Isolation of a psaF-deficient mutant of Chlamydomonas reinhardtii: efficient interaction of plastocyanin with the photosystem I reaction center is mediated by the PsaF subunit.

Farah, Joseph A.; Rappaport, Fabrice; Choquet, Yves; Joliot, Pierre; Rochaix, Jean‐David

doi:10.1002/j.1460-2075.1995.tb00180.x

Cited by 134 publications

(111 citation statements)

References 48 publications

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“…The pigments of subunits PsaL and PsaM play a key role in the excitonic connectivity of PSI monomers within a trimer (Sener et al, 2004). A further subunit, PsaF, is located on the side of the PSI monomer opposite to PsaL; in green algae and plants, the lumenal face of this subunit is involved in binding plastocyanin and cytochrome c 6 (Farah et al, 1995), although not in T. elongatus (Mühlenhoff and Chauvat, 1996). The remaining subunits, PsaI, PsaJ, PsaK, PsaM, and PsaX, are small polypeptides believed to be involved with stabilizing PSI; loss of any one of these proteins does not significantly reduce the functionality of the protein complex (Schluchter et al, 1996;Xu et al, 1994;Naithani et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Lateral Segregation of Photosystem I in Cyanobacterial Thylakoids

et al. 2017

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Photosystem I (PSI) is the dominant photosystem in cyanobacteria and it plays a pivotal role in cyanobacterial metabolism. Despite its biological importance, the native organization of PSI in cyanobacterial thylakoid membranes is poorly understood. Here, we use atomic force microscopy (AFM) to show that ordered, extensive macromolecular arrays of PSI complexes are present in thylakoids from Thermosynechococcus elongatus, Synechococcus sp PCC 7002, and Synechocystis sp PCC 6803. Hyperspectral confocal fluorescence microscopy and three-dimensional structured illumination microscopy of Synechocystis sp PCC 6803 cells visualize PSI domains within the context of the complete thylakoid system. Crystallographic and AFM data were used to build a structural model of a membrane landscape comprising 96 PSI trimers and 27,648 chlorophyll a molecules. Rather than facilitating intertrimer energy transfer, the close associations between PSI primarily maximize packing efficiency; short-range interactions with Complex I and cytochrome b 6 f are excluded from these regions of the membrane, so PSI turnover is sustained by long-distance diffusion of the electron donors at the membrane surface. Elsewhere, PSI-photosystem II contact zones provide sites for docking phycobilisomes and the formation of megacomplexes. PSI-enriched domains in cyanobacteria might foreshadow the partitioning of PSI into stromal lamellae in plants, similarly sustained by long-distance diffusion of electron carriers.

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Section: Introductionmentioning

confidence: 99%

Lateral Segregation of Photosystem I in Cyanobacterial Thylakoids

et al. 2017

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“…enables efficient interaction between the cyanobacterial PSI and the algal donors (26). It is, however, not clear why this binding site within the N-terminal part of PsaF evolved, because the electron transfer between PSI and the cytochrome b 6 /f complex is not limiting for linear photosynthetic electron transfer under moderate light conditions, even in the absence of PsaF (21).…”

Section: Discussionmentioning

confidence: 99%

“…One major difference concerns the PsaF subunit that is partly exposed to the lumenal space of the thylakoids. The PsaF-deficient mutant of C. reinhardtii, 3bF, is drastically impaired in electron transfer from both plastocyanin and cytochrome c 6 to PSI (21,22). In contrast, the specific deletion of the psaF gene in cyanobacteria does not affect photoautotrophic growth (23).…”

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confidence: 99%

Limitation in Electron Transfer in Photosystem I Donor Side Mutants of Chlamydomonas reinhardtii

Hippler¹,

Biehler²,

Krieger‐Liszkay³

et al. 2000

Journal of Biological Chemistry

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Strains of Chlamydomonas reinhardtii lacking thePsaF gene or containing the mutation K23Q within the N-terminal part of PsaF are sensitive to high light (>400 E m ؊2 s ؊1 ) under aerobic conditions. In vitro experiments indicate that the sensitivity to high light of the isolated photosystem I (PSI) complex from wild type and from PsaF mutants is similar. In vivo measurements of photochemical quenching and oxygen evolution show that impairment of the donor side of PSI in the PsaF mutants leads to a diminished linear electron transfer and/or a decrease of photosystem II (PSII) activity in high light. Thermoluminescence measurements indicate that the PSII reaction center is directly affected under photo-oxidative stress when the rate of electron transfer becomes limiting in the PsaF-deficient strain and in the PsaF mutant K23Q. We have isolated a high light-resistant PsaF-deficient suppressor strain that has a high chlorophyll a/b ratio and is affected in the assembly of light-harvesting complex. These results indicate that under high light a functionally intact donor side of PSI is essential for protection of C. reinhardtii against photo-oxidative damage when the photosystems are properly connected to their light-harvesting antennae.Photosynthesis is driven by light. Photons are absorbed by pigments of the light harvesting chlorophyll-carotenoid-protein complexes that are associated with the membrane embedded photosynthetic reaction centers. Excitation energy can be transferred to the reaction centers where it induces charge separation across the membrane. This leads to a series of electron transfer reactions resulting in oxidation of water and the production of chemical energy in the form of ATP and NADPH, which are used for CO 2 fixation. If the absorption of light exceeds the capacity of photosynthetic energy consumption, over-reduction of the electron transport carriers and increase of the lifetime of excited states in the light-harvestingantennae occur. Over-reduction of the electron carriers can lead to photo-oxidative damage by reactive oxygen species. O 2 can be directly reduced by PSI 1 (1) generating superoxide anion radical (O 2 . ) and other reactive oxygen species. Increase in the lifetime of excited singlet chlorophyll increases the probability of triplet chlorophyll formation, which can react with O 2 to produce 1 O 2 (2, 3). Reactive oxygen species cause photo-oxidative damage, especially to PSII, which is considered to be the primary target for photoinhibition (4 -6). Thus, mechanisms that balance energy input through photochemistry with energy consumption through CO 2 assimilation and other metabolic pathways are essential for plant survival.Mechanisms that balance energy input and consumption can be divided into short and long term responses. Short term responses include nonphotochemical dissipation of excess energy (7, 8) and reduction of energy transfer to PSII through state transition, a process that leads to a redistribution of excitation energy to PSI by a reorganization of the antennae (...

