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Han Guangye

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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 Shen^2,3 and Győző Garab^1,4

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 (PSII_C) – induces only an F₁(<F_m) fluorescence level, and additional excitations with sufficiently long Δτ waiting times between them are required to reach the maximum (F_m) level. We also revealed that the F₁-to-F_m transition is linked to the gradual formation of the light-adapted charge-separated state, PSII_L, which possesses an increased stabilization of charges [2]. Recently, we studied the effects of different physicochemical environments of PSII on the half-rise time (Δτ_1/2) 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 Δτ_1/2 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 Δτ_1/2 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 Δτ_1/2 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 PSII_C-PSII_Ltransition.

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.