Photophosphorylation in vivo

Gimmler, H.

doi:10.1007/978-3-642-66505-9_34

Cited by 18 publications

(9 citation statements)

References 142 publications

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“…Therefore, bundle-sheath plastids have to establish a high capacity for cyclic electron transport. According to the classical view, cyclic electron transport involves the action of PSI and the cytochrome b6/fcomplex (Gimmler 1977). However, the part of the cyclic pathway from PSI back to the cytochrome b6/f-complex is not well defined.…”

Section: Discussionmentioning

confidence: 99%

Differential expression of plastome-encoded ndh genes in mesophyll and bundle-sheath chloroplasts of the C4 plant Sorghum bicolor indicates that the complex I-homologous NAD(P)H-plastoquinone oxidoreductase is involved in cyclic electron transport

Kubicki

Funk

Westhoff

et al. 1996

Planta

102

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Abstract. Cyanobacteria and plastids harbor a putative NAD(P)H-or ferredoxin-plastoquinone oxidoreductase that is homologous to the NADH-ubiquinone oxidoreductase (complex I) of mitochondria and eubacteria. The enzyme is a multimeric protein complex that consists of at least 11 subunits (NDH-A-K) and is localized in the stroma lamellae of the thylakoid membrane system. We investigated the expression of the different subunits of the enzyme in mesophyll and bundle-sheath chloroplasts of Sorghum bicolor [L.] Moench, a C4 plant of the NADPmalic enzyme type. The relative amounts of the subunits NDH-H, -J and -K were strongly increased in bundlesheath plastids as compared to mesophyll plastids. This increase was accompanied by enhanced transcript levels for all subunits except NDH-I. Because the main function of the protein complexes in the thylakoid membranes of bundle-sheath chloroplasts (photosystem I, cytochrome b6/J:complex and ATPase) is the generation of ATP for C02 fixation via cyclic electron transport, we conclude that the NAD(P)H/ferredoxin-plastoquinone oxidoreductase is an essential component of the cyclic electrontransport pathway in chloroplasts.

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Section: Discussionmentioning

confidence: 99%

Differential expression of plastome-encoded ndh genes in mesophyll and bundle-sheath chloroplasts of the C4 plant Sorghum bicolor indicates that the complex I-homologous NAD(P)H-plastoquinone oxidoreductase is involved in cyclic electron transport

Kubicki

Funk

Westhoff

et al. 1996

Planta

102

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“…The results of these experiments indicate that two modes of cyclic electron transfer activity, which differ in their antimycin A sensitivity, can operate in the thylakoid membrane. Regulation of these activities can occur at the level of ferredoxin and is governed by the NADPH/NADP ratio.Evidence has accumulated for the existence of PSI cyclic photophosphorylation activity and its importance for CO2 fixation in chloroplasts (6,7,15,24,25). One of the remaining questions about PSI cyclic electron flow pertains to the mechanism by which the chloroplast regulates cyclic and noncyclic electron transport in order to maintain the necessary balance between ATP and NADPH for CO2 fixation activity.…”

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confidence: 99%

Regulation of Cyclic Photophosphorylation during Ferredoxin-Mediated Electron Transport

Hosler¹,

Yocum²

1987

Plant Physiol.

