Emrich-Mills, T.Z. orcid.org/0000-0002-4440-626X, Proctor, M.S. orcid.org/0000-0002-1484-850X, Degen, G.E. orcid.org/0000-0002-0804-4169 et al. (9 more authors) (2025) Tethering ferredoxin-NADP+ reductase to photosystem I promotes photosynthetic cyclic electron transfer. The Plant Cell, 37 (3). koaf042. ISSN 1040-4651
Abstract
Fixing CO2 via photosynthesis requires ATP and NADPH, which can be generated through linear electron transfer (LET). However, depending on the environmental conditions, additional ATP may be required to fix CO2, which can be generated by cyclic electron transfer (CET). How the balance between LET and CET is determined remains largely unknown. Ferredoxin-NADP+ reductase (FNR) may act as the switch between LET and CET, channeling photosynthetic electrons to LET when it is bound to photosystem I (PSI) or to CET when it is bound to cytochrome b6f. The essential role of FNR in LET precludes the use of a direct gene knock-out to test this hypothesis. Nevertheless, we circumvented this problem using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-mediated gene editing in Chlamydomonas reinhardtii. Through this approach, we created a chimeric form of FNR tethered to PSI via PSAF. Chimeric FNR mutants exhibited impaired photosynthetic growth and LET along with enhanced PSI acceptor side limitation relative to the wild type due to slower NADPH reduction. However, the chimeric FNR mutants also showed enhanced ΔpH production and NPQ resulting from increased CET. Overall, our results suggest that rather than promoting LET, tethering FNR to PSI promotes CET at the expense of LET and CO2 fixation.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Author(s) 2025. Published by Oxford University Press on behalf of American Society of Plant Biologists. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. |
Keywords: | Photosystem I Protein Complex; Photosynthesis; Ferredoxin-NADP Reductase; Electron Transport; Chlamydomonas reinhardtii; CRISPR-Cas Systems; NADP |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Biosciences (Sheffield) |
Funding Information: | Funder Grant number ROYAL SOCIETY URF\R1\191548 BIOTECHNOLOGY AND BIOLOGICAL SCIENCES RESEARCH COUNCIL BB/V006630/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 21 Mar 2025 12:09 |
Last Modified: | 21 Mar 2025 12:09 |
Status: | Published |
Publisher: | Oxford University Press (OUP) |
Refereed: | Yes |
Identification Number: | 10.1093/plcell/koaf042 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:224688 |