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PubMed1998

Chlorophyll alpha synthesis upon interruption and deletion of por coding for the light-dependent NADPH: protochlorophyllide oxidoreductase in a photosystem-I-less/chlL- strain of Synechocystis sp. PCC 6803.

The gene coding for the light-dependent NADPH:protochlorophyllide oxidoreductase (POR) was interrupted or deleted in a Synechocystis sp. PCC 6803 strain lacking photosystem I (PS I) as well as ChlL, which takes part in light-independent catalysis of protochlorophyllide reduction. Interruption of por by a kanamycin-resistance cartridge between the codons for M263 and V264 (about 83% into the coding region) did not abolish POR activity, but resulted in a decrease in the protochlorophyllide-(PChlide)-binding capacity of POR. Deletion of por in the PS I-less/chlL- strain generated a mutant [PS I-less/chlL-/por (del)] which accumulated both monovinyl-PChlide and divinyl-PChlide and excreted PChlides into the medium. This mutant also synthesized small amounts of protochlorophyllide dihydrogeranylgeraniol ester (protochlorophyll) when it was grown under light-activated heterotrophic growth conditions. However, the mutant was still able to synthesize small amounts of normal chlorophyll a under weak continuous illumination, even though the quantum yield of chlorophyll a formation was reduced. Either protochlorophyll or PChlide reduction by an unspecific reductase or by a ChlB/ChlN complex could account for chlorophyll a synthesis in the PS I-less/chlL-/por (del) strain. Functional photosystem II (PS II) was assembled in this mutant, but the PS II/chlorophyll ratio was fourfold lower than in the PS I-less strain with normal chlorophyll synthesis. The PS I-less/chlL-/por (del) mutant had a 77-K fluorescence emission maximum at 685 nm but no peak or shoulder at 695 nm when the cells were excited at 435 nm. Much of the chlorophyll in the PS I-less/chlL-/por (del) mutant therefore seems to be associated with components other than PS II.

Chlorophyll↗
PubMed2000

Stable insertion of the early light-induced proteins into etioplast membranes requires chlorophyll a.

Etiolated plant seedlings exposed to light respond by transient accumulation of the nucleus-encoded, plastid-located early light-inducible proteins (Elips). These proteins are distant relatives of the light-harvesting chlorophyll a/b-binding gene family and bind pigments with unusual characteristics. To investigate whether accumulation of Elips in plastid membranes is post-translationally regulated by pigments, reconstitution studies were performed, where in vitro transcribed and translated low molecular mass Elip precursors of barley were combined with lysed barley etioplasts complemented with various compositions of isolated pigments. We showed that the membrane insertion of Elips, as proven by protease protection assays and washes with a chaotropic salt or alkali, depended strictly on chlorophyll a but not on chlorophyll b or xanthophyll zeaxanthin. The amount of inserted Elips increased almost linearly with the chlorophyll a concentration, and the insertion efficiency was not significantly influenced by a light intensity between 1 and 1,000 micromol x m(-2) x s(-1). In contrast, in vitro import of Elip precursors into greening plastids was enhanced by high intensity light. Thus, we conclude that although chlorophylls bound to Elips seem to not be involved in light harvesting, they are crucial for a stable insertion of these proteins into the plastid membrane.

Arabidopsis Proteins↗
PubMed2003

Chlorophyll content monitoring in sugar maple (Acer saccharum).

We conducted two experiments to determine the usefulness of a chlorophyll content meter (CCM) for the measurement of foliar chlorophyll concentration in sugar maple (Acer saccharum Marsh.) in the fall color period. In Experiment 1, four sugar maple trees were visually assigned to each of four fall foliage color categories in October 1998. On four dates in the fall of 1999, leaves were taken from the trees and analyzed for chlorophyll concentration by absorbance of pigment extracts and by determination of the chlorophyll content index (CCI) with a CCM. The two measures of chlorophyll concentration were strongly correlated (P < 0.001, r2 = 0.72). In Experiment 2, the CCI of leaves from sugar maple trees subjected to one of four fertilization treatments (lime, lime + manure, lime + 10:10:10 N,P,K fertilizer and an untreated control) were determined with a CCM. Treatment effects were distinguishable between all pairwise comparisons (P < 0.001), except for the lime versus lime + NPK fertilizer treatments.

Acer↗
PubMed1960

Two forms of chlorophyll a in vivo with distinct photochemical functions.

