Photo-oxidative stress in a xanthophyll-deficient mutant of Chlamydomonas
Photo-oxidative stress in a xanthophyll-deficient mutant of Chlamydomonas
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DOI：
10.1074/jbc.m312919200
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发表时间：
2004-02-20
影响因子：
4.8
通讯作者：
Niyogi, KK
中科院分区：
文献类型：
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作者：
Baroli, I;Gutman, BL;Niyogi, KK
当光合作用有机体吸收的光能与光合作用可利用的光能之间存在不平衡时，光氧化应激会损害色素、蛋白质、脂质和核酸。在这项工作中，我们比较了莱茵衣藻野生型和叶黄素缺乏突变体对高光的响应。野生型衣藻细胞在从弱光条件下转移后能够适应高强度的光。相反，npq1lor1双突变体在叶绿体中缺乏保护性叶黄素(玉米黄素和叶黄素)，随着类囊体膜蛋白-色素复合体的破坏，活性氧和膜脂过氧化产物的积累，逐渐丧失了活力和光合作用能力。低氧分压部分挽救了活性的丧失，表明突变体对光胁迫的高度敏感性是由叶绿体中产生的活性氧引起的。在生长介质中添加有机碳源并不能防止细胞死亡，这表明除了光合作用之外，光氧化损伤还可以针对其他必要的叶绿体过程。根据突变体对外源促氧化剂的不同敏感性，我们推测npq1lor1在光胁迫下产生的活性氧可能是单线态氧和/或超氧化物，而不是过氧化氢。Npq1lor1的漂白表型不是由于对光系统II的光损伤增强，而是由于光氧化产物在叶绿体膜上积累的较少局部化现象。
When there is an imbalance between the light energy absorbed by a photosynthetic organism and that which can be utilized in photosynthesis, photo-oxidative stress can damage pigments, proteins, lipids, and nucleic acids. In this work we compared the wild type and a xanthophyll-deficient mutant of Chlamydomonas reinhardtii in their response to high amounts of light. Wildtype Chlamydomonas cells were able to acclimate to high amounts of light following transfer from low light conditions. In contrast, the npq1 lor1 double mutant, which lacks protective xanthophylls (zeaxanthin and lutein) in the chloroplast, progressively lost viability and photosynthetic capacity along with destruction of thylakoid membrane protein-pigment complexes and accumulation of reactive oxygen species and membrane lipid peroxides. Loss of viability was partially rescued by lowered oxygen tension, suggesting that the high sensitivity of the mutant to light stress is caused by the production of reactive oxygen species in the chloroplast. Cell death was not prevented by the addition of an organic carbon source to the growth medium, demonstrating that the photo-oxidative damage can target other essential chloroplast processes besides photosynthesis. From the differential sensitivity of the mutant to exogenously added pro-oxidants, we infer that the reactive oxygen species produced during light stress in npq1 lor1 may be singlet oxygen and/or superoxide but not hydrogen peroxide. The bleaching phenotype of npq1 lor1 was not due to enhanced photodamage to photosystem II but rather to a less localized phenomenon of accumulation of photo-oxidation products in chloroplast membranes.