Molecular Plant Biology, Department of Biochemistry, University of Turku, Turku, Finland.
Plant Biochemistry, Faculty of Biology & Biotechnology, Ruhr-University Bochum, Bochum, Germany.
Plant J. 2020 Aug;103(4):1460-1476. doi: 10.1111/tpj.14812. Epub 2020 Jun 16.
In oxygenic photosynthetic organisms, excluding angiosperms, flavodiiron proteins (FDPs) catalyze light-dependent reduction of O to H O. This alleviates electron pressure on the photosynthetic apparatus and protects it from photodamage. In Synechocystis sp. PCC 6803, four FDP isoforms function as hetero-oligomers of Flv1 and Flv3 and/or Flv2 and Flv4. An alternative electron transport pathway mediated by the NAD(P)H dehydrogenase-like complex (NDH-1) also contributes to redox hemostasis and the photoprotection of photosynthesis. Four NDH-1 types have been characterized in cyanobacteria: NDH-1 and NDH-1 , which function in respiration; and NDH-1 and NDH-1 , which function in CO uptake. All four types are involved in cyclic electron transport. Along with single FDP mutants (∆flv1 and Δflv3) and the double NDH-1 mutants (∆d1d2, which is deficient in NDH-1 and ∆d3d4, which is deficient in NDH-1 ), we studied triple mutants lacking one of Flv1 or Flv3, and NDH-1 or NDH-1 . We show that the presence of either Flv1/3 or NDH-1 , but not NDH-1 , is indispensable for survival during changes in growth conditions from high CO /moderate light to low CO /high light. Our results show functional redundancy between FDPs and NDH-1 under the studied conditions. We suggest that ferredoxin probably functions as a primary electron donor to both Flv1/3 and NDH-1 , allowing their functions to be dynamically coordinated for efficient oxidation of photosystem I and for photoprotection under variable CO and light availability.
在产氧光合作用生物中，除了被子植物外，黄素铁蛋白（FDP）催化 O 到 H O 的光依赖性还原。这减轻了光合作用装置上的电子压力，并保护其免受光损伤。在集胞藻 PCC 6803 中，四种 FDP 同工型作为 Flv1 和 Flv3 和/或 Flv2 和 Flv4 的异源寡聚体发挥作用。由 NAD(P)H 脱氢酶样复合物（NDH-1）介导的替代电子传递途径也有助于氧化还原平衡和光合作用的光保护。在蓝藻中已经鉴定出四种 NDH-1 类型：在呼吸中起作用的 NDH-1 和 NDH-1 ；以及在 CO 摄取中起作用的 NDH-1 和 NDH-1 。所有四种类型都参与循环电子传递。除了单个 FDP 突变体（∆flv1 和 Δflv3）和双 NDH-1 突变体（∆d1d2，缺乏 NDH-1 和 ∆d3d4，缺乏 NDH-1 ）外，我们还研究了缺乏 Flv1 或 Flv3 之一的三突变体，以及 NDH-1 或 NDH-1 。我们表明，在从高 CO /适度光照到低 CO /高光的生长条件变化期间，存在 Flv1/3 或 NDH-1，但不存在 NDH-1 ，对于生存是必不可少的。我们的结果表明，在研究条件下，FDP 和 NDH-1 之间存在功能冗余。我们建议铁氧还蛋白可能作为 Flv1/3 和 NDH-1 的主要电子供体发挥作用，允许它们的功能动态协调，以有效地氧化光系统 I 并在可变的 CO 和光照可用性下进行光保护。
