Isolation of chlorophyll-protein complexes and quantification of electron transport components in Synura petersenil and Tribonema aequale

The chlorophyll-protein complexes of the yellow alga Synura petersenii (Chrysophyceae) and the yellow-green alga Tribonema aequale (Xanthophyceae) were studied. The sodiumdodecylsulfate/sodiumdesoxycholate solubilized photosynthetic membranes of these species yielded three distinct pigment-protein complexes and a non-proteinous zone of free pigments, when subjected to SDS polyacrylamid gel electrophoresis. The slowest migrating protein was identical to complex I (CP I), the P-700 chlorophyll a-protein, which possessed 60 chlorophyll a molecules per reaction center in Tribonema and 108 in Synura. The zone of intermediate mobility contained chlorophyll a and carotenoids. The absorption spectrum of this complex was very similar to the chlorophyll a-protein of photosystem II (CP a), which is known from green plants. The fastest migrating pigment protein zone was identified as a light-harvesting chlorophyll-protein complex. In Synura this protein was characterized by the content of chlorophyll c and of fucoxanthin. Therefore this complex will be named as LH Chl a/c-fucocanthin protein. In addition to the separation of the chlorophyll-protein complexes the cellular contents of P-700, cytochrome f (bound cytochrome) and cytochrome c-553 (soluble cytochrome) were measured. The stoichiometry of cytochrome f: cytochrome c-553:P-700 was found to be 1:4:2.4 in Tribonema and 1:6:3.4 in Synurá.     

Preferential accumulation of apoproteins of the light-harvesting chlorophyll a/b-protein complex in greening barley leaves treated with 5-aminolevulinic acid

In order to study the coordinate accumulation of chlorophyll (Chl) and apoproteins of Chl-protein complexes (CPs) during chloroplast development, we examined changes in the accumulation of the apoproteins in barley (Hordeum vulgare L.) leaves when the rate of Chl synthesis was altered by feeding 5-aminolevulinic acid (ALA), a precursor of Chl biosynthesis. Pretreatment with ALA increased the accumulation of Chl a and Chl b 1.5- and 2.3-fold, respectively, after 12 cycles of intermittent light (2 min light followed by 28 min darkness). Apoproteins of the light-harvesting Chl a/b-protein complex of photosystem II (LHCII) were increased 2.4-fold with ALA treatment. However, apoproteins of the P700-Chl a-protein complex (CP1) and the 43-kDa apoprotein of a Chl a-protein complex of photosystem II (CPa) were not increased by ALA application. With respect to CPs themselves, LHCII was increased when Chl synthesis was raised by ALA feeding, whereas CP1 exhibited no remarkable increase. These results indicate that LHCII serves a role in maintaining the stoichiometry of Chl to apoproteins by acting as a temporary pool for Chl molecules.Abbreviations ALA 5-aminolevulinic acid - Chl chlorophyll - CP chlorophyll-protein complex - CPa chlorophyll a-protein complex of PSII - CP1 P700-chlorophyll a-protein complex - LDS lithium dodecyl sulfate - LHCII light-harvesting chlorophyll a/b-protein complex of PSII This work was supported by the Grants-in-Aid for Scientific Research (04304004) from the Ministry of Education, Science and Culture, Japan.     

Chlorophyll-protein-complexes of thylakoids of wild type and chlorophyll b mutants of Arabidopsis thaliana

Pigment-protein-complexes of two chlorophyll b deficient mutants of Arabidopsis and from the wild type were separated electrophoretically. Light-harvesting proteins were absent in the chlorophyll b free mutant ch¹ and their amount was reduced in the mutant ch² which has a reduced content of chlorophyll b. The ratio of CPa:CP I increased with decreasing chlorophyll b content which indicated that the stoichiometry of photosystem II to photosystem I is not constant.Abbreviations Chl chlorophyll - CPa chlorophyll a-protein - CP I P-700 chlorophyll a-protein - LHCP light-harvesting chlorophyll a/b-protein - PAGE polyacrylamide gel electrophoresis - PAR photosynthetically active radiation - SDS sodium dodecyl sulfate     

Chlorophyll-protein-complexes of thylakoids of wild type and chlorophyll b mutants of Arabidopsis thaliana

