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<p>Oxygenic photosynthesis generates ATP and NADPH via linear electron flow from water to NADP<sup>+</sup>, a process thought to require photosystem I (PSI) for reductant formation. Here we demonstrate that oxygenic photosynthesis can operate without PSI in the cyanobacterium <i>Synechocystis</i> sp.&#xa0;PCC 6803. Using genetic engineering and adaptive laboratory evolution, we obtained PSI-deficient lineages capable of photoautotrophic growth, inorganic carbon fixation, and light-driven oxygen evolution. PSI-independent photoautotrophy arose from co-mutations in at least two proteins, including the translation elongation factor G (FusA), and required a functional NDH-1 complex. We propose that the light-driven electron transport in the evolved strains is reorganised in two branches: one involving terminal oxidases to generate proton motive force, and a second in which reverse NDH-1 activity exploits this gradient to produce reductant. These findings uncover unexpected plasticity in the thylakoid electron transport network and prompt a reassessment of the canonical requirement for PSI in oxygenic photosynthesis.</p>

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Photosystem I-independent oxygenic photosynthesis in cyanobacteria

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月10日

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  • Marta Ludwiczak,
  • Marcel Dann,
  • Theo Figueroa-Gonzalez,
  • Eslam M. Abdel-Salam,
  • Weiyang Chen,
  • Serena Schwenkert,
  • Martin Lehmann,
  • Milena Zhivkovikj,
  • Maysoon Noureddine,
  • Markéta Linhartová,
  • Sadanand Gupta,
  • Josef Komenda,
  • Arthur Guljamov,
  • Stefania Viola,
  • Feng Liu,
  • Dario Leister

摘要

Oxygenic photosynthesis generates ATP and NADPH via linear electron flow from water to NADP+, a process thought to require photosystem I (PSI) for reductant formation. Here we demonstrate that oxygenic photosynthesis can operate without PSI in the cyanobacterium Synechocystis sp. PCC 6803. Using genetic engineering and adaptive laboratory evolution, we obtained PSI-deficient lineages capable of photoautotrophic growth, inorganic carbon fixation, and light-driven oxygen evolution. PSI-independent photoautotrophy arose from co-mutations in at least two proteins, including the translation elongation factor G (FusA), and required a functional NDH-1 complex. We propose that the light-driven electron transport in the evolved strains is reorganised in two branches: one involving terminal oxidases to generate proton motive force, and a second in which reverse NDH-1 activity exploits this gradient to produce reductant. These findings uncover unexpected plasticity in the thylakoid electron transport network and prompt a reassessment of the canonical requirement for PSI in oxygenic photosynthesis.