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Identification of tenuazonic acid as a novel type of natural photosystem II inhibitor binding in QB-site of Chlamydomonas reinhardtii |
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| Authors: | Shiguo Chen |
| Institution: | Weed Research Laboratory, Nanjing Agricultural University, Nanjing 210095, China |
| Abstract: | Tenuazonic acid (TeA) is a natural phytotoxin produced by Alternaria alternata, the causal agent of brown leaf spot disease of Eupatorium adenophorum. Results from chlorophyll fluorescence revealed TeA can block electron flow from QA to QB at photosystem II acceptor side. Based on studies with D1-mutants of Chlamydomonas reinhardtii, the No. 256 amino acid plays a key role in TeA binding to the QB-niche. The results of competitive replacement with 14C]atrazine combined with JIP-test and D1-mutant showed that TeA should be considered as a new type of photosystem II inhibitor because it has a different binding behavior within QB-niche from other known photosystem II inhibitors. Bioassay of TeA and its analogues indicated 3-acyl-5-alkyltetramic and even tetramic acid compounds may represent a new structural framework for photosynthetic inhibitors. |
| Keywords: | DCMU (3-(3 4-dichlorophenyl)-1 1-dimethylurea) Fo FM initial and maximal fluorescence F300 μs fluorescence at 300 μs FJ fluorescence at the J-step VJ relative variable fluorescence at the J-step tFM time to reach maximal fluorescence FM Mo approximated initial slope of the fluorescence transient V = f(t) Sm normalized total complementary area above the O-J-I-P transient QA QB primary and secondary quinone acceptor N number of QA reduction events between time o and tFM ψo probability that a trapped exciton moves an electron into the electron transport chain beyond QA&minus φEo quantum yield for electron transport (at t = 0) RC reaction center ET energy flux for electron transport PDB Protein Data Bank |
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