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See detailSpectroscopic properties of protochlorophyllide analyzed in situ in the course of etiolation and in illuminated leaves
Schoefs, B.; Bertrand, M.; Franck, Fabrice ULg

in Photochemistry & Photobiology (2000), 72(1), 85-93

The spectroscopic properties of photoactive (ie. flash-transformable) and nonphotoactive protochlorophyll(ide)s (Pchl(ide)) were reinvestigated during the development of bean leaves in darkness. Two ... [more ▼]

The spectroscopic properties of photoactive (ie. flash-transformable) and nonphotoactive protochlorophyll(ide)s (Pchl(ide)) were reinvestigated during the development of bean leaves in darkness. Two phases in the process of Pchl(ide) accumulation were apparent from quantitative measurements of pigment content: a lag phase (first week) during which photoactive Pchl(ide) accumulated faster than nonphotoactive Pchl(ide); and a fast phase (second week), showing parallel accumulation of both types of Pchl(ide). 'Flashed-minus-dark' absorbance difference spectra recorded in situ at 77 K showed that P650-655 was the predominant form of photoactive protochlorophyllide regardless of developmental stage. Quantitative analysis of energy migration processes between the Pchl(ide) forms showed the existence of energy transfer units containing a 1:8 ratio of nonphotoactive and photoactive Pchl(ide)s during development. Gaussian deconvolution of in situ 77 K fluorescence spectra indicated that the 633 nm band of nonphotoactive Pchl(ide) was made of four bands, at 625, 631, 637 and 643 nm, whose relative amplitudes only slightly changed during development. The emission band of photoactive Pchlide was also analyzed using the same method. Three components were found at 644, 652 and 657 nm, The emission band of P650-655 included the last two components, which become predominant only in fully etiolated plants. Photoactive Pchlide with an emission maximum at 653 nm was detected in the light during development of leaves of photoperiodically grown plants. [less ▲]

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See detailAnalysis of fluorescence lifetime of protochlorophyllide and chlorophyllide in isolated etioplast membranes measured from multifrequency cross-correlation phase fluorometry
Mysliwa-Kurdziel, B.; Franck, Fabrice ULg; Strzalka, K.

in Photochemistry & Photobiology (1999), 70(4), 616-623

The fluorescence decays of protochlorophyllide (Pchlide) and of chlorophyllide (Chlide) in wheat etioplast membranes were analyzed using a multiexponential fluorescence decay model. Using different ... [more ▼]

The fluorescence decays of protochlorophyllide (Pchlide) and of chlorophyllide (Chlide) in wheat etioplast membranes were analyzed using a multiexponential fluorescence decay model. Using different excitation wavelengths from 430 to 470 nm, we found that a triple-exponential model at 14 degrees C and a double-exponential model at -170 degrees C were adequate to describe the Pchlide fluorescence decay. We discuss the origin of the three fluorescence lifetime components at 14 degrees C on the basis of the dependence of their fractional intensities on the excitation wavelength and by correlating the fractional intensities with integrated fluorescence intensities of different Pchlide forms in steady-state fluorescence spectra, The fluorescence decay of the main Pchlide form, photoactive Pchlide-F657, is shown to have a complex character with a fast component of 0.25 ns and a slower component of about 2 ns. Two lifetime components of 2 ns and 5.5-6.0 ns are ascribed to the second photoactive form, Pchlide-F645, and to nonphotoactive Pchlide forms, respectively. In etioplast membranes preilluminated by a short saturating fight pulse, we found a single 5.0 ns component for Chlide-F688 (the Chlide-NADPH :protochlorophyllide oxidoreductase [POR]-NADP(+) complex) and an additional 1.6 ns component when the formation of Chlide-F696 (the Chlide-POR-NADPH complex) was promoted by exogenous NADPH, From the fluorescence lifetime results we evaluated the quantum yield of the primary photoreaction by Chlide-F696 as being 70%. [less ▲]