Pigment-protein-complexes of two chlorophyll b deficient mutants of Arabidopsis and from the wild type were separated electrophoretically. Light-harvesting proteins were absent in the chlorophyll b free mutant ch¹ and their amount was reduced in the mutant ch² which has a reduced content of chlorophyll b. The ratio of CPa:CP I increased with decreasing chlorophyll b content which indicated that the stoichiometry of photosystem II to photosystem I is not constant.Abbreviations Chl chlorophyll - CPa chlorophyll a-protein - CP I P-700 chlorophyll a-protein - LHCP light-harvesting chlorophyll a/b-protein - PAGE polyacrylamide gel electrophoresis - PAR photosynthetically active radiation - SDS sodium dodecyl sulfate     

Chlorophyll-protein complex composition during chloroplast development: A species comparison

Barley, maize, pea, soybean, and wheat exhibited differences in chlorophyll a/b ratio and chlorophyll-protein (CP) complex composition during the initial stages of chloroplast development. During the first hours of greening, the chlorophyll a/b ratios of barley, pea, and wheat were high (a/b8) and these species contained only the CP complex of photosystem I as measured by mild sodium dodecyl sulfate polyacrylamide gel electrophoresis. A decrease in chlorophyll a/b ratio and the observation of the CP complexes associated with photosystem II and the light-harvesting apparatus occurred at later times in barley, pea, and wheat. In contrast, maize and soybean exhibited low chlorophyll a/b ratios (a/b<8) and contained the CP complexes of both photosytem I and the light-harvesting apparatus at early times during chloroplast development. The species differences were not apparent after 8 h of greening. In all species, the CP complexes were stabilized during the later stages of chloroplast development as indicated by a decrease in the percentage of chlorophyll released from the CP complexes during detergent extraction. The results demonstrate that CP complex synthesis and accumulation during chloroplast development may not be regulated in the same way in all higher plant species.Abbreviations Chl chlorophyll - CP chlorophyll-protein - CPI P700 chlorophyll-a protein complex of photosystem I - CPa electrophoretic band that contains the photosystem II reaction center complexes and a variable amount of the photosystem I light-harvesting complex - LHC the major light-harvesting complex associated with photosystem II - PSI photosystem I - PSII photosystem II - SDS sodium dodecyl sulfate - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601. Paper No. 10335 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601.     

Chlorophyll-protein complex composition and photochemical activity in developing chloroplasts from greening barley seedlings

The time course for the observation of intact chlorophyll-protein (CP) complexes during barley chloroplast development was measured by mild sodium dodecyl sulfate polyacrylamide gel electrophoresis. The procedure required extraction of thylakoid membranes with sodium bromide to remove extrinsic proteins. During the early stages of greening, the proteins extracted with sodium bromide included polypeptides from the cell nucleus that associate with developing thylakoid membranes during isolation and interfere with the separation of CP complexes by electrophoresis. Photosystem I CP complexes were observed before the photosystem II and light-harvesting CP complexes during the initial stages of barley chloroplast development. Photosystem I activity was observed before the photosystem I CP complex was detected whereas photosystem II activity coincided with the appearance of the CP complex associated with photosystem II. Throughout chloroplast development, the percentage of the total chlorophyll associated with photosystem I remained constant whereas the amount of chlorophyll associated with photosystem II and the light-harvesting complex increased. The CP composition of thylakoid membranes from the early stages of greening was difficult to quantitate because a large amount of chlorophyll was released from the CP complexes during detergent extraction. As chloroplast development proceeded, a decrease was observed in the amount of chlorophyll released from the CP complexes by detergent action. The decrease suggested that the CP complexes were stabilized during the later stages of development.Abbreviations Chl chlorophyll - CP chlorophyll-protein - CPI P700 chlorophyll-a protein complex of photosystem I - CPa electrophoretic band that contains the photosystem II reaction center complexes and a variable amount of the photosystem I light-harvesting complex - CP A/B the major light-harvesting complex associated with photosystem II - DCIP 2,6-dichlorophenolindophenol - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DPC diphenyl carbazide - MV methyl viologen - PAR photosynthetically active radiation - PSI photosystem I - PSII photosystem II - SDS sodium dodecyl sulfate - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - TEMED N,N,N,N-tetramethylethylenediamine - TMPD N,N,N,N-tetramethyl-p-phenylenediamine Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601. Paper No. 9949 of the Journal Series of the North Carolina Agricultural Research Service, Raleight, NC 27695-7601.     