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Addition of ferredoxin to isolated thylakoid membranes reconstitutes electron transport from water to NADP and to 02 (the Mehler reaction).This electron flow is coupled to ATP-synthesis, and both cyclic and noncyclic electron transport drive photophosphorylation. Under conditions where the NADPH/NADP+ ratio is varied, the amount of ATP synthesis due to cyclic activity is also varied, as is the amount of cyclic activity which is sensitive to antimycin A. Partial inhibition of photosystem II activity with DCMU (which affects reduction of electron carriers of the interphotosystem chain) also affects the level of cyclic activity. The results of these experiments indicate that two modes of cyclic electron transfer activity, which differ in their antimycin A sensitivity, can operate in the thylakoid membrane. Regulation of these activities can occur at the level of ferredoxin and is governed by the NADPH/NADP ratio.Evidence has accumulated for the existence of PSI cyclic photophosphorylation activity and its importance for CO2 fixation in chloroplasts (6,7,15,24,25). One of the remaining questions about PSI cyclic electron flow pertains to the mechanism by which the chloroplast regulates cyclic and noncyclic electron transport in order to maintain the necessary balance between ATP and NADPH for CO2 fixation activity. Partial inhibition of PSII electron flow has been shown to stimulate cyclic photophosphorylation in intact chloroplasts ( 11,12,15) and in isolated thylakoids supplied with ferredoxin (3) as long as anaerobic conditions are maintained. This 'poising' effect presumably reflects a redistribution of electron flow in favor of reduced ferredoxin to PQ3 (with possible intermediate carriers) concurrent with restriction of electron flow from PSII to PQ. Addition of NADPH to isolated thylakoids in the presence of ferredoxin also stimulates cyclic photophosphorylation (1), and the NADPH/NADP+ ratio has been proposed to regulate the partitioning of electrons between the cyclic and noncyclic pathways at the level of ferredoxin (1,2,16,17,21 cyclic photophosphorylation, catalyzed by electron transport from water to ferredoxin/02 or to ferredoxin/NADP+. These experiments, performed under aerobic conditions using saturating light, provide a closer approximation of the activity of PSI cyclic photophosphorylation in vivo than does measurement of a cyclic reaction poised independently of noncyclic electron transport. Our previous studies on this reconstituted electron transport system have shown that electron transport to either ferredoxin/02 or to ferredoxin/NADP+ produces elevated P/O ratios (1.6 versus 1.25 with MeV as the acceptor); the increased P/O ratio is due to the induction, by ferredoxin, of a cyclic or Q-loop electron transfer mechanism (10). This work also suggests the existence of two separate pathways of cyclic photophosphorylation: one pathway is characterized by sensitivity to antimycin A and the requirement for a substantial pool of reduced ferredoxin, while a second pathway is insensitive to anti...

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“…They show a reduction of 50-75% in the photosynthetic rate when CPP was blocked with Antimycin in high-light-adapted cells, but not in lowlight-adapted cells. Gimmler (1977) lists a number of ATP-requiring processes in green cells which can be supported by ATP generated by cyclic photophosphorylation. Among these he includes 'extra ATP' for the photoassimilation of organic compounds, the uptake of ions and the synthesis of proteins, all of these processes being increased in rapidly growing cells.…”

Section: Discussionmentioning

confidence: 99%

Effect of photoacclimation on the energy partitioning between cyclic and non‐cyclic photophosphorylation

Herzig

Dubinsky

1993

New Phytologist

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SUMMARY wasThe effect of photoacclimation on cyclic (CPP), non-cyclic (NCPP), and oxidative phosphorylation investigated in three algal species: Isochrisisgalbana, Scenedesmus quadricauda and Synechococcus leopoliensis. The relative contribution of the three phosphorylative pathways to the incorporation of '^P into soluble and particulate cellular pools was assessed. To block NCPP we used 1 //M dichlorophenyl-dimethylurea (DCMU) which does not interrupt CPP. Oxidative phosphorylation was blocked by purging oxygen with N.^. In all three species the ratio of CPP to the total photophosphorylation (PP) increased in the process of photoacclimation to high light. We suggest that the observed increase in CPP in high-light-adapted cells allows bypassing the relatively slow enzymatic reactions in NCPP while channelling excess electrons to the faster CPP. This redistribution of energy increases ATP supply for the augmented metabolic requirements of fast growing, high-light-adapted cells.

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Photophosphorylation in vivo

Cited by 18 publications

References 142 publications

Differential expression of plastome-encoded ndh genes in mesophyll and bundle-sheath chloroplasts of the C4 plant Sorghum bicolor indicates that the complex I-homologous NAD(P)H-plastoquinone oxidoreductase is involved in cyclic electron transport

Differential expression of plastome-encoded ndh genes in mesophyll and bundle-sheath chloroplasts of the C4 plant Sorghum bicolor indicates that the complex I-homologous NAD(P)H-plastoquinone oxidoreductase is involved in cyclic electron transport

Regulation of Cyclic Photophosphorylation during Ferredoxin-Mediated Electron Transport

Effect of photoacclimation on the energy partitioning between cyclic and non‐cyclic photophosphorylation

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