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PubMedDate not supplied

[Pigment composition and photosynthetic activity of pea chlorophyll mutants].

Pea chlorophyll mutants chlorotica 2004 and 2014 have been studied. The mutants differ from the initial form (pea cultivar Torsdag) in stem and leaf color (light green in the mutant 2004 and yellow-green in the mutant 2014), relative chlorophyll content (approximately 80 and 50%, respectively), and the composition of carotenoids: the mutant 2004 contains a significantly smaller amount of carotene but accumulates more lutein and violaxanthine; in the mutant 2014, the contents of all carotenoids are decreased proportionally to the decrease in chlorophyll content. It is shown that the rates of CO2 assimilation and oxygen production in the mutant chlorotica 2004 and 2014 plants are reduced. The quantum efficiency of photosynthesis in the mutants is 29-30% lower than in the control plants; in their hybrids, however, it is 1.5-2 higher. It is proposed that both the greater role of dark respiration in gas exchange and the reduced photosynthetic activity in chlorotica mutants are responsible for the decreased phytomass increment in these plants. On the basis of these results, the conclusion is drawn that the mutations chlorotica 2004 and 2014 affect the genes controlling the formation and functioning of various components of the photosynthetic apparatus.

Carbon Dioxide↗
PubMed2003

[Mapping of QTLs controlling chlorophyll content in rice].

Mapping of QTLs controlling chrolophyll content was conducted with the method of multiple-trait composite interval mapping, based on a recombinant inbred (RI) population consisting of 131 lines (F10) derived from a cross between two indica rice varieties, Acc8558 and H359, and on a corresponding genetic map comprising 147 RFLP and 78 AFLP markers. Six QTLs for contents of chlorophyll a and chlorophyll b were detected, respectively. Among them, five QTLs were the same between the two characters. These QTLs were mainly distributed on chromosomes 1 and 4, indicating that the two chromosomes were more important for chlorophyll content. qChlA1c and qChlB1b (these two QTLs were mapped at the same location) showed relatively large effects at all the four observation times and showed the largest effects at the sword leaf period. Another two QTLs (qChlA4a/qChlB4a and qChlA4b/qChlB4b) exhibited significant effects only at the second observation time, suggesting that they might act only at specific developmental stages.

Chlorophyll↗
PubMed1991

[Photocontrol of the synthesis of chlorophyll a and phycocyanin in the cyanobacterium Calothrix crustacea Schousboe].

Chlorophyll a and phycocyanin synthesis in the cyanobacterium Calothrix crustacea Schousboe (ecophene Rivularia bullata) have been studied in white light after the application of red and green light pulses. The light quality produces a complementary pattern in the pigment synthesis. Chlorophyll synthesis is stimulated by red light pulses whereas phycocyanin synthesis is by green light pulses. Because the effect of red light on chlorophyll synthesis shows some far-red photoreversibility, the action of phytochrome is proposed. The green light effect on phycocyanin synthesis is only partially reversed by far-red light. This reversion is lost after incubation in white light for two hours. The effect of green light on phycocyanin synthesis could not only be due to phytochrome since theoretically in green light the level of the active form of phytochrome is lower than in red light. Thus, the action of a specific green light photoreceptor is proposed.

Chlorophyll↗
PubMedDate not supplied

Chlorophyll orientation and exciton migration in the photosynthetic membrane.

Measurements of the linear dichroism and of the polarization of the fluorescence with oriented chloroplasts have revealed a definite orientation of the pigment molecules with respect to the membrane plane. The Qy transition moments of the chlorophyll a molecules are more closely inclined with respect to this plane for the forms absorbing at longer wavelengths than for those absorbing at shorter wavelengths. The fluorescence depolarization by energy transfer, determined with magnetically-oriented chloroplasts, indicates that the degree of local order increases with wavelength for the different (absorption wavelength) forms of chlorophyll a in vivo. Laser pulses of either picosecond or microsecond duration have been used to probe the emission spectrum, lifetime and quantum yield of fluorescence of chloroplasts at various temperatures. With single picosecond pulses, singlet-singlet annihilations occur within the light-harvesting chlorophyll molecules. In the case of microsecond pulses, triplet excitions act as efficient quenchers of the singlets. By monitoring both the yield of carotenoid triplets and of the fluorescence during and after a laser flash, one can show that the carotenoid triplets account for part of but not all the fluorescence quenching.

Chlorophyll↗
PubMed1992

A chloroplast gene is required for the light-independent accumulation of chlorophyll in Chlamydomonas reinhardtii.