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See detailProtochlorophyllide-NADP(+) and protochlorophyllide-NADPH complexes and their regeneration after flash illumination in leaves and etioplast membranes of dark-grown wheat
Franck, Fabrice ULg; Bereza, B.; Boddi, B.

in Photosynthesis Research (1999), 59(1), 53-61

The fast (1 min) regeneration process of the photoactive Pchlide forms after a light flash was studied in etiolated wheat leaves, and this process was simulated in vitro by incubating etioplast inner ... [more ▼]

The fast (1 min) regeneration process of the photoactive Pchlide forms after a light flash was studied in etiolated wheat leaves, and this process was simulated in vitro by incubating etioplast inner membranes of wheat with excess NADPH or NADP(+). The 77 K fluorescence spectra were recorded after flash illumination, dark incubation and a subsequent flash illumination of the samples. A non-photoactive Pchlide form with an emission maximum at 650 nm was transiently detected in leaves during regeneration of a photoactive Pchlide form with an emission maximum at 654 nm. Gaussian deconvolution of fluorescence spectra of isolated membranes showed that this 650 nm form appeared in conditions of excess NADP(+), as suggested in previous studies. Additionally a Pchlide form emitting at 638.5 nm was detected in the same conditions. The analysis of the spectra of leaves at different times after a flash indicated that these two non-photoactive forms are involved as intermediates in the regeneration of photoactive Pchlide. This regeneration is in correlation with the production of the Chlide form emitting at 676 nm. The results demonstrate that, in vivo, part of the NADPH:protochlorophyllide oxidoreductase is reloading with nonphotoactive Pchlide on a fast time-scale and that the 676 nm Chlide form is the released product of the phototransformation in this process. [less ▲]

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See detailChanges in endothermic transitions associated with light-induced chlorophyllide formation, as investigated by differential scanning calorimetry
Mysliwa-Kurdziel, B.; Franck, Fabrice ULg; Chahdi, M. A. O. et al

in Physiologia Plantarum (1999), 107(2), 230-239

The changes in thermal transitions associated with protochlorophyllide (Pchlide) into chlorophyllide (Chlide) phototransformation were investigated using sensitive differential scanning calorimetry (DSC ... [more ▼]

The changes in thermal transitions associated with protochlorophyllide (Pchlide) into chlorophyllide (Chlide) phototransformation were investigated using sensitive differential scanning calorimetry (DSC), Two groups of endothermic transitions, each composed of several components, were observed between 25 and 90 degrees C for prolamellar body (PLB) membranes isolated from etiolated wheat (Triticum aestivum) leaves. The first group, located in the 20-45 degrees C region, was strongly affected by a short light pulse given prior to measurement, A decrease of this group of transitions was observed shortly after illumination and it was hardly detected in PLBs measured after the Chlide Shibata shift. Calorimetric results were supported by 77-K fluorescence emission spectra measured for continuously heated samples at different temperatures. We interpreted the DSC band observed between 20 and 45 degrees C as due to the disaggregation of Pchlide- (or Chlide-)-reductase-NADPH complexes, More detailed analysis using Gaussian deconvolution showed that this band was composed of three transitions at 32, 39 and 41 degrees C. The second group of transitions was detected in the 45-80 degrees C region, the same as for mature thylakoids. Its main component at 60 degrees C was not affected significantly by a short light pulse. By comparison of thermograms obtained for PLBs with those for mature thylakoid membranes, this transition was identified as the ATPase denaturation band. [less ▲]

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See detailChlorophyll Synthesis in Dark-Grown Pine Primary Needles
Schoefs, B.; Franck, Fabrice ULg

in Plant Physiology (1998), 118(4), 1159-68

The pigment content of dark-grown primary needles of Pinus jeffreyi L. and Pinus sylvestris L. was determined by high-performance liquid chromatography. The state of protochlorophyllide a and of ... [more ▼]

