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D1 fragmentation in photosystem II repair caused by photo-damage of a two-step model

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Abstract

Light energy drives photosynthesis, but it simultaneously inactivates photosynthetic mechanisms. A major target site of photo-damage is photosystem II (PSII). It further targets one reaction center protein, D1, which is maintained efficiently by the PSII repair cycle. Two proteases, FtsH and Deg, are known to contribute to this process, respectively, by efficient degradation of photo-damaged D1 protein processively and endoproteolytically. This study tested whether the D1 cleavage accomplished by these proteases is affected by different monochromic lights such as blue and red light-emitting-diode light sources, remaining mindful that the use of these lights distinguishes the current models for photoinhibition: the excess-energy model and the two-step model. It is noteworthy that in the two-step model, primary damage results from the absorption of light energy in the Mn-cluster, which can be enhanced by a blue rather than a red light source. Results showed that blue and red lights affect D1 degradation differently. One prominent finding was that D1 fragmentation that is specifically generated by luminal Deg proteases was enhanced by blue light but not by red light in the mutant lacking FtsH2. Although circumstantial, this evidence supports a two-step model of PSII photo-damage. We infer that enhanced D1 fragmentation by luminal Deg proteases is a response to primary damage at the Mn-cluster.

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Abbreviations

CBB:

Coomassie brilliant blue

F v/F m :

Maximum quantum yield of PSII

LED:

Light-emitting diode

LHCII:

Light-harvesting complex II

OEC:

Oxygen-evolving complex

PSII:

Photosystem II

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Acknowledgments

We would like to thank Rie Hijiya for her technical assistance. This work was partly supported by the Japan Science and Technology Agency (Core Research for Evolutional Science and Technology, to W.S.) and by the Oohara Foundation.

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Correspondence to Wataru Sakamoto.

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Kato, Y., Ozawa, Si., Takahashi, Y. et al. D1 fragmentation in photosystem II repair caused by photo-damage of a two-step model. Photosynth Res 126, 409–416 (2015). https://doi.org/10.1007/s11120-015-0144-7

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  • DOI: https://doi.org/10.1007/s11120-015-0144-7

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