Sulfur metabolism: different tolerances of two aquatic macrophytes exposed to arsenic.
The toxicity of arsenic (As) and the mechanisms of response to this pollutant were analyzed in two aquatic plant species, one sensitive and one tolerant to the pollutant, Salvinia minima and Lemna gibba, respectively. The plants, grown in nutrient solution at pH 6.5, were exposed to As concentrations of 0.0 and 1.0mgL(-1) for 3 days. Both species accumulated As in their tissues, which resulted in increases in H2O2 production. L. gibba accumulated eleven times more As than S. minima. However, L. gibba was more tolerant, as shown by the absence of cell membrane damage and, despite greater accumulation, smaller growth reduction than S. minima. Indeed, the index of tolerance to As was twenty percent higher in L. gibba than in S. minima, which most likely results from the presence of a more efficient defense system. This defense system in L. gibba is most likely based on sulfate absorption, assimilation and metabolism. L. gibba showed an increase in sulfate absorption and adenosine-5'-triphosphate (ATP) sulfurylase activity (the first enzyme of the inorganic sulfate assimilation pathway) following exposure to As. Consequently, the plant produced greater concentrations of sulfur-containing compounds that are involved in cellular detoxification, such as glutathione and non-protein thiols, and demonstrated greater enzymatic activity of γ-glutamylcysteine synthetase, glutathione S-transferase and glutathione reductase. Therefore, the plant׳s ability to increase absorption, assimilation and metabolism of sulfur are key steps for tolerance to oxidative stress triggered by metals.
Department of Plant Biology, Federal University of Viçosa, Viçosa, Minas Gerais (MG) 36570-000, Brazil.
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Leão
Department of General Biology, Federal University of Viçosa, Viçosa, Minas Gerais (MG), 36570-000, Brazil. Electronic address: jalves@ufv.br.
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JA
Oliveira
Department of Plant Biology, Federal University of Viçosa, Viçosa, Minas Gerais (MG) 36570-000, Brazil.
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Farnese
Department of Plant Biology, Federal University of Viçosa, Viçosa, Minas Gerais (MG) 36570-000, Brazil.
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Gusman
Department of Plant Biology, Federal University of Viçosa, Viçosa, Minas Gerais (MG) 36570-000, Brazil.
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Felipe
D029064:Araceae / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D001151:Arsenic / Q000633:toxicity*; D002734:Chlorophyll / Q000032:analysis; D005978:Glutathione / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D013438:Sulfhydryl Compounds / Q000032:analysis; D013455:Sulfur / Q000378:metabolism*; D064028:Tracheophyta / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D013438:Sulfhydryl Compounds; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D013455:Sulfur; D005978:Glutathione; D001151:Arsenic
Lemna gibba; Oxidative stress; Phytochelatins; Phytoremediation; Salvinia minima; Thiols