Effects of Metal Combinations on the Production of Phytochelatins and Glutathione by the Marine Diatom Phaeodactylum tricornutum

Abstract

Copper, Cd and Zn can be found at elevated concentrations in contaminated estuarine and coastal waters and have potential toxic effects on phytoplankton species. In this study, the effects of these metals on the intracellular production of the polypeptides phytochelatin and glutathione by the marine diatom Phaeodactylum tricornutum were examined in laboratory cultures. Single additions of Cu and Cd (0.4 microM Cu2 and 0.45 microM Cd2+) to the culture medium induced the production of short-chained phytochelatins ((gamma-Glu-Cys)n-Gly where n = 2-5), whereas a single addition of Zn (2.2 microM Zn2+) did not stimulate phytochelatin production. Combination of Zn with Cu resulted in a similar phytochelatin production compared with a single Cu addition. The simultaneous exposure to Zn and Cd led to an antagonistic effect on phytochelatin production, which was probably caused by metal competition for cellular binding sites. Glutathione concentrations were affected only upon exposure to Cd (85% increase) or the combination of Cd with Zn (65% decrease), relative to the control experiment. Ratios of phytochelatins to glutathione indicated a pronounced metal stress in response to exposures to Cu or Cd combined with Zn. This study indicates that variabilities in phytochelatin and glutathione production in the field can be explained in part by metal competition for cellular binding sites.

Copper Uptake, Intracellular Localization, and Speciation in Marine Microalgae Measured by Synchrotron Radiation X-ray Fluorescence and Absorption Microspectroscopy

“…10,31,35 The intracellular synthesis of metal binding proteins also occurs, such as phytochelatins (high in cysteine residues rich in sulfur). 8,[36][37][38][39][40][41] Enzymes capable of scavenging damaging reactive oxygen species, e.g. catalase, superoxide dismutase, can also be altered when cells are exposed to Cu.…”

Changes in phytochelatins and their biosynthetic intermediates in red spruce (Picea rubens Sarg.) cell suspension cultures under cadmium and zinc stress

“…The response of plant cell cultures in vitro avoids this complexity and allows us to study the effects of a specific metal. Even though studies are available for the PCs and their precursor metabolites in cell cultures of tomato (Scheller et al 1987), Silene vulgaris (Leopold et al 1999), marine green alga (Hirata et al 2001), sunflower (Gallego et al 2005), cucumber (Gzyl and Gwó źdź 2005), a marine diatom (Kawakami et al 2006), and a perennial shrub (Israr et al 2006), paucity of information is available for tree species under Cd and Zn toxicity. Therefore, the present investigation is mainly focused to evaluate the changes in non-protein thiols and free amino acids associated with Cd or Zn stress in red spruce (Picea rubens Sarg.)…”

Phytochelatins in the Diatom Phaeodactylum tricornutum Bohlin: An Evaluation of their Use as Biomarkers of Metal Exposure in Marine Waters

“…It has been reported (Wei et al 2003;Le Faucheur et al 2005) that the PC production can be not only related to the exposure to a single metal, but can be the result of antagonistic and synergistic effects of multiple metals. According to Kawakami et al (2006a), Zn did not affect the amount of PC induced in P. tricornutum cells by Cu, whereas it had an antagonistic effect on the induction of PC by Cd. So, the inability of Zn to affect the PC response to Cu in P. tricornutum supports the hypothesis that the induction of PC in this alga incubated in our seawater samples was triggered by copper, although a contribution of Cd in station 6, which exhibited the highest PC response, cannot be excluded.…”

“…In all the assayed samples, Zn and Cu were higher than in the control seawater. For as regards Zn, it has been reported (Morelli and Scarano 2001;Kawakami et al 2006a) that cells of P. tricornutum exposed to Zn at 1 lM did not exhibit PC synthesis in short-term experiments, so the hypothesis could be made that copper is mainly responsible for the response. It has been reported (Wei et al 2003;Le Faucheur et al 2005) that the PC production can be not only related to the exposure to a single metal, but can be the result of antagonistic and synergistic effects of multiple metals.…”