Moller Ian M
Department of Plant Physiology, Lund University, Lund, Box 117, S-221 00 Sweden;, Plant Biology and Biogeochemistry Department, Riso National Laboratory, Building 301, P.O. Box 49, DK-4000 Roskilde, Denmark; e-mail:
Annu Rev Plant Physiol Plant Mol Biol. 2001 Jun;52:561-591. doi: 10.1146/annurev.arplant.52.1.561.
The production of reactive oxygen species (ROS), such as O2- and H2O2, is an unavoidable consequence of aerobic metabolism. In plant cells the mitochondrial electron transport chain (ETC) is a major site of ROS production. In addition to complexes I-IV, the plant mitochondrial ETC contains a non-proton-pumping alternative oxidase as well as two rotenone-insensitive, non-proton-pumping NAD(P)H dehydrogenases on each side of the inner membrane: NDex on the outer surface and NDin on the inner surface. Because of their dependence on Ca2+, the two NDex may be active only when the plant cell is stressed. Complex I is the main enzyme oxidizing NADH under normal conditions and is also a major site of ROS production, together with complex III. The alternative oxidase and possibly NDin(NADH) function to limit mitochondrial ROS production by keeping the ETC relatively oxidized. Several enzymes are found in the matrix that, together with small antioxidants such as glutathione, help remove ROS. The antioxidants are kept in a reduced state by matrix NADPH produced by NADP-isocitrate dehydrogenase and non-proton-pumping transhydrogenase activities. When these defenses are overwhelmed, as occurs during both biotic and abiotic stress, the mitochondria are damaged by oxidative stress.
活性氧（ROS）如超氧阴离子（O2-）和过氧化氢（H2O2）的产生是有氧代谢不可避免的结果。在植物细胞中，线粒体电子传递链（ETC）是ROS产生的主要部位。除了复合体I-IV外，植物线粒体ETC还包含一种不质子泵的交替氧化酶以及内膜两侧各两个对鱼藤酮不敏感、不质子泵的NAD(P)H脱氢酶：外表面的NDex和内表面的NDin。由于它们对Ca2+的依赖性，两个NDex可能仅在植物细胞受到胁迫时才具有活性。复合体I是正常条件下氧化NADH的主要酶，也是与复合体III一起产生ROS的主要部位。交替氧化酶以及可能的NDin（NADH）通过使ETC保持相对氧化状态来限制线粒体ROS的产生。在基质中发现了几种酶，它们与谷胱甘肽等小抗氧化剂一起有助于清除ROS。抗氧化剂通过NADP-异柠檬酸脱氢酶和不质子泵转氢酶活性产生的基质NADPH保持还原状态。当这些防御机制不堪重负时，如在生物和非生物胁迫期间发生的情况，线粒体就会受到氧化应激的损害。