The light-independent pathway of chlorophyll synthesis which occurs in some lower plants and algae is still largely unknown. We have characterized a chloroplast mutant, H13, of Chlamydomonas reinhardtii which is unable to synthesize chlorophyll in the dark and is also photosystem I deficient. The mutant has a 2.8 kb deletion as well as other rearrangements of its chloroplast genome. By performing particle gun mediated chloroplast transformation of H13 with defined wild-type chloroplast DNA fragments, we have identified a new chloroplast gene, chlN, coding for a 545 amino acid protein which is involved in the light-independent accumulation of chlorophyll, probably at the step of reduction of protochlorophyllide to chlorophyllide. The chlN gene is also found in the chloroplast genomes of liverwort and pine, but is absent from the chloroplast genomes of tobacco and rice.

Algal Proteins↗
PubMed1993

Olive: a key gene required for chlorophyll biosynthesis in Antirrhinum majus.

Olive (oli) is a recessive nuclear mutation of Antirrhinum majus which reduces the level of chlorophyll pigmentation and affects the ultrastructure of chloroplasts. The oli-605 allele carries a Tam3 transposon insertion which has allowed the locus to be isolated. The oli gene encodes a large putative protein of 153 kDa which shows homology to the products of two bacterial genes necessary for tetrapyrrole-metal chelation during the synthesis of bacteriochlorophyll or cobyrinic acid. We therefore propose that the product of the oli gene is necessary for a key step of chlorophyll synthesis: the chelation of magnesium by protoporphyrin IX. Somatic reversion of the oli-605 allele produces chimeric plants which indicate that the oli gene functions cell-autonomously. Expression of oli is restricted to photosynthetic cells and repressed by light, suggesting that it may be involved in regulating the rate of chlorophyll synthesis in green tissues.

Amino Acid Sequence↗
PubMed2004

Semiempirical PM5 molecular orbital study on chlorophylls and bacteriochlorophylls: comparison of semiempirical, ab initio, and density functional results.

The semiempirical PM5 method has been used to calculate fully optimized structures of magnesium-bacteriochlorin, magnesium-chlorin, magnesium-porphin, mesochlorophyll a, chlorophylls a, b, c(1), c(2), c(3), and d, and bacteriochlorophylls a, b, c, d, e, f, g, and h with all homologous structures. Hartree-Fock/6-31G* ab initio and density functional B3LYP/6-31G* methods were used to optimize structures of methyl chlorophyllide a, chlorophyll c(1), and methyl bacteriochlorophyllides a and c for comparison. Spectroscopic transition energies of the chromophores and their 1:1 or 1:2 solvent complexes were calculated with the Zindo/S CIS method. The self-consistent reaction field model was used to estimate solvent shifts. The PM5 calculations predict planar structure of the porphyrin ring and central position of the four coordinated magnesium atoms in all pigments studied, in accord with the experimental, ab initio, and density functional results, a significant improvement as compared to the older semiempirical PM3 approach. Only small differences in PM5 and B3LYP/6-31G* or Hartree-Fock/6-31G* minimum energy geometries of the reference molecules were observed. Calculations show that in 1:1 solvent complexes, where the magnesium atom is five coordinated, the magnesium atom is shifted out of the plane of the porphyrin ring towards the solvent molecule, while the hexa coordinated 1:2 complexes are again planar. The PM5 method gives atomic charges that are comparable with those obtained from the Hartree-Fock/6-31G* and B3LYP/6-31G* calculations. The single point ZINDO/S CIS calculations with PM5 minimum energy structure gave excellent correlations between calculated and experimental transition energies of the chlorophylls and bacteriochlorophylls studied. Such correlations may be used for prediction of transition energies of the chromophores in protein binding sites. Calculations also predict existence of dark electronic states below the main Soret absorption band in all chromophores studied. The results suggest that the semiempirical PM5 method is a fairly reliable and computationally efficient method in predicting molecular parameters of porphyrin-like molecules.

Bacteriochlorophylls↗
PubMed1996

Isolation of high-chlorophyll-fluorescence mutants of Arabidopsis thaliana and their characterisation by spectroscopy, immunoblotting and northern hybridisation.

Thirty-four recessive photosynthetic mutants of the high-chlorophyll-fluorescence (hcf) phenotype have been isolated by screening 7700 M2 progenies of ethyl methane sulfonate-treated seeds of Arabidopsis thaliana. Most of the mutants isolated were found to be seedling-lethal, but could be grown on sucrose-supplemented media. Chlorophyll (Chl) fluorescence induction, absorption changes in the reaction-centre chlorophyll of PS I (P700) at 830 nm and Chl a/Chl b ratios were recorded in order to probe the photosynthetic functions and to define the mutational lesion. These studies were complemented by immunoblot and Northern analyses which finally led to the classification of the mutants into six different groups. Four classes of mutants were affected in PS I, PS II (two different classes) or the intersystem electron-transport chain, respectively. A fifth mutant class was of pleiotropic nature and the sixth class comprised a Chl b-deficient mutant. Several of the mutants showed severe deficiencies in the levels of subunits of PS I, PS II or the cytochrome b6/f complex. Thus the mutational lesions could be located precisely. Only one mutant was defective in the transcript patterns of some plastid-encoded photosynthesis genes. Hence most of the mutants isolated appear to be affected in translational and post-translational regulatory processes of thylakoid membrane biogenesis or in structural genes encoding constituent subunits of the thylakoid protein complexes.

