Chromatic Regulation of Photosystem Composition in the Photosynthetic System of Red and Blue-Green Algae

A chromatic adaptation in the photosynthetic quantum yield forthe light mainly absorbed by chlorophyll a (Chl a light) firstfound by Yocum (1951) was studied with one red and three blue-greenalgal strains. When the cells were grown under a weak Chl alight, the quantum yield in all the strains increased. Comparisonof photosystem (PS) compositions, including phycobilin (PBP)and Chl a antennae, reaction centers I and II, in the cellsgrown under the light mainly absorbed by PBP and Chl a revealedthat changes in quantum yield could be attributed to changesin the ratio of PS I/II; PS I/II becomes larger than 1 underPBP light but decreases to 1 in most cases under Chl a light.The change in the PS I/II ratio is due solely to the changesin the PS I population in the cell; PS II remains constant.These results are similar to the intensity-dependent responsein PS composition. A common hypothesis for both the chromatic and intensity-inducedregulation of PS composition was proposed based on the ideaof balance between the electron flow from H₂O to NADP drivenby PS I and II and the cyclic one driven by PS I. (Received May 16, 1985; Accepted September 4, 1985)     

Regulation of Photosystem Composition in Cyanobacterial Photosynthetic System: Evidence Indicating that Photosystem I Formation is Controlled in Response to the Electron Transport State

The quantitative composition of thylakoid components such asthe photosystem (PS) I/PS II ratio in the cyanobacterial photosyntheticsystem is regulated in response to the light regime. The regulationoccurs as changes in PS I content due to control of either PSI formation or decomposition. In order to determine which ofthese two is controlled in this regulation, experiments wereperformed to determine the light-induced PS I decrease in cellsof Synechocystis PCC 6714 under conditions where protein synthesiswas suppressed, i.e. the incubation without a nitrogen sourcefor cell growth or with chloramphenicol. The results revealedthat light-induced PS I decrease did not occur when synthesisof the thylakoid system was suppressed by incubation withouta nitrogen source or by the addition of chloramphenicol, indicatingthat (1) the thylakoid composition is regulted in the processof thylakoid formation and (2) the regulation is achieved bythe control of PS I formation. (Received November 6, 1987; Accepted March 2, 1988)     

Regulation of Photosystem Composition in the Cyanobacterial Photosynthetic System: the Regulation Occurs in Response to the Redox State of the Electron Pool Located between the Two Photosystems

Regulation of electron transport composition was studied withSynechocystis (Aphanocapsa) PCC 6714 grown under various trophicconditions. Photosystem (PS) composition, PS I/IIratio, wasused as the index for the composition of the electron transportsystem. Special attention was paid to the relationship betweenchanges in the PS I/II ratio and features of electron transport.Results indicated that (1) the change of composition of theelectron transport system is induced not only by the light conditionsbut also by changes in the electron influx and efflux. (2) Thechange occurs so as to relieve the imbalance between the electroninflux and the efflux, caused by changes in the conditions forthe electron transport, and (3) the redox state of plastoquinonepool is probably related to the primary stimulus of the regulation. (Received August 14, 1986; Accepted December 16, 1986)     

Regulation of Electron Transport Composition in Cyanobacterial Photosynthetic System: Stoichiometry among Photosystem I and II Complexes and Their Light-Harvesting Antennae and Cytochrome b6/fComplex

This study was done to confirm our previous observation withthe pattern of changes in electron transport composition inducedby an imbalance of the electron transport state. Contents ofphotosystem (PS) I and II complexes and their antennae and Cytb₆/f complex were determined for systems of cyanobacterium SynechocystisPCC 6714 of different PS I/PS II ratios. The results indicatedthat (1) the observed changes in the PS I/PS II ratio are not-dueto regulation of the activities of the respective PS's but tochanges in their contents, (2) the molar ratio between PS IIand Cyt b₆/f complexes was fairly constant when marked changesoccurred in the PS I content, and (3) the PS II and Cyt b₆/fcontents per cell remained fairly constant while the PS I contentchanged markedly. These findings agree with our previous observationwith autotrophic cells of Anacystis nidulans Tx 20 and supportour argument that in cyanobacterial and red algal electron transportsystems, the content of the terminalcomponent(s), such as PSI complex, is regulated in order to maintain a balance betweenthe electron influx by PS II action to the system and the effluxby PS I action from it. (Received June 3, 1987; Accepted September 20, 1987)     

