Multiple Rieske Proteins Enable Short- and Long-term Light Adaptation of Synechocystis sp. PCC 6803

Abstract

In contrast to eukaryotes, most cyanobacteria contain several isoforms of the Rieske iron-sulfur protein, PetC, resulting in heterogeneity in the composition of the cytochrome b 6 f complexes. Of three isoforms in the mesophilic cyanobacterium Synechocystis PCC 6803, PetC1 is the major Rieske protein in the cytochrome b 6 f complex, whereas the physiological function of PetC2 and PetC3 is still uncertain. Comparison of wild type and various petC-deficient strains under selected light conditions revealed distinct functional differences: high-light exposure of wild type cells resulted in a significantly enhanced petC2 transcript level, whereas a ⌬petC1 mutant showed a low cytochrome b 6 f content, low electron flux, and a considerably increased accumulation of cytochrome-bd oxidase. In contrast to wild type and ⌬petC1, ⌬petC2 and ⌬petC3 strains still grew fast under high-light conditions although all three Rieske proteins are required for maximal electron transport rates. Although the presence of PetC3 appears to be required for activation of the cyclic electron transport, state transitions were more effective in the absence of PetC2 and/or PetC3. In summary, our data suggest defined roles of the various PetC proteins in short-and long-term light adaptation.

Distinguishing the roles of thylakoid respiratory terminal oxidases in the cyanobacterium Synechocystis sp. PCC 6803

“…Importantly, the gross oxygen production rates were about 4 times higher in the wild-type and Δcox cells compared with Δcyd and Δcox/cyd, suggesting that the quinol-oxidizing activity of Cyd contributes to the alleviation of PSII acceptor side limitation and facilitates gross oxygen production in the presence of DBMIB. This is corroborated by earlier reports that demonstrated an increased level of Cyd associated with an impairment of the Cyt b 6 f complex in mutants lacking LepB1 and PetC1 (Tsunoyama et al, 2009;Zhang et al, 2013).…”

Distinct Roles of Multiple NDH-1 Complexes in the Cyanobacterial Electron Transport Network as Revealed by Kinetic Analysis of P700 + Reduction in Various ndh -Deficient Mutants of Synechocystis sp. Strain PCC6803

“…This light intensity was high enough to oxidize P700 substantially at low electron inflow but was subsaturating at high electron inflow. Both the maximal P700 oxidation level during the pulse and the subsequent P700 ϩ rereduction kinetics in the dark provide information on the electron transport through the PQ pool and the cytochrome (cyt) b 6f complex (2,13,14,17,18), which are shared components of the photosynthetic and respiratory electron transport chains. Also, as FR light selectively excites PS1, electron transport originating from water-splitting PS2, which may complicate the interpretation of the data, could be neglected.…”

“…The cultures were bubbled with ambient air overnight, harvested by centrifugation, and resuspended in fresh BG11 medium. Kinetics of P700 oxidation-reduction was determined in a Dual-PAM-100 system (Walz, Effeltrich, Germany) using standard 1-cm cuvettes as described previously (2,13,14). P700 was specifically excited by 5-s far-red (FR) pulses at 730 nm with maximal intensity (75 W/m 2 ).…”

New insights into the function of the iron deficiency-induced protein C from Synechococcus elongatus PCC 7942

“…Complete P 700 oxidation was achieved by 100 ms saturation pulses (I = 10,000 lmol photons/m 2 s). Rate constants (k) were determined by fitting the decays by single exponential functions and the relative LEF, CEF and REF were calculated as differences of certain rate constant combinations (Bernat et al , 2011Tsunoyama et al 2009). These relative rates were then normalized to the maximal (linear) ETR (ETR max ) as determined by chlorophyll fluorescence light curves (see above).…”