The pigment content of dark-grown primary needles of Pinus jeffreyi L. and Pinus sylvestris L. was determined by high-performance liquid chromatography. The state of protochlorophyllide a and of chlorophylls during dark growth were analyzed by in situ 77 K fluorescence spectroscopy. Both measurements unambiguously demonstrated that pine primary needles are able to synthesize chlorophyll in the dark. Norflurazon strongly inhibited both carotenoid and chlorophyll synthesis. Needles of plants treated with this inhibitor had low chlorophyll content, contained only traces of xanthophylls, and accumulated carotenoid precursors. The first form of chlorophyll detected in young pine needles grown in darkness had an emission maximum at 678 nm. Chlorophyll-protein complexes with in situ spectroscopic properties similar to those of fully green needles (685, 695, and 735 nm) later accumulated in untreated plants, whereas in norflurazon-treated plants the photosystem I emission at 735 nm was completely lacking. To better characterize the light-dependent chlorophyll biosynthetic pathway in pine needles, the 77 K fluorescence properties of in situ protochlorophyllide a spectral forms were studied. Photoactive and nonphotoactive protochlorophyllide a forms with emission properties similar to those reported for dark-grown angiosperms were found, but excitation spectra were substantially red shifted. Because of their lower chlorophyll content, norflurazon-treated plants were used to study the protochlorophyllide a photoreduction process triggered by one light flash. The first stable chlorophyllide photoproduct was a chlorophyllide a form emitting at 688 nm as in angiosperms. Further chlorophyllide a shifts usually observed in angiosperms were not detected. The rapid regeneration of photoactive protochlorophyllide a from nonphotoactive protochlorophyllide after one flash was demonstrated. [less ▲]

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See detailChanges of chlorophyll(ide) fluorescence yield induced by a short light pulse as a probe to monitor the early steps of etioplast phototransformation in dark-grown leaves
Eullaffroy, P.; Popovic, R.; Franck, Fabrice ULg

in Photochemistry & Photobiology (1998), 67(6), 676-682

The fluorescence yield of chlorophyll(ide) (ChI[ide]) excited by weak modulated light was recorded at room temperature during a 2 h period after a short actinic light pulse that transformed all ... [more ▼]

The fluorescence yield of chlorophyll(ide) (ChI[ide]) excited by weak modulated light was recorded at room temperature during a 2 h period after a short actinic light pulse that transformed all photoactive protochlorophyllide in dark-grown barley leaves. A typical pattern of fluorescence yield variations was found whatever the age of the leaf but with age-dependent changes in rates. Its successive phases were related to the Chl(ide) spectral shifts observed in low-temperature emission spectra. The fluorescence yield started at a high level and strongly declined during the formation of Chlide(695) from Chlide(688) within a few seconds. It increased to a transient maximum during the Shibata shift (15-25 min) that resulted in ChI(ide)(682). A final, slow decrease to a steady state occurred during the final red shift to ChI(685). Pretreatments with delta-aminolevulinic acid, chloramphenicol or 1,10-phenanthroline resulted in correlated modifications of Chl(ide) fluorescence yield transients and shifts of the low-temperature Chl(ide) emission band. The complex response of the final decrease phase of the fluorescence yield to these compounds suggests that it results both from the assembly of photosynthetic Chi proteins and from the reorganization of the etioplast membrane system. From these results it is concluded that continuous recordings of CN(ide) fluorescence yield after a short light pulse represent a useful tool to monitor the kinetics of pigment-protein organization and primary thylakoid assembly triggered by Pchlide photoreduction. [less ▲]

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See detailEtioplast differentiation in Arabidopsis: Both PORA and PORB restore the prolamellar body and photoactive protochlorophyllide-F655 to the cop1 photomorphogenic mutant
Sperling, U.; Franck, Fabrice ULg; van Cleve, B. et al

in Plant Cell (1998), 10(2), 283-296

The etioplast plastid type of dark-grown angiosperms is defined by the accumulation of the chlorophyll (Chi) precursor protochlorophyllide (Pchlide) and the presence of the paracrystalline prolamellar ... [more ▼]

