箭舌豌豆根系抗坏血酸及相关酶对镉胁迫的响应

以箭舌豌豆(Vicia sativa L.)品种L3(耐镉)和ZM(镉敏感)为材料,研究了不同程度镉胁迫下箭舌豌豆幼苗根系抗坏血酸(AsA)含量、脱氢抗坏血酸还原酶(DHAR)同工酶活性、抗坏血酸过氧化物酶(APX)同工酶活性以及APX基因表达的变化。结果显示:(1)2个箭舌豌豆品种根系AsA和脱氢抗坏血酸(DHA)含量在镉胁迫下显著升高;AsA/DHA比值在镉耐性品种L3中显著升高,在敏感品种ZM中显著下降;相同镉处理浓度下,L3根系AsA含量和AsA/DHA比值显著大于ZM。(2)2个品种根系DHAR的活性电泳共显示4条同工酶条带,它们的活性均随镉处理浓度的升高而升高;其中DHAR1只在L3显示,DHAR4只在ZM显示;相同镉处理浓度下,品种L3的DHAR的总活性大于品种ZM。(3)2个品种根系APX的活性电泳共显示11条同工酶条带,其中的APX1、2、4仅在敏感品种ZM中受镉胁迫诱导,APX 8在耐性品种L3中受到比敏感品种ZM更显著的诱导;克隆得到1个箭舌豌豆APX基因,荧光定量RT-PCR结果显示该基因的转录在L3和ZM根系均受镉处理诱导。研究表明,镉胁迫下2个箭舌豌豆品种根系AsA含量,AsA代谢相关酶DHAR和APX的活性以及APX的转录水平均显著升高;镉耐性品种L3较敏感品种ZM能更有效地促进AsA循环,维持更高的AsA水平,从而更有效地缓解镉胁迫诱导产生的氧化胁迫,这可能是L3较ZM具有更高镉耐性的重要机制之一。

Study on Ascorbic Acid and Relative Enzymes Against Cadmium Stress in the Roots of Vicia sativa L.

Two varieties of Vicia sativa L. with different Cd tolerances (Cd tolerant variety L3, Cd sensitive variety ZM) were studied to compare concentrations of ascorbic acid (AsA), activities of dehydroascorbate reductase (DHAR) isoenzymes and ascorbate peroxidase (APX) isoenzymes, and APX gene expression in response to Cd treatment in the roots. Results showed that: (1) Cd treatment significantly increased the concentrations of AsA and dehydroascorbate (DHA) in the roots of both L3 and ZM. Cd treatment also tended to increase ratio of AsA/DHA in L3, but to decrease the ratio in ZM. At the same Cd treatment, L3 roots had higher AsA concentration and AsA/DHA ratio than that of ZM. (2) Four isoforms of DHAR were obtained in L3 and ZM roots by native PAGE and their activities generally increased with increasing Cd concentration. DHAR1 was obtained only in L3 and DHAR4 only in ZM. At equivalent Cd concentrations, the total activity of DHAR was higher in roots of L3 than that in ZM. (3) Eleven APX isoforms were obtained in both L3 and ZM roots by native PAGE. APX1, 2, 4 were induced by Cd treatment only in ZM and the activity of APX8 was more significantly induced in L3 than that in ZM. An APX gene was cloned and subjected to RT PCR analysis. The gene expression level was upregulated under Cd stress in the roots of both varieties. These results suggested that concentration of AsA, activities of DHAR and APX, and APX gene expression level increased in response to cadmium stress in the roots of two V. sativa varieties. It is possible that the more effective AsA recycle in the roots of L3 contributed to its higher AsA concentration than that in ZM, and this could be related to its stronger protection from ROS generation and finally contributed to its higher tolerance to Cd stress.