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See detailLa photosynthèse: aujourd'hui, hier et demain
Franck, Fabrice ULg

Conference (2012, November 30)

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See detailPhotosynthesis and state transitions in mitochondrial mutants of Chlamydomonas reinhardtii affected in respiration
Cardol, Pierre ULg; Gloire, Geoffrey ULg; Havaux, M. et al

in Plant Physiology (2003), 133(4), 2010-2020

Photosynthetic activities were analyzed in Chlamydomonas reinhardtii mitochondrial mutants affected in different complexes (I, III, IV, I + III, and I + IV) of the respiratory chain. Oxygen evolution ... [more ▼]

Photosynthetic activities were analyzed in Chlamydomonas reinhardtii mitochondrial mutants affected in different complexes (I, III, IV, I + III, and I + IV) of the respiratory chain. Oxygen evolution curves showed a positive relationship between the apparent yield of photosynthetic linear electron transport and the number of active proton-pumping sites in mitochondria. Although no significant alterations of the quantitative relationships between major photosynthetic complexes were found in the mutants, 77 K fluorescence spectra showed a preferential excitation of photosystem I (PSI) compared with wild type, which was indicative of a shift toward state 2. This effect was correlated with high levels of phosphorylation of light-harvesting complex II polypeptides, indicating the preferential association of light-harvesting complex II with PSI. The transition to state 1 occurred in untreated wild-type cells exposed to PSI light or in 3-(3,4-dichlorophenyl)-1,1-dimethylurea-treated cells exposed to white light. In mutants of the cytochrome pathway and in double mutants, this transition was only observed in white light in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. This suggests higher rates of non-photochemical plastoquinone reduction through the chlororespiratory pathway, which was confirmed by measurements of the complementary area above the fluorescence induction curve in dark-adapted cells. Photo-acoustic measurements of energy storage by PSI showed a stimulation of PSI-driven cyclic electron flow in the most affected mutants. The present results demonstrate that in C. reinhardtii mutants, permanent defects in the mitochondrial electron transport chain stabilize state 2, which favors cyclic over linear electron transport in the chloroplast. [less ▲]

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See detailPhotosynthesis in picoeucaryote algae, the Ostreococcus case
Cardol, Pierre ULg

Conference (2007, June 19)

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See detailPhotosynthesis within porous silica gel: Viability and activity of encapsulated cyanobacteria
Rooke, J. C.; Léonard, Alexandre ULg; Sarmento, H. et al

in Journal of Materials Chemistry (2008), 18(24), 2833-2841

In the framework of designing novel bioreactors, the encapsulation of photosynthetic cyanobacterial strains of the genus Synechococcus, PCC 6301, PCC 7002 and Cyanothece PCC 7418, within mesoporous silica ... [more ▼]

In the framework of designing novel bioreactors, the encapsulation of photosynthetic cyanobacterial strains of the genus Synechococcus, PCC 6301, PCC 7002 and Cyanothece PCC 7418, within mesoporous silica networks has been achieved via the acidification of aqueous colloidal silica precursors at ambient temperature. The effect of the silica matrix on the external membrane of the cells has been studied. The viability of the cells over a three month duration has been assessed using transmission electron microscopy, epifluorescence microscopy, UV-visible spectroscopy and high-performance liquid chromatography. The bioactivity of the encapsulated cyanobacteria was detected via the assimilation of NaH14CO3. Although most cells entrapped within the silica gel remain undivided, some cells continued to divide even when there was limited space. TEM studies have revealed an interaction between the silica gel and the cell membrane. HPLC studies highlight that the photoactive pigments in PCC 6301 and PCC 7002 can be preserved for up to 12 weeks whilst PCC 7418 lost its photosynthetic pigments after two weeks post-immobilisation. These results suggest that certain strains of cyanobacteria are able to photosynthesise within a hybrid gel yielding the possibility of novel photobioreactors. © The Royal Society of Chemistry 2008. [less ▲]

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See detailPhotosynthesis-dependent isoprene emission from leaf to planet in a global carbon-chemistry-climate model
Unger, N.; Harper, K.; Zheng, Y. et al

in Atmospheric Chemistry and Physics (2013), 13

We describe the implementation of a biochemical model of isoprene emission that depends on the electron requirement for isoprene synthesis into the Farquhar–Ball–Berry leaf model of photosynthesis and ... [more ▼]

