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PubMed1988

Possible control of transcript levels by chlorophyll precursors in Chlamydomonas.

Steady-state mRNA levels of the three nuclear genes cab1, rbcS1 and rbcS2 (coding for the light-harvesting chlorophyll-binding protein (LHCP) and the small subunit of ribulose 1,5-bisphosphate carboxylase, respectively) and of the two plastid-encoded genes rbcL and psaA2 (coding for the large subunit of the carboxylase and a member of the P700 chlorophyll a protein, respectively) have been investigated in synchronized Chlamydomonas cells in response to light and inhibitors interfering with chlorophyll synthesis. The accumulation of cab1, rbcS1 and psaA2 transcripts is light-dependent, whereas transcripts from rbcS2 and rbcL genes are present in high amounts in the light and in the dark. Dioxoheptanoic acid, an inhibitor blocking chlorophyll synthesis prior to porphyrin formation, does not affect the accumulation of all five mRNAs. However, inhibition of chlorophyll synthesis by incubating cells with dipyridyl, cycloheximide or nitrogen promotes the accumulation of porphyrin compounds, but specifically prevents the accumulation of light-dependent transcripts. Although functionally unrelated, these inhibitors are known to block an Fe-dependent oxygenase, which is involved in the formation of the isocyclic ring in the chlorophyll molecule. The data are explained as a control by chlorophyll precursors over the accumulation of light-dependent transcripts.

2,2'-Dipyridyl↗

PubMedDate not supplied

Optical properties of intact leaves for estimating chlorophyll concentration.

Changes in leaf chlorophyll content can serve as relative indicators of plant vigor and environmental quality. This study identified reflectance, transmittance, and absorptance wavebands and band ratios within the 400- to 850-nm range for intact leaves that could be used to estimate extracted leaf chlorophyll per unit leaf area (areal concentration) with minimal error. Leaf optical properties along with chlorophyll a, b, and a + b concentrations were measured for the planar-leaved sweetgum (Liquidambar styraciflua L.), red maple (Acer rubrum L.), wild grape (Vitis rotundifolia Michx.), and switchcane [Arundinaria gigantea (Walter) Muhl.], and for needles of longleaf pine (Pinus palustris Miller). Generally, reflectance, transmittance, and absorptance corresponded most precisely with chlorophyll concentrations at wavelengths near 700 nm, although regressions were also strong in the 550- to 625-nm range. A power function was superior to a simple linear function in yielding low standard deviations of the estimate (s). When data were combined among the planar-leaved species, s values were low at approximately 50 mumol/m2 out of a 940 mumol/m2 range in chlorophyll a + b at best-fit wavelengths of 707 to 709 nm. Minimal s values for chlorophyll a + b ranged from 32 to 62 mumol/m2 across species when band ratios having numerator wavelengths of 693 to 720 nm were used with the application of a power function. Optimal denominator wavelengths for the band ratios were 850 nm for reflectance and transmittance and 400 nm for absorptance. This information can be applied in designing field portable chlorophyll meters and in the landscape-scale remote sensing of plant responses to the environment.

Chlorophyll↗

PubMedDate not supplied

[ESR of adsorbed chlorophyll a].

Oxygen and water vapour effect on the dark ESR signal of chlorophyll a adsorbed on silica in vacuum has been studied. It has been determined that when O2 and H2O are absent chlorophyll a adsorption is accompanied by an increase of the paramagnetic states portion (PSP) of the pigment. The PSP is increasing when oxygen is admitted. Water vapour does not increase the PSP of the adsorbed chlorophyll a. It has been supposed that the ESR signal of chlorophyll a in solution belongs to the chlorophyll-oxygen complex and that any strengthening of the pi-pi-interactions results in intensification of the ESR signal. It has been concluded that the ESR signal of adsorbed chlorophyll a belongs to the charge transfer complex of the molecular oxygen and the chlorophyll aggregate with strong pi-pi-interactions.

