Iron transport, storage and metabolism in the model seaweed Ectocarpus siliculosus
Final Report Abstract
Genetic data suggest that Ectocarpus may use a stategy I approach for iron uptake. Short-term radio-iron uptake studies verified that iron is taken up by Ectocarpus in a time and concentration dependent manner consistent with an active transport process. Based on inhibitor and other studies in Tetraselmis suecica it appears that a reductiveoxidative pathway such as that found in yeast and the green alga Chlamydomonas reinhardtii is likely. In the Coccolithophore Emiliania huxleyi. Short term iron uptake is an active transport process. Based on inhibitor studies it appears that iron is taken up directly as Fe(III). Upon long term exposure to 57Fe two metabolites have been identified in Ectocarpus using a combination of Mössbauer and XAS spectroscopies. These include an iron-sulfur cluster accounting for approximately 26% of the total intracellular iron pool and a second component with spectra typical of a (Fe3+O6) system with parameters similar to the amorphous phosphorus-rich mineral core of bacterial and plant ferritins. This iron metabolite accounts for approximately 74% of the cellular iron pool and suggests that Ectocarpus contains a non-ferritin but mineral based iron storage pool which is, however, not located in the plastides. Tetraselmis displays similar iron metabolites as Ectocarpus whereas E. huxleyi exhibits solely a phosphorus-rich iron mineral core. NFS spectra of Ectocarpus and Tetraselmis differ from that of E.huxleyi. In summary iron transport mechanisms as well as iron storage strategies in display considerable differences in various algae. Short term iron uptake processes cannot be observed by classical transmission Mössbauer spectroscopy in organisms exhibiting very low overall iron uptake. Synchrotron X-ray microprobes appear to offer the best combination of analytical sensitivity and spatial resolution while imparting the least radiation damage to the sample. We could show that it is potentially possible to examine the subcellular distribution of iron in single cells. In addition, this technique will allow to differentiate iron accumulation patterns between different cell types and filament patterns (and to establish spatial correlations with the abundance of other biologically relevant elements). Further, significant progress (especially with regard to µm-scale resolution) can be expected from the inauguration of brilliant, new synchrotron radiation sources such as the PETRA III storage ring at DESY in Hamburg. The P01-NRS beamline within the PETRA III-system is based on the very high brilliance and beam stability of PETRA III and unique sub-micro focusing devices will exhibit, for the first time in the world, variable focus diameters down to about 1 micron at 14.4 keV allowing a NRS scanning of single cells. For comparison, microfocusing at the ESRF-NRS beam line has a resolution limit of 10-20µm.
Publications
- A multidisciplinary study of iron transport and storage in the marine green alga Tetraselmis suecica. J Inorg Biochem. 2012 Nov;116:188-94. Epub 2012 Jun 19
(See online at https://doi.org/10.1016/j.jinorgbio.2012.06.009) - Atypical iron storage in marine brown algae: a multidisciplinary study of iron transport and storage in Ectocarpus siliculosus. J Exp Bot. 2012 Sep;63(16):5763-72. Epub 2012 Sep 3
L. Böttger, E. Miller, C. Andresen, B.F. Matzanke, F. Küpper, C. Carrano
(See online at https://doi.org/10.1093/jxb/ers225) - hydoxydecylidene)-5-(2-hydroxyethyl)pyrrolidine-2,4dione:Novel tetramic acid degradation products of homoserine lactone bacterial quorum sensing molecules. J Inorg Biochem. 2012 Feb;107(1):96-103. Epub 2011 Oct 29
A.A. Romano, T. Hahn, C. Lowery, K.D. Janda, L. Böttger, B.F. Matzanke, C. Carrano
- Iron transport and storage in the coccolithophore Emiliania huxleyi. Metallomics. 2012 Nov 24;4(11):1160-6. Epub 2012 Sep 26
A. Hartnett,, L.H. Böttger, B.F. Matzanke, C. Carrano
(See online at https://doi.org/10.1039/c2mt20144e)