The concentration of Cytochrome f and P700 in chlorophyll-deficient mutants of Chlorella fusca

The ratio of Chlorophyll: Cytochrome f and of Chlorophyll: P700 (reaction center pigment in photosystem I) is essentially lower in chlorophyll-deficient mutants than in the normal green strain. On a dry weight basis, the mutants have the same or a higher content of redox enzymes than the normal form. The size of the photosynthetic unit of the mutants is 4 to 7 times smaller than that of the normal strains, due mainly to a deficiency of the light-harvesting chlorophyll-protein complex.Abbreviations Chl chlorophyll - Cyt f Cytochrome f - P700 reaction center pigment in photosystem I - PS photosystem - LH light-harvesting     

Effect of nuclear mutation in maize on photosynthetic activity and content of chlorophyll-protein complexes

A number of new nuclear mutants have been isolated from maize by selection for high chlorophyll (Chl) fluorescence. These mutants show reduced rates of photosynthesis and/or are deficient in Chl. Electrophoretic examination of wild type thylakoid membranes revealed five Chl-protein complexes, two containing only Chl a and three containing Chl a and Chl b. A class of nonviable, photosystem I-deficient mutants was found to be lacking one (A-1) of the two Chl a-protein complexes. A second class of nonviable, photosystem I-lacking mutants was found to be missing not only this A-1 complex but also one or more of the three Chl a and b-containing, light-harvesting Chl-protein complexes. Viable mutants were obtained which appeared to have lost just one of the Chl b-containing complexes, whereas a second class of viable mutants was missing all three of the Chl b-complexes. The results confirm that the A-1 band is associated with the P700-Chl a-protein complex characterized previously. The data also indicate the existence of structurally different forms of the light-harvesting Chl a- and b-containing complexes. The results also show a lower molecular weight band (A-2) containing primarily Chl a and which appears to be required for viability.     

Measurements of cytochrome f and P-700 in intact leaves of Sinapis alba grown under high-light and low-light conditions

The oxidation and reduction of cytochrome f and P-700 is measured spectrophotometrically in leaves of low-light and high-light plants. After illumination with red light, an induction phenomenon for cytochrome f oxidation is observed which indicates a regulation of photosystem I activity through energy distribution between the pigment systems by the energy state of the membrane. After far-red excitation the reduction of cytochrome f in the dark is much slower in low-light leaves. This shows that cyclic electron transport is not improved in low-light plants under these conditions. P-700 is oxidized on excitation with far-red light. However, with high intensities of far-red light, P-700 is partially reduced again which is due to a low extent of photosystem II excitation with the far-red used in the experiments. The low-light leaves show greater sensitivity of photosystem II to this excitation. The initial rate of the cytochrome f oxidation-rate is the same in low-light and high-light leaves. This shows that several P-700 are connected with only one electron transport chain. The consequences of these results concerning the tripartite concept and the photosynthetic unit are discussed. In the high-light plants the experimental data can be well explained by the tripartite organization of the photosynthetic unit. In low-light plants, however, a multipartite organization has to be postulated. In the partition regions of the grana, several antennae systems I, antennae systems II, and light-harvesting complexes can communicate with one electron transport chain.Abbreviations CP I P-700-chlorophyll a-protein - Cyt f cytochrome f - DCMU 3-(3,4 dichlorophenyl)-1,1-dimethylurea - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - LA leaf-area - PhAR photosynthetically active radiation - PS photosystem     

The energy distribution between the photosystems and light-induced changes in the stoichiometry of system I and II reaction centers in the chlorophyll b-containing alga Mantoniella squamata (Prasinophyceae)

