We have taken a genetic approach to eliminating the presence of photosystem I (PSI) in site-directed mutants of photosystem II (PSII) in the cyanobacterium Synechocystis sp. PCC 6803. By selecting under light-activated heterotrophic conditions, we have inactivated the psaA-psaB operon encoding the PSI reaction center proteins in cells containing deletions of the three psbA genes. We have also i...

Abbreviations: a*PSII, optical cross section for photosys factor; Chl a, chlorophyll a; Ci, inorganic carbon; CO2, carb anhydrase; ETR, electron transport rate; FIRe, fluorescence Fm′ , light-adapted maximum fluorescence; Fv/Fm, maximum tochemistry in photosystem II; HCO3, bicarbonate; HEPE according to Lavergne and Trissl (1995); MIMS, membran enine dinucleotide phosphate; NaHCO3, sodium bicar...

M aria Teresa Giardi Institute of Biochemistry and Ecophysiology of Plants, C N R Area della ricerca di Roma, Via Salaria km 29.3, 00016 M onterotondo Scalo, Italy Z. Naturforsch. 48c, 241 2 4 5 (1993); received November 9, 1992 Photosystem II Core, Phosphorylation, Heterogeneity, Phosphatase, Herbicide-Binding Domain In recent papers the heterogeneous nature of photosystem (PS) II core phospho...

In isolated barley chloroplasts, the presence of 2 millimolar ZnSO(4) inhibits the electron transport activity of photosystem II, as measured by photoreduction of dichlorophenolindophenol, O(2) evolution, and chlorophyll a fluorescence. The inhibition of photosystem II activity can be restored by the addition of the electron donor hydroxylamine or diphenylcarbazide, but not by benzidine and MnC...

Photosystem II is a reaction center protein complex located in photosynthetic membranes of plants, algae, and cyanobacteria. Using light energy, photosystem II catalyzes the oxidation of water and the reduction of plastoquinone, resulting in the release of molecular oxygen. A key component of photosystem II is cytochrome b559, a membrane-embedded heme protein with an unknown function. The cytoc...

Incubation of KCN-Hg-NH(2)OH-inhibited spinach (Spinacia oleracea L.) chloroplasts with p-phenylenediamine for 10 minutes in the dark prior to illumination produced rates of photosystem II cyclic photophosphorylation up to 2-fold greater than the rates obtained without incubation. Partial oxidation of p-phenylenediaine with ferricyanide produced a similar stimulation of ATP synthesis; addition ...

The role of the light-harvesting complex Lhcb4 (CP29) in photosynthesis was investigated in Arabidopsis thaliana by characterizing knockout lines for each of the three Lhcb4 isoforms (Lhcb4.1/4.2/4.3). Plants lacking all isoforms (koLhcb4) showed a compensatory increase of Lhcb1 and a slightly reduced photosystem II/I ratio with respect to the wild type. The absence of Lhcb4 did not result in a...

The efficiency of oxygenic photosynthesis depends on the presence of core antenna chlorophyll closely associated with the photochemical reaction centers of both photosystem II (PSII) and photosystem I (PSI). Although the number and overall arrangement of these chlorophylls in PSII and PSI differ, structural comparison reveals a cluster of 26 conserved chlorophylls in nearly identical positions ...

Photosynthetic organisms must regulate photosystem stoichiometry (photosystem I-to-photosystem II ratio) under various light conditions. Transcriptional regulation of the psaAB genes is a critical process for this photoacclimation in cyanobacteria. In the course of our screening of transcriptional regulators in the cyanobacterium Synechocystis sp. PCC 6803, we found that chlorophyll accumulatio...