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Proc Natl Acad Sci U S A. 2016 Dec 20;113(51):14864-14869. doi: 10.1073/pnas.1607695114. Epub 2016 Dec 5.

UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii.

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Department of Botany and Plant Biology, Sciences III, University of Geneva, Geneva CH-1211, Switzerland.
Laboratoire de Physiologie Cellulaire et Végétale, Commissariat à l'Énergie Atomique et aux Énergies Alternatives/Centre National de la Recherche Scientifique/Université Grenoble Alpes/Institut National de la Recherche Agronomique, 38054 Grenoble, France.
Howard Hughes Medical Institute, Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720.
Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
Department of Botany and Plant Biology, Sciences III, University of Geneva, Geneva CH-1211, Switzerland;
Institute of Genetics and Genomics of Geneva, University of Geneva, Geneva CH-1211, Switzerland.


Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here, we report in the green alga Chlamydomonas reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast.


LHCSR1; PSBS; UV-B photoreceptor; nonphotochemical quenching; photoprotection

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