Photosynthetic Responses of Pisum sativum to an Increase in Irradiance During Growth. II. Thylakoid Membrane Components

1987 ◽  
Vol 14 (1) ◽  
pp. 9 ◽  
Author(s):  
WS Chow ◽  
JM Anderson
Keyword(s):  
Thylakoid Membrane ◽  
High Light ◽  
Cytochrome F ◽  
Reaction Centre ◽  
Leaf Photosynthesis ◽  
Low Light ◽  
Ps Ii ◽  
Reaction Centres ◽  
Ps I ◽  
Membrane Components

Following the transfer of pea plants grown at low irradiance (60 �mol photons m-2 s-1, 16 h light/8 h dark cycles) to high irradiance (390 �mol photons m-2 s-1), the extents and time courses of the increase in the concentrations of thylakoid membrane components on a chlorophyll basis have been determined. The increase in cytochrome f (~ 70%) and plastoquinone (~ 50%) contents occurred with no noticeable lag phase. The increase in photosystem Il reaction centres (PS II, ~ 35%) and ATP synthetase (~ 90%) occurred possibly with a lag period of 1-2 days. In contrast, there was no significant increase in the concentration of P700 (reaction centre) of PS I complex. The concentration of PS II reaction centres measured by atrazine-binding exceeded that from the O2 yield per single-turnover flash by a factor of 1.17 (compared with the expected value of 1.14); this contrasts with the factor of 1.8 obtained by P. A. Jursinic and R. Dennenberg [Arch. Biochem. Biophys. (1985) 241, 540-9]. It is suggested that both methods are equivalent for the determination of PS II reaction centres in active chloroplasts. The stoichiometry of PS II : cyt f: PS I was highly flexible, and not fixed at 1 : 1 : 1. We obtained the stoichiometries of 1.25 : 0.7 : 1.0 for low-light pea chloroplasts and 1.7 : 1.25 : 1.0 for chloroplasts in pea plants that had been transferred to high light for about 10 days, demonstrating the dynamic nature of thylakoid composition and function. In the first 2 days after transferring low light pea plants to high light, the time course of the increase in CO2- and light-saturated rate of leaf photosynthesis corresponded better with that of cyt f and plastoquinone than that of other chloroplast components examined. This suggests that, during the transition period, the relatively prompt increase of cyt b/f and plastoquinone plays a part in enhancing the CO2- and light-saturated rate of leaf photosynthesis.

Lipids in and around photosynthetic reaction centres

2005 ◽  
Vol 33 (5) ◽  
pp. 924-930 ◽  
Author(s):  
P.K. Fyfe ◽  
M.R. Jones
Keyword(s):  
Membrane Lipids ◽  
Protein Complexes ◽  
Reaction Centre ◽  
Photosynthetic Membrane ◽  
Ps Ii ◽  
X Ray Crystallography ◽  
Structural Support ◽  
Reaction Centres ◽  
Ps I ◽  
Pigment Protein Complexes

Reaction centres are membrane-embedded pigment–protein complexes that transduce the energy of sunlight into a biologically useful form. The most heavily studied reaction centres are the PS-I (Photosystem I) and PS-II complexes from oxygenic phototrophs, and the reaction centre from purple photosynthetic bacteria. A great deal is known about the compositions and structures of these reaction centres, and the mechanism of light-activated transmembrane electron transfer, but less is known about how they interact with other components of the photosynthetic membrane, including the membrane lipids. X-ray crystallography has provided high-resolution structures for PS-I and the purple bacterial reaction centre, and revealed binding sites for a number of lipids, either embedded in the protein interior or attached to the protein surface. These lipids play a variety of roles, including the binding of cofactors and the provision of structural support. The challenges of modelling surface-associated electron density features such as lipids, detergents, small amphiphiles and ions are discussed.

Photoinactivation of Photosynthetic Electron Transport under Anaerobic and Aerobic Conditions in Isolated Thylakoids of Spinach

1992 ◽  
Vol 47 (1-2) ◽  
pp. 63-68 ◽  
Author(s):  
Rekha Chaturvedi ◽  
M. Singh ◽  
P. V. Sane
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Oxygen Evolving Complex ◽  
Reaction Centre ◽  
Ps Ii ◽  
Ps I ◽  
S2 State ◽  
The Stability ◽  
Oxygen Evolving ◽  
Spinach Thylakoids

Abstract The effect of exposure to strong white light on photosynthetic electron transport reactions of PS I and PS II were investigated in spinach thylakoids in the absence or presence of oxygen. Irrespective of the conditions used for photoinactivation, the damage to PS II was always much more than to PS I. Photoinactivation was severe under anaerobic conditions compared to that in air for the same duration. This shows that the presence of oxygen is required for prevention of photoinactivation of thylakoids. The susceptibility of water-splitting complex in photoinactivation is indicated by our data from experiments with chloride-deficient chloroplast membranes wherein it was observed that the whole chain electron transport from DPC to MV was much less photoinhibited than that from water. The data from the photoinactivation experiments with the Tris-treated thylakoids indicate another photodam age site at or near reaction centre of PS II. DCMU-protected PS II and oxygen-evolving complex from photoinactivation. DCMU protection can also be interpreted in terms of the stability of the PS II complex when it is in S2 state.