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“…Such analyses have revealed that PSI-K plays a role in organizing LHCI (Jensen et al, 2000), PSI-N is necessary for the interaction of plastocyanin with PSI (Haldrup et al, 1999), and PSI-H putatively is the attachment site for LHCII during state transitions (Lunde et al, 2000). Loss of PSI-E or -F has far more dramatic consequences on the photoautotrophic growth of Arabidopsis than corresponding mutations in cyanobacteria or algae (Chitnis et al, 1989(Chitnis et al, , 1991 Zhao et al, 1993; Xu et al, 1994;Farah et al, 1995) Article, publication date, and citation information can be found at www.plantphysiol.org/cgi …”

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confidence: 99%

Single and Double Knockouts of the Genes for Photosystem I Subunits G, K, and H of Arabidopsis. Effects on Photosystem I Composition, Photosynthetic Electron Flow, and State Transitions

Varotto¹,

Pesaresi²,

Jahns

et al. 2002

Plant Physiology

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Zentrum zur Identifikation von Genfunktionen durch Insertionsmutagenese bei Arabidopsis thaliana (C.V., P.P., A.L., D.L.), and Abteilung fü r Pflanzenzü chtung und Ertragsphysiologie, Max-Planck-Institut fü r Zü chtungsforschung, Carl-von-Linné Weg 10, 50829 Kö ln, Germany (M.T., F.Sc., F.Sa., D.L.); and Institut fü r Biochemie der Pflanzen, Heinrich-Heine-Universität Dü sseldorf, Universitätsstra␤e 1, 40225 Dü sseldorf, Germany (P.J.)Photosystem I (PSI) of higher plants contains 18 subunits. Using Arabidopsis En insertion lines, we have isolated knockout alleles of the genes psaG, psaH2, and psaK, which code for PSI-G, -H, and -K. In the mutants psak-1 and psag-1.4, complete loss of PSI-K and -G, respectively, was confirmed, whereas the residual H level in psah2-1.4 is due to a second gene encoding PSI-H, psaH1. Double mutants, lacking PSI-G, and also -K, or a fraction of -H, together with the three single mutants were characterized for their growth phenotypes and PSI polypeptide composition. In general, the loss of each subunit has secondary, in some cases additive, effects on the abundance of other PSI polypeptides, such as D, E, H, L, N, and the light-harvesting complex I proteins Lhca2 and 3. In the G-less mutant psag-1.4, the variation in PSI composition suggests that PSI-G stabilizes the PSI-core. Levels of light-harvesting complex I proteins in plants, which lack simultaneously PSI-G and -K, indicate that PSI subunits other than G and K can also bind Lhca2 and 3. In the same single and double mutants, psag-1. 4, psak-1, psah2-1.4, psag-1.4/psah2-1.4, and psag-1.4/psak-1 photosynthetic electron flow and excitation energy quenching were analyzed to address the roles of the various subunits in P700 reduction (mediated by PSI-F and -N) and oxidation (PSI-E), and state transitions (PSI-H). Based on the results, we also suggest for PSI-K a role in state transitions.PSI mediates light-driven electron transport from plastocyanin to ferredoxin across the thylakoid membrane. The PSI complexes in plants and cyanobacteria are basically similar, but there are some notable differences (Scheller et al., 1997): The plant PSI is slightly larger (Kitmitto et al., 1997), trimer formation has been observed only in cyanobacteria (Chitnis and Chitnis, 1993), and the plant PSI core is associated with the light-harvesting complex I (LHCI), which is made up of the four different chlorophyll (Chl)/carotenoidbinding polypeptides Lhca1-4 (Jansson, 1999). In addition, among the 14 subunits that form the core of PSI in flowering plants (PSI-A through -O; Scheller et al., 1997Scheller et al., , 2001; H.V. Scheller, personal communication), four subunits (PSI-G, -H, -N, and -O; Okkels et al., 1989Okkels et al., , 1992 Knoetzel and Simpson, 1993; H.V. Scheller, personal communication) are not present in cyanobacteria. Conversely, no homolog of the cyanobacterial PSI-M has been found yet in higher plants.Most essential for PSI function are the three subunits PSI-A, -B, and -C, which bind the electron acceptors. These acceptor-bi...

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Isolation of a psaF-deficient mutant of Chlamydomonas reinhardtii: efficient interaction of plastocyanin with the photosystem I reaction center is mediated by the PsaF subunit.

Cited by 134 publications

References 48 publications

Lateral Segregation of Photosystem I in Cyanobacterial Thylakoids

Lateral Segregation of Photosystem I in Cyanobacterial Thylakoids

Limitation in Electron Transfer in Photosystem I Donor Side Mutants of Chlamydomonas reinhardtii

Single and Double Knockouts of the Genes for Photosystem I Subunits G, K, and H of Arabidopsis. Effects on Photosystem I Composition, Photosynthetic Electron Flow, and State Transitions

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