The role of photorespiration in redox and energy balance of photosynthetic plant cells:: A study with a barley mutant deficient in glycine decarboxylase
The role of photorespiration in redox and energy balance of photosynthetic plant cells:: A study with a barley mutant deficient in glycine decarboxylase
复制标题
DOI：
10.1034/j.1399-3054.2001.1110402.x
复制
发表时间：
2001-04-01
影响因子：
6.4
通讯作者：
Gardeström, P
中科院分区：
文献类型：
--
作者：
Igamberdiev, AU;Bykova, NV;Gardeström, P
从甘氨酸脱羧酶复合物缺陷的纯合大麦（Hordeum vulgare L）突变体（GDC，EC 2.1.2.10）和野生型植物的叶中分离原生质体和线粒体。从突变体和野生型植物的分离的原生质体的光合速率饱和CO，是相似的，但突变体的呼吸速率是两倍高。抗霉素A对突变体的呼吸抑制作用比野生型强得多，线粒体中的替代氧化酶蛋白水平较低。突变体中依赖NADP和NAD的苹果酸脱氢酶活性也增加，表明苹果酸-草酰乙酸交换被激活，细胞器之间的氧化还原转移被激活。突变体植物具有升高的NADH和NADPH依赖的乙醛酸/羟丙酮酸还原酶活性，其可能参与氧化过量的NAD（P）H和清除乙醛酸。我们估计了腺苷酸、NAD（H）和NADP（H）在叶绿体、细胞质和线粒体之间的分布。在光呼吸条件下，ATP/ADP和NADPH/NADP的比率在突变体中的叶绿体中较高，与野生型植物相比。胞质中的NADH/NAD比值增加，而线粒体中的比值降低。因此，光呼吸是叶绿体氧化还原传递的有效机制，GDC含量低的植物缺乏这种机制，导致叶绿体过度还原和过度降解。
Protoplasts and mitochondria were isolated from leaves of homozygous barley (Hordeum vulgare L,) mutant deficient in glycine decarboxylase complex (GDC, EC 2.1.2.10) and wild-type plants. The photosynthetic rates of isolated protoplasts from the mutant and wild-type plants under saturating CO, were similar, but the respiratory rate of the mutant was two-fold higher. Respiration in the mutant plants was much more strongly inhibited by antimycin A than in wild-type plants and a low level of the alternative oxidase protein was found in mitochondria, The activities of NADP- and NAD-dependent malate dehydrogenases were also increased in mutant plants, suggesting an activation of the malate-oxaloacetate exchange for redox transfer between organelles. Mutant plants had elevated activities of NADH- and NADPH-dependent glyoxylate/hydroxypruvate reductases, which may be involved in oxidizing excess NAD(P)H and the scavenging of glyoxylate. We estimated distribution of pools of adenylates, NAD(H) and NADP(H) between chloroplasts, cytosol and mitochondria. Under photorespiratory conditions, ATP/ADP and NADPH/NADP ratios in the mutant were higher in chloroplasts as compared to wild-type plants. The cytosolic NADH/NAD ratio was increased, whereas the ratio in mitochondria decreased. It is concluded that photorespiration serves as an effective redox transfer mechanism from the chloroplast, Plants with a lowered GDC content are deficient in this mechanism, which leads to over-reduction and over-energization of the chloroplasts.