We describe the implementation of a biochemical model of isoprene emission that depends on the electron requirement for isoprene synthesis into the Farquhar–Ball–Berry leaf model of photosynthesis and stomatal conductance that is embedded within a global chemistry-climate simulation framework. The isoprene production is calculated as a function of electron transport-limited photosynthesis, intercellular and atmospheric carbon dioxide concentration, and canopy temperature. The vegetation biophysics module computes the photosynthetic uptake of carbon dioxide coupled with the transpiration of water vapor and the isoprene emission rate at the 30 min physical integration time step of the global chemistry-climate model. In the model, the rate of carbon assimilation provides the dominant control on isoprene emission variability over canopy temperature. A control simulation representative of the present-day climatic state that uses 8 plant functional types (PFTs), prescribed phenology and generic PFT-specific isoprene emission potentials (fraction of electrons available for isoprene synthesis) reproduces 50% of the variability across different ecosystems and seasons in a global database of 28 measured campaign-average fluxes. Compared to time-varying isoprene flux measurements at 9 select sites, the model authentically captures the observed variability in the 30 min average diurnal cycle (R2 = 64–96 %) and simulates the flux magnitude to within a factor of 2. The control run yields a global isoprene source strength of 451 TgC yr−1 that increases by 30% in the artificial absence of plant water stress and by 55% for potential natural vegetation. [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 detailThe photosynthetic electron transport network: occurrence and function of cyclic and side pathways
Franck, Fabrice ULg

Conference (2006, September 07)

The current knowledge on cyclic and side pathways of the thylakoidal electron transport system will be discussed. Cyclic or pseudo-cyclic pathways include the PSI-driven cyclic electron transport, the ... [more ▼]

The current knowledge on cyclic and side pathways of the thylakoidal electron transport system will be discussed. Cyclic or pseudo-cyclic pathways include the PSI-driven cyclic electron transport, the cytochrome b6/f plastoquinone cycle and the oxygen-dependent water/water cycle. Side pathways altogether make up the chlororespiratory pathway, including the non-photochemical, NAD(P)H-dependent plastoquinone reduction by chloroplastic dehydrogenases and plastoquinol oxidation by a putative chloroplastic oxidase. The state of knowledge concerning the components, the importance and function of these pathways will be discussed. Results obtained in Liège using the unicellular green alga Chlamydomonas reinhardtii or higher plant chloroplasts will be presented. The importance of specific pathways in the context of mitochondria-chloroplast metabolic interactions and global cellular bio-energetics will be highlighted. Some of the methodological aspects in this field will be shortly described, in particular the use of fluorescence and absorbance spectroscopy. In some micro-algae, the electron transport chain can also use protons as terminal electron acceptors under anaerobic conditions, thereby allowing hydrogen evolution in the light. The potential of this fascinating reaction in perspective of the photobiological production of ‘bio-hydrogen’ will be briefly discussed. [less ▲]

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See detailPhotosystem II assembly in 2-day-old bean leaves during the first 16 hrs. of greening
Schoefs, Benoît; Franck, Fabrice ULg

in Comptes Rendus de l'Académie des Sciences. Série III, Sciences de la Vie (1991), 313(10), 441-445

We have studied the assembly of the photosynthetic apparatus during the greening of 2-day-old bean leaves in continuous white light by using fluorimetric methods. We have recorded 77 and 298 K ... [more ▼]

We have studied the assembly of the photosynthetic apparatus during the greening of 2-day-old bean leaves in continuous white light by using fluorimetric methods. We have recorded 77 and 298 K fluorescence kinetics at 690 nm in order to detect electron flow through the photosystem II reaction centre (RC(II)) at increasing greening periods. In those experiments, the 77 K fluorescence spectra were also considered. Charge separation is detected 1 hr. after the onset of the illumination. Room temperature fluorescence variation showing the << O-I-P >> phases are detected after 4 hrs. of illumination. Typical fluorescence bands at 688, 697 and 735 nm appear after 14 hrs. of illumination. [less ▲]

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See detailLa phrase à rallonge chez Tacite
Longrée, Dominique ULg

in Haase, W. (Ed.) Aufstieg und Niedergang der Römischen Welt, II, 33, 4 (1991)

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See detailLa phrase latine : structure, ordre, rythme
Longrée, Dominique ULg

in Berthelier, Marie (Ed.) CD-DVD-ROM de latin (in press)

