5.5.2020

Metal metabolism in plants - from the whole-plant to the molecular level with a focus on biochemistry and biophysics

Hendrik Küpper

(Department of Plant Biophysics & Biochemistry, Institute of Plant Molecular Biology, Biology Centre, Czech Academy of Sciences, Czech Republic.

Department of Experimental Plant Biology, Faculty of Science, University of South Bohemia, Czech Republic)

Many trace metals are essential micronutrients, and all of them can become toxic when they become bioavailable in excess. Bioavailable concentrations of trace metals in the environment and agriculture are vastly different (with natural and anthropogenic causes) in various habitats, ranging from deficient to toxic levels. Therefore, research has focused on response to trace metals by photosynthetic organisms (higher plants, algae and bacteria) in terms of uptake, transport, sequestration, speciation, deficiency, toxicity and detoxification. Most early and even numerous recent studies have used environmentally not relevant conditions. This applies in particular to extremely high, environmentally and agriculturally not relevant concentrations of toxic metals and metalloids. Further, individual processes often were not mechanistically interconnected, so that causes and consequences of metal(loid) effects remained unclear. In our work, we focussed on the analysis of metal metabolism under environmentally relevant conditions in terms of concentrations, with a simulation of natural light- and temperature cycles. We used a combination of biophysical and biochemical methods for measurements in vivo (photosynthesis measurements, formation of reactive oxygen species, metal transport), in situ (e.g. quantitative (sub)cellular distribution and speciation of metals, mRNA levels) as well as on isolated proteins (for identification and characterization of metalloproteins) and metabolites (metabolomics).

The combination of these methods with different model organisms, solved questions about the interdependence of different mechanisms that diminish the primary productivity of these organisms during sublethal deficiency and toxicizy by As, Cd, Cu, Ni and Zn. It could be shown that metal(loid) (As, Cd, Cu) concentrations that were previously considered as not having any effect actually are toxic to the plants, and with a different sequence of events than observed at very high concentrations. Examples of interactions between metal metabolism and pathogens were found for Ni and Zn. Using metalloproteomics via HPLC-ICPMS of protein extracts from stressed plants and bacteria, changes in target sites of metal binding to proteins from deficient to toxic concentrations could be analysed. X-ray absorption (XANES) and fluorescence (µXRF) provided information about metal(loid) speciation and distribution. The combination of techniques clearly showed metal(loid)-induced changes in the metabolism, already at very low concentrations, and allowed for new insights into the mechanisms of sublethal toxicity of As, Cd and Cu. Finally, the comparison of the vastly different model organisms and metal(loid)s has shown a lot of similarities, but also important differences between specific organisms and metal(loid)s.

Related papers

• Andresen E, Peiter E, Küpper H (2018) Trace metal metabolism in plants. Journal of Experimental Botany 69, 909-954
• Küpper H, Andresen E (2016) Mechanisms of metal toxicity in plants. Metallomics 8, 269-285

List of all papers HERE.

Invitation to the talk HERE.