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Cadmium accumulation in the chloroplast of Euglena gracilis
Author(s) -
MendozaCozatl David,
Devars Silvia,
LozaTavera Herminia,
MorenoSánchez Rafael
Publication year - 2002
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2002.1150214.x
Subject(s) - chloroplast , euglena gracilis , cytosol , cysteine , biochemistry , glutathione , cadmium , intracellular , biology , thiol , chemistry , microbiology and biotechnology , enzyme , gene , organic chemistry
Intracellular distribution of Cd, cysteine, glutathione, and Cd‐induced thiol peptides in Euglena gracilis cultured under photoheterotrophic conditions was studied. After 3 days of culture with 0.2 m M CdCl 2 , 62% of the Cd accumulated by cells was equally distributed between the cytosolic and chloroplastic fractions. However, after 8 days, metal content increased in the crude chloroplastic fraction to 40% of total and decreased to 19% in the cytosol; in Percoll‐purified chloroplasts the estimated content of Cd raised to 62%. Accumulation of Cd in chloroplasts could be mediated by a transporter of free Cd 2+ , since uptake of added CdCl 2 in isolated chloroplasts exhibited a hyperbolic type of kinetics with a K m of 57 µ M and V max of 3.7 nmol (mg protein) −1 min −1 . The contents of cysteine and glutathione markedly increased in both chloroplasts (7–19 times) and cytosol (4–9 times) by exposure to Cd 2+ , although they were always higher in the cytosol. Thiol‐containing peptides induced by Cd were mainly located in the cytosol after 3 days, and in the chloroplasts after 8 days of culture. The data suggested that Cd was compartmentalized into chloroplasts in a process that may involve the transport of free Cd and the participation of thiol‐peptides.