Control of chloroplast electron transport by phosphorylation of thylakoid proteins

Horton, Peter

doi:10.1016/0014-5793(83)80479-7

Cited by 130 publications

(36 citation statements)

References 43 publications

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“…Their combined effects are represented by the quench coefficient, qNp (10, 1 1), or briefly, qN. This coefficient includes the 'energy-dependent' quench coefficient, qE, which describes the degree of quenching caused by the pH gradient across the thylakoid membrane (1,3,15,17,18) as well as transfer of quanta to PSI (10,12) or their resonant transfer to other molecules, ultimately generating heat (4). Increases in nonphotochemical quenching can be measured as a decrease in the variable fluorescence elicited by a brief pulse of intense light applied in addition to any actinic light used to drive photosynthesis (15).…”

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confidence: 99%

Topography of Photosynthetic Activity of Leaves Obtained from Video Images of Chlorophyll Fluorescence

Daley¹,

Raschke²,

Ball³

et al. 1989

Plant Physiol.

192

111

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The distribution of photosynthetic activity over the area of a leaf and its change with time was determined (at low partial pressure of 02) by recording images of chlorophyll fluorescence during saturating light flashes. Simultaneously, the gas exchange was being measured. Reductions of local fluorescence intensity quantitatively displayed the extent of nonphotochemical quenching; quench coefficients, qN, were computed pixel by pixel. Because rates of photosynthetic electron transport are positively correlated with (1 -qN), computed images of (1 -qN) represented topographies of photosynthetic activity. Following application of abscisic acid to the heterobaric leaves of Xanthium strumarium L., clearly delineated regions varying in nonphotochemical quenching appeared that coincided with areoles formed by minor veins and indicated stomatal closure in groups.Until recently, photosynthesis in leaves was studied under the assumption of a uniform distribution of photosynthetic activity. However, there is evidence that this is not always the case. For instance, Farquhar et al. (8) (5) showed the appearance of such patterns during the assimilation of CO2 by leaves that had been given 'ABA by starch-printing or '4C-autoradiography. Areas differing in apparent photosynthetic activity coincided with the areoles which, in heterobaric leaves,

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confidence: 99%

Topography of Photosynthetic Activity of Leaves Obtained from Video Images of Chlorophyll Fluorescence

Daley¹,

Raschke²,

Ball³

et al. 1989

Plant Physiol.

192

111

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“…It has been suggested (7) that these transitions could stem from controlled changes in the concentration of (various) cations in the vicinity of the photosynthetic membranes; these changes in isolated thylakoids were shown to affect the balance between the two photosystems (8 are imbalanced. The changes in the balance between the two photosystems have been mostly explained by opposite changes in the cross sections for light absorption of the photosystems caused by partial migration of antennae (possibly LHChl) from one photosystem to the other, and vice versa (22)(23)(24). Such migration possibly arises from changes in electrostatic interactions induced by the charged phosphoryl group (25).…”

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confidence: 99%

Evidence that phosphorylation and dephosphorylation regulate the distribution of excitation energy between the two photosystems of photosynthesis in vivo : Photoacoustic and fluorimetric study of an intact leaf

Canaani

Barber

Malkin

1984

Proc. Natl. Acad. Sci. U.S.A.

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State 1-state 2 transitions in an intact tobacco leaf were monitored by the photoacoustic method. Modulated oxygen evolution yield and its enhancement by continuous far-red light ("Emerson enhancement") were used to characterize the balance of light distribution between the two photosystems. These measurements were additionally supported by fluorituetry. Adaptation of the leaf to far-red light (X ; 700 nm), mainly absorbed in photosystem I (light 1), results in state 1 'where short-wavelength light (light 2) is distributed in favor of photosystem II. This is shown by a low yield of oxygen evolution, a high extent of Emerson enhancement, a concomitantly high extent of fluorescence quenching by far-red light, and a low ratio of the 77 K emission peaks at 730 and 695 nm. The magnitudes of these parameters were reversed when the leaf was adapted to light 2 (state 2), indicating a change towards a more equal' distribution of the excitation between the two photosystems. Preincubation of an intact leaf with NaF, a specific phosphatase inhibitor, stimulated the extent of adaptation to light 2, shown by all the above criteria, and completely abolished adaptation to light 1. Light 1 preillumination prior to NaF treatment resulted initially in state 1, but then a transition to'state 2 was irreversibly induced by any light. The NaF effect was specific because NaCl did not affect the state 1-state 2 transitions. Leaching out the NaF restored the original physiological'transitions of the leaf. NaF presumably acts here in the same way as it acts in isolated thylakoids-by blocking the dephosphorylation of membranal proteins ( over-excites PSI (light 1-e.g., far-red li'ght, A ; 700 nm). In this state, shorter-wavelength light (light 2-most typically 650 nm) will be initially distributed so that PSII receives excess excitation relative to PSI. Conversely, state 2 results from an adaptation of an initial over-excitation of PSII by light 2, leading towards a more balanced distribution. These changes are reflected in the levels of oxygen evolution, chlorophyll a fluorescence, and the immediate effect of far-red light on them: enhancement of oxygen evolution (Emerson enhancement) and quenching of fluorescence. The extent of the immediate far-red light effect indicates the degree of over-excitation in PSII relative to PSI. These changes are also reflected in the low-temperature '(77 K) chlorophyll a emission spectrum (5). In state 2 the longer wavelength emission peak (between 715 and 730 nm), originating from PSI, is enhanced relative to the shorter wavelength peaks (=684 and =695 nm) associated with PSII, compared to those of cells adapted to state 1. In leaves, state 1-state 2 transitions were also observed, but only by room-temperature fluorimetry (9).The molecular mechanism behind the above transitions is still not resolved conclusively. It has been suggested (7) that these transitions could stem from controlled changes in the concentration of (various) cations in the vicinity of the photosynthetic membranes; these change...

