期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：51
页码：14864-14869
DOI：10.1073/pnas.1607695114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceLife on earth largely depends on the capture of light energy by plants through photosynthesis. Light is essential, but excess light is dangerous. Energy dissipation as heat is a major mechanism induced to protect the photosynthetic machinery. We report that UV-B perception by a specific photoreceptor in the nucleocytosolic compartment leads to protection of the photosynthetic machinery in the chloroplast of a green alga. The underlying mechanism is markedly different from the response to high light. UV-B photoreceptor-mediated signaling activates a safety valve, allowing the release of the excess energy as heat, helping the algae to cope with too much light energy. 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.
