PHOTOSYNTHETICA

Photosynthetica 2022, 60(1):147-156 | DOI: 10.32615/ps.2022.016

Dependence of the rate-limiting steps in the dark-to-light transition of photosystem II on the lipidic environment of the reaction center

M. MAGYAR¹, P. AKHTAR¹, G. SIPKA¹, W. HAN², X. LI², G. HAN², J.-R. SHEN^{2, 3}, P.H. LAMBREV¹, G. GARAB^{1, 4}

¹ Institute of Plant Biology, Biological Research Centre, Szeged, Hungary

² Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China

³ Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan

⁴ Faculty of Science, University of Ostrava, Ostrava, Czech Republic

In our earlier works, we have identified rate-limiting steps in the dark-to-light transition of PSII. By measuring chlorophyll a fluorescence transients elicited by single-turnover saturating flashes (STSFs) we have shown that in diuron-treated samples an STSF generates only F₁ (< F_m) fluorescence level, and to produce the maximum (F_m) level, additional excitations are required, which, however, can only be effective if sufficiently long Δτ waiting times are allowed between the excitations. Biological variations in the half-rise time (Δτ_1/2) of the fluorescence increment suggest that it may be sensitive to the physicochemical environment of PSII. Here, we investigated the influence of the lipidic environment on Δτ_1/2 of PSII core complexes of Thermosynechococcus vulcanus. We found that while non-native lipids had no noticeable effects, thylakoid membrane lipids considerably shortened the Δτ_1/2, from ~ 1 ms to ~ 0.2 ms. The importance of the presence of native lipids was confirmed by obtaining similarly short Δτ_1/2 values in the whole T. vulcanus cells and isolated pea thylakoid membranes. Minor, lipid-dependent reorganizations were also observed by steady-state and time-resolved spectroscopic measurements. These data show that the processes beyond the dark-to-light transition of PSII depend significantly on the lipid matrix of the reaction center.

Additional key words: closed state of PSII; conformational changes; dielectric relaxation; light-adapted state of PSII, light-induced changes; proteoliposomes.

Received: December 16, 2021; Revised: March 4, 2022; Accepted: March 7, 2022; Prepublished online: March 14, 2022; Published: March 18, 2022  Show citation