Steady State of Photosynthesis in Cyanobacterial Photosynthetic Systems Before and After Regulation of Electron Transport Composition: Overall Rate of Photosynthesis and PSI/PS II Composition

The effect of regulation of photosystem (PS) composition onthe photosynthetic steady state was examined using the cyanobacteriumSynechocystis PCC 6714. Photosynthetic rates under orange lightabsorbed by phycobiliprotein (PBP) (PBP light) and under redlight absorbed mainly by chlorophyll a (Chi a light) were comparedfor the cells before and after adaptation to the respectivelight regimes. Results were as follows: (1) Photosynthetic ratesper absorbed light quantum became higher after adaptation thanthose before adaptation. (2) Under Chi a light, the low turnoverrate of PS I before adaptation was markedly enhanced after adaptation(decrease in PS I content), but in the case of adaptation toPBP light (increase in PS I content), a marked enhancement ofPS II turnover occurred after adaptation. (3) In the formercase, a low turnover rate of PS I before adaptation was dueto the occurrence of a large number of closed PS I complexes,but in the latter, limited excitation of PS I caused a largenumber of closed PS II complexes before adaptation. Resultsfor the latter case indicate that the energy transfer from phycobilisome(PBS) to one PS I complex is far smaller than that from PBSto one PS II complex, and that the imbalance of energy distributionfrom PBS to the two photosystems is compensated for by the increasein the number of PS I complexes. (Received September 10, 1987; Accepted December 9, 1987)     

Kinetic Mechanisms of Biological Regulation in Photosynthetic Organisms

Principles of regulation on different levels of photosynthetic apparatus are discussed. Mathematical models of isolated photosynthetic reaction centers and general system of energy transduction in chloroplast are developed. A general approach to model these complex metabolic systems is suggested. Regulatory mechanisms in plant cell are correlated with the different patterns of fluorescence induction curve at different internal physiological states of the cells and external (environmental) conditions. Light regulation inside photosynthetic reaction centers, diffusion processes in thylakoid membrane, generation of transmembrane electrochemical potential, coupling with processes of CO₂ fixation in Calvin Cycle are considered as stages of control of energy transformation in chloroplasts in their connection with kinetic patterns of fluorescence induction curves and other spectrophotometric data.     

Regulation of Photosystem Stoichiometry in the Photosynthetic System of the Cyanophyte Synechocystis PCC 6714 in Response to Light-Intensity

Light-induced changes in stoichiometry among three thylakoidcomponents, PS I, PS II and Cyt b₆-f complexes, were studiedwith the cyanophyte Synechocystis PCC 6714. Special attentionwas paid to two aspects of the stoichiometric change; first,a comparison of the patterns of regulation in response to differencesin light-intensity with those induced by differences in light-quality,and second, the relationship between regulation of the stoichiometryand the steady state of the electron transport system. Resultsfor the former indicated that (1) the abundance of PS I on aper cell basis was reduced under white light at the intensityas high as that for light-saturation of photosynthesis, butPS I per cell was increased under low light-intensity, (2) PSII and Cyt b₆-f complexes remained fairly constant, and (3)changes in the abundance of PS I depended strictly on proteinsynthesis. The pattern was identical with that of chromaticregulation. For the second problem, the redox steady-statesof Cyt f and P700 under white light of various intensities weredetermined by flash-spectroscopy. Results indicated that (1)Cyt f and P700 in cells grown under low light-intensity [highratio of PS I to PS II (PS I/PS II)] were markedly oxidizedwhen the cells were exposed to high light-intensity, while theyremained in the reduced state under low light-intensity. (2)After a decrease in the abundance of PS I, most of P700 remainedin the reduced state even under high light-intensity, whilethe level of reduced Cyt f remained low. (3) Both Cyt f andP700 in cells of low PS I/PS II were fully reduced under lowlight-intensity, and Cyt f reduction following the flash wasrapid, which indicates that the turnover of PS I limits theoverall rate of electron flow. After an increase in the abundanceof PS I, the electron transport recovered from the biased state.(4) The redox steady-state of the Cyt b₆-f complex correlatedwell with the regulation of PS I/PS II while the state of thePQ pool did not. Based on these results, a working model ofthe regulation of assembly of the PS I complex, in which theredox steady-state of the Cyt b₆-f complex is closely relatedto the primary signal, is proposed. (Received August 2, 1990; Accepted December 10, 1990)     