Adsorption↗

PubMed1982

[Enzymatic system transforming chlorophyllide into chlorophyll in etiolated leaves using exogenous substrates].

The substrate specificities of the enzymatic system, which transforms chlorophyllide into chlorophyll in etioplasts of whole leaves and of the chlorophyllase enzyme, which performs the inverse reaction, i. e. chlorophyll hydrolysis, were compared. Infiltration of chlorophyllide a of b into the excised etiolated leaves of rye results in a formation of chlorophylls a and b in the dark, whereas pheophorbide a or b does not cause pheophytin to appear under the same conditions. Consequently, for the in vivo esterification reaction to occur, substitution of the methyl group by the formyl one in position 3 of the tetrapyrrole ring is not essential, but the presence of the central magnesium atom in the molecule is necessary. On the other hand, chlorophyllase from the same etiolated leaves equally hydrolyzes both chlorophylls and pheophytins. It is concluded that the enzymes present in etioplasts which catalyze chlorophyllide esterification and chlorophyll hydrolysis are not identical. The optimal temperature of the in vivo esterification of exogenous chlorophyllide to chlorophyll (37 degrees) was determined and the ability of this chlorophyll to be hydrolyzed by chlorophyllase was established.

Chlorophyll↗

PubMedDate not supplied

[Molecular organization of aggregated forms of chlorophyll and its analogs].

Infrared spectra (in the region of 1800-1600 cm-1) of aggregated protochlorophyll, chlorophyll a and b, bacterioviridin, protopheophytin, pheophytin a (in the solid films) with different absorption spectra were studied. The formation of various types of aggregates is due to the realization of different modes of intermolecular bonding. The mode of interaction depends upon the chemical structure of the pigment and upon the inclusion of low-molecular addenda into the structure of aggregates. The forms 677 nm of chlorophyll a and 658 nm of chlorophyll b appear when the coordination bonds between the keto groups of the cyclopentanone ring and central magnesium atom are formed. The longwave forms of chlorophyll a (745 nm) and chlorophyll b (675 nm, 725 nm) are formed when methanol molecules are involved in the intermolecular bonds. The coordination bonds between C=O and magnesium atom in the longwave aggregate of bacterioviridin (750 nm) are observed without participation of the low-molecular addenda, The formation of the protochlorophyl 635 nm form and aggregated forms of magnesium-free pigments occurs without participation of carbonyl groups probably by direct interaction between the eta-electron systems of molecules. The frequencies of carbonyl groups of the solid films in dioxane vapours causing absorption maxima at 690 nm (chlorophyll a) and 670 nm (chlorophyll b) are not shifted as compared to the dissolved pigments. Thipoints to the intermolecular interaction without participation of C=O groups.

Chemical Phenomena↗

PubMed1994

Spectroscopic characterization of three different monomeric forms of the main chlorophyll a/b binding protein from chloroplast membranes.

A detailed comparison has been made between dichroic steady-state spectroscopic properties at 77 K of several trimeric and monomeric forms of the major chlorophyll a/b binding protein (LHC-II) from pea. Monomeric forms were obtained by applying high concentrations of nonionic detergents, by a lipase treatment, or by a chymotrypsin/trypsin treatment. The latter treatments removed phosphatidyl glycerol essential for trimer formation. The absorption and dichroism spectra indicate that for trimeric LHC-II the chlorophyll b absorption region is centered around 649 nm and is composed of at least five subbands near 640, 647, 649, 652, and 656 nm. The chlorophyll a absorption region is centered around 670 nm and is composed of at least five bands near 661, 668, 671, 673, and 676 nm. The chlorophyll b band near 647 and 652 nm and the chlorophyll a bands near 668 and 673 nm are absent in the circular dichroism spectrum after monomerization. A configuration in which pigments of the same nature located on different monomers become excitonically coupled in the trimer could explain these results. In monomers obtained in high concentrations of nonionic detergents, no additional bands have disappeared, but the absorption spectra of the other two types of monomers lack the bands at 640 and 661 nm. These monomers have lost some chlorophyll a and b according to the fluorescence emission spectra, which show contributions from free chlorophyll a and b. The results suggest that phosphatidyl glycerol not only is involved in trimer formation but also has a structural role within the monomers.

