Subcellular localisation of Cd and Zn in the leaves of a Cd-hyperaccumulating ecotype of Thlaspi caerulescens
Subcellular localisation of Cd and Zn in the leaves of a Cd-hyperaccumulating ecotype of Thlaspi caerulescens
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DOI：
10.1007/s00425-004-1392-5
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发表时间：
2005-03-01
期刊：
影响因子：
4.3
通讯作者：
McGrath, SP
中科院分区：
文献类型：
--
作者：
Ma, JF;Ueno, D;McGrath, SP
Thlaspi caerulescens（恒河生态型）能够在叶片中积累高浓度的镉（Cd）和锌（Zn）而没有显示出任何毒性，表明其具有强的内部解毒作用。研究了Cd和Zn在叶片中的分布。虽然Cd和Zn在表皮组织中的含量是叶肉组织的2倍，但叶肉组织中Cd和Zn的含量占总含量的65-70%，说明叶肉是Cd和Zn在叶片中的主要贮存部位。要检查亚细胞定位的镉和锌在叶肉组织中，原生质体和液泡被分离出植物暴露于50 μ M镉和锌水培。通过光镜观察和细胞质及液泡标记酶活性测定，获得了纯质的原生质体和液泡。在叶肉组织中，91%和77%，分别存在于原生质体中，和所有的镉和91%的锌在原生质体中定位在液泡中。此外，约70%和86%的总镉和锌，分别在叶片中提取的细胞汁液中，这表明，大多数镉和锌在叶片中是以可溶性形式存在。这些结果表明，内部解毒的Cd和Zn在Thlaspi caerulescens叶是通过液泡区室化。
Thlaspi caerulescens (Ganges ecotype) is able to accumulate large concentrations of cadmium (Cd) and zinc (Zn) in the leaves without showing any toxicity, suggesting a strong internal detoxification. The distribution of Cd and Zn in the leaves was investigated in the present study. Although the Cd and Zn concentrations in the epidermal tissues were 2-fold higher than those of mesophyll tissues, 65-70% of total leaf Cd and Zn were distributed in the mesophyll tissues, suggesting that mesophyll is a major storage site of the two metals in the leaves. To examine the subcellular localisation of Cd and Zn in mesophyll tissues, protoplasts and vacuoles were isolated from plants exposed to 50 muM Cd and Zn hydroponically. Pure protoplasts and vacuoles were obtained based on light-microscopic observation and the activities of marker enzymes of cytosol and vacuoles. Of the total Cd and Zn in the mesophyll tissues, 91% and 77%, respectively, were present in the protoplast, and all Cd and 91% Zn in the protoplast were localised in the vacuoles. Furthermore, about 70% and 86% of total Cd and Zn, respectively, in the leaves were extracted in the cell sap, suggesting that most Cd and Zn in the leaves is present in soluble form. These results indicate that internal detoxification of Cd and Zn in Thlaspi caerulescens leaves is achieved by vacuolar compartmentalisation.