Is the in vivo Photosystem I Function Resistant to Photoinhibition? An Answer from Photoacoustic and Far-Red Absorbance Measurements in Intact Leaves

1991 ◽  
Vol 46 (11-12) ◽  
pp. 1038-1044 ◽  
Author(s):  
Michel Havaux ◽  
Murielle Eyletters
Keyword(s):  
Light Stress ◽  
Red Light ◽  
Light Treatment ◽  
High Light ◽  
Saturation Curve ◽  
Strong Light ◽  
Ps Ii ◽  
Fluorescence Measurements ◽  
Ps I

Abstract Preillumination of intact pea leaves with a strong blue-green light of 400 W m-2 markedly inhibited both photoacoustically monitored O2-evolution activity and PS II photochemistry as estimated from chlorophyll fluorescence measurements. The aim of the present work was to examine, with the help of the photoacoustic technique, whether this high-light treatment deteriorated the in vivo PS I function too. High-frequency photoacoustic measurements indicated that photochemical conversion of far-red light energy in PS I was preserved (and even transiently stimulated) whereas photochemical energy storage monitored in light exciting both PS I and PS II was markedly diminished. Low-frequency photoacoustic measurements of the Emerson enhancement showed a spectacular change in the PS II/PS I activity balance in favor of PS I. It was also observed that the linear portion of the saturation curve of the far-red light effect in the Emerson enhancement was not changed by the light treatment. Those results lead to the conclusion that, in contrast to PS II, the in vivo PS I photofunctioning was resistant to strong light stress, thus confirming previous suggestions derived from in vitro studies. Estimation of the redox state of the PS I reaction center by leaf absorbance measurements at ca. 820 nm suggested that, under steady illumination, a considerably larger fraction of PS I centers were in the closed state in high-light pretreated leaves as compared to control leaves, presumably allowing passive adjustment of the macroscopic quantum yield of PS I photochemis­ try to the strongly reduced photochemical efficiency of photoinhibited PS II.

Degradation of unassembled and damaged thylakoid proteins

2001 ◽  
Vol 29 (4) ◽  
pp. 427-430 ◽  
Author(s):  
Z. Adam ◽  
O. Ostersetzer
Keyword(s):  
Thylakoid Membrane ◽  
D1 Protein ◽  
Thylakoid Membranes ◽  
Reaction Centre ◽  
Ps Ii ◽  
Plant Genomes ◽  
Thylakoid Membrane Proteins ◽  
Luminal Side ◽  
Cytochrome Complex ◽  
Aaa Protein

To study protein degradation in thylakoid membranes we identified, characterized and cloned thylakoid proteases, and then linked them to known proteolytic processes. Several families of chloroplast proteases were identified and characterized to different extents. FtsH, an ATP-dependent metalloprotease that belongs to the AAA-protein family, was found to be integral to the thylakoid membrane, facing the stroma. It is involved in both the degradation of unassembled subunits of membrane complexes, such as the Rieske Fe-S protein of the cytochrome complex, and the degradation of oxidatively damaged proteins such as the D1 protein of the photosystem II (PS II) reaction centre. Plant genomes contain multiple isomers of this protease but the functional significance of this multiplication is not clear yet. A second protease, the serine ATP-independent DegP, was found to be strongly associated with the luminal side of the thylakoid membrane. Although a specific role has not yet assigned for it, its location suggests that it can degrade luminal soluble proteins as well as luminally exposed regions of thylakoid membrane proteins.

Changes in Photosynthetic Apparatus in the Juvenile Rice Canopy and a Possible Function of Photosystem I in the Bottom Leaves

1999 ◽  
Vol 54 (11) ◽  
pp. 915-922 ◽  
Author(s):  
Jun-ya Yamazaki ◽  
Yasumaro Kamimura ◽  
Yasutomo Sugimura
Keyword(s):  
Electron Transport ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Performance ◽  
Cytochrome F ◽  
Transport Capacity ◽  
Ps Ii ◽  
Electrochromic Shift ◽  
The Third ◽  
Ps I ◽  
Light Utilization

