Glutathione reductase activity and isoforms in leaves and roots of wheat plants subjected to cadmium stress

YANNARELLI, GUSTAVO G.; FERNÁNDEZ-ALVAREZ, ANA J.; SANTA-CRUZ, DIEGO M.; TOMARO, MARÍA L.

PHYTOCHEMISTRY

Elsevier

Lugar: Amsterdam; Año: 2007 vol. 68 p. 505 - 512

0031-9422

The behavior of glutathione reductase (GR, EC 1.6.4.2) activity and isoforms were analyzed in wheat (Triticum aestivum L.) leaves and roots exposed to a chronic treatment with a toxic cadmium (Cd) concentration. A significant growth inhibition (up to 55%) was found in wheat leaves at 7, 14 and 21 days, whereas roots were affected (51%) only after three weeks. Wheat plants grown in the presence of 100 µM Cd showed a time-dependent accumulation of this metal, being Cd concentration 10-fold higher in roots than in leaves. Nevertheless, lipid peroxidation was augmented in leaves all over the experiment, but not in roots until 21 days. Cadmium treatment altered neither the GR activity nor the isoform pattern in the leaves. However, GR activity increased 111 and 200% in roots at 7 and 14 days, respectively, returning to control values after 21 days. Three GR isoforms were found in roots of control and treated plants, two of them were enhanced by Cd treatment at 7 and 14 days, as assessed by activity staining on native gels. These changes in the isoform pattern modified the global kinetic properties of GR decreasing significantly (2.5-fold) the Michaelis constant (Km) value for oxidized glutathione. The isozymes induction was not associated to an enhancement of GR mRNA and protein expression, indicating that a post-translational modification could occur. Our data demonstrated that the up-regulation of GR activity by the induction of distinctive isoforms occurs as a defensive mechanism against Cd-generated oxidative stress in roots.