镍胁迫对菹草(Potamogeton crispus L.)活性氧及脯氨酸代谢的影响

摘要

Sterile seedlings of Potamogeton crispus were cultured by tissue culture technique, and used as experimental materials. In this study, different concentrations of Ni2+ (0, 0. 05, 0. 10, 0. 15 and 0. 20 mmol/ L) on contents of hydrogen peroxide ( H2 O2 ) , superoxide anion ( O2- ) and malondialdehyde ( MDA) , antioxidant defense system and proline metabolism were investigated. The results indicated that (1) Ni + stress triggered the generation of reactive oxygen species ( ROS) as evidenced by a substantial accumulation of H2O2 and O2 - , accompanied by the increased MDA content with the increasing of Ni 2+ concentration; (2) Activities of superoxide dismutase (SOD), peroxides (POD) and catalase (CAT) , as well as contents of reduced glutathione (GSH) and non-protein thiols (NP-SH) increased at first and then decreased, while no outstanding changes were observed in ascorbate ( AsA) content, and level of phytochelatins ( PCs) increased significantly; (3 ) Analysis of enzyme activities showed that the accumulation of proline induced by Ni2+ stress is due to the increases of omithine-8-aminotransferase (OAT) at 0.05 -0. 10 mmol/L and pyrroline-5-carboxylate synthetase (P5CS) activity at 0. 15 - 0.20 mmol/ L, respectively, but there was not a statistically significant difference in ProDH activity. Our results demonstrated that Ni2 + induced the enhancement of reactive oxygen species level, aggravated lipid peroxidation and interfere with intrinsic balance of antioxidant defense system. In addition, pro-line accumulation is mediated by increased biosynthesis from ornithine at low concentrations (0. 05 and 0. 10 mmol/L) , while glu-tamate pathway, instead of the ornithine pathway, plays a vital role when exposed to higher concentrations of Ni2+ .%本文以组织培养技术培养的菹草无菌苗为实验材料,研究了不同浓度(0、0.05、0.10、0.15、0.20 mmol/L) Ni2+胁迫对菹草过氧化氢(H2O2)、超氧阴离子(O2)和丙二醛(MDA)的含量、抗氧化系统、脯氨酸代谢途径的影响.结果显示:(1) Ni2+胁迫影响了活性氧水平,主要表现为H2O2和O2-的大量积累；MDA含量也随着Ni2+浓度的升高呈上升趋势；(2)随着Ni2+浓度的升高,超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性及还原型谷胱甘肽(GSH)、非蛋白巯基(NP-SH)含量均表现为先升后降趋势；抗坏血酸(AsA)含量变化不明显；植物络合素(eCs)则表现为上升趋势；(3)脯氨酸代谢关键酶在Ni2+胁迫下表现为:鸟氨酸转氨酶(OAT)活性在0～0.10 mmol/L Ni2+胁迫下高于对照组；吡咯啉-5-羧酸合成酶(P5CS)活性在Ni2+大于0.10 mmol/L时,显著增加；脯氨酸脱氢酶(ProDH)活性无显著变化；脯氨酸(Pro)含量则均显著高于对照组.以上结果表明,Ni2+胁迫提高了活性氧的水平,加重了膜脂过氧化的程度,干扰了抗氧化系统的内在平衡；此外,低浓度Ni2+胁迫下菹草脯氨酸积量主要依赖于鸟氨酸途径,而高浓度下则主要依靠谷氨酸途径.