| Biological sciences & biotechnology |
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| Effect of cadmium stress on the content of phytochelatins in Salix variegata |
| LIU Yuan1, WANG Niya1, ZHANG Wen2, YU Jia1，WEI Hong1* |
| (1. Key Laboratory of Eco-environments in Three Gorges Reservoir Region of the Ministry of Education/Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region/School of Life Sciences, Southwest University, Chongqing 400715, China; 2. Panlong Primary School in Panlong District, Kunming 650051, China) |
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Abstract With rapid development of industrialization and urbanization in China, large amounts of heavy metals have been directly or indirectly released into the soil environment through solid wastes, waste air, and waste water from industrial activities over the recent decades. In particular, cadmium (Cd) is one of the most toxic pollutants causing environmental problems. With excellent water solubility, Cd can be absorbed by plants easily and transferred to human body, eventually threatening the health of human beings. Lots of herb plants have tolerance for Cd and can accumulate to eliminate the Cd pollution in soils. However, with relative low biomass, the accumulation capacity of herb plants is limited. Little is known about the phytoremediation application of woody plants, which have large biomass and fast growth rate. Salix variegata has strong bioaccumulation on Cd and exceptionally high tolerance to Cd stress, especially planted along the sloping banks, thus it has the potential for phytoremediation of Cd polluted environments. However, the mechanism of tolerance and detoxification for Cd still needs further study. Metal binding ligands are effective for detoxification of heavy metals, mainly phytochelatins (PCs) and metallothioneins (MTs).
In this study, in order to explore the detoxification mechanism of S. variegata, and improve the potential enrichment and detoxification ability of S. variegata, hydroponic experiments were conducted under different Cd2+ concentrations, including 0 mg/L Cd2+ (CK), 2 mg/L Cd2+ (T1), 10 mg/L Cd2+ (T2), 20 mg/L Cd2+ (T3) and 50 mg/L Cd2+ (T4), and the Cd2+ and thiol-peptide contents in leaves and roots of S. variegata were determined.
The results showed that under the Cd stress, four kinds of thiol- peptides (PC2, PC3, PC4 and PC5) were detected in the leaves, and two kinds of thiol-peptides (PC2 and PC3) were detected in the roots. The total content of thiol-peptides in the leaves and roots of S. variegata increased with the Cd concentration and treatment time. The contents of glutathione (GSH) in the leaves and roots of S. variegata under different levels of Cd stress were significantly higher than that of the control treatment. Besides, the content of thiol-peptides in the leaves of S. variegata also increased significantly than the control. The increase of thiolpeptides was proportional related to the increase of Cd concentration. Meanwhile, the PC2 and PC3 contents of the T4 group in the roots of S. variegata were significantly higher than the control. Significant positive correlations between thiol-peptide content and Cd accumulation were observed in the leaves and roots of S. variegata. Altogether, these results indicated that the thiolpeptide content increased with the Cd accumulation in the leaves and roots of S. variegata.
In conclusion, with intensified Cd stress, the chelating ability of phytochelatin to Cd increased significantly, and the tolerance and the detoxification ability of S. variegata to Cd stress were substantially improved. The PC2 content of each Cd concentration treatment in the leaves and roots of S. variegata was the highest among the thiol-peptides, especially in the roots of S. variegata. Therefore, the chelating ability of PC2 to Cd in S. variegata is the best among the thiol- peptides, especially the chelating ability of PC2 to Cd in the root.
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Received: 23 August 2016
Published: 23 November 2016
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Corresponding Authors:
weihong@swu.edu.cn
E-mail: weihong@swu.edu.cn
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镉胁迫对秋华柳植物螯合肽含量的影响
以秋华柳为试验对象，采用水培法，设置0 mg/L Cd2+（CK）、2 mg/L Cd2+（T1）、10 mg/L Cd2+（T2）、20 mg/L Cd2+（T3）、50 mg/L Cd2+（T4）5种镉处理水平，通过对不同时间、不同质量浓度Cd2+处理下秋华柳叶片和根系中镉含量和各巯基肽含量的测定，研究Cd胁迫下秋华柳植物体内巯基肽的螯合解毒机制。结果表明：1）在Cd胁迫下，叶片诱导生成4种植物螯合肽（PC2、PC3、PC4和PC5），根系诱导生成2种植物螯合肽（PC2和PC3）。2）各处理组秋华柳叶片和根系中的巯基肽总量明显高于对照，且随着处理时间的延长和Cd胁迫程度的增加而升高。秋华柳叶片和根系中的谷胱甘肽含量均高于对照，且在一定质量浓度的Cd2+处理水平下差异有统计学意义；在秋华柳叶片中，各处理组的PCs含量均显著高于对照，且随着Cd胁迫程度的增加而升高；在秋华柳根系中，各处理组的PC2含量均显著高于对照，T4处理组的PC3含量显著高于对照。秋华柳叶片和根系中各巯基肽含量与其对应的Cd积累量之间均呈显著正相关。3）各处理组秋华柳叶片和根系中的PC2为含量最高的巯基肽，且根系中PC2占的比例更大。综上表明：在Cd胁迫下，秋华柳叶片和根系中的巯基肽含量随Cd积累量的增加而增加，从而增强其对Cd的螯合作用，提高对Cd的耐受和解毒能力；且秋华柳细胞内的PC2对Cd的螯合作用最强，尤其是在根部。
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