Fig. 3: CurT depletion causes cell division defects in Synechococcus.
a Multiple sequence alignment of Synechocystis and Synechococcus CurT and Chlamydomonas reinhardtii CURT1 isoforms. Predicted α-helices are indicated; residues forming helices (Jpred4, TMHMM) are in bold. Identical and physiochemically similar amino acids conserved in ≥80% of sequences are shaded black and grey, respectively. Amphipathic, transmembrane, and soluble helices are indicated in magenta, blue, and black. Predicted chloroplast transit peptides are shown in lower case. b Confocal micrographs of Synechococcus curT knock-out (KO) and complementation (compl.) mutants. Magenta represents chlorophyll a and phycobilin red fluorescence (red FL). c Growth curves of WT, KO, and compl. strains cultivated for 108 h at 30 °C and 50 µmol photons m−2 s−1 recorded as OD720 by PSI Multicultivator inbuilt photometer (i.e., apparent OD720; mean ± SD of n = 4 biological replicates). d Exponential growth phase cell duplication times derived from growth curves shown in (c). e Final OD730 of cultures shown in (c). f Dividing daughter cell-length distributions of Synechococcus WT (n = 60), KO (n = 120), and compl. (n = 120) mutant cells obtained from two independent clones each. Insert shows corresponding cell shape maps generated though MicrobeJ (see Methods). g Dividing daughter-cell length ratios (longest:shortest cell pole-to-pole-length) for cells represented in (f). Boxplots centre line = median; cross = mean; boxes = 25th–75th percentiles; whiskers = 1.5 × IQR; circles = outliers; all datapoints shown. Sample sizes n as shown in (f). Numbers below boxplots correspond to means ± SD. For d,e,g: Uppercase letters indicate statistically significant differences (p ≤ 0.05) according to multiple simultaneous comparisons in post hoc Bonferroni-Holm-corrected Tukey HSD tests after significant among-group differences were detected by two-sided one-way ANOVA (p = 8.00 × 10−4 (d); 1.55 × 10−9 (e); 1.11 × 10−16 (g). h Representative transmission electron micrographs (TEM) of WT (n = 12) and KO (n = 47) cell longitudinal sections. White arrowheads indicate thylakoid layer dissociation sites in the KO mutant.
