Abstract:

Effects of exogenous Cu2+ and Cd2+ stresses on SOD expression were investigated in wheat roots. Both SOD activities and Cu/ZnSOD gene expression in wheat roots were detected with different concentrations (0 mg/L, 5 mg/L, 30 mg/L and 60 mg/L) of Cu2+ and Cd2+ solution for different times (24 h, 48 h, 72 h and 96 h), respectively. The results indicated that with Cu2+ exposed time extended to 72 h , the SOD activities were significantly higher than those of the control (P<0.01). It was increased to 3.67 times of the control when exposed to 30 mg/L Cu2+. Under the Cd2+ stress treatment, the SOD activities showed the tendency of increasing-decreasing-increasing again in wheat roots. It was significantly declined with an increase of concentration in earlier stage, while the activities reduced to a minimum after 72 h-treatment. The results detected by Real-time Q-PCR showed that Cu/ZnSOD gene expression under Cd2+ stress were obviously higher than those exposed of Cu2+. When exposed to 5 mg/L Cu2+, the gene expression of Cu/ZnSOD was always higher than those of 60 mg/L and 30 mg/L Cu2+ treatments. Under Cd2+ stress, the expression of Cu/ZnSOD gene decreased remarkably with the increased of concentration and the extent of time and maintained a rather low level till 96 h. Under Cu2+ and Cd2+ stresses treatment, concentration had more obvious effect on gene expression than time. The above results would provide a theoretical reference and technical support for further discussion on SOD characteristics of wheat radicle under heavy metal stress.

Key words: wheat, Cu2+ and Cd2+ stress, superoxide dismutase, Real-time Q-PCR, gene expression

摘要：

采用水培试验探索不同浓度(0 mg/L、5 mg/L、30 mg/L和60 mg/L)Cu2+或Cd2+胁迫(24 h、48 h、72 h和96 h)后对小麦幼根超氧化物歧化酶(SOD)活性的影响,并通过实时荧光定量聚合酶链式反应(real-time fluorescence quantitative PCR, Real-time Q-PCR)检测Cu/ZnSOD基因表达。结果表明,Cu2+胁迫处理72 h后,各处理SOD活性均较对照极显著提高(P<0.01),且30 mg/L浓度下SOD酶活性最高,是对照的3.67倍;而Cd2+胁迫处理后,幼根SOD活性整体呈现“升-降-升”的趋势,胁迫前期酶活性的降低程度与Cd2+浓度成正比,至72 h酶活性最低。Cd2+胁迫条件下Cu/ZnSOD的表达量明显高于Cu2+胁迫。不同时间Cu2+胁迫下,Cu/ZnSOD基因表达均呈现5 mg/L浓度处理高于60 mg/L和30 mg/L,表明低浓度促进而高浓度抑制该基因表达;而对于Cd2+胁迫,Cu/ZnSOD基因随浓度的升高和时间的延长呈现明显下降趋势,至96 h最低。本实验结果表明,Cu2+、Cd2+胁迫处理后浓度对基因表达的影响较大。该结果为深入探讨重金属胁迫下小麦幼根中SOD特性的研究提供理论参考和技术支持。

关键词: 小麦;Cu2+和Cd2+胁迫;超氧化物歧化酶;Real-time Q-PCR;基因表达