小麦幼苗根系抗氧化酶对镍胁迫的响应

Nickel-induced Oxidative Stress and Responses of the Antioxidant Enzymes in Roots of Triticum aestivum L. Seedlings

为阐明Ni对小麦（Triticum aestivum L.）毒害的生理生化机理,研究了不同浓度Ni（0、50、100、200、400μmol·L^-1）对小麦幼苗根系生长和活性氧代谢的影响。结果表明,50μmol·L^-1Ni处理小麦幼苗6 d对根系生长和活性氧含量及抗氧化酶活性无显著影响。100~400μmol·L-1Ni处理时,随着Ni处理浓度增加,根系鲜重和长度逐渐降低,H2O2和MDA含量及O2-·产生速率则逐渐升高;超氧化物歧化酶（SOD）、谷胱甘肽还原酶（GR）、谷胱甘肽转硫酶（GST）、谷胱甘肽过氧化物酶（GPX）和葡萄糖-6-磷酸脱氢酶（G6PDH）活性逐渐提高,抗坏血酸过氧化物酶（APX）活性先上升后下降,100μmol·L-1Ni浓度时APX活性最大;过氧化物酶（POD）活性则无显著变化。采用聚丙烯酰胺凝胶电泳分析抗氧化酶同工酶谱发现,100μmol·L-1Ni处理诱导新的同工酶带APX-3和APX-4;对照组SOD出现了2条同工酶带,G6PDH出现4条同工酶带;100和400μmol·L-1Ni处理增强SOD和G6PDH同工酶带活性。由此可见,过量Ni处理抑制小麦根系生长、诱导活性氧水平升高而导致氧化胁迫,而SOD、APX、GST和GPX等抗氧化酶活性增加可能是根系为抵御氧化胁迫而产生的一种适应性响应。

To illustrate the physiological and biochemical mechanism of Ni on the toxic effects of wheat. Effects of different concentrations Ni （0, 50, 100, 200 and 400 μmol. L^-1） on the growth of roos and the metabolism of reactive oxygen species （ROS） in roots of early Triticum aestivum L. seedlings were explored. The results indicated that treatment with 50 μ mol. L^-1 Ni for 6d had no significant effect on roots growth, the contents of reactive oxygen species and activities of antioxidative enzymes. 100-400μmol.L^-1 of Ni resulted in a decrease of fresh weight and length of roots, but the contents of H2O2 and MDA, production rate of O2 -·increased with increasing Ni concentration. The activities of superoxide dismutase（ SOD, EC 1. 1.5. 1. 1 ） , glutathione reductase （ GR, EC 1.6.4.2） , glutathione S- tansferase （ GST, EC2.5.1.18 ） and glucose - 6 - phosphate dehydrogenase （ G6PDH, EC 1.1. 1.49） augmented gradually with increasing Ni concentration, being the maximum at 400 μmol. L^- 1 of Ni. Ascorbate peroxidase （ APX, EC 1. 11. 1. 11） increased first, and then depressed, being the maximum at 100 μmol.L^-1 of Ni, while the activities of peroxidase （POD, EC 1. 11. 1.7 ） remained unaltered under the tested Ni concentrations. Polyacrylamide gel electrophoresis native analysis revealed that 100μ mol.L^-1 of Ni induced two additional isozymes bands of APX- 3 and APX -4. Two isozymes bands of SOD and four bands of G6PDH in the control seedlings were found and there was a continuous enhancement in the intensity of SOD and G6PDH bands in roots treated with 100 and 400 μ mol.L^-1Ni. The present study confirmed that excess Ni inhibits root growth and induced oxidative stress by inducing ROS formation, while a increase of activities of SOD,APX,GST and GPX appears adaptive response of wheat roots against Ni-induced oxidative stress, not being able to eliminate ROS in roots.