Action spectra of the Emerson effect in Chlorella and Navicula reveal peaks at 670 mut, in addition to those at 650 mu (Chlorella) and 630 mmicro (Navicula) attributable to chlorophylls b and c. Thus, excitation of chlorophyll a form "chlorophyll a 670" can supplement, in these algae, the excitation of the form "chlorophyll a 680-700." The effect of the auxiliary pigments in these algae may be mediated by energy transfer to "chlorophyll a 670."

Chlorophyll↗
PubMed2005

A preliminary study on ultra high frequency electromagnetic fields effect on black locust chlorophylls.

Chlorophylls were quantitatively studied in the leaves of black locust (Robinia pseudoacacia L.) seedlings exposed to electromagnetic fields of high frequency. Exposure system was designed and built up to make possible simultaneous exposure of seedling lots (3 months old) to low power density electromagnetic fields corresponding to a frequency of 400 MHz. After three weeks of daily exposures (1, 2, 3 and 8 hours), chlorophyll levels were measured using adequate spectral device. Statistical analysis of experimental results was performed by means of t-test to identify significant modifications induced by electromagnetic treatment in exposed samples in comparison to the control. Chlorophyll-a as well as chlorophyll-b level was found to decrease except the exposure time of two hours, where a considerable enhancement was noticed. It was revealed that the ratio of the two main types of chlorophyll was decreasing logarithmically to the increase of daily exposure time.

Chlorophyll↗
PubMed2001

Chlorophyll fluorescence as a bioindicator of effects on growth in aquatic macrophytes from mixtures of polycyclic aromatic hydrocarbons.

Chlorophyll-a fluorescence induction is a rapid technique for measuring photosynthetic electron transport in plants. To assess chlorophyll-a fluorescence as a bioindicator of effects of polycyclic aromatic hydrocarbon mixtures, chlorophyll-a fluorescence parameters and plant growth responses to exposure to the wood preservative creosote were examined in the aquatic plants Lemna gibba and Myriophyllum spicatum. Exposure to creosote inhibited growth of L. gibba (EC50 = 7.2 mg/L total polycyclic aromatic hydrocarbons) and M. spicatum (EC50 = 2.6 mg/L) despite differences in physiology. Creosote also diminished maximum PSII efficiency (Fv/Fm) (EC50 = 36 and 13 mg/L for L. gibba and M. spicatum) and the effective yield of photosystem II photochemistry (deltaF/Fm') (EC50 = 13 and 15 mg/L for L. gibba and M. spicatum). The similarity between growth and chlorophyll-a fluorescence EC50s and slopes of the response curves suggests a close mechanistic link between these end points. The predictive power of chlorophyll-a fluorescence as a bioindicator of whole-organism effects applied to complex contaminant mixtures is discussed.

Chlorophyll↗
PubMed1998

Potent suppressive activity of chlorophyll a and b from green tea (Camellia sinensis) against tumor promotion in mouse skin.

Potent antigenotoxic and anti-tumor promoting activities of chlorophyll a from green tea (camellia sinensis) have been shown using in vitro cell culture experiments (Okai Y. et al. (1996) Mutation Res., 370, 11-17). In the present study, the authors analyzed in vivo effects of chlorophyll a and b from green tea on tumor promotion in mouse skin in the following ways. 1. When chlorophyll a and b from green tea were applied before each treatment by a tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on BALB/c mouse skin initiated by 7, 12-dimethylbenz [a] an-thracene (DMBA), they caused significant suppression in a dose-dependent manner against BALB/c mouse skin tumorigenesis. 2. Chlorophyll a and b showed significant suppressive effects against TPA-induced inflammatory reaction such as edema formation in BALB/c mouse ear skin in a dose-dependent fashion. These results suggest that chlorophyll a and b possess potent suppressive activities against tumor promotion in mouse skin.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2005

Seasonal variations of chlorophyll-a in Demirdöven Dam Reservoir (Erzurum, Turkey) in relation to phytoplankton density and environmental factors.

The seasonal variations of Chlorophyll-a was examined in relation to phytoplankton density and physico-chemical factors in Demirdöven Dam Reservoir during 2000-2001. Chlorophyll-a concentrations ranged from 0.62 to 7.19 mg/m3 and from 0.67 to 8.88 mg/m3 in 2000 and 2001, respectively. Maximum Chlorophyll-a concentrations were found near the metalimnion and decreased with depth. Chlorophyll-a concentrations showed positive correlation to phytoplankton density, water temperature and nutrient concentrations, and negative correlations to Secchi depth. Demirdöven Dam Reservoir can be classified as a mesotrophic reservoir according to Chlorophyll-a concentrations.

Chlorophyll↗
PubMed2005

Application of Bayesian regularized BP neural network model for analysis of aquatic ecological data-a case study of chlorophyll-a prediction in Nanzui water area of Dongting Lake.

