期刊
ENVIRONMENTAL AND EXPERIMENTAL BOTANY
卷 131, 期 -, 页码 19-31出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.envexpbot.2016.06.009
关键词
Zn2+ preconditioning; Zinc accumulation; Cadmium accumulation; Glutathione; Phytochelatins; Polyphosphates
资金
- CONACyT-Mexico [239930]
To determine the interplay between zinc and cadmium on the heavy metal accumulation capacity of Euglena gracilis, the effects of increasing Zn2+ concentrations (13-65.4 ppm or 200-1,000 mu M) were analyzed on growth; O-2 consumption; photosynthesis; ascorbate (APX) and glutathione peroxidase (GPX) activities; chlorophyll a and b (Chl a+b) content; essential metals, thiol-metabolites and polyphosphates (polyPs) levels; as well as on zinc and cadmium accumulation capacities. Control cells (EgZn(20); grown with 20 mu M Zn2+) showed a half-maximal inhibition of growth (IC50) of 1,700 mu M by external Zn2+. O-2 consumption, and APX and GPX activities were unaltered by Zn2+ treatments. Cells cultured with 500 or 1,000 mu M Zn2+ showed photosynthesis impairment but normal Chl a+b contents. Zn2+ preconditioning increased the intracellular contents of zinc (25-54 times) and calcium (2-27 times); thiol-metabolites and polyPs were only marginally altered. The growth of cells preconditioned to 400 mu M Zn2+ (EgZn(400) cells) was less susceptible to Cd2+ than that of EgZn(20) cells, although no differences in photosynthesis and respiration were observed. In cells chronically grown with Zn2+, the cadmium accumulation capacity was unchanged or slightly increased in the same culture media with high Zn2+, and increased by 42-90% in media with 20 mu M Zn2+. The thiol-metabolites increased at similar levels in both EgZn(20) and EgZn(400) cells when further exposed to 200 mu M Cd2+ and polyPs were at high levels independently of Zn2+ or Cd2+ treatments. It was concluded that chronic exposure to high Zn2+ (1) was innocuous for E. gracilis at concentrations lower than 0.5 mM and (2) promoted protection against Cd2+ toxicity and increased cadmium accumulation; and (3) these zinc effects involved GSH and polyPs metabolism and were associated with high intracellular zinc contents. (C) 2016 Elsevier B.V. All rights reserved.
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