Distinct roles of the cytochrome pathway and alternative oxidase in leaf photosynthesis
Distinct roles of the cytochrome pathway and alternative oxidase in leaf photosynthesis
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DOI：
10.1093/pcp/pci219
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发表时间：
2006-01-01
影响因子：
4.9
通讯作者：
Noguchi, K
中科院分区：
文献类型：
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作者：
Yoshida, K;Terashima, I;Noguchi, K
在光照下的叶片中，线粒体被认为在优化光合作用中发挥作用。然而，细胞色素途径（CP）和替代氧化酶（AOX）在光合作用中的作用，特别是在光合电子传递链的氧化还原状态下，并没有单独表征。研究了不同光强下特异性抑制CP和AOX两种呼吸途径对蚕豆叶片光合释氧和光合电子传递链氧化还原状态的影响。在饱和光合光子通量密度(PPFD； 700 μ mol光子m（-2) s(-1)）下，抑制任一途径均导致光合O-2进化速率和PSH运行效率Phi（II）的稳态水平降低。由于这些抑制剂，在施用于叶片的浓度下，对完整叶绿体的光合作用几乎没有影响，两个呼吸途径对于维持饱和PPFD下的高光合速率是必不可少的。CP和AOX抑制对Chl荧光参数（如光化学猝灭和非光化学猝灭）的影响不同，说明CP和AOX对光合作用的贡献方式不同。在低PPFD （100 μ mol光子M-2 s(-1)）条件下，只有AOX的抑制降低了光合速率和Phi(II)，而CP的抑制没有降低。即使在低PPFD水平下，AOX抑制也降低了Phi(II)/Phi(I)比值。这些数据表明，即使在低PPFD下，AOX抑制也会导致光合电子传递链的过度还原，并诱导PSI周围的循环电子流（CEF-PSI）。基于这些结果，我们讨论了CP和AOX在光中的可能作用。
In illuminated leaves, mitochondria are thought to play roles in optimizing photosynthesis. However, the roles of the cytochrome pathway (CP) and alternative oxidase (AOX) in photosynthesis, in particular in the redox state of the photosynthetic electron transport chain, are not separately characterized. We examined the effects of specific inhibition of two respiratory pathways, CP and AOX, on photosynthetic oxygen evolution and the redox state of the photosynthetic electron transport chain in broad bean (Vicia faba L.) leaves under various light intensities. Under saturating photosynthetic photon flux density (PPFD; 700 mu mol photon m(-2) s(-1)), inhibition of either pathway caused a decrease in the steady-state levels of the photosynthetic O-2 evolution rate and the PSH operating efficiency, Phi(II). Because these inhibitors, at the concentrations applied to the leaves, had little effect on photosynthesis in the intact chloroplasts, two respiratory pathways are essential for maintenance of high photosynthetic rates at saturating PPFD. CP or AOX inhibition affected to Chl fluorescence parameters (e.g. photochemical quenching and non-photochemical quenching) differently, suggesting that CP and AOX contribute to photosynthesis in different ways. At low PPFD (100 mu mol photon M-2 s(-1)), only the inhibition of AOX, not CP, lowered the photosynthetic rate and Phi(II). AOX inhibition also decreased the Phi(II)/Phi(I), ratio even at low PPFD levels. These data suggest that AOX inhibition caused the over-reduction of the photosynthetic electron transport chain and induced the cyclic electron flow around PSI (CEF-PSI) even at the low PPFD. Based on these results, we discuss possible roles for CP and AOX in the light.