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A Study On Physiological And Biochemical Properties, Antioxidant Enzymes And Related Proteins In A Mangrove Plant Bruguiera Gymnorrhiza Under Cadmium And Lead Stress

Posted on:2008-01-13Degree:MasterType:Thesis
Country:ChinaCandidate:Y M TaoFull Text:PDF
GTID:2120360215983446Subject:Biochemistry and Molecular Biology
Abstract/Summary:PDF Full Text Request
This study was carried out to investigate the effect of cadmium and lead on the growth, chlorophyll content, antioxidant enzymes and protein expression in a mangrove plant Bruguiera gymnorrhiza. The similarities and differences of Cd and Pb effects on B. gymnorrhiza are also discussed. The major resultes are summerized as follows:1. Under 20-30 mmol·L-1 Cd and 20-40 mmol·L-1 Pb treatment, B. gymnorrhiza seedlings grew slower than those treated with other concentrations and in control, with significant differences in plant height increasement. Concentrations of 30 mmol·L-1 Cd and 40 mmol·L-1 Pb led to wilt.2. Chlorophyll a, b, total chlorophyll and carotenoids experienced significant declines in all Cd and Pb treatments. The destruction of Pb to chlorophyll was stronger than Cd. The value of chlorophyll a/b increased suggesting that Cd and Pb exerted more destruction on chlorophyll b than on cholorophyll a in seedlings. Both Cd and Pb induced membrane lipid peroxidation in B. gymnorrhiza seedlings. The extent of lipid peroxidation caused by these two heavy metals was equivalent.3. The effects of Cd and Pb on POD and SOD activities in root and leaf extracts of B. gymnorrhiza seedlings were similar. The enzyme activites were stimulated in lower metal ion concentrations but were inhibited in higher concentrations. However, the effects of Cd and Pb on CAT activities in seedlings were quite different. The CAT activities were significantly inhibited when 1 mmol·L-1 Cd supplied suggesting the sensitivity of root CAT activities to Cd, while the enzyme activities experienced an initial increase and subsequent decrease when Pb supplied. 4. The effects of Cd and Pb on the isoform of antioxidant enzymes in root and leaf of B. gymnorrhiza seedlings were analyzed by means of PAGE. The effects of Cd and Pb on the expression of POD isoenzyme in root and leaf extracts of seedlings were similar, but the effects on the expression of SOD and CAT isoenzyme were different. The expression of SOD isoenzyme in root was stimulated in lower Cd and Pb concentrations but was inhibited in higher concentrations. Pb induced a new Cu/Zn-SOD isoenzyme in leaf . The expression of CAT isoenzyme in root was significantly inhibited by Cd, but a new CAT isoenzyme in root and two in leaf was induced by Pb. It seems that there might be a similar mechanism of POD and two different of SOD and CAT isoenzyme expression regulated and controled by Cd and Pb in B. gymnorrhiza seedlings.5. The effects of Cd and Pb on the protein expression in B. gymnorrhiza seedlings were investigaed by means of SDS-PAGE. It is found that the protein content in leaf was extremely negatively-related to Cd and Pb concentration. 60-97kDa protein decreased or even disappeared under Cd and Pb stress. Morever, protein at 11kDa was induced by Cd and Pb. These proteins were closely related to the tolerance of B. gymnorrhiza seedlings under Cd and Pb stress.6. It is suggested that the analysis of POD, SOD and CAT isoenzyme expression, as well as protein expression, is a useful tool for monitor mangrove ecosystem. The results shows that in spite of no visible symptom in shape, the expression of antioxidant isoenzymes and protein changed, which could be detected by means of electrophoresis. Compared to the shape description and the determination of enzyme activities, the analysis of isoenzyme and protein expression is more accurate and without delay to reflect the heavy metal pollution state and helps us a lot to monitor the mangrove ecosystem. Considering the sensitivity, we suggest that the analysis of POD isoenzyme in leaf, CAT isoenzyme in root and 60-97kDa proteins expression could be used as a method for monitoring.
Keywords/Search Tags:Bruguiera gymnorrhiza, Cd, Pb, chlorophyll, lipid peroxidation, antioxidant enzyme, isoenzyme, protein, SDS-PAGE
PDF Full Text Request
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