The etioplast plastid type of dark-grown angiosperms is defined by the accumulation of the chlorophyll (Chi) precursor protochlorophyllide (Pchlide) and the presence of the paracrystalline prolamellar body (PLB) membrane. Both features correlate with the presence of NADFH:Pchlide oxidoreductase (FOR), a light-dependent enzyme that reduces photoactive Pchlide-F655 to chlorophyllide and plays a key role in chloroplast differentiation during greening. Two differentially expressed and regulated FOR enzymes, FORA and FORB, have recently been discovered in angiosperms. To investigate the hypothesis that etioplast differentiation requires FORA, we have constitutively overexpressed PORA and FORB in the Arabidopsis wild type and in the constitutive photomorphogenic cop1-18 (previously det340) mutant, which is deficient in the PLB and Pchlide-F655. In both genetic backgrounds, FOR overexpression increased PLB size, the ratio of Pchlide-F655 to nonphotoactive Pchl[ide]-F632, and the amount of Pchlide-F655. Dramatically, restoration of either FORA or FORB to the cop1 mutant led to the formation of etioplasts containing an extensive PLB and large amounts of photoactive Pchlide-F655. [less ▲]

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See detailIsolation and characterization of photoactive complexes of NADPH : protochlorophyllide oxidoreductase from wheat
Chahdi, M. A. O.; Schoefs, B.; Franck, Fabrice ULg

in Planta (1998), 206(4), 673-680

A photoactive substrate-enzyme complex of the NADPH:protochlorophyllide oxidoreductase (POR; EC 1.3.1.33) was purified from etiolated Triticum aestivum L. by gel chromatography after solubilization of ... [more ▼]

A photoactive substrate-enzyme complex of the NADPH:protochlorophyllide oxidoreductase (POR; EC 1.3.1.33) was purified from etiolated Triticum aestivum L. by gel chromatography after solubilization of prolamellar bodies by dodecyl-maltoside. Irradiation by a 1-ms flash induced the phototransformation of protocholorophyllide a (Pchlide) with -196 degrees C absorbance and emission maxima at 640 and 643 nm, respectively. The apparent molecular weight of this complex was 112 +/- 24 kDa, which indicates aggregation of enzyme subunits. By lowering the detergent concentration in the elution buffer, a 1080 +/- 250-kDa particle was obtained which displayed the spectral properties of the predominant form of photoactive Pchlide in vivo (-196 degrees C absorbance and fluorescence maxima at 650 and 653 nm). In this complex, FOR was the dominant polypeptide. Gel chromatography in the same conditions of an irradiated sample of solubilized prolamellar bodies indicated rapid disaggregation of the complex after Pchlide phototransformation. High performance liquid chromatographic analysis of the FOR complexes obtained using two detergent concentrations indicates a possible association of zeaxanthin and violaxanthin with the photoactive complex. [less ▲]

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See detailStudies on the O-J-I-P transient of chlorophyll fluorescence in relation to photosystem II assembly and heterogeneity in plastids of greening barley
Barthelemy, X.; Popovic, R.; Franck, Fabrice ULg

in Journal of Photochemistry and Photobiology B : Biology (1997), 39(3), 213-218

The polyphasic variable fluorescence in saturating light (O-J-I-P transient, Strasser et al. (1995) Photochem. Photobiol. 61: 21-42) has been investigated in etiochloroplasts during the greening of ... [more ▼]

