Thioredoxins Play a Crucial Role in Dynamic Acclimation of Photosynthesis in Fluctuating Light
Thioredoxins Play a Crucial Role in Dynamic Acclimation of Photosynthesis in Fluctuating Light
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DOI：
10.1016/j.molp.2016.11.012
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发表时间：
2017-01-09
期刊：
影响因子：
27.5
通讯作者：
Geigenberger, Peter
中科院分区：
文献类型：
--
作者：
Thormaehlen, Ina;Zupok, Arkadiusz;Geigenberger, Peter
阳光是光合作用和植物生长的能源。当在田间生长时，植物的光合作用必须管理强烈的光强波动。基于硫氧还蛋白(TRX)系统的调节被认为确保叶绿体中的光合作用反应的光响应控制。然而，该系统在调节光合作用在波动条件下的动态适应中所起作用的直接证据很少。在这份报告中，我们证明了依赖于铁氧还蛋白的Trxs m1和m2以及依赖于NADPH的ntrc对于光合作用在光强波动中的适应都是不可或缺的。同时缺失Trxsm1和m2的拟南芥突变体在恒定光照条件下表现出野生型生长和光合作用，而在强光和弱光快速交替的条件下，光合作用参数发生了强烈的变化。两个独立的trxm1m2突变体在强光下表现出较低的光合作用效率，但在弱光下表现出令人惊讶的显著提高。我们的数据表明，Trx m1和m2的一个主要靶标是NADP-苹果酸脱氢酶，该酶参与叶绿体过剩还原力的输出。因此，高光峰光合作用效率的降低可能是由于trxm1m2突变体对该酶的快速光激活能力降低所致。在ntrc突变体中，激发能量的非光化学猝灭和叶绿体对苯二酚还原状态的动态响应在波动的光强下都被强烈地衰减，导致PSII量子效率的大幅下降和植物在这些条件下的特定生长减少。这可能是由于NTRC突变体控制基质NADP(H)氧化还原平衡的能力降低所致。综上所述，我们的结果表明，NTRC在确保光合作用的全部动态响应以优化光合作用和维持波动光下的生长方面是不可或缺的，而Trxs m1和m2是在强光时期充分激活光合作用所必需的，但在波动光的弱光时期对光合作用效率产生负面影响。
Sunlight represents the energy source for photosynthesis and plant growth. When growing in the field, plant photosynthesis has to manage strong fluctuations in light intensities. Regulation based on the thioredoxin (Trx) system is believed to ensure light-responsive control of photosynthetic reactions in the chloroplast. However, direct evidence for a role of this system in regulating dynamic acclimation of photosynthesis in fluctuating conditions is largely lacking. In this report we show that the ferredoxin-dependent Trxs m1 and m2 as well as the NADPH-dependent NTRC are both indispensable for photosynthetic acclimation in fluctuating light intensities. Arabidopsis mutants with combined deficiency in Trxs m1 and m2 show wildtype growth and photosynthesis under constant light condition, while photosynthetic parameters are strongly modified in rapidly alternating high and low light. Two independent trxm1m2 mutants show lower photosynthetic efficiency in high light, but surprisingly significantly higher photosynthetic efficiency in low light. Our data suggest that a main target of Trx m1 and m2 is the NADP-malate dehydrogenase involved in export of excess reductive power from the chloroplast. The decreased photosynthetic efficiency in the high-light peaks may thus be explained by a reduced capacity of the trxm1m2 mutants in the rapid light activation of this enzyme. In the ntrc mutant, dynamic responses of non-photochemical quenching of excitation energy and plastoquinone reduction state both were strongly attenuated in fluctuating light intensities, leading to a massive decrease in PSII quantum efficiency and a specific decrease in plant growth under these conditions. This is likely due to the decreased ability of the ntrc mutant to control the stromal NADP(H) redox poise. Taken together, our results indicate that NTRC is indispensable in ensuring the full range of dynamic responses of photosynthesis to optimize photosynthesis and maintain growth in fluctuating light, while Trxs m1 and m2 are indispensable for full activation of photosynthesis in the high-light periods but negatively affect photosynthetic efficiency in the low-light periods of fluctuating light.