粳稻胚乳细胞增殖与蔗糖代谢的关系

蔗糖代谢为水稻胚乳发育提供物质和能量。为明确二者的量化关系,本研究通过调节源库关系获得不同源供应水平下的代表性粒位籽粒,进而分析了蔗糖、果糖、葡萄糖及可溶性总糖的含量与胚乳细胞增殖的关系。结果表明,改变品种的源库比例（源大库小）,下部粒位籽粒胚乳细胞数目明显增加,总体上,可溶性总糖含量与细胞数目呈极显著负相关,与细胞增殖速率呈极显著正相关,高的蔗糖/葡萄糖、蔗糖/果糖有利于胚乳细胞数目增多。在细胞增殖前期（花后5d）,高葡萄糖、己糖含量有利于提高胚乳细胞数目,高葡萄糖含量还可提高细胞增殖速率。细胞增殖中后期（花后7d）,蔗糖、果糖和葡萄糖含量与胚乳细胞数目、增殖速率呈显著负相关。     

Structural Analysis of Photosystem II: Comparative Study of Cyanobacterial and Higher Plant Photosystem II Complexes

Oxygen evolving photosystem II (PSII-OEC) complexes and PSII core complexes were isolated from spinach and the thermophilic cyanobacteriumSynechococcussp. OD24 and characterized by gel electrophoresis, immunoblotting, and absorbance spectroscopy. The mass of the core complexes was determined by scanning transmission electron microscopy (STEM) and found to be 281 ± 65 kDa for spinach and 313 ± 52 kDa forSynechococcussp. OD24. The mass of the spinach PSII-OEC complex was 327 ± 64 kDa. Digital images of negatively stained PSII-OEC and PSII core complexes were recorded by STEM and analyzed by single particle averaging. All monomeric complexes showed similar morphologies and were of comparable length (14 nm) and width (10 nm). The averages revealed a pseudo-twofold symmetry axis, which is a prominent structural element of the monomeric form. Difference maps between the averaged projections of the oxygen evolving complexes and the core complexes from both species indicated where the 33-kDa extrinsic manganese stabilizing protein is bound. A symmetric organization of the PSII complex, with the PsbA and the PsbD proteins in the center and symmetrically arranged PsbB and PsbC proteins at the periphery of the monomeric complex, is proposed.     

Chromatic Regulation of Cytochrome Composition and Electron Transfer from Cytochrome b6-f Complex to Photosystem I in Anacystis nidulans (Tx 20)

Cytochrome composition of the cyanobacterial photosyntheticsystem was studied with Anacystis nidulans (Tx 20) in relationto the chromatic regulation of photosystem composition. Comparisonof cytochrome compositions in cells with a high PS I/II ratio(3.0, grown under weak orange light) and with a low ratio (1.6,grown under weak red light) indicated that cytochrome compositionwas also changed in the chromatic regulation of photosystemcomposition. Two types of cytochrome change were observed: 1)contents of cytochromes C₅₅₃ and c₅₄₈ were changed in parallelwith the changes in PS I content, and 2) cytochrome b₅₅₃ andcytochrome b₆-f complex were held at a constant molar ratioto PS II. The molar ratio, PS II : cytochrome b₅₅₉ : cytochromeb₆-f complex : cytochrome c₅₅₃ : PS I : cytochrome C₅₄₈, inthe red-grown cells was 1 : 2.5 : 1.3 : 0.17 : 1.6 : 0.67, andthe ratio in the orange-grown cells, 1:2.4:0.9:0.32:3.0:1.2.In both types of cells, almost all cytochrome f in the cytochromeb₆-f complex was rapidly oxidized after multiple flash activation,indicating that all cytochrome b₆-f complexes in cells of bothtypes are functionally connected to PS I, even when the molarratio to PS I is largely changed. The content of cytochromeC₅₅₃ was at most 0.14 of PS I, suggesting that the cytochrometurns over several times per one turnover of PS I. ¹Present address: Department of Biology, Faculty of Science,Tokyo Metropolitan University, Fukazawa 2-1-1, Setagaya, Tokyo158, Japan. (Received January 20, 1986; Accepted March 17, 1986)     

The Regulation and Distribution of LHC-I and LHCP2 between the Photosystem I and Photosystem II