Biopolymers↗

PubMed2003

Fucoxanthin-chlorophyll proteins in diatoms: 18 and 19 kDa subunits assemble into different oligomeric states.

Fucoxanthin-chlorophyll proteins were purified from the centric diatom Cyclotella meneghiniana. Two major fractions were observed that differed in their polypeptide composition and oligomeric state. Trimers consist of mainly 18 kDa polypeptides. Higher oligomers are tightly assembled from different trimers, which contain mostly 19 kDa subunits. In both oligomeric states, the excitation energy coupling between fucoxanthin and chlorophyll a was preserved, and chlorophyll c was shown to transfer energy efficiently to chlorophyll a. Circular dichroism spectra showed close interaction between fucoxanthin and chlorophyll a, and different chlorophyll a molecules were demonstrated to interact excitonically. The assembly of trimers of antenna proteins with a distinct subunit composition into higher oligomeric states was not reported so far and differs from the situation found in higher plants. The differences in the supramolecular structure of the fucoxanthin-chlorophyll proteins reflect the dissimilar arrangement of the thylakoid membranes in diatoms, which lack the grana-stroma distinction.

Chromatography, Gel↗

PubMed2000

Chlorophyll breakdown in oilseed rape.

Chlorophyll catabolism accompanying leaf senescence is one of the most spectacular natural phenomena. Despite this fact, the metabolism of chlorophyll has been largely neglegted until recently. Oilseed rape has been used extensively as a model plant for the recent elucidating of structures of chlorophyll catabolites and for investigation of the enzymic reactions of the chlorophyll breakdown pathway. The key reaction which causes loss of green color is catalyzed in a two-step reaction by pheophorbide a oxygenase and red chlorophyll catabolite reductase. In this Minireview, we summarize the actual knowledge about catabolites and enzymes of chlorophyll catabolism in oilseed rape and discuss the significance of this pathway in respect to chlorophyll degradation during Brassica napus seed development.

Journal Article↗

PubMed2003

Phytol as one of the determinants of chlorophyll interactions in solution.

Optical absorption and fluorescence parameters of chlorophyll a and the phytol-free chlorophyllide a, as well as of their Mg-depleted derivatives, were compared in a series of organic solvents. In contrast to prevailing opinion, the spectral properties of chlorophyll are not indifferent to the removal of phytol. The electronic absorption spectra of chlorophyll a and chlorophyllide a differ and display a different dependence on the nature of the solvent, which cannot be explained solely by the location of a charged carboxylic group in the proximity of the pi- electron system. In fact, measurements in media of varying basicity show that deprotonation of the free carboxylic group in chlorophyllide, i.e., the presence of a negative point charge near the macrocycle, has no effect on pigment absorption spectra. Analysis of the solvent effect on the Q(Y) energies in terms of solvent polarity reveals that the phytyl moiety perturbs the spectral features of chlorophyll, mainly due to its interactions with the pigment solvation shell. The phytyl residue might also be thus partly involved in controlling the central metal ligation in chlorophylls. This influence of phytol on the spectral features of chlorophyll should be taken into account when comparing the spectra in solution with various spectral forms of chlorophyll in vivo.

Journal Article↗

PubMed1978

Photosynthetic characteristics and organization of chlorophyll in marine dinoflagellates.

