title: Light-induced gradual activation of photosystem II in dark-grown Norway spruce seedlings.
abstract: Gymnosperms, unlike angiosperms, are able to synthesize chlorophyll and form photosystems in complete darkness. Photosystem I (PSI) formed under such conditions is fully active, but photosystem II (PSII) is present in its latent form with inactive oxygen evolving complex (OEC). In this work we have studied light-induced gradual changes in PSII function in dark-grown cotyledons of Norway spruce (Picea abies) via the measurement of chlorophyll a fluorescence rise, absorption changes at 830 nm, thermoluminescence glow curves (TL) and protein analysis. The results indicate that in dark-grown cotyledons, alternative reductants were able to act as electron donors to PSII with inactive OEC. Illumination of cotyledons for 5 min led to partial activation of PSII, which was accompanied by detectable oxygen evolution, but still a substantial number of PSII centers remained in the so called PSII-Q(B)-non-reducing form. Interestingly, even 24 h long illumination was not sufficient for the full activation of PSII centers. This was evidenced by a weak attachment of PsbP protein and the absence of PsbQ protein in PSII particles, the absence of PSII supercomplexes, the suboptimal maximum yield of PSII photochemistry, the presence of C band in TL curve and also the presence of up-shifted Q band in TL in DCMU-treated cotyledons. This slow light-induced activation of PSII in dark-grown cotyledons could contribute to the prevention of PSII overexcitation before the light-induced increase in PSI/PSII ratio allows effective operation of linear electron flow.
authors.affiliation: Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in Olomouc, Šlechtitelů 27, Olomouc CZ-783 71, Czech Republic. Electronic address: andrej.pavlovic@upol.cz.
authors.forename: Andrej
authors.initials: A
authors.lastname: Pavlovič
authors.affiliation: Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in Olomouc, Šlechtitelů 27, Olomouc CZ-783 71, Czech Republic.
authors.forename: Tibor
authors.initials: T
authors.lastname: Stolárik
authors.affiliation: Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in Olomouc, Šlechtitelů 27, Olomouc CZ-783 71, Czech Republic.
authors.forename: Lukáš
authors.initials: L
authors.lastname: Nosek
authors.affiliation: Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in Olomouc, Šlechtitelů 27, Olomouc CZ-783 71, Czech Republic.
authors.forename: Roman
authors.initials: R
authors.lastname: Kouřil
authors.affiliation: Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University in Olomouc, Šlechtitelů 27, Olomouc CZ-783 71, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Ilík
mesh_terms: D015153:Blotting, Western; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism; D000077194:Chlorophyll A; D018548:Cotyledon / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D003624:Darkness; D004579:Electron Transport / Q000528:radiation effects; D008027:Light; D008163:Luminescent Measurements / Q000379:methods; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D028222:Picea / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D010940:Plant Proteins / Q000378:metabolism*; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D013696:Temperature; D020524:Thylakoids / Q000378:metabolism / Q000528:radiation effects
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D010100:Oxygen; D000077194:Chlorophyll A
keywords: Chlorophyll biosynthesis; Chlorophyll fluorescence; DPOR; Norway spruce; Oxygen evolving complex; PSII supercomplex