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Magyar Melinda

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Magyar Melinda
Rate-limiting steps in the dark-to-light transition of photosystem II: Dependence on the temperature and the lipidic environment of the reaction center

Aug 31 - csütörtök

10:45 – 11:00

Bioenergetika és fotobiofizika

E41

Rate-limiting steps in the dark-to-light transition of photosystem II: Dependence on the temperature and the lipidic environment of the reaction center

Melinda Magyar1, Gábor Sipka1, Parveen Akhtar1, Guangye Han2, Petar H. Lambrev1, Jian-Ren Shen2,3 and Győző Garab1,4

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

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

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

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

Photosystem II (PSII) is the redox-active pigment–protein complex embedded in the thylakoid membrane (TM) that catalyzes the oxidation of water and the reduction of plastoquinone. We performed single-turnover saturating flash-induced (STSF) variable chlorophyll-a fluorescence transient measurements on PSII, and we have identified rate-limiting steps in the dark-to-light transition of PSII [1]. It was demonstrated in diuron-treated samples that the first STSF – generating the closed state (PSIIC) – induces only an F1(<Fm) fluorescence level, and additional excitations with sufficiently long Δτ waiting times between them are required to reach the maximum (Fm) level. We also revealed that the F1-to-Fm transition is linked to the gradual formation of the light-adapted charge-separated state, PSIIL, which possesses an increased stabilization of charges [2]. Recently, we studied the effects of different physicochemical environments of PSII on the half-rise time (Δτ1/2) and probed its presence during later steps (F2, F3 etc.) [3, 4]. In particular, we investigated the influence of the lipidic environment [3] and the temperature dependence of Δτ1/2 of PSII core complexes (CC) of Thermosynechococcus (T.) vulcanus and pea TMs [4]. We showed that (i) while non-native lipids has no effect, TM lipids shorten the Δτ1/2 of PSII CCs of T. vulcanus to that of TMs – uncovering the role of lipid matrix in the rate limiting steps; (ii) PSII CCs of T. vulcanus and spinach TMs exhibit very similar temperature dependences, with enhanced values at low temperatures; and (iii) the Δτ1/2 values in PSII CC are essentially independent at all temperatures on the number of the STSF-induced increments. These data suggest that the same physical mechanism is involved during the PSIIC-PSIILtransition.

References

[1] Magyar M et al. (2018) Sci Rep 8: 2755

[2] Sipka G et al. (2021) Plant Cell 33: 1286-1302.

[3] Magyar M et al. (2022) Photosynthetica 60: 147-156.

[4] Magyar M et al. (2022) IJMS 24: 94-104.