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首页> 美国卫生研究院文献>Plant Physiology >Complexation and Toxicity of Copper in Higher Plants. II. Different Mechanisms for Copper versus Cadmium Detoxification in the Copper-Sensitive Cadmium/Zinc Hyperaccumulator Thlaspi caerulescens (Ganges Ecotype)
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Complexation and Toxicity of Copper in Higher Plants. II. Different Mechanisms for Copper versus Cadmium Detoxification in the Copper-Sensitive Cadmium/Zinc Hyperaccumulator Thlaspi caerulescens (Ganges Ecotype)

机译：高等植物中铜的络合和毒性。二。铜敏感性镉/锌超富集性拟南芥（恒生生态型）中铜与镉解毒的不同机理

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The cadmium/zinc hyperaccumulator Thlaspi caerulescens is sensitive toward copper (Cu) toxicity, which is a problem for phytoremediation of soils with mixed contamination. Cu levels in T. caerulescens grown with 10 μm Cu2+ remained in the nonaccumulator range (<50 ppm), and most individuals were as sensitive toward Cu as the related nonaccumulator Thlaspi fendleri. Obviously, hyperaccumulation and metal resistance are highly metal specific. Cu-induced inhibition of photosynthesis followed the “sun reaction” type of damage, with inhibition of the photosystem II reaction center charge separation and the water-splitting complex. A few individuals of T. caerulescens were more Cu resistant. Compared with Cu-sensitive individuals, they recovered faster from inhibition, at least partially by enhanced repair of chlorophyll-protein complexes but not by exclusion, since the content of Cu in their shoots was increased by about 25%. Extended x-ray absorption fine structure (EXAFS) measurements on frozen-hydrated leaf samples revealed that a large proportion of Cu in T. caerulescens is bound by sulfur ligands. This is in contrast to the known binding environment of cadmium and zinc in the same species, which is dominated by oxygen ligands. Clearly, hyperaccumulators detoxify hyperaccumulated metals differently compared with nonaccumulated metals. Furthermore, strong features in the Cu-EXAFS spectra ascribed to metal-metal contributions were found, in particular in the Cu-resistant specimens. Some of these features may be due to Cu binding to metallothioneins, but a larger proportion seems to result from biomineralization, most likely Cu(II) oxalate and Cu(II) oxides. Additional contributions in the EXAFS spectra indicate complexation of Cu(II) by the nonproteogenic amino acid nicotianamine, which has a very high affinity for Cu(II) as further characterized here.
机译：镉/锌超蓄积藻对铜（Cu）毒性敏感，这对于混合污染土壤的植物修复是一个问题。在10μmCu 2 + 下生长的淡色锥虫中的Cu含量保持在非累积量范围（<50 ppm），大多数个体对Cu的敏感性与相关的非累积性Thlaspi fendleri一样。显然，过度积累和金属电阻是高度金属特异性的。铜诱导的对光合作用的抑制作用遵循“太阳反应”类型的破坏，同时抑制了光系统II反应中心的电荷分离和水分解复合物。淡色锥虫的一些个体对铜的抗性更高。与对铜敏感的个体相比，它们从抑制中恢复得更快，至少部分地通过增强叶绿素-蛋白质复合物的修复而不能通过排除，因为排除了芽，因为它们芽中的铜含量增加了约25％。在冷冻水合叶片样品上进行的扩展X射线吸收精细结构（EXAFS）测量表明，芥蓝中的大部分Cu被硫配体结合。这与相同物种中已知的镉和锌的结合环境形成对比，后者以氧配体为主。显然，与非累积金属相比，高累积物对高累积金属的排毒方式有所不同。此外，在归因于金属-金属贡献的Cu-EXAFS光谱中发现了强大的功能，特别是在耐Cu的样品中。这些特征中的一些可能是由于Cu与金属硫蛋白的结合所致，但似乎更大的比例似乎是由于生物矿化产生的，最有可能是草酸Cu（II）和Cu（II）氧化物。 EXAFS光谱中的其他贡献表明非蛋白质氨基酸烟碱胺可与Cu（II）络合，这对Cu（II）具有非常高的亲和力，如本文进一步所述。

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