Tethering ferredoxin-NADP+ reductase to photosystem I promotes photosynthetic cyclic electron transfer

• DOI: 10.1093/plcell/koaf042
• Publication Date: 2025-03-04T23:34:41Z
• Authors: Tom Z Emrich-Mills; Matthew S Proctor; Gustaf E Degen; Philip J Jackson; Katherine H Richa...; Frederick R Hawkings; Felix Buchert; Andrew Hitchcock; C Neil Hunter; Luke C M Mackinder; Michael Hippler; Matthew P Johnson
• Keywords: Ferredoxin—NADP(+) reductase

Fixing CO2 via photosynthesis requires ATP and NADPH, which can be generated through linear electron transfer (LET). However, depending on the environmental conditions, additional may required to fix CO2, by cyclic (CET). How balance between LET CET is determined remains largely unknown. Ferredoxin-NADP+ reductase (FNR) act as switch CET, channelling photosynthetic electrons when it bound photosystem I (PSI) or cytochrome b6f. The essential role of FNR in precludes use a direct gene knock-out test this hypothesis. Nevertheless, we circumvented problem using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-mediated editing Chlamydomonas reinhardtii. Through approach, created chimeric form tethered PSI PSAF. Chimeric mutants exhibited impaired growth along with enhanced acceptor side limitation relative wild type due slower NADPH reduction. also showed ΔpH production NPQ resulting from increased CET. Overall, our results suggest that rather than promoting LET, tethering promotes at expense fixation.