A1 Refereed original research article in a scientific journal
Daily Heat Stress Induces Donor‐Side Limitation of PSI Via Downregulation of the Cyt b6f Complex; 
Authors: Laihonen, Laura; Tomberg, Tutta; Vuorijoki, Linda; Nikkanen, Lauri; Mulo, Paula; Rantala, Marjaana
Publisher: Wiley
Publication year: 2026
Journal: Plant, Cell and Environment
Article number: pce.70730
ISSN: 0140-7791
eISSN: 1365-3040
DOI: https://doi.org/10.1111/pce.70730
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Partially Open Access publication channel
Web address : https://doi.org/10.1111/pce.70730
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/527039712
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
The rapidly warming climate is driving increasingly frequent and intense heat waves worldwide, posing major challenges to plant metabolism and growth. Despite the central role of photosynthesis in plant growth, the effects of prolonged heat stress on the primary reactions of photosynthesis remain poorly understood. Here, we studied how long-term heat exposure affects growth and photosynthetic performance in the model plant Arabidopsis thaliana. Plants were exposed daily to high temperature (38°C) for 4 h throughout the growth period. Conflicting to earlier studies, we show that PSII-LHCII remain relatively intact under prolonged heat despite slightly reduced ∆F/Fm’, relative electron transfer rate (rETRII) and proportion of open reaction centers (qL). Strikingly, the content of the Cytochrome b6f complex, which mediates electron transfer between the photosystems, was reduced by 30–40%. This leads to more oxidized downstream electron acceptors and prevents PSI over-reduction in conditions where carbon assimilation is inhibited.
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Funding information in the publication:
We thank Prof. Eva-Mari Aro for valuable advice on TEM sample preparation and for expert guidance with the imaging. Dr. Steffen Grebe, Dr. Laura Wey, Dr. Tapio Lempiäinen, Dr. Minna Konert, Dr. Esa Tyystjärvi and Prof. Gyozo Garab are thanked for discussions and valuable insights. Versa Elements is thanked for building the heat chamber and Mika Keränen, Tapio Ronkainen and Samuli Pyytövaara are thanked for the technical assistance. TEM specimen preparation and imaging was done at Laboratory of Electron Microscopy, the Institute of Biomedicine, University of Turku. Special thanks to Jenni Laine and Markus Peurla in technical guidance at TEM Laboratory. The PHOTOSYN infrastructure (University of Turku; https://sites.utu.fi/photosyn/) is acknowledged for the excellent research environment. This work was supported by the Research Council of Finland grants 355787 (L.L., T.T., L.V., M.R. and P.M.) and 354876 (L.N.), the Finnish Cultural Foundation (00220578 Keskusrahasto for L.L., 00230972 for M.R.). Climate chamber was built with funding from BioCity Turku. Open access publishing facilitated by Turun yliopisto, as part of the Wiley - FinELib agreement.