The chlorophyll b-containing alga Mantoniella squamata was analyzed with respect to its capacity to balance the energy distribution from the light-harvesting antenna to photosystem I or photosystem II. It was shown, that this alga is unable to alter the absorption cross section of the two photosystems in terms of short-time regulations (state transitions). The energy absorbed by the LHC, which contains 60% of total photosynthetic pigments, is transferred to both photosystems without any preference. The stoichiometry of the two photosystems is found to be extremely unequal and variable during light adaptation. In high light, the molar ratio of P-680 per P-700 is found to be two, whereas under low light conditions this ratio accounts to nearly four. This very unbalanced stoichiometry of the reaction centers gives some new insights into the concept of the photosynthetic unit as well as in the importance of the regulation of the energy distribution. It is assumed that the high concentration of photosystem II can be understood as a mechanism to prevent the overexcitation of photosystem I. In addition, the changes im membrane protein pattern are not accompanied by variations in the ratio of appressed to nonappressed membranes as probed by ultrastructural analysis. It is suggested that the thylakoids are organized like a homogenous pigment bed. The lack of state transitions can be interpreted as a consequence of this unusual membrane morphology.Abbreviations Chl chlorophyll - CPa chlorophyll a-protein of PSII - CPl P-700 chlorophyll a-protein - CPD Chlorophyll packing density index - cyt f cytochrome f - FP free pigments - LHC light-harvesting complex - P_max light saturated photosynthetic rates per chlorophyll - n number of experiments - PQ plastoquinone - PS photosystem - PSU photosynthetic unit - Q_E non-photochemical quenching - Q_Q photochemical quenching     

Differential changes in degradation of chlorophyll-protein complexes of photosystem I and photosystem II during flag leaf senescence of rice.

The stability of chlorophyll-protein complexes of photosystem I (PSI) and photosystem II (PSII) was investigated by chlorophyll (Chl) fluorescence spectroscopy, absorption spectra and native green gel separation system during flag leaf senescence of two rice varieties (IIyou 129 and Shanyou 63) grown under outdoor conditions. During leaf senescence, photosynthetic CO(2) assimilation rate, carboxylase activity of Rubisco, chlorophyll and carotenoids contents, and the chlorophyll a/b ratio decreased significantly. The 77 K Chl fluorescence emission spectra of thylakoid membranes from mature leaves had two peaks at around 685 and 735 nm emitting mainly from PSII and PSI, respectively. The total Chl fluorescence yields of PSI and PSII decreased significantly with senescence progressing. However, the decrease in the Chl fluorescence yield of PSI was greater than in the yield of PSII, suggesting that the rate of degradation in chlorophyll-protein complexes of PSI was greater than in chlorophyll-protein complexes of PSII. The fluorescence yields for all chlorophyll-protein complexes decreased significantly with leaf senescence in two rice varieties but the extents of their decrease were significantly different. The greatest decrease in the Chl fluorescence yield was in PSI core, followed by LHCI, CP47, CP43, and LHCII. These results indicate that the rate of degradation for each chlorophyll-protein complex was different and the order for the stability of chlorophyll-protein complexes during leaf senescence was: LHCII>CP43>CP47>LHCI>PSI core, which was partly supported by the green gel electrophoresis of the chlorophyll-protein complexes.     

Conversion of Chlorophyll b to Chlorophyll a and the Assembly of Chlorophyll with Apoproteins by Isolated Chloroplasts

The photosynthetic apparatus is reorganized during acclimation to various light environments. During adaptation of plants grown under a low-light to high-light environment, the light-harvesting chlorophyll a/b-protein complexes decompose concomitantly with an increase in the core complex of photosystem II. To study the mechanisms for reorganization of photosystems, the assembly of chlorophyll with apoproteins was investigated using isolated chloroplasts. When [14C]chlorophyllide b was incubated with chloroplasts in the presence of phytyl pyrophosphate, it was esterified and some of the [14C]chlorophyll b was converted to [14C]chlorophyll a via 7-hydroxymethyl chlorophyll. [14C]Chlorophyll a and b were incorporated into chlorophyll-protein complexes. Light-harvesting chlorophyll a/b-protein complexes of PSII had a lower [14C]chlorophyll a to [14C]chlorophyll b ratio than P700-chlorophyll a-protein complexes, indicating the specific binding of chlorophyll to apoproteins in our systems. 7-Hydroxymethyl chlorophyll, an intermediate molecule from chlorophyll b to chlorophyll a, did not become assembled with any apoproteins. These results indicate that chlorophyll b is released from light-harvesting chlorophyll a/b-protein complexes of photosystem II and converted to chlorophyll a via 7-hydroxymethyl chlorophyll in the lipid bilayer and is then used for the formation of core complexes of photosystems. These mechanisms provide the fast, fine regulation of the photosynthetic apparatus during construction of photosystems.     

