Effects of nanomolar heavy metal concentrations on plants - comparison of biochemical&biophysical mechanisms of deficiency and sublethal toxicity under environmentally relevant conditions

在这个项目中，我们正在研究重金属毒性和缺乏的机制。我们开始在水生植物金鱼藻作为芽的模型，现在也从这个模型中获得的知识转移到作物植物。虽然已经提出了许多潜在的金属毒性引起的损伤机制，但其中大多数仅在相当人工的实验室条件下进行了研究。因此，我们正在评估在环境相关条件下金属诱导抑制的不同拟议机制的相关性，并将这些结果与在确定推定毒性机制的条件下获得的结果进行比较。我们选择铜、铬和镉作为模型重金属，加上砷作为有毒准金属，因为它们在污染环境中最常达到有毒浓度。我们在浓度、生物量/水体积比、光照和温度循环以及孵育时间方面应用环境相关条件。在过去39个月的项目中，重点是在一开始就分析阿梅尔谢恩湖样品的毒性，并通过系统地重新建立实验室的实地条件来确定其毒性的原因。随后系统地研究了铜、铬缺乏的机理以及砷、镉、铜的毒性。缺陷和毒性分析始于光合作用生物物理学的体内测量，活性氧的形成和氧交换，结合色素，淀粉和金属分析，目前正在继续分析细胞和亚细胞金属分布和形态，以及金属蛋白质组学。在未来几年，我们希望将从模型植物中获得的知识转移到农作物物种（主要是大豆和大麦），特别强调细胞和亚细胞金属分布（通过µXRF）和物种形成（通过µXANES），以及金属蛋白质组学和代谢组学。因此，我们想进一步研究如何在植物中金属缺乏和金属毒性的发病导致不同组织，不同的细胞室和不同的金属结合蛋白之间的金属分布的变化，而不是在许多组织中的一般浓度的变化。此外，我们希望克隆新的金属结合蛋白的基因，以进一步研究它们，并通过改变它们在作物和拟南芥中的表达来揭示它们的功能。这特别适用于在最佳和Cr缺乏条件下结合Cr的蛋白质，其中我们已经初步鉴定了这些蛋白质之一。

In this project we are investigating mechanisms of heavy metal toxicity and deficiency. We started this in the water plant Ceratophyllum demersum as a model for shoots, and now also transfer the knowledge obtained from this model to crop plants. While many potential mechanisms of metal toxicity induced damage have been proposed, most of them were investigated only under rather artificial laboratory conditions. Therefore, we are evaluating the relevance of different proposed mechanisms of metal-induced inhibition under environmentally relevant conditions and are comparing these results with those obtained under conditions that were used in identifying the putative toxicity mechanisms. We have chosen copper, chromium and cadmium as model heavy metals, plus arsenic as a toxic metalloid, because they most frequently reach toxic concentrations in contaminated environments. We apply environmentally relevant conditions in terms of concentrations, biomass/water volume ratios, light and temperature cycles and incubation times. In the past 39 months of the project, the focus was at the beginning on the analysis of the toxicity of lake Ammelshain samples and the determination of reasons for their toxicity by systematic re-constitution of field conditions in the laboratory. Afterwards we systematically investigated mechanisms of deficiency of copper and chromium, as well as toxicity of arsenic, cadmium and copper. The deficiency & toxicity analysis was started with in vivo measurements of photosynthesis biophysics, formation of reactive oxygen species and oxygen exchange, combined with pigment, starch and metal analyses, and is currently being continued by analysis of cellular and subcellular metal distribution and speciation, as well as metalloproteomics. In the coming years, we want to transfer the knowledge obtained with the model plant to crop species (mainly soybean and barley), with special emphasis on cellular and subcellular metal distribution (via µXRF) and speciation (via µXANES), as well as metalloproteomics and metabolomics. Thus we want to investigate further how in plants metal deficiency and onset of metal toxicity lead to a change in metal distribution between different tissues, different cellular compartments and different metal-binding proteins, rather than a general concentration change in many tissues. Further, we want to clone the genes of novel metal-binding proteins to further characterise them and reveal their function by modifying their expression in the crop species and Arabidopsis thaliana. This particularly applies the proteins that bind Cr under optimal and Cr-deficient conditions, where we already have a preliminary identification of one of these proteins.