Evidences were provided in this paper that the relative distribution of chl-protein complexes of PSⅠ and PSⅡ could be regulated by Mg2+. addition of Mg2+ led to decrease in the amount of chl-protein complexes of PSⅠ and increase in the amount of chl-protein in complexes of PSⅡ. There was no effect of Mg2+ on the spectral property of LHCP1, but the addition of Mg2+ could change the spectral property of LHCP2 so that it became similar to that of the LHC-Ⅰ. CPIa2 was a complex of reaction centre of PSⅠ and LHC-I. LHC-I might be contacted specially with LHCP2 in chloroplast membranes. Addition of Mg2+ probably cansed the motion of LHC-I from PSⅠ to PSⅡ and became more closely connected with LHCP2. The relative amount of CPIa2, CPIa1, LHCP1 and LHCP2 in chloroplast membranes could be regulated by different light intensity. There were more CPIa2, LHCP1 and less LHCP2 in chloroplast membranes from the shade plant Malaxis monophyllos and sunflower grown under weak light, both of them lacked equally CPIa1. There were less CPIa2, LHCP1 and more LHCP2 in the sun plant spinach and sunflower grown under strong light, and they possessed equally CPIa1 chl-protein complexes. It is suggested that LHCP1 and LHCP2 are different light-harvesting Chl-protein complexes. The LHC-I and LHCP2 are mobile light-harvesting chl-protein complexes and shuttle back and forth between PSⅠ and PSⅡ They play an important role in the regulation and distribution of excitation energy between the two photosystems.     

Chromatic Regulation in Chlamydomonas reinhardtii: Time Course of Photosystem Stoichiometry Adjustment Following a Shift in Growth Light Quality

Photosystem stoichiometry adjustments in Chlamydomonas reinhardtiiwere induced upon a sudden shift in the light quality duringcell growth. Reversible changes in the PSI/PSII ratio were acompensation response to changes in the balance of light absorptionby the two photosystems. Quantitations of PSII, Cyt b₆-f complexand PSI revealed a constancy in the cellular content of PSIIand the Cyt b₆-f complex, and variable amounts of PSI in C.reinhardtii. These results strengthen the notion that PSI isthe thyla-koid component subject to chromatic regulation andresponsible for the adjustment and optimization of the PSI/PSII ratio in the thylakoid of oxygenic photosynthesis. Additionalresults, obtained upon the use of protein biosynthesis translationinhibitors (chloramphenicol and cyclohex-imide), suggested thata chromatically-induced lowering of the PSI/PSII ratio in C.reinhardtii occurs by suppression of de novo biosynthesis ofPSI components and, therefore, by dilution of the PSI complexin the thylakoid membrane, rather than by active degradationof assembled PSI in chlo-roplasts. (Received November 8, 1996; Accepted December 6, 1996)     

过敏性哮喘小鼠树突状细胞负荷Der p2后改变及与T细胞增殖分化的关系研究

目的:探讨哮喘小鼠与正常小鼠骨髓源性树突状细胞(DC)负荷Der p2抗原后表达表面分子(CD11c、CD86)和细胞因子(IL-10、IL-12p70)的差异及其对Th1和Th2型细胞因子平衡的影响,进一步研究过敏性哮喘发生中DC的可能作用。方法:分别从哮喘组和对照组提取骨髓培养DC,第五天负荷Der p2,24小时后吹打收集细胞,观察DC形态,用流式细胞仪检测孵育后细胞表面CD11c、CD86表达。并留取负荷Der f2前后培养上清,ELISA法检测IL-10及IL-12p70含量。同时以DC:反应细胞比例为1:10混合培养,72 h后ELISA法检测混合培养上清中IL-4、IL-5、IFN-γ的水平。结果:1负荷Der p2后,哮喘组CD86、CD11c表达比对照组高,分别为(t=11,P0.05)(t=4.9,P0.05),差异有统计学意义;2在细胞因子分泌方面,Der p2负荷前,两组DC均能分泌IL-10与IL-12p70,IL-10水平哮喘组高(t=9.5,P0.05),而IL-12p70水平对照组高(P0.05);负荷Der p2后,对照组IL-10、IL-12p7分泌量比负荷前明显增加(P0.05),哮喘组无明显差异(P0.05);3在DC刺激同种T细胞因子分泌方面,负荷Der p2后哮喘组DC刺激T细胞分泌IL-4、IL-5分泌能力明显增强(P0.05),而刺激INF-γ能力降低(P0.05)。结论:DC在过敏性哮喘中起着重要作用,异常DC通过增加CD86、CD11c的表达和减少IL-10及IL-12的合成,致使T细胞向Th2细胞优势分化。     

