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Biochim Biophys Acta. 2016 Jun;1857(6):799-809. doi: 10.1016/j.bbabio.2016.02.009. Epub 2016 Feb 18.

Light-induced gradual activation of photosystem II in dark-grown Norway spruce seedlings.

Author information

1
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.
2
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.

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.

KEYWORDS:

Chlorophyll biosynthesis; Chlorophyll fluorescence; DPOR; Norway spruce; Oxygen evolving complex; PSII supercomplex

PMID:
26901522
DOI:
10.1016/j.bbabio.2016.02.009
[Indexed for MEDLINE]
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