Cobalt ions inhibit electron-transport activity of Photosystem II without affecting Photosystem I

Tripathy, Baishnab C.; Bhatia, B.; Mohanty, Prasanna

doi:10.1016/0005-2728(83)90160-3

Cited by 35 publications

(11 citation statements)

References 17 publications

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“…Adding a saturating concentration of DPC, NH2OH and MnCl2 restored the Agtinduced inhibition of PS II (DCPIP photoreduction and Chl a fluorescence) but failed to do so for the Nittinduced inhibition. This indicates that Ag+ inhibits electron transport at the oxidizing side of PS II, and Ni2+ either destroys the photosynthetic membranes or inactivates the PS II reaction center, as reported for Ni2+ and Co2+ in barley chloroplasts (19,20). There is every likelihood that Ni2+ like Cu2+ also tends to acquire or donate electrons and reacts with oxygen to produce free radicals such as superoxide and hydroxyl and thus may cause peroxidative degradation of membrane lipids and chlorophyll, as is known for Cu in spinach chloroplasts (15) and Scenedesmus (16).…”

Section: And Discussionsupporting

confidence: 63%

Inhibition of photosynthetic electron transport in Nostoc muscorum by Ni2+ and Ag+.

Singh¹,

Prasad²,

C.³

1991

J. Gen. Appl. Microbiol.

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This paper presents the inhibition of photosynthetic electron transport chain of Nostoc muscorum by divalent Ni2+ and monovalent Ag+. PS I (DCPIP/ASC-MV) and PS II (H20-*PBQ) activities were markedly inhibited by Ni2+ and Ag+ in a concentration-dependent fashion but PS II was more susceptible than PS I to Ni2+. Ago was more toxic to PS I than PS II. The greater sensitivity of PS II to Ni2+ was further confirmed by the inhibition of DCPIP photoreduction and Chl a fluorescence. Restoration of Agtinduced inhibition of DCPIP photoreduction and Chl a fluorescence by artificial electron donors (DPC, NH2OH, MnCl2) and their failure to restore Ni2t induced inhibition suggests that Ni24 inactivates PS II by causing alteration and destruction of photosynthetic membranes, but Ag+ inhibits the electron flow at the oxidizing side of PS II. Nevertheless, the suppression of the fluorescence intensity at low concentrations of both metal cations points to the involvement of phycobilisomes in the inhibition of PS II activity.Though a considerable amount of work has been done on the metabolic processes of algae (12,22), compared to higher plants, the photosynthetic system of algae and cyanobacteria as affected by heavy metals are least explored. Interest in work on metal toxicity in cyanobacteria stems from: (i) their prokaryotic nature but higher plant type photosynthesis, (ii) their role in the nitrogen economy of the biosphere, and (iii) the ease of experimentally manipulating them.The effects of Hg2+, Cd2+, Zn2+ and Ni2+ on the electron transport of isolated chloroplasts to ascertain the modes of action of these cations on the photosynthesis have been documented (3,7,18,19). These studies indicate that the metal ions specifically affect the carriers and reaction centers thereby interrupting the flow of

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Section: And Discussionsupporting

confidence: 63%

Inhibition of photosynthetic electron transport in Nostoc muscorum by Ni2+ and Ag+.

Singh¹,

Prasad²,

C.³

1991

J. Gen. Appl. Microbiol.

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“…PSII is more susceptible to photodynamic damage than PSI. The latter is usually more resistant to the damages caused by stress such as drought, heat, and heavy metals ( 13,23,24). In photodynamically damaged plants, the DCMUinsensitive electron transport from H20 to MV and the increase of the above DCMU-insensitive rate with the exposure time to the sunlight is of interest.…”

Section: Discussionmentioning

confidence: 99%

5-Aminolevulinic Acid Induced Photodynamic Damage of the Photosynthetic Electron Transport Chain of Cucumber (Cucumis sativus L.) Cotyledons

Tripathy

Chakraborty²

1991

Plant Physiol.

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Cucumber (Cucumis sativus L. cv Poinsette) plants were sprayed with 20 millimolar 5-aminolevulinic acid (ALA) and then incubated in dark for 14 hours. Upon transfer to sunlight (=800 watts per square meter) the plants died after 5 hours of exposure due to photosensitization reaction of metalloporphyrins. Due to the photodynamic damage, photosystem 11 (PSII), photosystem I (PSI), and whole chain reactions were impaired. PSII activity was more susceptible to photodynamic damage than PSI. The variable fluorescence was significantly reduced in ALA-treated plants within 1 hour of exposure to sunlight. At low temperature (770K), the PSI fluorescence peak height (F734) was drastically reduced and blue shifted by 6 nanometers. The photodynamic damage was irreversible; rather, it continued upon dark incubation of ALAtreated cucumber plants exposed to sunlight for 15 minutes. In

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“…It inhibits the photosynthetic electron transport at PS II reaction center and has no effect on PSI (Tripathy et al 1983). Unlike many other metal ions, cobalt ions do not have a strong affinity for SH-groups (Van Assche and Clijsters 1990).…”

Section: Introductionmentioning

confidence: 99%

Cobalt induced changes in photosystem activity in Synechocystis PCC 6803: Alterations in energy distribution and stoichiometry

Tiwari

Mchanty

1996

Photosynth Res

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Adaptive responses to excess (supraoptimal) level of cobalt supplied to the growth medium were studied in the cyanobacterium Synechocystis PCC 6803. Growth of cells in the medium containing 10 μM CoCl2 led to a large stimulation (50%) in O2-evolution and an overall increase (∼30%) in the photosynthetic electron transport rates. Analysis of variable Chl a fluorescence yield of PS II and immuno-detection of Photosystem II (PS II) reaction-center protein D1, showed a small increase (15-20%) in the number of PS II units in cobalt-grown cells. Cobalt-grown cells, therefore, had a slightly elevated PS II/PS I ratio compared to control.We observed alteration in the extent of energy distribution between the two photosystems in the eobalt grown cells. Energy was preferentially distributed in favour of PS II accompanied by a reduction in the extent of energy transfer from PS II to PS I in cobalt-grown cells. These cells also showed a smaller PS I absorption cross-section and a smaller size of intersystem electron pool than the control cells. Thus, our results suggest that supplementation of 10 μM CoCl2, to the normal growth medium causes multiple changes involving small increase in PS II to PS I ratio, enhanced funneling of energy to PS II and an increase in PS I electron transport, decrease PS I cross section and reduction in intersystem pool size. The cumulative effects of these alterations cause stimulation in electron transport and O2 evolution.

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Cobalt ions inhibit electron-transport activity of Photosystem II without affecting Photosystem I

Cited by 35 publications

References 17 publications

Inhibition of photosynthetic electron transport in Nostoc muscorum by Ni2+ and Ag+.

Inhibition of photosynthetic electron transport in Nostoc muscorum by Ni2+ and Ag+.

5-Aminolevulinic Acid Induced Photodynamic Damage of the Photosynthetic Electron Transport Chain of Cucumber (Cucumis sativus L.) Cotyledons

Cobalt induced changes in photosystem activity in Synechocystis PCC 6803: Alterations in energy distribution and stoichiometry

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