Bayesian regularized BP neural network(BRBPNN) technique was applied in the chlorophyll-a prediction of Nanzui water area in Dongting Lake. Through BP network interpolation method, the input and output samples of the network were obtained. After the selection of input variables using stepwise/multiple linear regression method in SPSS 11.0 software, the BRBPNN model was established between chlorophyll-a and environmental parameters, biological parameters. The achieved optimal network structure was 3-11-1 with the correlation coefficients and the mean square errors for the training set and the test set as 0.999 and 0.00078426, 0.981 and 0.0216 respectively. The sum of square weights between each input neuron and the hidden layer of optimal BRBPNN models of different structures indicated that the effect of individual input parameter on chlorophyll-a declined in the order of alga amount > secchi disc depth (SD) > electrical conductivity (EC). Additionally, it also demonstrated that the contributions of these three factors were the maximal for the change of chlorophyll-a concentration, total phosphorus (TP) and total nitrogen (TN) were the minimal. All the results showed that BRBPNN model was capable of automated regularization parameter selection and thus it may ensure the excellent generation ability and robustness. Thus, this study laid the foundation for the application of BRBPNN model in the analysis of aquatic ecological data(chlorophyll-a prediction) and the explanation about the effective eutrophication treatment measures for Nanzui water area in Dongting Lake.

Bayes Theorem↗
PubMedDate not supplied

Resonance Raman spectroscopy of chlorophyll-protein complexes.

Resonance Raman spectra of chlorophyll a (Chl a) and of Chl b were selectively obtained, at low temperature, from chlorophyll-protein complexes prepared from green and blue-green algae and from higher plants. Antenna Chl a in the Chl a-P700-protein complexes (CP I) and in the light-harvesting Chl a/b-protein complexes (CP ii gives resonance Raman spectra extremely close in all their features to those previously obtained from intact cells and chloroplasts. In particular, the same multiplicity of binding sites for the ketone carbonyl groups of Chl a is observed in both CP I and CP II as in intact membranes. These bindings sites are probably the same types as those observed in the intact membranes and are not the magnesium atoms of other chlorophylls. The magnesium atoms of most Chl a molecules in both CP I and CP II bind a single external ligand. Resonance Raman spectra of Chl b in CP II preparations, although very similar to those from intact membranes, show partial rearrangement of one of the two environmental subspecies of Chl b previously found in intact membranes. These results provide evidence that chlorophyll-protein complexes closely represent the state of the bulk of antenna chlorophyll in vivo.

Binding Sites↗
PubMedDate not supplied

In vivo monitoring of chlorophyll fluorescence response to low-dose gamma-irradiation in pumpkin (cucurbita pepo) leaves.

The effect of gamma-irradiation on the in vivo-measured chlorophyll fluorescence in a pumpkin leaves (Cucurbita pepo) has been investigated. Plants were grown in the same environment, then divided into several groups and irradiated at ambient conditions at small dose levels (up to 13.4 Gy) with (60)Co gamma-rays. The post-irradiation effect on chlorophyll status in the leaves was examined by measuring chlorophyll fluorescence 2 days (48 h) after exposure. It is undoubtedly found that the value of fluorescence intensity ratio (FIR) at 690 nm and 735 nm (F(690)/F(735)) depends upon the ionizing radiation dose. Even with the smallest dose of 3.35 Gy, ionizing radiation notably altered the fluorescence spectra of leaves. The spectra difference was manifested by decrease of FIR due to changed chlorophyll luminescence, the possible reason for which could be increase of chlorophyll concentration during the recovery process of the plant. The potential implications of these results for plant physiological status monitoring, as well as for pollution detection and assessment, are discussed in brief.

Chlorophyll↗
PubMed1988

Flow cytometric characterization of the chlorophyll contents and size distributions of plant protoplasts.

We have employed flow cytometry for the characterization of populations of protoplasts prepared from tobacco (Nicotiana tabacum) leaf tissues. We first investigated the possibility of using flow cytometric analysis of the emission of chlorophyll autofluorescence for measurement of the chlorophyll contents of leaf protoplasts. Defined numbers of leaf protoplasts were sorted according to different, nonoverlapping windows placed on the one-dimensional histograms of chlorophyll autofluorescence emission. The amounts of cellular chlorophyll were measured in cell-free extracts of these sorted protoplasts using fluorometry. A high degree of correlation (r2 = 0.983) was observed between these two parameters. We then examined the distribution of protoplast diameters in these protoplast populations through the use of pulse-width time-of-flight (TOF) analysis. Through sorting of protoplasts using a series of narrow, nonoverlapping TOF windows, we were able to demonstrate that the TOF parameter was linearly correlated with protoplast diameter, over the range of 15-55 micron (r2 greater than 0.99). We also compared the use of fluorescein diacetate (FDA) fluorochromasia and chlorophyll autofluorescence as the source of fluorescent signals for TOF analysis. We found that the presence of chloroplasts introduced distortions into the measurement of apparent size afforded by TOF analysis of FDA fluorochromasia. These results are discussed in terms of the application of techniques of flow analysis and sorting for the measurement of gene expression within the various different cell types found in plant tissues and organs.

