Glutathione peroxidase-like protein of Synechocystis PCC 6803 confers tolerance to oxidative and environmental stresses in transgenic Arabidopsis

Abstract

Glutathione peroxidase (GPX)-like proteins (GPX-1 and GPX-2) of Synechocystis PCC 6803 (S. PCC 6803) reduce unsaturated fatty acid hydroperoxides using NADPH, but not reduced glutathione (GSH), as an electron donor. Here, we generated transgenic Arabidopsis plants overexpressing S. PCC 6803 GPX-2 in the cytosol (AcGPX2) or chloroplasts (ApGPX2). The activities toward α-linolenic acid hydroperoxide in ApGPX2 and AcGPX2 plants were 6.5-11.5 and 8.2-16.3 nmol min-1 mg protein-1, respectively, while no activity (<0.1 nmol min-1 mg protein -1) was detected in the wild-type plants. Both transgenic lines (AcGPX2 and ApGPX2) showed enhanced tolerance to oxidative damage caused by treatment with H2O2 (10 mM), Fe ions (200 μM) or methylviologen (50 μM) and environmental stress conditions, such as chilling with high light intensity (4°C, 1000 μmol photons m-2 s -1), high salinity (100 mM NaCl) or drought. The degree of tolerance of the transgenic plants to all types of stress was correlated with the levels of lipid peroxide suppressed by the overexpression of S. PCC 6803 GPX-2. Under conditions of oxidative stress due to the H2O2 treatment, the NADPH/(NADP+ + NADPH) ratio in the transgenic plants was lower than that in the wild-type plants. The data reported here indicate that the expression of S. PCC 6803 GPX-2 contributes to the reduction in unsaturated fatty acid hydroperoxides using NADPH in situ under stress conditions in the transgenic plants. Copyright © Physiologia Plantarum 2006.