Isolation of an intrinsic antenna chlorophyll a-protein from the photosystem I reaction center complex of the thermophilic cyanobacterium Synechococcus sp

A chlorophyll-protein was isolated from a Synechococcus P700-chlorophyll a-protein complex free from small subunits (CP1-e) by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis after treatment with 2% 2-mercaptoethanol and 2% SDS. In contrast to CP1-e which, when electrophoresed under denaturating conditions, showed two polypeptide bands of 62 and 60 kDa, the chlorophyll-protein contained only the 60-kDa polypeptide and hence is called CP60. The yield of CP60 was maximal with 1-2% SDS and 2-4% sulfhydryl reagents because the chlorophyll-protein was denatured at higher concentrations of the reagents. The absorption spectrum of CP60, which retained more than half of the chlorophyll alpha molecules originally associated with the 60-kDa subunit of the photosystem I reaction center complex, showed a red band maximum at 672 nm and a small absorption band around 700 nm at liquid nitrogen temperature. CP60 emitted a fluorescence band at 717 to 725 nm at 77 degrees K. The temperature dependence of the far red band of CP60 was essentially the same as that of CP1-e between 77 and 273 degrees K. No photoresponse of P700 was detected in CP60. The results suggest that the two polypeptides resolved by SDS-gel electrophoresis from CP1-e are apoproteins of two distinct chlorophyll-proteins and that CP60 represents a chlorophyll-bearing 60-kDa subunit functioning as an intrinsic antenna protein of the photosystem I reaction center complex. It will also be shown that the temperature dependence of the far red fluorescence band is not related to the photosystem I photochemistry.     

The light-harvesting system of Euglena gracilis during the cell cycle

The apoproteins of the light-harvesting chlorophyll-protein complexes LHCI and CP29 (apparent molecular weights of 27 kDa and 29 kDa, respectively) of Euglena gracilis were identified immunologically. Both complexes are present in the thylakoids of autotrophically cultured Euglena cells during the whole cell cycle. The relative amount of each apoprotein tends to increase towards the end of the cell cycle. The light-harvesting chlorophyll-protein complex of photosystem II, LHCII, of E. gracilis contains chlorophyll a, chlorophyll b, neoxanthin, diadinoxanthin and beta-carotene. Its chlorophyll a/b ratio is about 1.7 during the whole cell cycle. About 9 h after cell division the ratio of diadinoxanthin to chlorophyll a is doubled for a time of 3–4 h. The relevance of this increase during one developmental stage is discussed in relation to the insertion and-or assembly of newly synthesized LHCII.Abbreviations LHCP light-harvesting chlorophyll-protein complex - PS photosystem This research was partly supported by the Deutsche Forschungsge meinschaft.     

The action of lipase on chloroplast membranes: II. Polypeptide patterns of bean galactolipase- and phospholipase A2-treated thylakoid membranes

Thylakoid membranes obtained from bean chloroplasts treated with bean galactolipase or phospholipase A₂ (from Crotalus terr. terr.) showed marked changes in their polypeptide patterns when separated on SDS-PAGE. The obtained results have been discussed with regard to the relationship between chloroplast lipids and polypeptides originating from chlorophyll-protein complexes of bean thylakoids. A coexistence between galactolipids and the peripheral antennae in PS I complex and LHCP³ as well as a conspicuous role of phospholipids in PSI and PSII centre chlorophyll-protein complexes has to be underlined.Abbreviations CP1 chlorophyll a-protein complex of PSI - CPa chlorophyll a-protein complex of PSII - D₁₀ digitonin subchloroplast particles enriched in PSII - D₁₄₄ digitonin subchloroplast particles enriched in PSI - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - LHCP^1–3 light harvesting chlorophyll a/b protein complexes - PAGE polyacrylamide gel electrophoresis - PSI photosystem I - PSII photosystem II - SDS sodium dodecyl sulphate - TCA trichloroacetic acid - Tricine N-Tris-(hydroxymethyl)-methylglycine - Tris Tris-(hydroxymethyl)-aminomethan     

Influence of energy flux and quality of light on the molecular organization of the photosynthetic apparatus in Scenedesmus

