition of the Drosophila melanogaster fertility is as follows:4 generation> 3 generation> 2 generation> 1 generation. There are significant difference about the Drosophila melanogaster fertility between treatment group of male and female and the treatment group of male. The fertility of inhibition can pass generation to generation under cadmium coercion.3. After cadmium coercion, Real-time PCR results shows that the Drosophila melanogaster methylation genes (dMBD2/3, dDnmt2) rise at mRNA expression level rise compared with the control group (p< 0.05). The more treatment generations, the higher the expression of genes increase (4 generation> 3 generation> 2 generation> 1 generation). Different treatment groups of female, male treatment group and male and female treatment group have no regular expression differences. Under the condition of cadmium coercion, the change of the expression of dDnmt2 and dMBD2/3 can pass backard 2 generations. The results suggest that the toxic effects of heavy metal cadmium stress on Drosophila melanogaster may be associated with DNA methylation process.4. The gene about the Drosophila melanogaster apoptosis of p53 and Caspase-3 rise at the mRNA expression level, compared with the control group with significant difference (p< 0.05) after cadmium coercion. The more treatment generations, the higher the expression of genes increase. In addition, the genes(p53, Caspase-3) of the different treatment group of female group, male and male and female group have no significant difference at the expression of mRNA level. Under the condition of cadmium coercion, the change of the expression of p53 and Caspase-3 can pass backard 1 generations. So we speculate that cadmium coercion may regulate the expression of apoptosis related gene in epigenetic way, thus induced Drosophila melanogaster die off.Research on heavy metal cadmium in Drosophila melanogaster, the influence of life, the fertility of drosophila DNA methylation, the expression of apoptosis related gene changes, and heritability of these changes have laid the experiment foundation of further discussing the toxicology effect and molecular mechanism of cadmium. And it also provides the experimental basis of epigenetic changes induced by environmental factors and genetic research. This research lay the theoretical foundation of epigenetic changes to avoid environmental factors (such as heavy metals) may cause the influence of the ecological system and risk in the future. |
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