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Plant Cell. 2014 Apr;26(4):1781-1791. Epub 2014 Apr 18.

The Cyanobacterial Photoactive Orange Carotenoid Protein Is an Excellent Singlet Oxygen Quencher.

Author information

1
Commissariat à l'Energie Atomique, Institut de Biologie et Technologies de Saclay, 91191 Gif sur Yvette, France CNRS, Unité Mixte de Recherche 8221, 91191 Gif sur Yvette, France Phycosource, 95092 Cergy Cedex, France.
2
Commissariat à l'Energie Atomique, Institut de Biologie et Technologies de Saclay, 91191 Gif sur Yvette, France CNRS, Unité Mixte de Recherche 8221, 91191 Gif sur Yvette, France.
3
Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
4
Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318 INRA-AgroParisTech, INRA Versailles-Grignon, F-78026 Versailles, France.
5
Phycosource, 95092 Cergy Cedex, France.
6
Commissariat à l'Energie Atomique, Institut de Biologie et Technologies de Saclay, 91191 Gif sur Yvette, France CNRS, Unité Mixte de Recherche 8221, 91191 Gif sur Yvette, France diana.kirilovsky@cea.fr.

Abstract

Cyanobacteria have developed a photoprotective mechanism that decreases the energy arriving at the photosynthetic reaction centers under high-light conditions. The photoactive orange carotenoid protein (OCP) is essential in this mechanism as a light sensor and energy quencher. When OCP is photoactivated by strong blue-green light, it is able to dissipate excess energy as heat by interacting with phycobilisomes. As a consequence, charge separation and recombination leading to the formation of singlet oxygen diminishes. Here, we demonstrate that OCP has another essential role. We observed that OCP also protects Synechocystis cells from strong orange-red light, a condition in which OCP is not photoactivated. We first showed that this photoprotection is related to a decrease of singlet oxygen concentration due to OCP action. Then, we demonstrated that, in vitro, OCP is a very good singlet oxygen quencher. By contrast, another carotenoid protein having a high similarity with the N-terminal domain of OCP is not more efficient as a singlet oxygen quencher than a protein without carotenoid. Although OCP is a soluble protein, it is able to quench the singlet oxygen generated in the thylakoid membranes. Thus, OCP has dual and complementary photoprotective functions as an energy quencher and a singlet oxygen quencher.

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