ALUMINUM INDUCES OXIDATIVE STRESS GENES IN ARABIDOPSIS-THALIANA

Changes in gene expression induced by toxic levels of Al were characte rized to investigate the nature of Al stress. A cDNA library was const ructed from Arabidopsis thaliana seedlings treated with Al for 2 h. We identified five cDNA clones that showed a transient induction of thei r mRNA levels, four cDNA clones that showed a longer induction period, and two down-regulated genes. Expression of the four long-term-induce d genes remained at elevated levels for at least 48 h. The genes encod ed peroxidase, glutathione-S-transferase, blue copper-binding protein, and a protein homologous to the reticuline:oxygen oxidoreductase enzy me. Three of these genes are known to be induced by oxidative stresses and the fourth is induced by pathogen treatment. Another oxidative st ress gene, superoxide dismutase, and a gene for Bowman-Birk protease i nhibitor were also induced by Al in A. thaliana. These results suggest ed that Al treatment of Arabidopsis induces oxidative stress. In confi rmation of this hypothesis, three of four genes induced by Al stress i n A. thaliana were also shown to be induced by ozone. Our results demo nstrate that oxidative stress is an important component of the plant's reaction to toxic levels of Al.