Enhancement of stress tolerance in transgenic tobacco plants overexpressing Chlamydomonas glutathione peroxidase in chloroplasts or cytosol.
To evaluate the physiological potential of the defense system against hydroperoxidation of membrane-lipid components caused by environmental stresses in higher plants, we generated transgenic tobacco plants expressing a glutathione peroxidase (GPX)-like protein in the cytosol (TcGPX) or chloroplasts (TpGPX). The activities toward alpha-linolenic acid hydroperoxide in TcGPX and TpGPX plants were 47.5-75.3 and 32.7-42.1 nM min(-1) mg(-1) protein, respectively, while no activity was detected in wild-type plants. The transgenic plants showed increased tolerance to oxidative stress caused by application of methylviologen (MV: 50 microM) under moderate light intensity (200 micro E m(-2) sec(-1)), chilling stress under high light intensity (4 degrees C, 1000 microE m(-2) sec(-1)), or salt stress (250 mM NaCl). Under these stresses, the lipid hydroperoxidation (the production of malondialdehyde (MDA)) of the leaves of TcGPX and TpGPX plants was clearly suppressed compared with that of wild-type plants. Furthermore, the capacity of the photosynthetic and antioxidative systems in the transgenic plants remained higher than those of wild-type plants under chilling or salt stress. These results clearly indicate that a high level of GPX-like protein in tobacco plants functions to remove unsaturated fatty acid hydroperoxides generated in cellular membranes under stress conditions, leading to the maintenance of membrane integrity and increased tolerance to oxidative stress caused by various stress conditions.
Yoshimura
Kazuya
K
Advanced Life Science, Graduate School, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
Miyao
Kazuhiro
K
Gaber
Ahmed
A
Takeda
Toru
T
Kanaboshi
Haruo
H
Miyasaka
Hitoshi
H
Shigeoka
Shigeru
S
D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D002696:Chlamydomonas / Q000201:enzymology*; D002736:Chloroplasts / Q000201:enzymology; D003080:Cold Temperature; D003593:Cytoplasm / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism*; D008027:Light; D015227:Lipid Peroxidation / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D010269:Paraquat / Q000494:pharmacology; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D017382:Reactive Oxygen Species; D012965:Sodium Chloride / Q000494:pharmacology; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*
D020418:Algal Proteins; D017382:Reactive Oxygen Species; D012965:Sodium Chloride; D005979:Glutathione Peroxidase; D010269:Paraquat