The photosystem I reaction center complex, the P-700-chlorophyll a-protein, has been isolated from the photosynthetic membranes of two marine dinoflagellates, Gonyaulax polyedra and Glenodinium sp., by detergent solubilization with Triton X-100. The complexes isolated from the two species were indistinguishable, exhibiting identical absorption properties (400-700 nm) at both room (300 K) and low (77 K) temperature. The room temperature, red wavelength maximum was at 675 nm. The absorption properties, kinetics of photobleaching, sodium dodecyl sulfate electrophoretic mobilities, and chlorophyll a/P-700 ratio (50 +/- 10) of the P-700-chlorophyll a-protein complexes from the two species also were essentially the same and similar to those properties characterizing P-700-chlorophyll a-protein complexes of higher plants and green algae.Photosynthetic unit sizes were determined for cells grown at 1000 muW/cm(2). Both dinoflagellates had unit sizes (total chlorophyll/P-700 ratios) of about 600, even though the distribution of chlorophyll a, chlorophyll c, and peridinin in the light-harvesting components differed in Gonyaulax and Glenodinium. The number of photosynthetic units per cell in the two species correlates directly with their photosynthetic activities. A model is presented for the distribution of chlorophyll in the photosynthetic apparatus of these dinoflagellates which accounts for the known role of the isolated pigment-protein complexes and for the known photoadaptive physiology in pigmentation and photosynthesis for these species.

Journal Article↗

PubMed2000

Diatom fucoxanthin chlorophyll a/c-binding protein (FCP) and land plant light-harvesting proteins use a similar pathway for thylakoid membrane Insertion.

The light-harvesting proteins in plastids of different lineages including algae and land plants represent a superfamily of chlorophyll-binding proteins that seem to be phylogenetically related, although some of the light-harvesting complex (LHC) proteins bind different carotenoids. LHCs can be divided into chlorophyll a/b-binding proteins found in green algae, euglenoids, and higher plants and into chlorophyll a/c-binding proteins of various algal taxa. LHC proteins from diatoms are named fucoxanthin-chlorophyll a/c-binding proteins (FCP). In contrast to chlorophyll a/b-binding proteins, there is no information so far about the way FCPs integrate into thylakoid membranes. The diatom FCP preproteins have a bipartite presequence that is necessary to enable transport into the four membrane-bound diatom plastids, but similar to chlorophyll a/b-binding proteins there is apparently no presequence present for targeting to the thylakoid membrane. By establishing an in vitro import assay for diatom thylakoids, we demonstrated that thylakoid integration of diatom FCP depends on the presence of stromal factors and GTP. This indicates that a pathway involving signal recognition particles (SRP) is involved in membrane integration just as shown for LHCs in higher plants. We also demonstrate integration of diatom FCP into thylakoids of higher plants and vice versa SRP-dependent targeting of LHCs from pea and Arabidopsis into diatom thylakoids. The similar SRP-dependent modes of thylakoid integration of land plant LHCs and FCPs support recent analyses indicating a common origin of chlorophyll a/b- and a/c-binding proteins.

Amino Acid Sequence↗

PubMed1966

Chlorophyll Synthesis in Chlorella II. Effect of Glucose and Light Intensity on the Lag Phase.

Dense cultures of Chlorella grown under our conditions contain large amounts of chlorophyll on a packed cell basis. Upon dilution the cells are, in effect, put into an environment in which light is not limiting and chlorophyll seemingly in excess (at least temporarily). Thus it is not economical for the cell to produce more chlorophyll until it is the limiting factor. It is our contention that the cell may sense this situation by the piling up of products such as glucose or starch. The observed light intensity effect which causes a stimulation of chlorophyll production at lowered intensities is analogous to that previously reported by others and is felt to be related to the rate of photosynthate production.Chlorophyll synthesis commences after a period of about 12 hours. Once it has become established, added substrate or light have a smaller effect. At 36 hours addition of glucose stimulates growth markedly but chlorophyll production continues at the control rate. This suggests that the effect of substrate is not upon the action of an enzyme involved in the actual synthesis of the chlorophyll molecule. Glucose has been known to influence production of certain enzymes involved usually in substrate catabolism. It is quite possible that the role of glucose here is quite similar. The data are consistent with such an explanation. The substrate would have to influence the production of an enzyme in the magnesium branch of the biosynthetic pathway of porphyrin compounds and not in the portion common to both iron and magnesium porphyrins. Accordingly the lag period is viewed as both an inhibitory period as well as a preparatory period for subsequent chlorophyll synthesis.

