Photosystem I-independent oxygenic photosynthesis in cyanobacteria.
basic_science · Level V
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- Record sourced from PubMed, PMID 42431894.
- Also identified by DOI 10.1038/s41467-026-74903-2.
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Abstract
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 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.