Abstract Changes in the photosynthetic apparatus and relative antenna sizes of photosystem (PS) I and PS II were measured in the rice canopy. We used juvenile rice seedlings to examine light utilization and its absorption in the bottom leaves and obtained the following results: (1) When referred to chlorophyll (Chl), levels of the electrochromic shift at 550 nm and cytochrome ƒ decreased from the sixth to the third leaves, but there was no loss of pigment (P)-700. As a consequence, the PS II/PS I ratio significantly decreased from 1.5 in the sixth leaves to 0.9 in the third leaves. (2) The electron transport capacity in the sixth leaves was 1.5-times larger than that in the third leaves. (3) The levels of cytochrome b6 referred to Chl were almost constant from top to bottom. (4) The photosynthetic performance of the leaf de­creased concomitant with the depth, whereas the respiration was slightly increased. From these results, we hypothesize that there are maintenance mechanisms when the imbalances of light absorption and electron transport capacity occur in the bottom leaves.

scholarly journals Regulation of chloroplast membrane function: protein phosphorylation changes the spatial organization of membrane components.

1983 ◽  
Vol 97 (5) ◽  
pp. 1327-1337 ◽  
Author(s):  
L A Staehelin ◽  
C J Arntzen
Keyword(s):  
Protein Complex ◽  
Spatial Organization ◽  
Regulatory Mechanism ◽  
Feedback System ◽  
Cytochrome F ◽  
Chloroplast Membranes ◽  
Ps Ii ◽  
Membrane Function ◽  
Ps I ◽  
Membrane Adhesion

A chlorophyll-protein complex of chloroplast membranes, which simultaneously serves as light-harvesting antenna and membrane adhesion factor, undergoes reversible, lateral diffusion between appressed and nonappressed membrane regions under the control of a protein kinase. The phosphorylation-dependent migration process regulates the amount of light energy that is delivered to the reaction centers of photosystems I and II (PS I and PS II), and thereby regulates their rate of turnover. This regulatory mechanism provides a rationale for the finding that the two photosystems are physically separated in chloroplast membranes (PS II in appressed, grana membranes, and PS I in nonappressed, stroma membranes). The feedback system involves the following steps: a membrane-bound kinase senses the rate of PS II vs. PS I turnover via the oxidation-reduction state of the plastoquinone pool, which shuttles electrons from PS II via cytochrome f to PS I. If activated, the kinase adds negative charge (phosphate) to a grana-localized pigment-protein complex. The change in its surface charge at a site critical for promoting membrane adhesion results in increased electrostatic repulsion between the membranes, unstacking, the lateral movement of the complex to adjacent stroma membranes, which differ in their functional composition. The general significance of this type of membrane regulatory mechanism is discussed.

High-Light-Intensity Damage to the Foliose Lichen Lobaria Pulmonaria within Natural Forest: The Applicability of Chlorophyll Fluorescence Methods

2000 ◽  
Vol 32 (3) ◽  
pp. 271-289 ◽  
Author(s):  
Yngvar Gauslaa ◽  
Knut Asbjørn Solhaug
Keyword(s):  
Light Intensity ◽  
Recovery Period ◽  
Substantial Reduction ◽  
High Light Intensity ◽  
Early Spring ◽  
High Light ◽  
Low Light ◽  
Ps Ii ◽  
Low Light Intensity ◽  
Significant Seasonal Variation

AbstractThe annual course of irradiance was recorded at two vertical and even-aged neighbouring Quercus stems, one rich in L. pulmonaria, one without. Irradiance never exceeded 610 μmol photons m−2 s−1 at the L. pulmonaria site, whereas the L. pulmonaria-deficient site could experience 2 h daily 2000 μmol photons m−2 s−1, and 6 h above 1000 μmol photons m−2 s−1 during a clear day in early spring. Thalli of L. pulmonaria were transplanted to these two stems. During the first 40 days (April–May), transplants at the L. pulmonaria-deficient site developed severe chlorophyll degradation, and a substantial reduction in maximal PS II efficiency (Fv/Fm) even when measured after a 48-h recovery period at low light intensity. Extensive bleaching was formed along light-exposed sides of the tiny ridges on the upper side. Subsequent to this damage, FV/FM gradually rose to nearly normal levels during the following year. This apparent recovery was probably mainly due to irreversible loss of damaged chlorophyll, but also to some level of acclimation. No damage was observed in control transplants on the L. pulmonariarich tree, which were the only transplants gaining sufficient growth for new attachment to the new substratum during the 397-day transplantation period. Nevertheless, a fine-scale, but highly significant seasonal variation in FV/FM of control transplants reflected variations of even low irradiance levels. FV/FM, as measured after a 48-h recovery period at low light intensity, is an efficient meth for recording permanent high light damages at and shortly after damage is formed. However, FV/FM is not a useful estimator of chronic long-term damage.

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