Journal Article↗

PubMed1967

Temperature and plant adaptation. I. Interaction of temperature and light in the synthesis of chlorophyll in corn.

The effect of temperature and light intensity have been studied in relation to the greening of etiolated corn (Zea mays cv. Pioneer 309-B) seedlings. Chlorophyll accumulation is rapid at high temperature (28 degrees ) under all conditions of light intensity. At low temperature (16 degrees ), and particularly in combination with high light intensity (3000-4500 ft-c), the accumulation of both chlorophyll and carotene is inhibited.Low pigment content at 16 degrees is not directly due to a block in the pigment synthesizing mechanism, but rather to the photodestruction of chlorophyll prior to its stabilization in the membrane structure of the chloroplast lamellae. The parallel reduction in carotene content at high light intensity is probably a contributing factor, because of its role in protecting chlorophyll from photodestruction. The greater severity of photo-oxidation of chlorophyll at low temperature in corn when compared with wheat, appears to be due to a slower rate of protochlorophyllide synthesis and subsequent esterification. Thus in corn at 16 degrees there is a prolongation of the photosensitive stage during chlorophyll synthesis. Photo-oxidation at 16 degrees has also been shown to be a function of the incident light energy, with the photosynthetic pigments acting as receptors for their own destruction.In comparison with the behavior of corn, wheat seedlings green rapidly at high light intensity at both 16 degrees and 28 degrees . This contrasting temperature response with respect to chlorophyll synthesis may underlie a fundamental difference in adaptation of these 2 species to growth in the temperate zones of the world.

Journal Article↗

PubMed1977

Water stress effects on the content and organization of chlorophyll in mesophyll and bundle sheath chloroplasts of maize.

The consequences of drought stress on the organization of chlorophyll into photosynthetic units and on the chlorophyll-protein composition of mesophyll and bundle sheath chloroplasts of Zea mays L. were studied. It was found that the majority of chlorophyll lost in response to water stress occurs in the mesophyll cells with a lesser amount being lost from the bundle sheath cells. All of the chlorophyll loss could be accounted for by reduction in the lamellar content of the light-harvesting chlorophyll a/b-protein, a rather specific target for water stress. The decreased content of this chlorophyll-protein accounts for the elevated chlorophyll a/b ratios and the reduced photosynthetic unit sizes of the two cell types in stressed plants. The implications of the selective catabolism of this major membrane component are discussed.

Journal Article↗

PubMed1977

Measurement of ozone injury by determination of leaf chlorophyll concentration.

A simple, rapid procedure is described for evaluating ozone injury to leaves of Phaseolus vulgaris L. cv. Pinto. Leaf chlorophyll is extracted with ethanol and analyzed spectrophotometrically; the concentration is expressed on the basis of leaf dry weight.The per cent chlorophyll reduction of ozone-injured leaves was highly correlated with the per cent visible necrosis and chlorosis (r = 0.96). The variability in injury estimates with chlorophyll analysis was slightly less than with visual evaluation. An evaluation of chlorophyll a and b concentrations separately showed that the chlorophyll a/b ratio decreased with increasing amounts of injury. Chlorophyll determinations made for leaves harvested at intervals after an ozone treatment indicated that maximum chlorophyll reduction had occurred by 4 days.This procedure for measuring ozone injury should be useful in eliminating the human bias associated with visible estimates of injury.

Journal Article↗

PubMed1981

Involvement of ethylene in chlorophyll degradation in peel of citrus fruits.

