title: Rescue of heavy metal effects on cell physiology of the algal model system Micrasterias by divalent ions.
abstract: Recent studies have shown that metals such as copper, zinc, aluminum, cadmium, chromium, iron and lead cause severe dose-dependent disturbances in growth, morphogenesis, photosynthetic and respiratory activity as well as on ultrastructure and function of organelles in the algal model system Micrasterias denticulata (Volland et al., 2011, 2012; Andosch et al., 2012). In the present investigation we focus on amelioration of these adverse effects of cadmium, chromium and lead by supplying the cells with different antioxidants and essential micronutrients to obtain insight into metal uptake mechanisms and subcellular metal targets. This seems particularly interesting as Micrasterias is adapted to extremely low-concentrated, oligotrophic conditions in its natural bog environment. The divalent ions of iron, zinc and calcium were able to diminish the effects of the metals cadmium, chromium and lead on Micrasterias. Iron showed most ameliorating effects on cadmium and chromium in short- and long-term treatments and improved cell morphogenesis, ultrastructure, cell division rates and photosynthesis. Analytical transmission electron microscopic (TEM) methods (electron energy loss spectroscopy (EELS) and electron spectroscopic imaging (ESI)) revealed that chromium uptake was decreased when Micrasterias cells were pre-treated with iron, which resulted in no longer detectable intracellular chromium accumulations. Zinc rescued the detrimental effects of chromium on net-photosynthesis, respiration rates and electron transport in PS II. Calcium and gadolinium were able to almost completely compensate the inhibiting effects of lead and cadmium on cell morphogenesis after mitosis, respectively. These results indicate that cadmium is taken up by calcium and iron transporters, whereas chromium appears to enter the algae cells via iron and zinc carriers. It was shown that lead is not taken up into Micrasterias at all but exerts its adverse effects on cell growth by substituting cell wall bound calcium. The antioxidants salicylic acid, ascorbic acid and glutathione were not able to ameliorate any of the investigated metal effects on the green alga Micrasterias when added to the culture medium.
authors: Plant Physiology Division, Cell Biology Department, University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria.
authors: Stefanie
authors: S
authors: Volland
authors: Plant Physiology Division, Cell Biology Department, University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria.
authors: Elisabeth
authors: E
authors: Bayer
authors: Plant Physiology Division, Cell Biology Department, University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria.
authors: Verena
authors: V
authors: Baumgartner
authors: Plant Physiology Division, Cell Biology Department, University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria.
authors: Ancuela
authors: A
authors: Andosch
authors: Institute of Botany, Faculty of Biology, University of Innsbruck, Sternwartestraße 15, 6020 Innsbruck, Austria.
authors: Cornelius
authors: C
authors: Lütz
authors: Plant Physiology Division, Cell Biology Department, University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria.
authors: Evelyn
authors: E
authors: Sima
authors: Plant Physiology Division, Cell Biology Department, University of Salzburg, Hellbrunnerstraße 34, 5020 Salzburg, Austria. Electronic address: ursula.luetz-meindl@sbg.ac.at.
authors: Ursula
authors: U
authors: Lütz-Meindl
mesh_terms: D020418:Algal Proteins / Q000502:physiology*; D000975:Antioxidants / Q000502:physiology*; D001205:Ascorbic Acid; D005075:Biological Evolution; D027682:Cation Transport Proteins / Q000502:physiology*; D005978:Glutathione; D019216:Metals, Heavy / Q000378:metabolism*; D058120:Micrasterias / Q000378:metabolism* / Q000648:ultrastructure; D020156:Salicylic Acid
chemical_list: D020418:Algal Proteins; D000975:Antioxidants; D027682:Cation Transport Proteins; D019216:Metals, Heavy; D005978:Glutathione; D020156:Salicylic Acid; D001205:Ascorbic Acid
keywords: AA; Amelioration of metal effects; Antioxidants; Ca; Cd; Cr; EELS; ESI; Fe; Fe-EDTA; Fe-ethylenediaminetetraacetic acid; GSH; Gd; Green algae; HPLC; Heavy metals; Ions; PS II; Pb; ROS; SA; TEM; UPLC-MS; Zn; ascorbic acid; cadmium; calcium; chromium; electron energy loss spectroscopy; electron spectroscopic imaging; gadolinium; glutathione; high-performance liquid chromatography; iron; lead; photosystem II; reactive oxygen species; salicylic acid; transmission electron microscopy; ultra performance liquid chromatography–mass spectrometry; zinc