Arabidopsis↗
PubMed1992

A CCD-OMA device for the measurement of complete chlorophyll fluorescence emission spectra of leaves during the fluorescence induction kinetics.

A new device for the measurement of complete laser induced fluorescence emission spectra (maxima near 690 and 735 nm) of leaves during the induction of the chlorophyll fluorescence is described. In this the excitation light (cw He/Ne laser, 632.8 nm) is switched on by a fast electro-mechanical shutter which provides an opening time of 1 ms. The emitted fluorescence is imaged onto the entrance slit of a multichannel spectrograph through a red cut-off filter (greater than 645 nm). A charge coupled device (CCD) sensor with 2048 elements simultaneously detects the complete chlorophyll fluorescence emission spectrum in the 650-800 nm wavelength range. Scanning is accomplished electronically and the integration time for a complete fluorescence emission spectrum can be selected from 10 ms up to 260 ms. Shutter, detector system and data acquisition are controlled by an IBM-PC/AT compatible computer. A maximum of 32 spectra can be measured at selected times during the fluorescence induction kinetics with the shortest time resolution of 10 ms. The instrument permits the determination of various fluorescence parameters: a) the rise-time of the fluorescence to the maximum level fm, b) the changes in the shape of the fluorescence emission spectra during the induction kinetics, c) the induction kinetics in the fluorescence ratio F690/F735 as well as d) the fluorescence decrease ratio Rfd at any wavelength between 650 to 800 nm. These fluorescence parameters provide information about the functioning of photosynthesis. The ratio F690/F735 allows the non-destructive determination of the chlorophyll content of leaves. The application of this instrument in ecophysiological research and stress physiology of plants is outlined.

Chlorophyll↗
PubMed1986

Application of chlorophyll fluorescence in ecophysiology.

In vivo chlorophyll fluorescence measurements have become a valuable tool in ecophysiology. Fluorescence emission spectra are influenced by the reabsorption of the tissue and indicate the composition of the antenna system and are influenced by the chlorophyll content per leaf area. The fluorescence induction kinetics ("Kautsky effect") can be used to study photosynthetic activity. These rapid, non-destructive methods can be applied for ecophysiological field research to check the vitality of plants and to document stress effects on the photosynthetic apparatus. The Rfd-values (Rfd = fd/fs), the ratio of the fluorescence decrease (fd) to the steady state fluorescence (fs), can be taken as a rapid vitality index of the leaves and trees. We here describe fundamental chlorophyll fluorescence results of leaves which are needed for the interpretation of in vivo fluorescence signatures in stress physiology and in the forest dieback research.

Chlorophyll↗
PubMed1976

Pigment containing lipid vesicles. I. Preparation and characterization of chlorophyll a-lecithin vesicles.

Vesicles obtained by sonication of chlorophyll a-lecithin mixtures dispersed in anaqueous medium closely resemble the well-characterized vesicles similarly prepared from pure lipids. They are bounded by one spherical lipid bilayer which contains the chlorophyll a. Appropriate conditions for sonication prevent substantial degradation of the membrane constituents. Up to one chlorophyll a molecule per 55 lecithins can be incorporated into membranes. The average Stokes' radius of the vesicles determined by analytical sieve chromatography is 102 +/- 5 A and independent of the chloropyll a content. The membrane is visible in the electron-microscope when the vesicles are treated with osmium tetroxide prior to negative staining. The osmium fixation is, however, not strong enough to allow for a preparation of the vesicles for thin sectioning (dehydration, embedding in epoxide).

Chlorophyll↗
PubMed2002

Three-piece-ligation PCR and application in disruption of chlorophyll synthesis genes in Synechocystis sp. PCC 6803.

Linear DNA, consisting of a drug-resistance marker and long flanking sequences, was synthesized by one-step polymerase chain reaction after a three-piece ligating reaction. Chlorophyll synthesis genes, chlH and chlL in Synechocystis sp. PCC 6803, were replaced by a kanamycin-resistance marker through double recombinations with flanking homology regions. Under LAHG conditions, the chlL but not chlH mutant stopped chlorophyll synthesis, while both synthesized chlorophyll in the light.

Bacterial Proteins↗
PubMed2000

Chlorophyll is not the primary photoreceptor for the stimulation of P-type H+ pump and growth in variegated leaves of Coleus x hybridus.

