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Study on the Anti-oxygen Mechanism of Chinese Cabbage under Methamidophos

Author: TangHongFeng
Tutor: XiongLi
School: Central China Normal University
Course: Biochemistry and Molecular Biology
Keywords: Methamidophos Chinese cabbage Anti-oxygen enzyme P450 Induction
CLC: S634.3
Type: Master's thesis
Year: 2006
Downloads: 103
Quote: 3
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Abstract

Plant cells can produce a grate deal of reactive oxygen species （ROS or active oxygen species） even in normal physiological conditions. When the environment changes, such as heat, cold, drought, pesticide pollution, the output of ROS will greatly increase. The organelles of plant cell that generate ROS involve chloroplast, mitochondrion, peroxide enzyme, glyoxysome、 endoplasmic reticulum, microsomal, cell membrane , cell wall and so on. ROS include O₂、H₂O₂、 OH、HO₂ （hydyoperoxyl radical）、RO（alkoxy radical）、 ROO （peroxy radical）、 ROOH （hydroperoxide） -¹02 （singlet oxygen）、 HOX、 O₃ and so on . ROS are toxic to organisms, which can damage nonnal cells’ DNA, protein and membrane resin. So the cells’ ROS levels must be strictly controlled. The plant cells have perfect ROS-defense-system, which is composed of anti-oxygen enzyme and antioxidant.According to the study on the active changes of Anti-oxygen enzyme such as superoxide dismutase（SOD）、 catalase（CAT）、 Glutathione peroxidase（GPX）、 Cytochrome p450 of Chinese Cabbage and the changes of the content of GSH under Methamidophos and the total ROS and Anti-oxygen capacity of Chinese cabbage ,several sensitive biological indicators have been selected. Then the response mechanisms under Methamidophos stress is studied and some potential biochemical biomarkers of organic phosphorus on Chinese cabbage are suggested further.1. The Anti-oxygen Capacity of Chinese Cabbage Under MethamidophosIn this paper, the activities of superoxide dismutase （SOD） ,catalase （CAT） , glutathione peroxidase （GPX） , glutathione （GSH） in Chinese cabbage were determined in the following 7 days after sprayed by 0.5g/m2 Methamidophos. The results indicated that the activities of SOD, CAT and the content of GSH in Chinese cabbage were higher than that of the control in the 2-6 day, but the activities of GPX was lower than the control. Whereafter the activities of GPX and total anti-oxygen capacity have no significant change. At the 7th day, all parameters revived to the level of control sample. It suggested that stressed by Methamidophos, the cells of Chinese cabbage have produced a mass of Reactive Oxygen Species（ROS） in short time. So the activities of anti-oxidasemust be enhanced to eliminate damage by superfluous Reactive Oxygen Species. In order to keep healthy, the self-restore system of Chinese cabbage began to adjust the total anti-oxygen capacity. This paper indicate that the antioxidant compounds of Chinese cabbage were induced to withstand the toxicity of 0.5g/m2 Methamidophos.There parameters afforded a referenced standard for food inspection.2. Studies on the Induction of Chinese Cabbage Cytochrome p450 byMethamidophos and the spectrum charactersticsWhen irrigated Chinese Cabbage at 4.8g/L, 0.96g/L, 0.096g/L methamidophos, the result indicated that the protein contents of microsomal were higher than that of the control. Between the protein contents and the pesticide concentration was direct proportion. But the activities of NADPH-Cyt C reductase were lower than that of the control. The Cyt b5 wasn’t display obvious the relationship of dosage-effect. At the same time crude microsomal preparation stored at room temperature （25±1）°C for 200 minutes, the cytochrome P450 was transformed into the inactive form, cytochrome P420.3. Semi-Quantitive RT-PCR Assay for Chinese Cabbage （Brassica.chinensis. L） CAT & GSHSemi-Quantitive RT-PCR method was employed to detect Chinese cabbage gene expression profiles of, according to the enzymatic sensitive biomarkers, CAT and GSH. Leaves were collected and RNA were extracted after Chinese cabbage sprouts had been exposed to 4.8g/L methamidophos for 96 hours;then RNA from treated and control groups were reverse transcribed and polymerase chain reactions were applied subsequently. Agarose gel electrophoresis results indicated that RNA from both groups were pure enough for the following RT-PCR experiment. CAT mRNA was significantly increased whereas GSH mRNA was decreased treated by the organophosphate, it was consistent with the foregoing enzyme kinetics experiment. It was concluded that both genes, CAT and GSH, are potential sensitive biomarkers of Chinese cabbage exposure to methamidophos.

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