Cell Separation↗
PubMed1993

Chloroplast chlB gene is required for light-independent chlorophyll accumulation in Chlamydomonas reinhardtii.

Light-independent chlorophyll synthesis occurs in some algae, lower plants, and gymnosperms, but not in angiosperms. We have identified a new chloroplast gene, chlB, that is required for the light-independent accumulation of chlorophyll in the green alga Chlamydomonas reinhardtii. The chlB gene was cloned, sequenced, and then disrupted by performing particle gun-mediated chloroplast transformation. The resulting homoplasmic mutant was unable to accumulate chlorophyll in the dark and thus exhibited a 'yellow-in-the-dark' phenotype. The chlB gene encodes a polypeptide of 688 amino acid residues, and is distinct from two previously characterized chloroplast genes (chlN and chlL) also required for light-independent chlorophyll accumulation in C. reinhardtii. Three unidentified open reading frames in chloroplast genomes of liverwort, black pine, and Chlamydomonas moewusii were also identified as chlB genes, based on their striking sequence similarities to the C. reinhardtii chlB gene. A chlB-like gene is absent in chloroplast genomes of tobacco and rice, consistent with the lack of light-independent chlorophyll synthesis in these plants. Polypeptides encoded by the chloroplast chlB genes also show significant sequence similarities with the bchB gene product of Rhodobacter capsulatus. Comparisons among the chloroplast chlB and the bacterial bchB gene products revealed five highly conserved sequence areas that are interspersed by four stretches of highly variable and probably insertional sequences.

Algal Proteins↗
PubMed1993

The atypical chlorophyll a/b/c light-harvesting complex of Mantoniella squamata: molecular cloning and sequence analysis.

cDNA species encoding precursor polypeptides of the chlorophyll a/b/c light-harvesting complex (LHC) of Mantoniella squamata were cloned and sequenced. The precursor polypeptides have molecular weights of 24.2 kDa and are related to the major chlorophyll a/b polypeptides of higher plants. Southern analysis showed that their genes belong to the nuclear encoded Lhc multigene family; the investigated genes most probably do not contain introns. The chlorophyll a/b/c polypeptides contain two highly conserved regions common to all LHC polypeptides and three hydrophobic alpha-helices, which span the thylakoid membrane. The first membrane-spanning helix, however, is not detected by predictive methods: its atypical hydrophilic domains may bind the chlorophyll c molecules within the hydrophobic membrane environment. Homology to LHC II of higher plants and green algae is specifically evident in the C-terminal region comprising helix III and the preceding stroma-exposed domain. The N-terminal region of 29 amino acids resembles the structure of a transit sequence, which shows only minor similarities to those of LHC II sequences. Strikingly, the mature light-harvesting polypeptides of M. squamata lack an N-terminal domain of 30 amino acids, which, in higher plants, contains the phosphorylation site of LHC II and simultaneously mediates membrane stacking. Therefore, the chlorophyll a/b/c polypeptides of M. squamata do not exhibit any light-dependent preference for photosystem I or II. The lack of this domain also indicates that the attractive forces between stacked thylakoids are weak.

Amino Acid Sequence↗
PubMed1977

Possible role of cyclic AMP in the synthesis of chlorophyll in Chlorella fusca.

The intracellular concentration of cAMP in the green alga Chlorella fusca was in the range of 2.10(-9) to 10(-8) moles/g dry weight and was strongly dependent on the growth conditions. The cAMP level was high with high light intensity, low nitrate or glucose concentration. Intracellular cAMP increased only by factor of 2 when high amounts (up to 10(-3) M) of cAMP were added to the medium. Most of the given cAMP was converted to 5'-AMP. Addition of cAMP had little effect on the chlorophyll content of the cells, only at 10(-6) M some enhancement in photoautotrophic cultures was observed. On the other hand high amounts of cAMP in the medium increased the growth rate. DBcAMP* showed a positive effect on chlorophyll synthesis and growth rate at much lower concentrations compared to cAMP. Stimulation effects of exogenous cAMP on the synthesis of chlorophyll were also observed in mixotrophic cultures with a high glucose/nitrate ratio, conditions where chlorophyll synthesis is repressed. Similar to autotrophic conditions DBcAMP was more effective than cAMP. These data indicate that cAMP may act in a system controlling the chlorophyll content of the cells in response to nutrients or light.

