2024-03-28T23:10:52Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/613782023-10-05T03:12:37Zhdl_2115_20056hdl_2115_147Chlorophyll b degradation by chlorophyll b reductase under high-light conditionsSato, ReiIto, HisashiTanaka, AyumiChlorophyll b reductaseLight-harvesting complexHigh-light conditionsArabidopsisThe light-harvesting chlorophyll a/b binding protein complex of photosystem II (LHCII) is the main antenna complex of photosystem II (PSII). Plants change their LHCII content depending on the light environment. Under high-light conditions, the content of LHCII should decrease because over-excitation damages the photosystem. Chlorophyll b is indispensable for accumulating LHCII, and chlorophyll b degradation induces LHCII degradation. Chlorophyll b degradation is initiated by chlorophyll b reductase (CBR). In land plants, NON-YELLOW COLORING 1 (NYC1) and NYC1-Like (NOL) are isozymes of CBR. We analyzed these mutants to determine their functions under high-light conditions. During high-light treatment, the chlorophyll a/b ratio was stable in the wild-type (WT) and nol plants, and the LHCII content decreased in WT plants. The chlorophyll a/b ratio decreased in the nyc1 and nyc1/nol plants, and a substantial degree of LHCII was retained in nyc1/nol plants after the high-light treatment. These results demonstrate that NYC1 degrades the chlorophyll b on LHCII under high-light conditions, thus decreasing the LHCII content. After the high-light treatment, the maximum quantum efficiency of the PSII photochemistry was lower in nyc1 and nyc1/nol plants than in WT and nol plants. A larger light-harvesting system would damage PSII in nyc1 and nyc1/nol plants. The fluorescence spectroscopy of the leaves indicated that photosystem I was also damaged by the excess LHCII in nyc1/nol plants. These observations suggest that chlorophyll b degradation by NYC1 is the initial reaction for the optimization of the light-harvesting capacity under high-light conditions.SpringerJournal Articleapplication/pdfhttp://hdl.handle.net/2115/61378https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/61378/1/ito.pdf0166-8595Photosynthesis research12622492592015-04-21enginfo:pmid/25896488info:doi/10.1007/s11120-015-0145-6The final publication is available at Springer via http://dx.doi.org/10.1007/s11120-015-0145-6author