Effects of Cadmium on the Regulation of Antioxidant Enzyme Activity, Gene Expression, and Antioxidant Defenses in the Marine Macroalga Ulva Fasciata

鎘調節大型綠藻石蓴(Ulva fasciata)的抗氧化基因、酵素活性及抗氧化能力

吳宗孟(Tzure-Meng Wu) ； 許奕婷(Yi-Ting Hsu) ； 李澤民(Tse-Min Lee)

《Botanical Studies》 50卷1期 (2009/01) Pp. 25-34

摘要

本研究測定鎘逆境對大型綠藻(Ulva fasciata)抗氧化反應的影響。處理0、5、10、20、50μM氯化鎘四天不影響石蓴生長、2, 3, 5-triphenyltetrazolium chloride還原能力、H2O2產生量、或脂質過氧化，但是石蓴鎘含量隨外加處理鎘濃度由0-20μM增加而增加，僅在50μM沒有再增高，所以石蓴在0-50mM鎘之長時間處理沒有明顯的氧化逆境發生。Ascorbate (AsA) and dehydroascorbate (DHA)含量隨外加處理鎘濃度增加而增加，AsA/DHA比率也隨之增加，在10mM達到最大值。Glutathione (GSH)及氧化的GSH含量與GSH/氧化GSH比率隨外加處理鎘濃度增加而減少。鎘外加處理不影響Mn superoxide dismutase (MnSOD; EC 1.15.1.1)活性及mRNA量，50μM鎘外加處理造成FeSOD活性增加及UƒFesod1（FeSOD基因的isoform）mRNA量增加，但不影響UƒFesod2mRNA量。所以，FeSOD基因的表現只有UƒFesod1受鎘外加處理影響。Ascorbate peroxidase (APX; EC1.11.1.11)與catalase (CAT; EC1.11.1.6)活性隨外加處理鎘濃度增加而增加，但mRNA量不受影響。Glutathione reductase (GR; EC1.6.4.2)活性及mRNA量隨外加處理鎘濃度增加而增加。綜言之，AsA總量增加、GSH的消耗及FeSOD、APX、GR與CAT活性增高是石蓴去除鎘處理的氧化逆境機轉，所以沒有明顯氧化傷害產生。本研究也暗示FeSOD及GR活性增高可能是因為基因表現之關係。

關鍵字

抗氧化酵素 ； 抗氧化 ； 鎘 ； 基因表現 ； 石蓴

並列摘要

This study examined the antioxidative responses of the marine macroalga Ulva fasciata Delile to cadmium (Cd) stress. Exposure to 0, 5, 10, 20 and 50 μM CdCl2 for 4 days did not affect growth, 2, 3, 5-tri phenyltetrazolium chloride reduction ability, H2O2 production, or lipid peroxidation. The Cd contents in thalli increased linearly as CdCl2 concentrations increased from 0-20 μM CdCl2 and declined slightly at 50 μM CdCl2. This means that long-term exposure to Cd did not produce oxidative damage to the macroalga although Cd accumulated. Ascorbate (AsA) and dehydroascorbate (DHA) concentrations increased as Cd concentrations increased while AsA/DHA ratios increased with a peak at 10 μM. Glutathione (GSH) and oxidized GSH concentrations and GSH/oxidized GSH ratios decreased as Cd concentrations increased. Cd did not affect Mnsuperoxide dismutase (MnSOD; EC 1.15.1.1) activities or transcripts. Cd at 50 μM increased FeSOD activities and UƒFesod1 (a gene of FeSOD isoform) transcripts but did not affect UƒFesod2 transcripts. Among isoforms of the SOD gene, only UƒFesod1 was responsible for the increase of SOD activity by Cd. The activities of ascorbate peroxidase (APX; EC 1.11.1.11) and catalase (CAT; EC 1.11.1.6) increased as Cd concentrations increased, but their transcripts were not affected by Cd, suggesting that the induction of APX and CAT activities by Cd was not under transcriptional control. Glutathione reductase (GR; EC 1.6.4.2) activities and transcripts increased as Cd concentrations increased. The present results indicate that the increase in the AsA pool, the consumption of GSH, and the induction in the activities of FeSOD, APX, GR and CAT are used by U. fasciata to prevent the occurrence of oxidative damage under Cd stress. The increases in the activities of FeSOD and GR by Cd can be attributed to enhanced gene expression.

並列關鍵字

Antioxidant enzyme ； Antioxidant ； Cd ； Gene expression ； Ulva