title: Time-dependent changes in antioxidative enzyme expression and photosynthetic activity of Chlamydomonas reinhardtii cells under acute exposure to cadmium and anthracene.
abstract: Heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) are present in the freshwater environment at concentrations that can be hazardous to the biota. Among HMs and PAHs, cadmium (Cd) and anthracene (ANT) are the most prevalent and toxic ones. The response of Chlamydomonas cells to Cd and ANT at concentrations that markedly reduced the growth of algal population was investigated in this study. At such concentrations, both cadmium and anthracene were recognized as oxidative stress inducers, since high concentration of H2O2 in treated cultures was observed. Therefore, as a part of the "molecular phase" of the cell response to this stress, we examined the time-dependent expression of genes encoding the main antioxidative enzymes: superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), as well as the activity of these enzymes in cells, with special attention paid to chloroplastic and mitochondrial isoforms of SOD. To characterize the cell response at the "physiological level", we examined the photosynthetic activity of stressed cells via analysis of chlorophyll a fluorescence in vivo. In contrast to standard ecotoxicity studies in which the growth end-points are usually determined, herein we present time-dependent changes in algal cell response to Cd- and ANT-induced stress. The most significant effect(s) of the toxicants on photosynthetic activity was observed in the 6th hour, when strong depression of PI parameter value, an over 50 percent reduction of the active reaction center fraction (RC0) and a 3-fold increase in non-photochemical energy dissipation (DI0/RC) were noted. At the same time, the increase (up to 2.5-fold) in mRNA transcript of SOD and CAT genes, followed by the enhancement in the enzyme activity was observed. The high expression of the Msd 3 gene in treated Chlamydomonas cells probably complements the partial loss of chloroplast Fe-SOD and APX activity, while catalase and Mn-SOD 5 seem to be the major enzymes responsible for mitochondrion protection. The progressive increase in SOD and CAT activities seems to be involved in the recovery of photosynthesis within 12-24h after the application of the toxicants.
authors.affiliation: Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland. Electronic address: bioaak@ug.edu.pl.
authors.forename: Anna
authors.initials: A
authors.lastname: Aksmann
authors.affiliation: Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Pokora
authors.affiliation: Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Baścik-Remisiewicz
authors.affiliation: Department of Biochemistry, Medical University of Gdańsk, ul. Dębinki 1, 80-211 Gdańsk, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Dettlaff-Pokora
authors.affiliation: Department of Toxicology, Medical University of Gdańsk, Al. Gen. Hallera 107, 80-416 Gdańsk, Poland.
authors.forename: Bartosz
authors.initials: B
authors.lastname: Wielgomas
authors.affiliation: Department of Toxicology, Medical University of Gdańsk, Al. Gen. Hallera 107, 80-416 Gdańsk, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Dziadziuszko
authors.affiliation: Department of Plant Physiology and Biotechnology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Tukaj
mesh_terms: D000873:Anthracenes / Q000633:toxicity*; D000975:Antioxidants / Q000378:metabolism*; D060387:Ascorbate Peroxidases / Q000235:genetics / Q000378:metabolism; D002104:Cadmium / Q000633:toxicity*; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D004785:Environmental Pollutants / Q000633:toxicity*; D015870:Gene Expression / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D000873:Anthracenes; D000975:Antioxidants; D004785:Environmental Pollutants; D002104:Cadmium; D002734:Chlorophyll; D006861:Hydrogen Peroxide; D060387:Ascorbate Peroxidases; D002374:Catalase; D013482:Superoxide Dismutase; C034020:anthracene; D000077194:Chlorophyll A
keywords: Antioxidative enzymes; Chlamydomonas reinhardtii; Heavy metals; Hydrogen peroxide; Photosynthesis; Polycyclic aromatic hydrocarbons