The polyphasic variable fluorescence in saturating light (O-J-I-P transient, Strasser et al. (1995) Photochem. Photobiol. 61: 21-42) has been investigated in etiochloroplasts during the greening of etiolated leaves of Hordeum vulgare. The initial photochemical phase (O-J) due to reduction of the primary quinone acceptor Q(A) was found to represent a constant proportion (65-70%) of total variable fluorescence independent of greening time. The partial fluorescence quenching in the Q(A)-reduced state seems, therefore, to represent a basic property of PSII electron transport. The biphasic character of the slower J-I-P transient due to reduction of the plastoquinone pool developed progressively during the first hours of greening. in the same period of lime the proportion and rate constant of rapid PSII alpha sub-population increased, as calculated from the induction curve in the presence of DCMU. Etiochloroplasts or chloroplasts resuspended in low salt medium showed a low I level, which was restored upon readdition of 5 mM MgCl2 and NaCl. Salts also increased the apparent proportion of PSII alpha. These results suggest that the J-I and I-P phases of the induction curve are related to different rates of plastoquinone photoreduction by two distinct PSII populations. The effects of DMQ and of DCBQ on the O-J-I-P transient were also studied in (etio-)chloroplasts, In addition to the already reported quenching of the initial (F-0) and variable fluorescence by DCBQ, a slow fluorescence increase phase was found to appear upon the addition of DCBQ but not of DMQ. The latter observations confirm that DCBQ differs from DMQ by its higher efficiency as PSII electron acceptor. (C) 1997 Elsevier Science S.A. [less ▲]

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See detailRoom temperature fluorescence spectra of protochlorophyllide and chlorophyllide forms in etiolated bean leaves
Boddi, B.; Franck, Fabrice ULg

in Journal of Photochemistry and Photobiology B : Biology (1997), 41(1-2), 73-82

Room-temperature fluorescence emission and excitation spectra of 3-day or 10-day old dark-grown bean (Phaseolus vulgaris L. cv Commodore) leaves were measured. The excitation light was defocused in such ... [more ▼]

Room-temperature fluorescence emission and excitation spectra of 3-day or 10-day old dark-grown bean (Phaseolus vulgaris L. cv Commodore) leaves were measured. The excitation light was defocused in such way that only a low rate of phototransformation took place and protochlorophyllide (Pchlide) forms could be detected. The spectra were resolved into gaussian components using a new method based on the comparison of the 4th derivative of the experimental spectrum and that of the calculated spectrum, i.e. the sum of the gaussians. In addition to Pchlide emission bands with maxima at 631, 644, 655 and 667 nm which correspond to those described earlier in 77 K spectra, two new and unusally narrow bands were found at 637 and 650 nm. Tn the Chlide region, emission bands were found at 676, 682, 686 and 695 nm. Changes in the relative amplitudes of the Pchlide and Chlide room temperature emission bands as a function of age, of excitation wavelength and in response to a short light flash were studied. A model is given in which dynamic interconversions of the pigment forms are suggested and the presence of the new forms is explained with the differences in the aggregational states of the pigments and with their interaction with NADPH or NADP(+). (C) 1997 Elsevier Science S.A. [less ▲]

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See detailFormation of long-wavelength chlorophyllide (Chlide695) is required for the assembly of Photosystem II in etiolated barley leaves
Franck, Fabrice ULg; Eullaffroy, P.; Popovic, R.

in Photosynthesis Research (1997), 51(2), 107-118

Chlorophyll(ide) spectroscopic properties and Photosystem II assembly, monitored by 77 K variable fluorescence, were studied in etiolated barley leaves as a function of the extent of protochlorophyllide ... [more ▼]

Chlorophyll(ide) spectroscopic properties and Photosystem II assembly, monitored by 77 K variable fluorescence, were studied in etiolated barley leaves as a function of the extent of protochlorophyllide photoreduction by a single millisecond light flash of different intensities. Variable fluorescence, measured 2 hours after the flash, was only detected when the extent of phototransformation was higher than a threshold value of 0.4. Its development paralleled the formation of a chlorophyll emission component at 685 nm, which itself derived from long-wavelength chlorophyllide with an emission maximum at 695 nm. At low flash intensities, short-wavelength chlorophyllide forms preferentially accumulated and no Photosystem II fluorescence was detected after 2 hours. Chlorophyllide esterification was independent of the extent of phototransformation. These results suggested that the formation of long-wavelength chlorophyllide was essential for further assembly of Photosystem II. This interpretation was strengthened by the observed inhibition of both long-wavelength chlorophyllide formation and of variable fluorescence development in leaves treated with 6-aminolevulinic acid or in untreated leaves subjected to repeated flashes of low intensity. [less ▲]