The photosynthetic apparatus of the unicellular green alga Scenedesmus obliquus adapts to different levels and qualities of light as documented by the fluence-rate curves of photosynthetic oxygen evolution. Cultures adapted to low fluence rates of white light (5W·m^-2) have more chlorophyll (Chl) per cell mass, a higher chlorophyll to carotenoid ratio and a doubling of the chlorophyll to cytochrome f ratio compared with cells adapted to high fluence rates of white light (20W·m^-2). Only small differences can be observed in the halfrise time of fluorescence induction, the electrophoretic profile of the pigment-protein complexes and the Chl a/Chl b-ratio. Scenedesmus cells adapted to blue light of high spectral purity demonstrate, in comparison with those adapted to red light, a higher chlorophyll content, a higher ratio of chlorophyll to carotenoid and a much higher ratio of chlorophyll to cytochrome f. Regarding these parameters and the fluence-rate curves of photosynthesis, the blue light causes the same effects as low levels of white light. In contrast, the action of red light resembles rather that of high levels of white light. Blue-light-adapted Scenedesmus cells have a smaller Chl a to Chl b ratio, a faster half-rise time of fluorescence induction and more chlorophyll in the light-harvesting system than red-light-adapted cells, as shown in the electrophoretic profile of the pigment-protein complexes. Based on these results we propose a model for the adaptation of the photosynthetic apparatus of Scenedesmus to different levels and qualities of light. In this model low as compared with high levels of white light result in an increase in the number of photosystems per electron-transport chain, but not in an increase in the size of these photosystems. The same result is obtained by adaptation to blue light. The lack of sufficient Chl b formation in red-light-adapted cells results in a decrease in the light harvesting chlorophyll-protein complexes and a photosynthetic response like that found in cells adapted to high light levels. The findings reported here confirm our earlier results in comparing blue-and red-light adaptation of the photosynthetic apparatus with adaptation to low and high levels of white light, respectively.Abbreviations Chl chlorophyll - CP chlorophyll-protein complex - DCMU 3-(3,4-dichlorophenyl)-1,1 dimethyl-urea - LHCP light harvesting chlorophyll-protein complex - LiDS lithium dodecyl sulfate - PAGE polyacrylamide gel electrophoresis - PS photosystem     

The action of lipase on chloroplast membranes: II. Polypeptide patterns of bean galactolipase- and phospholipase A2-treated thylakoid membranes

Thylakoid membranes obtained from bean chloroplasts treated with bean galactolipase or phospholipase A₂ (from Crotalus terr. terr.) showed marked changes in their polypeptide patterns when separated on SDS-PAGE. The obtained results have been discussed with regard to the relationship between chloroplast lipids and polypeptides originating from chlorophyll-protein complexes of bean thylakoids. A coexistence between galactolipids and the peripheral antennae in PS I complex and LHCP³ as well as a conspicuous role of phospholipids in PSI and PSII centre chlorophyll-protein complexes has to be underlined.Abbreviations CP1 chlorophyll a-protein complex of PSI - CPa chlorophyll a-protein complex of PSII - D₁₀ digitonin subchloroplast particles enriched in PSII - D₁₄₄ digitonin subchloroplast particles enriched in PSI - DCMU 3-(3,4-dichlorophenyl)-1, 1-dimethylurea - LHCP^1-3 light harvesting chlorophyll a/b protein complexes - PAGE polyacrylamide gel electrophoresis - PSI photosystem I - PSII photosystem II - SDS sodium dodecyl sulphate - TCA trichloroacetic acid - Tricine N-Tris-(hydroxymethyl)-methylglycine - Tris Tris-(hydroxymethyl)-aminomethan     

