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.

Night Light-Adaptation Strategies for Photosynthetic Apparatus in Yellow-Poplar (Liriodendron tulipifera L.) Exposed to Artificial Night Lighting

“…The PSII as the heart of the photosynthetic process is highly sensitive to the environmental stresses. Its activity could be determined with one non-invasive time-resolved fluorescence measurement, which could measure the polyphasic rise with the basic steps of OJIP [43,[48][49][50][51][52][53][54]. Several studies have shown that the chlorophyll a transient has become one of the most popular tools to estimate stress-induced changes in photosynthetic performance.…”

Lipid Polymorphism of the Subchloroplast—Granum and Stroma Thylakoid Membrane–Particles. II. Structure and Functions

“…Proteins were extracted from TM preparations by dilution in a buffer according to [ 25 ] and incubated for 30 min at 70 °C. SDS-PAGE was carried out using 8.5% focusing and 12% resolving polyacrylamide gel containing 0.1 % sodium dodecyl sulfate (SDS, Sigma-Aldrich).…”

Alternative electron transport mediated by flavodiiron proteins is operational in organisms from cyanobacteria up to gymnosperms

“…Later, this fast PSI re‐oxidation was detected also in green alga Chlamydomonas reinhardtii and it was shown to be oxygen‐dependent, which indicated that Mehler type reaction is involved (Franck & Houyoux, ). Recently, this fast oxygen‐dependent PSI re‐oxidation upon dark‐to‐light transition was observed also in some representatives of gymnosperms (Shirao et al ., ; Pavlovič et al ., ).…”