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See detailThe early stages of photosystem II assembly monitored by measurements of fluorescence lifetime, fluorescence induction and isoelectric focusing of chlorophyll-proteins in barley etiochloroplasts
MysliwaKurdziel, B.; Barthelemy, X.; Strzalka, K. et al

in Plant & Cell Physiology (1997), 38(11), 1187-1196

The relationship between functional and structural aspects of PSII formation during greening of etiolated barley leaves has been investigated using fluorescence life-time measurements, fluorescence ... [more ▼]

The relationship between functional and structural aspects of PSII formation during greening of etiolated barley leaves has been investigated using fluorescence life-time measurements, fluorescence kinetics analysis and analysis of chlorophyll-protein complexes by IEF-PAGE, Two phases of different character could be distinguished in the course of the greening process in dark-grown plants, An early phase covering the first 3-4 h after the onset of illumination and a late phase covering the subsequent greening, During the first phase the formation of PSII reaction centers and their minor antenna components was observed as manifested by the IEF-PAGE polypeptide pattern, This was accompanied by shortening of the slow and middle components of the fluorescence lifetime, as well as by the rapid drop in the amplitude of the slow component, A room temperature emission band at 676 nm was associated with uncoupled chlorophyll and with the slow fluorescence lifetime component during the first hours of greening. During the late greening phase peripheral light-harvesting complexes of PSII were formed concomitantly to an increase in lifetime and amplitude of the fast component and to a further decrease in the lifetime of the middle component, The gradual increase in PSII complexity during both phases of greening was also manifested by changes in proportion and kinetic properties of PSIIalpha and PSIIbeta units. Similar changes in fluorescence lifetime components as in the late greening of dark-grown plants were also observed in intermittent-light plants during continuous greening associated with the development of PSII antenna. The relationships between fluorescence lifetime characteristics and development of PSII are discussed in terms of a stepwise mechanism invoving a first step of Chl integration into small size PSII units followed by progressive increase of antenna size. [less ▲]

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See detailChlorophyll synthesis in relation to the assembly of photosystems
Franck, Fabrice ULg; Schoefs, Benoît

in Bulletin de la Société Royale des Sciences de Liège (1996), 65(4-5), 269-278

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See detailChanges in nitrogen source modify distribution of excitation energy in the cyanobacterium Phormidium laminosum
deAlda, JAGO; Tapia, M. I.; Franck, Fabrice ULg et al

in Physiologia Plantarum (1996), 97(1), 69-78

In an attempt to clarify the interactions between the available nitrogen source and the photosystems in cyanobacteria, O-2 exchange and fluorescence emission were monitored in spheroplasts and intact ... [more ▼]

In an attempt to clarify the interactions between the available nitrogen source and the photosystems in cyanobacteria, O-2 exchange and fluorescence emission were monitored in spheroplasts and intact cells of the non N-2-fixing cyanobacterium Phormidium laminosum (strain OH-1-p.Cl-1) growing on different nitrogen sources or in the absence of nitrogen. Short-term (time scale of seconds to minutes), NH4+ addition to NO3--growing or N-starved cells and, to a minor extent, NO3- addition to N-starved cells, induced state 2 transitions both in light and dark. Long term (time scale of days), the fluorescence yield of PSI relative to that of PSII at 77 K was higher in NO3-- than in NH4-+ growing cells, and even higher in N-starved cells. In the dark, the plastoquinone pool was more reduced in NH4-+ than in NO3--growing cells. Both PSII and PSI activities and the degree of linking between both photosystems were affected in the long term, so that non-cyclic electron transport decreased in parallel to the ferredoxin requirement to assimilate each nitrogen source. Results indicate that nitrogen metabolism exerts short- and long-term control over the photosynthetic apparatus, which acclimates to the energy requirement of the available nitrogen source. [less ▲]

