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Application of a reduced mathematical model of photosystem II reaction centers to determine the heterogeneity of its antenna under stress conditionsстатья Тезисы
Дата последнего поиска статьи во внешних источниках: 1 мая 2024 г.
- Авторы: Pluysnina T.Y., Khruschev S.S., Degtereva N.S., Riznichenko G.Y., Rubin A.B.
- Журнал: Biophysical Reviews
- Том: 15
- Год издания: 2023
- Издательство: Springer Verlag
- Местоположение издательства: Germany
- Первая страница: 1569
- Последняя страница: 1570
- DOI: 10.1007/s12551-023-01150-w
- Аннотация: Under optimal conditions most of the PSII RCs form dimers and can attach light harvesting proteins, the so-called α-centers. Under unfavorable conditions, an increase of the portion of RCs with a reduced antenna, the β- and the γ-centers, is often observed. The ratio of PSII RCs with different sizes of light harvesting antenna depends on growth conditions and stress factors. The change in the ratio of different types of PSII RCs can serve as an indicator of the stress impact on the algae culture. The assessment of such changes can be useful for biotechnology and environmental monitoring. A common way to assess the ratio of reaction centers with different antenna size is to analyze chlorophyll fluorescence rise (FR) of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) treated samples. To quantify such ratios multiexponential decomposition of the complemental area above the FR is commonly used. However, this approach has certain limitations. To overcome these limitations, we propose an approach based on mathematical modeling. The constructed detailed mathematical model of the processes in the DCMU treated PSII contains 24 ordinary differential equations (ODEs) and includes redox changes of the oxygen evolving complex (OEC), photoexcitation and redox changes of the RC pigment P680, and redox changes of pheophytin and the primary quinone QA. The hierarchy of characteristic times of these processes makes it possible to reduce the model to a system of three ODEs. The solution of the reduced threestate model exactly reproduces the solution of the complete system in the range from microseconds to seconds. The combination of several such models made it possible to describe different types: α- β- and the γ-centers. The parameters of the reduced model were identified by fitting model solutions to the FR for DCMU- treated of Chlorella microalgae under nitrogen depletion and of Chlamydomonas microalgae under sulfur depletion. Using the model, we tested the existing hypotheses about the nature of additional phases on the fluorescence rise, whether they reflect RC with a different antenna or some process. The model demonstrates that the presence or absence of an additional phase on the fluorescence rise measured for DCMU treated samples may depend on the balance of reaction rates on the donor and acceptor sides of the PSII. If the characteristic time of reactions on the donor side is longer than the characteristic time of reactions on the acceptor side, the initial part of the FR till ~100 μs demonstrates a slower rise compared to an exponential increase. If, for example due to stress, transitions in OEC slow down, and the characteristic time of the processes on the donor side becomes shorter than the characteristic time of the processes on the acceptor side, then an additional positive phase with characteristic times of 1–10 ms is observed. An analysis of the experimental curves showed that under mineral starvation additional phases on the induction curve can indicate both the appearance of RCs with reduced antenna size and the slowing down of the S1–S2 transition in OEC. The model shows the fundamental possibility of the appearance of an additional phase on the FR obtained from samples treated with DCMU due to the processes in OEC. It is hypothesized that under normal conditions the phases on the curve reflect the presence of α- β- and the γ-centers, while under stress conditions, one of the positive phases may reflect a slowdown in processes on the PSII donor side.
- Добавил в систему: Хрущев Сергей Сергеевич
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