The effect of ethylene on chlorophyll degradation in the peel of Robinson tangerine (X Citrus reticulata Blanco) and calamondin (X Citrofortunellamitis [Blanco] Ingram and Moore) fruits was studied. The chlorophyll degrading system in the peel of these two citrus species was not self-sustaining but required ethylene to function. Chlorophyll degradation ceased immediately when fruit were removed from ethylene and held in ethylene-free air at 0.2 atmospheric pressure. However, at atmospheric pressure, chlorophyll degradation continued for 24 hours in the absence of exogenous ethylene. Although chlorophyllase levels were negatively correlated with chlorophyll content in the peel (r = -0.981; P < 0.01), the level of chlorophyllase activity did not change when fruit were removed from ethylene, even though chlorophyll degradation had stopped. From these observations, it was concluded that ethylene is necessary for chlorophyll degradation in the two species of citrus studied, but its primary role is not solely for the induction of chlorophyllase activity.

Journal Article↗

PubMed1982

Salt tolerance in crop plants monitored by chlorophyll fluorescence in vivo.

The potential of measurements of chlorophyll fluorescence in vivo to detect cellular responses to salinity and degrees of salt stress in leaves was investigated for three crop plants. Sugar beet (Beta vulgaris L.) (salt tolerant), sunflower (Helianthus annuus L.) (moderately salt tolerant), and bean (Phaseolus Vulgaris L. cv Canadian Wonder) (salt intolerant) were grown in pots and watered with mineral nutrient solution containing 100 millimolar NaCl. The fast rise in variable chlorophyll fluorescence yield that is correlated with photoreduction of photosystem II acceptors increased in leaves of sugar beet plants treated with salt suggesting stimulation of photosystem II activity relative to photosystem I. In sunflower, this fast rise was depressed by approximately 25% and the subsequent slow rate of quenching of the chlorophyll fluorescence was stimulated. These differences were more marked in the older mature leaves indicating an increasing gradient of salt response down the plant. The salt effect in vivo was reversible since chloroplasts isolated from mature leaves of salt-treated and control sunflower plants gave similar photosystem II activities. Unlike in sugar beet and sunflower, leaves of salt-treated bean progressively lost chlorophyll. The rate of slow quenching of chlorophyll fluorescence decreased indicating development of a partial block after photosystem II and possible initial stimulation of photosystem II activity. With further loss of chlorophyll photosystem II activity declined. It was concluded that measurements of chlorophyll fluorescence in vivo can provide a rapid means of detecting salt stress in leaves, including instances where photosynthesis is reduced in the absence of visible symptoms. The possible application to screening for salt tolerance is discussed.

Journal Article↗

PubMed1989

Functional Analysis of the Photosynthetic Apparatus of Prochlorothrix hollandica (Prochlorales), a Chlorophyll b Containing Procaryote.

Light-shade adaptation of the chlorophyll a/b containing procaryote Prochlorothrix hollandica was studied in semicontinuous cultures adapted to 8, 80 and 200 mumole quanta per square meter per second. Chlorophyll a contents based on dry weight differed by a factor of 6 and chlorophyll b by a factor of 2.5 between the two extreme light conditions. Light utilization efficiencies determined from photosynthesis response curves were found to decrease in low light grown cultures due to lower light harvesting efficiencies; quantum requirements were constant at limiting and saturating irradiances for growth. At saturating growth irradiances, changes in light saturated oxygen evolution rate originated from changes in chlorophyll a antenna relative to the number of reaction centers II. At light-limiting conditions both the number of reaction centers II and the antenna size changed. The amount of chlorophyll b relative to reaction center II remained constant. As in cyanobacteria, the ratio of reaction center I to reaction center II was modulated during light-shade adaptation. On the other hand, time constants for photosynthetic electron transport (4 milliseconds) were low as observed in green algae and diatoms. The occurrence of state one to two and state two to one transitions is reported here. Another feature linking photosynthetic electron transport in P. hollandica to that in the eucaryotic photosynthetic apparatus was blockage of the state one to two transition by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Although chlorophyll b was reported in association with photosystem I, the 630 nanometer light effect does not exclude that chlorophyll b is the photoreceptor for the state one to two transition.

Journal Article↗