Cyanobacterial PGRL1-LIKE is functionally analogous to plant PGRL1. a Bacterial two-hybrid analyses. The degree of interaction is indicated by differential β-galactosidase activity (i.e. activity above the baseline activity of the negative control). Known interacting proteins served as positive control, known noninteracting proteins as negative control (see Methods). Error bars correspond to the standard deviation for n = 3 independent experiments and statistically significant differences with respect to WT or synpgr5 according to Holm-corrected two-sided Student’s t-tests are indicated with asterisks (***P ≤ 0.001, n.s., not statistically significant). b Immunoblot detection of atPGRL1 and atPGR5 proteins in various strains of Synechocystis, all of which lack Sll1217/synPGRL1-LIKE (synpgrl1-like) and/or synPGR5. Extracts of the synpgrl1-like strain and WT A. thaliana were used as functional controls, and a segment of the Coomassie Brilliant Blue (CBB) stained blot is provided as a loading control. c Effects of the absence of synPGRL1-LIKE on CEF. Average t0.5P700ox values are provided for the Synechocystis strains from panel b, as well as other strains from Fig. 1 as controls. Error bars correspond to the standard deviation for n = 6/6/5/5/4/3/6/4 (order as displayed) independent experiments and statistically significant differences according to Holm-corrected two-sided Student’s t-tests are indicated with asterisks (*P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, n.s., not statistically significant).