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See detailLe Phreoryctes menkeanus dans les provinces de Liège et de Limbourg
Van Beneden, Édouard ULg

in Bulletins de l'Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique (1895), 29

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See detailPhylloblastia inexpectata (Verrucariaceae), a new species of foliicolous lichen from Western Europe and Madeira
Sérusiaux, Emmanuel ULg; Coppins, B. J.; Lucking, R.

in Lichenologist (2007), 39(Part 2), 103-108

Phylloblastia inexpectata Serus., Coppins

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See detailPhylogenetic analysis of the pearlfish Carapini (Ophidiiformes, Carapidae)
Parmentier, Eric ULg; Castillo Cabello, Gabriel ULg; Chardon, Michel ULg et al

in Acta Zoologica (2000), 81

Fishes of the tribe Carapini (Encheliophis and Carapus) share a noteworthy peculiarity: they shelter in holothurian echinoderms or bivalve hosts. Some species are considered parasitic, others commensal ... [more ▼]

Fishes of the tribe Carapini (Encheliophis and Carapus) share a noteworthy peculiarity: they shelter in holothurian echinoderms or bivalve hosts. Some species are considered parasitic, others commensal. This study focuses on the phylogeny of the tribe, using two other Carapidae species as an outgroup (Snyderidia canina and Onuxodon fowleri). Insofar as possible, the selected anatomical and behavioural characters where chosen in an ecomorphological perspective, as features that could be responses to various lifestyle-related constraints. Our character selection also took into account the fact that some features are (presumably) linked. Such features were grouped together as a single trait to avoid their overvaluation. This methodology enabled us to separate commensals from parasites, the former belonging to Carapus and the latter to Encheliophis. Carapus species reflect in their morphology the constraints imposed by a diet of hard, mobile, elusive prey, showing predator-type features: a strong dentition, a wide mouth opening, a robust food intake apparatus. On the other hand, the endoparasitic Encheliophis species show a generally weaker buccal apparatus and narrow mouth opening, in relation to the different constraints of their lifestyle where the diet constraints are less pronounced: they eat body parts of their host. We propose changes in both generic diagnoses and transfer three species from Encheliophis to Carapus. [less ▲]

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See detailPhylogenetic classification of the mitochondrial carrier family of Saccharomyces cerevisiae.
Elmoualij, Benaïssa ULg; Duyckaerts, Claire ULg; Brasseur, Josette ULg et al

in Yeast (Chichester, England) (1997), 13(6), 573-581

The screening of the open reading frames identified in the whole yeast genome has allowed us to discover 34 proteins belonging to the mitochondrial carrier family. By phylogenetic study, they can be ... [more ▼]

The screening of the open reading frames identified in the whole yeast genome has allowed us to discover 34 proteins belonging to the mitochondrial carrier family. By phylogenetic study, they can be divided into 27 subfamilies including ADP/ATP, phosphate and citrate carriers, putative oxoglutarate and GDC carriers and 22 new subfamilies. Topology predictions using the 'positive inside rule' approach have shown that the yeast carriers are similarly oriented with both extremities exposed to the cytosol. In each subfamily, a strict conservation of the charged residues in the six transmembrane alpha-helices is observed, suggesting a functional role for these residues and the existence of 27 functionally distinct carriers. [less ▲]

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See detailPhylogenetic placement, species delimitation, and cyanobiont identity of endangered aquatic Peltigera species (lichen-forming Ascomycota, Lecanoromycetes)
Miadlikowska, Jolanta; Richardson, David; Magain, Nicolas ULg et al

in American Journal of Botany (2014)

Premise of this study: Aquatic cyanolichens from the genus Peltigera section Hydrothyriae are subject to anthropogenic threats and, therefore, are considered endangered. In this study we addressed the ... [more ▼]