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See detailProtection of native chlorophyll(ide) forms ans of photosystem II against photodamage during early stages of chloroplast differentiation
Franck, Fabrice ULg; Schoefs, B.; Barthélemy, X. et al

in Acta Physiologiae Plantarum (1995), 17

The resistance of chlorophyllide to intense light and the integration of chlorophyll to photosystems have been studied during the early stages of the greening process in etiolated bean or barley leaves ... [more ▼]

The resistance of chlorophyllide to intense light and the integration of chlorophyll to photosystems have been studied during the early stages of the greening process in etiolated bean or barley leaves. The possible role of NADPH-protochlorophyllide-oxidoreductase in chlorophyllide protection is discussed on the basis of chlorophyllide absorbance data during photodegradation and of chlorophyllide fluorescence lifetime measurements. Free chlorophyll during continuous greening was evaluated through fluorescence spectroscopy and fluorescence lifetime measurements in isolated etiochloroplasts. Its relative amount was maximum after 2 hours and decreased rapidly to a low level in parallel to photosystem II variable fluorescence development. Photosystem II mediated electron transport was compared in etiochloroplasts from flashed leaves before or after photoactivation of the water-splitting system. The effects of exogenous quinones on rapid fluorescence transients suggest the occurrence of a cyclic electron flow in water-splitting deficient photosystem II. [less ▲]

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See detailTemperature dependence of chlorophyll(ide) spectral shifts and photoactive protochlorophyllide regeneration after flash in etiolated barley leaves
Eullaffroy; Salvetat; Franck, Fabrice ULg et al

in Photochemistry & Photobiology (1995), 62(4), 751-756

Absorbance spectroscopy at 77 K was used to investigate the effect of temperature on in vivo chlorophyllide shifts and photoactive protochlorophyllide regeneration after a saturating flash, which ... [more ▼]

Absorbance spectroscopy at 77 K was used to investigate the effect of temperature on in vivo chlorophyllide shifts and photoactive protochlorophyllide regeneration after a saturating flash, which transformed all protochlorophyllide to chorophyllide. Photoactive protochlorophyllide present in darkness was stable up to 40 degrees C. The rate of Shibata shift and protochlorophyllide regeneration after flash were strongly temperature dependent in the range 0-25 degrees C. At 0 degrees C, the shift was still observed but no regeneration occurred. Only slight effects were observed in the range 25-40 degrees C. At all temperatures, the process of protochlorophyllide regeneration was significantly slower than the Shibata shift. The final chlorophyll shift from 672 to 674 nm was observed up to 40 degrees C. The implication of these results concerning the pigment-protein interactions during the Shibata shift are discussed. [less ▲]

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See detailOPTICAL MULTICHANNEL ANALYSIS OF PROTOCHLOROPHYLLIDE PHOTOTRANSFORMATION IN DETERGENT-SOLUBILIZED ETIOPLAST MEMBRANES OF WHEAT
Franck, Fabrice ULg; OUAZZANI, M. A.; DUJARDIN, E. et al

in Zeitschrift Fur Naturforschung C-A Journal Of Biosciences (1994), 49(1-2), 125-131

Extracts of wheat etioplast membranes obtained after treatment with 7 mM n-octyl-beta-D-glucopyranoside (OG), n-dodecyl-beta-D-maltoside (DM) or Triton X-100 contained the three spectral forms of Pchlide ... [more ▼]

