Fig. 3: Photoreduction of O2 around PSI. | Nature Communications

Fig. 3: Photoreduction of O2 around PSI.

From: Flavodiiron-mediated O2 photoreduction at photosystem I acceptor-side provides photoprotection to conifer thylakoids in early spring

Fig. 3: Photoreduction of O2 around PSI.The alternative text for this image may have been generated using AI.

a Changes in PSI donor-side limitation [Y(ND)] and acceptor-side limitation [Y(NA)] measured by the SP method with increasing PAR (µmol of photons m−2 s−1) in S and ES pine needles (n = 3) (without antimycin A), and b in S (n = 4) and ES (n = 5) isolated thylakoid membranes (100 µg/ml) (with 30 µM antimycin A). Data in a, b indicate the mean ± SEM and n = number of measurements where needles/thylakoids were pooled from 3 to 5 biological replicates. c Schematic of SP-induced maximum P700 oxidation (Pm) followed by steady-state P700 oxidation (P) achieved by intermittent FR illumination. The effective P700 oxidation state was considered as the difference between the Pm and P signal at the 6th cycle of FR illumination. d Changes in P700 absorbance in S and ES pine thylakoid membranes (corresponding to 100 µg/ml chlorophyll) measured with six cycles of intermittent FR illumination in the presence of 30 µM antimycin A (n = 3). e O2 yields in S and ES thylakoid membranes in air-saturated buffer measured by a Clark- electrode with 1000 u ml−1 catalase supplementation in the absence of 250 µM PPBQ and 500 µM FeCy (-A). The colored shaded regions around the O2 yield curve (mean) indicate ±SEM (n = 3) in the Clark-electrode measurements. S and ES pine thylakoid membranes data represent O2 exchange corresponds to the same chlorophyll content (50 µg). d, e n = biological replicates. f Relative abundance of flavodiiron A protein in S and ES pine thylakoid membranes. Two summer samples (S1, S2) and three early spring samples (ES1, ES2, ES3) (Supplementary Table 1) corresponding to 4 µg of chlorophyll (100%) were loaded in separate lanes and 1 µg and 2 µg of chlorophyll (25% and 50%) of S1 were loaded in the first two lanes as quality controls, and the membrane was immunoblotted against anti-FlvA antibody. (For the relative quantitation of Flv proteins in S and ES, see Supplementary Table 4). A Coomassie-stained membrane is shown in the bottom panel. Similar immunoblotting results were obtained in four independent experiments. Source data are provided as a Source Data file.

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