Contribution of the Detoxication of Reactive Aldehydes to Protection against Environmental Stress in Plants

细胞的抗氧化防御在植物抵御环境胁迫中起着至关重要的作用。我们最近在拟南芥中发现了一种新的2-烯醛还原酶（AER），它可以催化2-烯醛的α，β-不饱和键的还原，2-烯醛是由脂质过氧化物产生的强效细胞毒素。在本研究中，我们旨在验证脂质过氧化物衍生的2-烯醛（活性醛）可能参与环境胁迫诱导的植物损伤。当拟南芥叶片受到氧化胁迫时，巴豆醛和丙烯醛的产量增加。与氧化应激动物细胞不同，丙二醛不是主要产物。因此，植物中脂质过氧化物的代谢与动物不同。丙烯醛和巴豆醛对离体叶绿体的co_2固定有较强的抑制作用，但对光合电子传递活性没有影响。因此，活性醛特异性地抑制卡尔文循环活性，引起光抑制。我们构建了三个转基因烟草品系，过量产生拟南芥AER。转基因植株对甲基紫素和强光表现出更高的耐受性，表明AER保护叶片细胞免受氧化胁迫。这些结果表明，活性醛参与了光氧化损伤，AER在叶片抗氧化防御中发挥了重要作用。

Antioxidative defense in cells is of critical importance in the plant protection against environmental stress.We have recently identified in Arabidopsis thaliana a novel enzyme 2-alkenal reductase (AER) that catalyzes the reduction of the α,β-unsaturated bond of 2-alkenals, potent cytotoxins produced from lipid peroxides. In this study, we aimed at verifying a possible involvement of the lipid peroxide-derived 2-alkenals (reactive aldehydes) in the environmental stress-induced damages of plants. When A.thaliana leaves were oxidatively stressed, production of crotonaldehyde and acrolein was enhanced. Unlike the case for oxidatively stressed animal cells, malondialdehyde was not a major product. Thus, the metabolism of lipid peroxides in plants differs from that in animals. Acrolein and crotonaldehyde inhibited CO_2-fixation in isolated chloroplasts strongly, but did not affect the photosynthetic electron transport activity. Thus the reactive aldehydes specifically inhibit Calvin cycle activity, causing photoinhibition. We constructed three transgenic tobacco lines that over produced the A.thaliana AER.The transgenic plants exhibited higher tolerance to methyl viologen and to intense light, indicating that AER protected leaf cells from oxidative stress. These results altogether indicate the involvement of the reactive aldehydes in the photooxidative injury and the significant contribution of AER to the antioxidative defense in leaves.