Extracts of wheat etioplast membranes obtained after treatment with 7 mM n-octyl-beta-D-glucopyranoside (OG), n-dodecyl-beta-D-maltoside (DM) or Triton X-100 contained the three spectral forms of Pchlide (the photoactive Pchlide(638) and Pchlide(638) and the inactive Pchlide(650)) in various relative amounds. The OG extract had a Pchlide composition close to that of the intact membranes whereas the DM extract was enriched in Pchlide(638) and the Triton extract was enriched in Pchlide(630). Measurements of the kinetics of phototransformation and of time-resolved absorbance spectra during phototransformation in continuous Light shows that the inactive Pchlide(630) is in fact slowly transformed to Chlide, especially in the Triton extract where this form is more abundant. Addition of NADPH favours the phototransformation of Pchlide(630) and the slow regeneration of Pchlide(638) and Pchlide(650) from Pchlide(630) in darkness after illumination. No such regeneration was however observed in the Triton extract. NADPH had only slight effects on the Chlide shift towards shorter wavelengths after phototransformation in solubilized membranes. [less ▲]

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See detailON THE FORMATION OF PHOTOSYSTEM-II CHLOROPHYLL PROTEINS AFTER A SHORT LIGHT FLASH IN ETIOLATED BARLEY LEAVES, AS MONITORED BY INVIVO FLUORESCENCE SPECTROSCOPY
Franck, Fabrice ULg

in Journal of Photochemistry and Photobiology B : Biology (1993), 18(1), 35-40

The biogenesis of photosystem II (PSII) was investigated using 77 K fluorescence spectroscopy in etiolated barley leaves subjected to a millisecond flash which reduced all protochlorophyllide (Pchlide ... [more ▼]

The biogenesis of photosystem II (PSII) was investigated using 77 K fluorescence spectroscopy in etiolated barley leaves subjected to a millisecond flash which reduced all protochlorophyllide (Pchlide) into chlorophyllide (Chlide). In darkness after the flash, a slow chlorophyll (Chl) band shift from 682 to 684 nm was associated with the development of PSII variable fluorescence. Two Chl fluorescence bands at 678 and 687 nm were formed during the shift, the 687 nm band corresponding to the spectrum of the PSII variable fluorescence. The development of PSII fluorescence was inhibited by chloramphenicol and enhanced by cyclobeximide, suggesting a competition between plastid- and nucleus-encoded proteins for Chl binding. [less ▲]

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See detailPhotosynthetic activities during early assembly of thylakoid membranes
Franck, Fabrice ULg

in Sundqvist, C.; Ryberg, M. (Eds.) Pigment-protein complexes in plastids: synthesis and assembly (1993)

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See detailPHOTOREDUCTION OF PROTOCHLOROPHYLLIDE TO CHLOROPHYLLIDE IN 2-D-OLD DARK-GROWN BEAN (PHASEOLUS-VULGARIS CV COMMODORE) LEAVES - COMPARISON WITH 10-D-OLD DARK-GROWN (ETIOLATED) LEAVES
SCHOEFS, B.; Franck, Fabrice ULg

in Journal of Experimental Botany (1993), 44(263), 1053-1057

Two-d-old leaves which do not contain prolamellar bodies synthesize active protochlorophyllide in darkness. When protochlorophyllide is photoreduced by one intense white flash, a main chlorophyllide ... [more ▼]

Two-d-old leaves which do not contain prolamellar bodies synthesize active protochlorophyllide in darkness. When protochlorophyllide is photoreduced by one intense white flash, a main chlorophyllide species emitting at 690 nm is formed. After the photoreduction, the emission maximum is shifted to 675 nm within 5 s. This result suggests that in young leaves, chlorophyllide formed after one flash is quickly released from the active site of NADPH: protochlorophyllide oxidoreductase. This interpretation is strenghtened by time-resolved fluorescence measurements at room temperature, showing that 675 nm emitting chlorophyllide does not transfer excitation energy to the 696 nm emitting chlorophyllide which is formed in very low amount. In 10-d-old bean leaves, the 690 nm chlorophyllide emitting species formed after one short flash undergoes the well-known rapid and Shibata spectral shifts. The 675 nm emitting chlorophyllide appears only as a shoulder. At both ages, the fluorescence intensity of the active protochlorophyllide strongly decreases during and after photoreduction, suggesting rapid modifications in the close environment of the pigment. [less ▲]

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