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“…The inhibition of the transition to state 2 could be due to several alternative reasons: inactivation of the kinase, changes in the physical (24) and compositional properties of the membranes, (1 1, 12) affecting the light harvesting complex diffusion in the lipid matrix (17,25). It is also possible that the excess level of electron transport products (NADPH and ATP) due to impaired stromal carbon metabolism could affect the kinase activity by a feedback mechanism in order to balance the rate of excitation of PSII with the rate of carbon assimilation, as suggested by Horton (19). Another possibility may arise from the effect of leaf dehydration on stromal ionic concentration.…”

Section: Discussionmentioning

confidence: 99%

Photosynthetic Responses of Leaves to Water Stress, Expressed by Photoacoustics and Related Methods

Havaux¹,

Canaani²,

Malkin³

1986

Plant Physiol.

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The effect of rapid dehydration of detached tobacco leaves (Nicotiana tabacum L.) on the photochemical apparatus of photosynthesis was studied in vivo by a combination of methods: photoacoustics, chlorophyll a fluorescence, and cytochrome fdifference spectroscopy. It was shown that the inhibition of gross 02 evolution was mainly caused by inactivation of PSII: (a) The saturation curve of cytochrome-fphotooxidation by farred (>710 nanometers) light was resistant to the stress, leading to the conclusion that photosystem I (PSI) was largely unaffected by the stress. (b) The extent of the chlorophyll a variable fluorescence arising from photosystem II (PSII) decreased with the progression of the stress, but was largely unaffected when the leaf was preincubated with electron donors to PSII, such as hydroxylamine. It is concluded that the drought damage to PSII occurred on the photooxidative side. Despite the extensive inhibition of PSII and the relative preservation of PSI, the apparent PSII/PSI activity balance was somewhat larger in stressed leaves than in the control, as indicated by photoacoustic measurements of Emerson enhancement. These measurements were performed continuously under conditions which favor transitions to either state 1 or 2, showing that the transition to state 2 was considerably inhibited. Simultaneous measurements of chlorophyll fluorescence induction at 680 and 730 nm at room temperature were also used to probe changes in energy distribution between PSII and PSI and indicated that the transition from a dark adapted state to state 2 was also affected in water-stressed leaves. The saturation curve of the far-red light effect in Emerson enhancement was not changed by the stress, giving another independent evidence for the drought resistance of PSI activity. This apparent preservation of the imbalance in photochemical activities in favor of PSII, despite the fact that PSII is strongly inhibited, and PSI is not, supports a previous suggestion that the electron transfer between the two photosystems is not random but that a large extent of PSII and PSI units are specifically linked.A photoacoustic study, reported in the first paper of this series (16), has confirmed that desiccation of tobacco leaves results in a substantial reduction of the in vivo quantum yield of gross 02 evolution and indicated a direct effect on whole chain electron transfer, independent of stomatal aperture. Work with algae and isolated chloroplasts pinpointed some partial reactions of electron transport to be more sensitive to water stress than others. ' Supported by the United States-Israel Binational Agricultural Research and Development Fund (BARD). Grant No. I-388-8 1.For example, in algae undergoing desiccation, both electron transport between PSII and PSI and water splitting were most sensitive to desiccation (31). Block of electron transport on the donor and acceptor side of PSII has also been reported in dried chloroplast films (23). In intact leaves exposed to water stress conditions, the peak P in the Chl a...

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Control of chloroplast electron transport by phosphorylation of thylakoid proteins

Cited by 130 publications

References 43 publications

Topography of Photosynthetic Activity of Leaves Obtained from Video Images of Chlorophyll Fluorescence

Topography of Photosynthetic Activity of Leaves Obtained from Video Images of Chlorophyll Fluorescence

Evidence that phosphorylation and dephosphorylation regulate the distribution of excitation energy between the two photosystems of photosynthesis in vivo : Photoacoustic and fluorimetric study of an intact leaf

Photosynthetic Responses of Leaves to Water Stress, Expressed by Photoacoustics and Related Methods

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