Up-regulation of mitochondrial alternative oxidase concomitant with chloroplast over-reduction by excess light
Up-regulation of mitochondrial alternative oxidase concomitant with chloroplast over-reduction by excess light
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DOI：
10.1093/pcp/pcm033
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发表时间：
2007-04-01
影响因子：
4.9
通讯作者：
Noguchi, Ko
中科院分区：
文献类型：
--
作者：
Yoshida, Keisuke;Terashima, Ichiro;Noguchi, Ko
交替氧化酶（AOX）是植物线粒体中唯一的末端氧化酶，催化高耗能的抗氰呼吸。虽然有人认为AOX可能通过有效地耗散过量的还原当量来防止叶绿体过度还原，但在生理学背景下缺乏直接证据。在这项研究中，我们研究了线粒体的呼吸特性，特别是AOX，连接到还原当量在叶绿体中的积累和运输还原当量所需的酶的活性。我们使用拟南芥突变体缺陷的PSI周围的循环电子流，其中还原当量积累在叶绿体基质中由于不平衡的ATP/NADPH生产比。这些突变体表现出更高的活性的酶需要运输的还原当量，即使在低光生长条件下。突变体中AOX蛋白和抗CN呼吸的量也高于野生型。高光处理后，AOX，即使在野生型，优先上调伴随着在叶绿体中的还原当量的积累和运输还原当量所需的酶的活性增加。这些结果表明，AOX可以消散多余的还原当量，这是从叶绿体运输，并在有效的光合作用服务。
Alternative oxidase (AOX), the unique terminal oxidase in plant mitochondria, catalyzes the energy-wasteful cyanide (CN)-resistant respiration. Although it has been suggested that AOX might prevent chloroplast over-reduction through the efficient dissipation of excess reducing equivalents, direct evidence for this in the physiological context has been lacking. In this study, we examined the mitochondrial respiratory properties, especially AOX, connected to the accumulation of reducing equivalents in the chloroplasts and the activities of enzymes needed to transport the reducing equivalents. We used Arabidopsis thaliana mutants defective in cyclic electron flow around PSI, in which the reducing equivalents accumulate in the chloroplast stroma due to an unbalanced ATP/NADPH production ratio. These mutants showed higher activities of the enzymes needed to transport the reducing equivalents even in low-light growth conditions. The amounts of AOX protein and CN-resistant respiration in the mutants were also higher than those in the wild type. After high-light treatment, AOX, even in the wild type, was preferentially up-regulated concomitant with the accumulation of reducing equivalents in the chloroplasts and an increase in the activities of enzymes needed to transport reducing equivalents. These results indicate that AOX can dissipate the excess reducing equivalents, which are transported from the chloroplasts, and serve in efficient photosynthesis.