Photoinhibition of photosynthesis in vivo results in singlet oxygen production detection via nitroxide-induced fluorescence quenching in broad bean leaves.
In plants experiencing environmental stress, the formation of reactive oxygen is often presumed. In this study, singlet oxygen was detected in broad bean (Vicia faba) leaves that were photoinhibited in vivo. Detection was based on the reaction of singlet oxygen with DanePy (dansyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole) yielding a nitroxide radical (DanePyO) which is EPR active and also features lower fluorescence compared to DanePy. The two (fluorescent and spin) sensor fuctions of DanePy are commensurate, which makes detecting singlet oxygen possible with a spectrofluorimeter in samples hard to measure with EPR spectroscopy [Kálai, T., Hideg, E., Vass, I., and Hideg, K. (1998) Free Radical Biol. Med. 24, 649-652]. We found that in leaves saturated with DanePy, the fluorescence of this double sensor was decreased when the leaves were photoinhibited by 1500 micromol m-2 s-1 photosynthetically active radiation. This fluorescence quenching is the first direct experimental evidence that photoinhibition of photosynthesis in vivo is accompanied by 1O2 production and is, at least partly, governed by the process characterized as acceptor side-induced photoinhibition in vitro.
Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, Szeged. ehideg@everx.szeged.hu
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D003619:Dansyl Compounds / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D007887:Fabaceae; D005454:Fluorescence Polarization; D005609:Free Radicals / Q000494:pharmacology; D009589:Nitrogen Oxides / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism*; D010777:Photochemistry; D010788:Photosynthesis / Q000187:drug effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010880:Piperidines / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism*; D010946:Plants, Medicinal; D026082:Singlet Oxygen; D013050:Spectrometry, Fluorescence; D013113:Spin Labels; D013997:Time Factors
C112332:DanePy; D003619:Dansyl Compounds; D005609:Free Radicals; D009589:Nitrogen Oxides; D045322:Photosynthetic Reaction Center Complex Proteins; D010880:Piperidines; D013113:Spin Labels; D026082:Singlet Oxygen; C039900:nitroxyl; D010100:Oxygen