Protection against photooxidative injury of tobacco leaves by 2-alkenal reductase. Detoxication of lipid peroxide-derived reactive carbonyls.
Degradation of lipid peroxides leads to the formation of cytotoxic 2-alkenals and oxenes (collectively designated reactive carbonyls). The novel NADPH-dependent oxidoreductase 2-alkenal reductase (AER; EC 1.3.1.74) from Arabidopsis (Arabidopsis thaliana), which is encoded by the gene At5g16970, catalyzes the reduction of the alpha,beta-unsaturated bond of reactive carbonyls, and hence is presumed to function in antioxidative defense in plants. Here we show that Arabidopsis AER (At-AER) has a broad substrate spectrum to biologically relevant reactive carbonyls. Besides 2-alkenals, the enzyme recognized as substrates the lipid peroxide-derived oxenes 9-oxo-octadeca-(10E),(12Z)-dienoic acid and 13-oxo-octadeca-(9E),(11Z)-dienoic acid, as well as the potent genotoxin 4-oxo-(2E)-nonenal, altogether suggesting AER has a key role in the detoxification of reactive carbonyls. To validate this conclusion by in vivo studies, transgenic tobacco (Nicotiana tabacum) plants that had 100- to 250-fold higher AER activity levels than control plants were generated. The engineered plants exhibited significantly less damage from either (1) the exogenously administered 4-hydroxy-(2E)-nonenal, (2) treatment with methyl viologen plus light, or (3) intense light. We further show that the At-AER protein fused with the Aequorea victoria green fluorescent protein localizes in cytosol and the nucleus in Bright-Yellow 2 cells. These results indicate that reactive carbonyls mediate photooxidative injury in leaf cells, and At-AER in the cytosol protects the cells by reducing the alpha,beta-unsaturated bond of the photoproduced reactive carbonyls.
Mano
Jun'ichi
J
Science Research Center , Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8515, Japan. mano@yamaguchi-u.ac.jp
Belles-Boix
Enric
E
Babiychuk
Elena
E
Inzé
Dirk
D
Torii
Yoshimitsu
Y
Hiraoka
Eiji
E
Takimoto
Koichi
K
Slooten
Luit
L
Asada
Kozi
K
Kushnir
Sergei
S
D001483:Base Sequence; D018744:DNA, Plant / Q000235:genetics; D007700:Kinetics; D008054:Lipid Peroxides / Q000378:metabolism; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D018462:Photobiology; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified; D017382:Reactive Oxygen Species / Q000378:metabolism; D013379:Substrate Specificity; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects
D018744:DNA, Plant; D008054:Lipid Peroxides; D017382:Reactive Oxygen Species; D010088:Oxidoreductases; C040723:alpha,beta-ketoalkene reductase