There has been persisting controversy over the role of photosynthesis in the stimulation of the plasma membrane H+-ATPase and growth of dicotyledonous leaves by light. To investigate this, we compared the effects of light on growth, H+ net efflux and membrane potential (Vm) of strips which contained either only chlorophyll-free (white) mesophyll cells or chlorophyll-containing (green) cells cut from variegated Coleus leaves. White mesophyll cells responded to white, blue and red light with a hyperpolarization of Vm, an acidification of the apoplast and a promotion of growth, all of which began after a lag of 2-7 min. In contrast, green mesophyll cells showed a biphasic light response in which the hyperpolarization and the acidification were preceded by a rapid depolarization of Vm and an alkalinization of the apoplast. Nevertheless, green and white tissues showed comparable growth promotions in response to light. The light response of the leaf mesophyll is a composite of two separate photosystems. The initial depolarization and alkalinization are mediated by photosynthesis and blocked by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The slower hyperpolarization, acidification and growth response, on the other hand, are clearly in response to light absorption by pigments other than chlorophyll.

Chlorophyll↗
PubMed2005

Distribution of chlorophyll-bearing organelles in the shoot apex of a range of dicotyledonous plants.

Confocal laser scanning microscopy was used to study the distribution of the smallest detectable autofluorescing, chlorophyll-bearing structures in fresh, 40 microm thick longitudinal sections of the shoot apex of four dicotyledonous plants (Arabidopsis thaliana, Nicotiana glauca, Lupinus alba, and Spinacia oleracea). In all species, the smallest chlorophyll-bearing particles were found in the outermost cell layers (L1 and L2) of the shoot apex. Their distribution between these layers differed in each species. The smallest such particles were about 0.5-1.0 microm in maximum dimension, approximating the size of a single granum in the developing leaf. Their size and abundance increased with increasing cell age and distance from the peak of the apex. Immediately beneath the L1 and L2 layers was a zone largely devoid of these particles. Below this nonfluorescing zone, in the region where the derivatives of the meristematic zone differentiate into cells of the central pith region, the size and abundance of the chlorophyll-bearing particles increased progressively with increasing distance from the nonfluorescing zone. The presence of these small autofluorescing particles in the L1 and L2 cell layers of the shoot apex places the development of photosystem II fluorescence at an earlier stage of leaf development than previously observed. The use of confocal laser scanning microscopy to study unfixed sections provides another useful metabolic marker for mapping patterns of differentiation and development in the cells of the shoot apex.

Arabidopsis↗
PubMed2005

Spectroscopic characterization of the excitation energy transfer in the fucoxanthin-chlorophyll protein of diatoms.

We characterized the energy transfer pathways in the fucoxanthin-chlorophyll protein (FCP) complex of the diatom Cyclotella meneghiniana by conducting ultrafast transient absorption measurements. This light harvesting antenna has a distinct pigment composition and binds chlorophyll a (Chl-a), fucoxanthin and chlorophyll c (Chl-c) molecules in a 4:4:1 ratio. We find that upon excitation of fucoxanthin to its S2 state, a significant amount of excitation energy is transferred rapidly to Chl-a. The ensuing dynamics illustrate the presence of a complex energy transfer network that also involves energy transfer from the unrelaxed or 'hot' intermediates. Chl-c to Chl-a energy transfer occurs on a timescale of a 100 fs. We observe no significant spectral evolution in the Chl-a region of the spectrum. We have applied global and target analysis to model the measured excited state dynamics and estimate the spectra of the states involved; the energy transfer network is discussed in relation to the pigment organization of the FCP complex.

Algal Proteins↗
PubMed1991

Resolution of 16 to 20 chlorophyll-protein complexes using a low ionic strength native green gel system.

Conventional native "green gel" systems resolve at most 10 chlorophyll-protein complexes from thylakoid membranes of higher plants and green algae. Such analyses suggest a simplicity of the thylakoid membrane that is not supported by a growing body of evidence on the heterogeneity of photosystems I and II (PSI and PSII) and their associated antennae (LHCI and LHCII). We report here the development and characterization of a low ionic strength native "green gel" system that resolves from 16 to 20, mostly large chlorophyll-protein complexes from a variety of higher plant and green algal species with very little release of free pigment. In Chlamydomonas, this system resolves multiple PSI-LHCI complexes, multiple PSII-LHCII complexes, four oligomeric LHCII complexes, as well as several low electrophoretic mobility reaction center complexes, and a number of small complexes. We have obtained similar resolution with a large number of higher plant and green algal species. We also demonstrate how this system can be used as a sort of "fingerprinting" technique to distinguish thylakoids of different species, and for the analysis of photosynthetic mutants, using the chlorophyll b-less chlorina f2 mutant of barley as an example.

Chlorophyll↗