Effect of light quality on chloroplast-membrane organization and function in pea

The effect of light quality during plant growth of chloroplast membrane organization and function in peas (Pisum sativum L. cv. Alaska) was investigated. In plants grown under photosystem (PS) I-enriched (far-red enriched) illumination both the PSII/PSI stoichiometry and the electrontransport capacity ratios were high, about 1.9. In plants grown under PSII-enriched (far-red depleted) illumination both the PSII/PSI stoichiometry and the electron-transport capacity ratios were significantly lower, about 1.3. In agreement, steady-state electron-transport measurements under synchronous illumination of PSII and PSI demonstrated an excess of PSII in plants grown under far-red-enriched light. Sodium dodecylsulfate polyacrylamide gel electrophoretic analysis of chlorophyll-containing complexes showed greater relative amounts of the PSII reaction center chlorophyll-protein complex in plants grown under farred-enriched light. Additional changes were observed in the ratio of light-harvesting chlorophyll a/b protein to PSII reaction center chlorophyll-protein under the two different light-quality regimes. The results demonstrate the dynamic nature of chloroplast structure and support the notion that light quality is an important factor in the regulation of chloroplast membrane organization and-function.Abbreviations and symbols Chl chlorophyll - CPa PSII reaction center chlorophyll protein complex - CPI PSI chlorophyll protein complex - FR-D light depleted in far-red sensitizing primarily PSII - FR-E light enriched in far-red sensitizing primarily PSI - LHCP PSII light-harvesting chlorophyll a/b protein complex - P ₇₀₀ primary electron donor of PSI - PSI, PSII photosystems I and II, respectively - Q primary electron acceptor of PSII     

Photosynthetic Membranes of Porphyridium cruentum: An Analysis of Chlorophyll-Protein Complexes and Heme-Binding Proteins

Three chlorophyll-protein complexes (CP I, CP III, CP IV) were electrophoretically separated from thylakoids of the eukaryotic red alga Porphyridium cruentum. CP I contained the primary photochemical reaction center of photosystem I as judged by its light-induced reversible absorbance change at 700 nanometers, by its fluorescence emission maximum at 720 nanometers (−196°C), and by the molecular weight of its apoprotein (68,000 daltons). CP III and CP IV appeared to belong with photosystem II as suggested by the absence of light-reversible absorbance at 700 nanometers, by their fluorescence maximum at 690 nanometers (−196°C), and by the presence of a chlorophyll-binding polypeptide with a molecular weight of about 52,000 daltons. CP IV when completely denatured had two additional polypeptides of about 40,000 and 48,000 daltons. All three chlorophyll-protein complexes contained carotenoids: the chlorophyll/carotenoid molar ratio of 15:1 for CP I, and 20:1 for CP III and CP IV. The thylakoid membranes of P. cruentum contained four cytochromes, detected by heme-dependent peroxidase activity, but there was no observed association with the electrophoretically separated chlorophyll-protein complexes.     

Development of the photosynthetic apparatus during light-dependent greening of a mutant of Chlorella fusca

The formation of chlorophyll, cytochrome f, P-700, ribulose bisphosphate carboxylase as well as photosynthesis and Hill reaction activities were tested during the light-dependent greening process of the Chlorella fusca mutant G 10. Neither chlorophyll nor protochlorophyllide was detected in the darkgrown cells. When transferred to light the mutant cells developed chlorophyll and established its photosynthetic capacity after a short lag phase. In the in vivo absorption spectra a spectral shift of the red absorption peak position from 674 to 680 nm was indicated during the first 3 h of greening. Cytochrome f was already present in the dark-grown cells, but during the greening phase a threefold increase in the cytochrome f content could be seen. At the early stages of greening a characteristic primary oscillation in the content of cytochrome f was observed. P-700 was lacking in the dark and during the first 30 min of illumination. From the first to the second h of light a forced synthesis of P-700 took place and the time-course curve for the ratios of P-700/chlorophyll rose to a sharp maximum. The synthesis of P-700 started together with photosystem I activity and showed similar kinetics. We found the simultaneous appearance of photosystem II, photosystem I, and photosynthetic activities 30 min after the beginning of the illumination. Based on chlorophyll content they attained maximum activity after 2 h of light, but at this time photosystem I capacity proved to be remarkably higher than photosynthetic and photosystem II activities. Highest carboxylase activity existed in darkgrown cells. During the greening process the activity of the enzyme decreased continuously. After 2 h of illumination chlorophyll synthesis partially served to increase the size of the photosynthetic unit, which consequently led to a decrease in the light energy needed to saturate photosynthesis and also to a decrease of photosynthetic rate based on chlorophyll content.Abbreviations Chl chlorophyll - Cyt f cytochrome f - DPIP 2,6-dichlorophenolindophenol - EDTA ethylenediaminetetraacetic acid - GSH glutathione - LH light-harvesting - PS photosystem - RuBP ribulose bisphosphate