Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1857, Issue 6, Pages 799-809Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2016.02.009
Keywords
Chlorophyll biosynthesis; Chlorophyll fluorescence; DPOR; Oxygen evolving complex; PSII supercomplex; Norway spruce
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Funding
- National Program of Sustainability I of the Ministry of Education, Youth and Sports of the Czech Republic [LO1204]
- Grant Agency of the Czech Republic [13-28093S/P501]
- Institutional fund of Palacky University in Olomouc, Czech Republic
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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. (C) 2016 Elsevier B.V. All rights reserved.
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