Fig. 6: Dri1 is involved directly or indirectly in photosynthetic and respiratory electron flow.
a Chlorophyll a fluorescence as measured with a pulse-amplitude modulated fluorometer in WT Synechocystis and ∆dri1 mutant. Cells were dark-acclimated for 30 min prior turning on the non-actinic measuring light (ML) followed by turning on orange actinic light (AL, 620 nm) for 5 min, and 2 min of dark relaxation period. F0 - minimum fluorescence in the dark. Fm′dark - maximum fluorescence in the dark. Fm′ - maximum fluorescence in the light. Arrows indicate saturating light pulses. b Whole cell absorption spectra of WT (dark green dashed line) and ∆dri1 (light green plain line), normalized to OD 750 nm. c BN-PAGE of membrane-bound protein complexes of WT and ∆dri1 cells grown in BG-11 for 6 days. Gel image is representative of two independent experiments. d Plastoquinone pool reduction kinetics over 6 min of WT, ∆dri1, and dri(H21A) in the dark to block PSI and PSII activity and in the presence of KCN to block the activity of oxidases (n = 2 biological replicates, individual datapoints are shown, lines represent the means). e–f SDH activity using DCPIP reduction of isolated membranes from Synechocystis grown without (e) or with (f) glucose for 6 days (mean ± SD, n = 3 biological replicates, p-values calculated using a two-sided pairwise t test with holm adjustment). g WT, ∆dri1, and complemented ∆dri1 expressing dri1 in trans grown on agar-solidified BG−11 with or without glucose and DCMU. The image is a composite of three separate plates incubated together and imaged at the same time. h Cultures of three ten-fold dilutions of WT and mutated strains grown as in (g). Images displayed are representative of several independent experiments. i–l Growth curves of cultures grown in BG−11 (i) BG−11 + glucose (j), and BG-11 + glucose + DCMU (k) for 6 days at 30 °C. (l) Growth curve in iron-deficient BG−11 in the presence of the iron chelator DFOA (mean ± SD, individual datapoints are depicted by crosses, n = 3 biological replicates). m Dri1 is a heme-dependent post-translational regulator of SdhB. Source data are provided as a Source Data file.