Chlorella↗
PubMed2006

Development of an efficient method for the preparative isolation and purification of chlorophyll a from a marine dinoflagellate Amphidinium carterae by high-speed counter-current chromatography coupled with reversed-phase high-performance liquid chromatography.

In our research into chlorophylls of marine dinoflagellates, chlorophyll a was separated rapidly from the hexane extract of Amphidinium carterae in three steps. The first step was silica gel column chromatography, where elution was performed with 0-50% ethyl acetate in n-hexane. The second was high-speed counter-current chromatography using a two-phase solvent system consisting of n-hexane-ethyl acetate-methanol-water (5:5:5:1, v/v), and the third step was preparative reversed-phase high-performance liquid chromatography using a solvent system of acetone-water (89:11, v/v). HPLC analysis showed that the purity of chlorophyll a from the second step was over 83%, and after the third it was over 99%. Thirty milligrams of chlorophyll a was isolated from a crude sample of 250 mg of chlorophylls, and its structure was identified by analyzing its MS, 1H NMR and 13C NMR spectra.

Animals↗
PubMed2002

Irreversible damage to photosystem I by chilling in the light: cause of the degradation of chlorophyll after returning to normal growth temperature.

The recovery process after chilling-induced photoinhibition of photosystem I (PSI) was studied in leaves of a chilling-sensitive plant, cucumber (Cucumis sativus L. cv. Nanshin). Determination of chlorophyll content, photosystem (PS) activities in vivo and in vitro, and the amount of reaction-center subunits of PSI revealed that: (i) The content of chlorophyll decreased to 70% of the original level gradually from 1 to 3 days after exposure to a low temperature. (ii) The amount of functional PSI per unit leaf area was reduced to 30% of the initial level by the chilling treatment. The amount of functional PSI gradually increased during the next 6 days but only to 50% of the original level. (iii) When expressed on a chlorophyll basis, however, the amount of functional PSI recovered to 90% of the original level 6 days after the treatment. (iv) The residual amount of chlorophyll on the third day after the treatment closely correlated with the amount of functional PSI at that point. These results indicate that the decrease in chlorophyll content at a normal growth temperature after chilling treatment is a consequence of the degradation of irreversibly damaged PSI complexes. Immunoblot analysis confirmed that PsaAB protein, the reaction-center subunits of PSI, was degraded during the 3 days after chilling treatment. Some characteristics of the chilling injury frequently reported, i.e. irreversibility of the injury and development of visible symptoms at room temperature, can be explained as a consequence of the chilling-induced photoinhibition of PSI.

Acclimatization↗
PubMed2000

Changes in carotenoids, tocopherols and diterpenes during drought and recovery, and the biological significance of chlorophyll loss in Rosmarinus officinalis plants.

Two-year-old rosemary (Rosmarinus officinalis L.) plants were subjected to severe stress by exposure to prolonged drought during a Mediterranean summer. Severely stressed plants recovered completely after the autumn rainfalls although the relative water content remained below 35% for 3 months and the chlorophyll content of leaves was reduced by up to 85% during the drought. In severe stress: (i) alpha-tocopherol increased 9-fold per g dry weight and 20-fold per unit of chlorophyll; (ii) lutein and beta-carotene contents decreased on a dry-weight basis, but an 80% increase in lutein and constant levels of beta-carotene were observed on a chlorophyll basis; (iii) there were transient and sustained increases in the de-epoxidation state of the xanthophyll cycle; and (iv) the highly oxidised abietane diterpene isorosmanol increased 8-fold as a result of the oxidation of carnosic acid. With the autumn rainfalls, water status, alpha-tocopherol and violaxanthin recovered first and the levels of photosynthetic pigments and abietane diterpenes increased later. The photoprotection conferred by the xanthophyll cycle and the antioxidant function of tocopherols, lutein and diterpenes may help to avoid irreversible damage in severe drought, making possible the recovery of functional membranes after the autumn rainfalls. Besides, chlorophyll loss reduces the amount of photons absorbed by leaves, which enhances the photoprotective and antioxidant capacity of leaves per amount of photons absorbed, since the ratios of xanthophylls, alpha-tocopherol and abietane diterpenes to chlorophyll increase.

Carotenoids↗