UHRF1在结肠癌中的表达及其与细胞增殖的关系

目的:探讨UHRF1(Ubiquitin-like with plant homeodomain and ring覱nger domains 1)在结肠癌组织中的表达,及其与结肠癌细胞增殖的关系。方法:采用免疫组织化学方法检测62例结肠癌组织和癌旁正常对照组织的UHRF1表达,统计分析其表达和临床病理资料和预后关系。采用si RNA抑制UHRF1表达,分析其与细胞增殖的关系。结果:结肠癌组织中UHRF1高表达,癌旁正常组织低表达。62例结肠癌组织中33例UHRF1阳性,阳性率为53.2%。UHRF1表达与淋巴结转移、远处器官转移和Dukes'分期相关(P0.05)。高表达UHRF1结肠患者的生存时间明显较低表达者短(P0.05)。单因素分析显示淋巴结转移、远处器官转移、UHRF1和Dukes'分期与患者累积生存率相关(P0.05)。多因素分析显示UHRF1可作为结肠癌患者预后的独立危险因子(P0.05)。采用si RNA转染HCT116后,UHRF1表达显著降低,细胞增殖被抑制。结论:UHRF1参与结肠癌细胞增殖,与结肠癌患者预后密切相关。     

Regulation of the Stoichiometry of Thylakoid Components in the Photosynthetic System of Cyanophytes: Model Experiments Showing that Control of the Synthesis or Supply of Chl a can Change the Stoichiometric Relationship between the Two Photosystems

Regulation of the assembly of the photosystem I (PS I) complexin response to the light regime in the photosynthetic systemof cyanophytes was studied in Synechocystis PCC 6714. The relationshipbetween the assembly of the PS I complex and synthesis of Chla was examined by model experiments in which synthesis of Chla was controlled by two inhibitors, gabaculine (GAB) and 2,2'-dipyridyl(DP). Both inhibitors caused a change to a lower ratio of PSI to PS II even under light that normally induces a high ratioof PS I to PS II. The change in stoichiometry induced by theseinhibitors was suppressed when protein synthesis was inhibitedby chloram-phenicol, similarly to the change in the stoichiometryinduced by light that excites mainly PS I (PS I light). Comparisonof the levels of PS I, PS II and Cyt b₆-f complexes per cellindicated that a selective suppression of the assembly of thePS I complex was induced by the inhibitors: the stoichiometricrelationship among PS I, PS II and Cyt b₆-f complexes was identicalto that induced by PS I light or white light of high intensity.GAB induced a decrease in size of the phycobilisome also, whileDP did not, similarly to PS I light. The results indicate thatthe ratio of PS I to PS II can be changed by the control ofsynthesis of Chl a. They also suggest that control of the synthesisor supply of Chl a probably exerted at site(s) in or after theprocess of the Mg-protoporphyrin branch, is involved in themechanism of regulation of the assembly of the PS I complexin cyanophytes. (Received September 7, 1989; Accepted November 20, 1989)     

Relationship between the Kinetic Properties and the Small Subunit Composition of Nicotiana Ribulose-1, 5-bisphosphate Carboxylase

Genetic variability in the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCase) in several Nicotiana species has been characterized by isoelectric focusing patterns. This heritable variation provides an opportunity to examine the functional role of each of these subunits. In this study, specifically designed RuBPCase enzymes composed of identical large subunits but different small subunits were constructed in vivo by interspecific hybridization between the species N. sylvestris, N. tabacum, N. glauca, N. glutinosa, N. plumbaginifolia, and N. tomentosiformis. Small subunit polypeptides were combined to form a sequence of one, two, three, and four polypeptides with the large subunit of N. sylvestris. Kinetic properties of these hybrid enzymes were compared. No differences in the specific activity of either carboxylation or oxygenation nor in K_m values for ribulose 1,5-bisphosphate, CO₂, or O₂ were detected among the RuBPCase enzymes from the various interspecific hybrids. Likewise, the ratio of carboxylation to oxygenation was constant.