Premise of this study: Aquatic cyanolichens from the genus Peltigera section Hydrothyriae are subject to anthropogenic threats and, therefore, are considered endangered. In this study we addressed the phylogenetic placement of section Hydrothyriae within Peltigera. We delimited species within the section and identified their symbiotic cyanobacteria. • Methods: Species delimitation and population structure were explored using monophyly as a grouping criterion (RAxML) and Structurama based on three protein-coding genes in combination with two nuclear ribosomal loci. The 16S and rbcLX sequences for the cyanobionts were analyzed in the broad phylogenetic context of free-living and symbiotic cyanobacteria. • Key results: We confirm with high confidence the placement of section Hydrothyriae within the monophyletic genus Peltigera; however, its phylogenetic position within the genus remains unsettled. We recovered three distinct monophyletic groups corresponding to three species: P. hydrothyria, P. gowardii s.s., and P. aquatica Miadl. & Lendemer, the latter being formally introduced here. Each species was associated with an exclusive set of Nostoc haplotypes. • Conclusions: The ITS region alone provides sufficient genetic information to distinguish the three morphologically cryptic species within section Hydrothyriae. Section Hydrothyriae seems to be associated with a monophyletic lineage of Nostoc, that has not been found in symbiotic association with other members of Peltigera. Capsosira lowei should be transferred to the genus Nostoc. Potential threats to P. aquatica should be re-examined based on the recognition of two aquatic species in western North America. [less ▲]

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See detailPhylogenetic position of the Ohiya rat (Srilankamys ohiensis) based on mitochondrial and nuclear gene sequence analysis
Buzan, Elena; Pagès, Marie ULg; Michaux, Johan ULg et al

in Zoologica Scripta (2011), 40(6), 545-553

We investigated the phylogenetic position the Ohiya rat, endemic to Sri Lanka, Srilankamys (Rodentia, Murinae), within the tribe Rattini based on the combined analysis of three independent genes (a ... [more ▼]

We investigated the phylogenetic position the Ohiya rat, endemic to Sri Lanka, Srilankamys (Rodentia, Murinae), within the tribe Rattini based on the combined analysis of three independent genes (a mitochondrial one and two nuclear exons). Three major lineages (the Maxomys, the Dacnomys and the Rattus divisions) were retrieved as monophyletic groups within the tribe Rattini. Srilankamys was not affiliated to any of the representatives of the Dacnomys division as it was supposed based on morphological characters, but clearly appeared as the first genus to diverge among the Rattus division. The Mindanao Shrew Mouse, Crunomys melanius, emerged as a part of the Maxomys division raising questions about the validity of the Crunomys and the Maxomys divisions as currently defined. Molecular date of divergence between Srilankamys and the other representatives of the Rattus division falls within the interval 6.7 ± 0.74 Mya, coinciding with the time of the isolation of Sri Lanka from the Deccan peninsula and the aridification period owing to the climate change at the end of the Miocene epoch. We suggest that the isolation of Sri Lanka from the continent, reinforced by the action of a seasonal monsoon-dominated climate, would have led to the isolation of some ancestral rodents of the Rattus division, which would have differentiated later into the Ohiya rat by a vicariant process. In a more general point of view, our study supports the previous results obtained on other organisms and evidence that Sri Lanka appears to be characterized by a particular fauna as compared to the Indian mainland. This island would therefore be considered as a specific distinct hotspot of biodiversity. [less ▲]

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See detailPhylogenetic relationships among filamentous helical cyanobacteria investigated on the basis of 16S ribosomal RNA gene sequence analysis
Nelissen, Bart; Wilmotte, Annick ULg; Neefs, Jean-Marc et al

in Systematic & Applied Microbiology (1994), 17

The cyanobacterial genera Spirulina and Arthrospira are both characterized by helical trichomes but their taxonomy is controversial and a phylogenetic study is necessary. The sequence of the 16S rRNA gene ... [more ▼]

The cyanobacterial genera Spirulina and Arthrospira are both characterized by helical trichomes but their taxonomy is controversial and a phylogenetic study is necessary. The sequence of the 16S rRNA gene and the spacer between the 16S and 23S rRNA genes (ITS) was determined for three filamentous coiled cyanobacteria: Spirulina PCC 6313, Arthrospira PCC 7345 and Arthrospira PCC 8005. A distance tree based on the 16S rRNA sequences was constructed using the neighbor-joining method. This tree shows that the two Arthrospira strains are not closely related to the Spirulina strain but belong to a cluster of strains assigned to the genera Oscillatoria, Lyngbya, and Microcoleus. The strain Spirulina PCC 6313 belongs to a branching containing unicellular cyanobacteria. For the two Arthrospira strains, the sequenced ITS region contains the tRNA(Ile) and tRNA(Ala) genes, whereas the spacer region of strain Spirulina PCC 6313 contains only the tRNA(Ile) gene. [less ▲]

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