References of "Cardol, Pierre"
     in
Bookmark and Share    
Peer Reviewed
See detailIsolation and characterization of mutants deficient in four steps of the phylloquinone biosynthesis pathway in Chlamydomonas reinhardtii.
Emonds-Alt, Barbara ULg; Remacle, Claire ULg; Cardol, Pierre ULg

Poster (2016, April 26)

In photosystem I (PSI), phylloquinone participates to electron transfer as secondary electron acceptor (A1). The phylloquinone biosynthesis pathway, previously characterized by reverse genetic in ... [more ▼]

In photosystem I (PSI), phylloquinone participates to electron transfer as secondary electron acceptor (A1). The phylloquinone biosynthesis pathway, previously characterized by reverse genetic in Synechocystis sp. PCC 6803, involves 8 enzymatic steps from chorismate [1]. In the green alga Chlamydomonas reinhardtii, characterization of phylloquinone biosynthesis was still partial and only one mutant deficient for MEND was characterized [2]. In the present work, we found MENA-H homologs in C. reinhardtii genomic database. In particular, MENF, MEND, MENC, and MENH catalytic domains are present in a single ORF (named PHYLLO by similarity to gene organisation in Arabidopsis). We then took advantage of the fact that a double reduction of plastoquinone (PQ) in PQH2 occurs in anoxia into the A1 site in the mend mutant, interrupting photosynthetic electron transfer [3], to isolate new phylloquinone-deficient strains. UPLC-MS analysis confirmed the absence of phylloquinone in four news mutants impaired in MENA, MENB, MENC (PHYLLO) and MENE. Despite this loss, men mutants are still able to grow in low light but are high light-sensitive. In low light, the level of active PSII in men mutants is identical to that of the wild-type, but the level of active PSI is reduced by 30-40% as assayed by spectroscopic measurements. This decrease is more pronounced when cells are exposed to high light intensities during 4 hours. The level of active PSI is ~ 10% of wild-type cells and the electron photosynthetic transfer is reduced accordingly. Reorganization of the photosynthetic apparatus following lack of phylloquinone in men mutants is discussed. [less ▲]

Detailed reference viewed: 22 (5 ULg)
Full Text
Peer Reviewed
See detailIsolation and characterization of mutants deficient in four steps of the phylloquinone biosynthesis pathway in Chlamydomonas reinhardtii.
Emonds-Alt, Barbara ULg; Remacle, Claire ULg; Cardol, Pierre ULg

Poster (2016, April 26)

In photosystem I (PSI), phylloquinone participates to electron transfer as secondary electron acceptor (A1). The phylloquinone biosynthesis pathway, previously characterized by reverse genetic in ... [more ▼]

In photosystem I (PSI), phylloquinone participates to electron transfer as secondary electron acceptor (A1). The phylloquinone biosynthesis pathway, previously characterized by reverse genetic in Synechocystis sp. PCC 6803, involves 8 enzymatic steps from chorismate [1]. In the green alga Chlamydomonas reinhardtii, characterization of phylloquinone biosynthesis was still partial and only one mutant deficient for MEND was characterized [2]. In the present work, we found MENA-H homologs in C. reinhardtii genomic database. In particular, MENF, MEND, MENC, and MENH catalytic domains are present in a single ORF (named PHYLLO by similarity to gene organisation in Arabidopsis). We then took advantage of the fact that a double reduction of plastoquinone (PQ) in PQH2 occurs in anoxia into the A1 site in the mend mutant, interrupting photosynthetic electron transfer [3], to isolate new phylloquinone-deficient strains. UPLC-MS analysis confirmed the absence of phylloquinone in four news mutants impaired in MENA, MENB, MENC (PHYLLO) and MENE. Despite this loss, men mutants are still able to grow in low light but are high light-sensitive. In low light, the level of active PSII in men mutants is identical to that of the wild-type, but the level of active PSI is reduced by 30-40% as assayed by spectroscopic measurements. This decrease is more pronounced when cells are exposed to high light intensities during 4 hours. The level of active PSI is ~ 10% of wild-type cells and the electron photosynthetic transfer is reduced accordingly. Reorganization of the photosynthetic apparatus following lack of phylloquinone in men mutants is discussed. [less ▲]

Detailed reference viewed: 20 (8 ULg)
Full Text
Peer Reviewed
See detailSubunit Asa1 spans all the peripheral stalk of the mitochondrial ATP synthase of the chlorophycean alga Polytomella sp.
Colina-Tenorio, Lilia; Miranda-Astudillo, Hector; Cano-Estrada, Araceli et al

in Biochimica et biophysica acta (2016)

Mitochondrial F1FO-ATP synthase of chlorophycean algae is dimeric. It contains eight orthodox subunits (alpha, beta, gamma, delta, epsilon, OSCP, a and c) and nine atypical subunits (Asa1 to 9). These ... [more ▼]

Mitochondrial F1FO-ATP synthase of chlorophycean algae is dimeric. It contains eight orthodox subunits (alpha, beta, gamma, delta, epsilon, OSCP, a and c) and nine atypical subunits (Asa1 to 9). These subunits build the peripheral stalk of the enzyme and stabilize its dimeric structure. The location of the 66.1kDa subunit Asa1 has been debated. On one hand, it was found in a transient subcomplex that contained membrane-bound subunits Asa1/Asa3/Asa5/Asa8/a (Atp6)/c (Atp9). On the other hand, Asa1 was proposed to form the bulky structure of the peripheral stalk that contacts the OSCP subunit in the F1 sector. Here, we overexpressed and purified the recombinant proteins Asa1 and OSCP and explored their interactions in vitro, using immunochemical techniques and affinity chromatography. Asa1 and OSCP interact strongly, and the carboxy-terminal half of OSCP seems to be instrumental for this association. In addition, the algal ATP synthase was partially dissociated at relatively high detergent concentrations, and an Asa1/Asa3/Asa5/Asa8/a/c10 subcomplex was identified. Furthermore, Far-Western analysis suggests an Asa1-Asa8 interaction. Based on these results, a model is proposed in which Asa1 spans the whole peripheral arm of the enzyme, from a region close to the matrix-exposed side of the mitochondrial inner membrane to the F1 region where OSCP is located. 3D models show elongated, helix-rich structures for chlorophycean Asa1 subunits. Asa1 subunit probably plays a scaffolding role in the peripheral stalk analogous to the one of subunit b in orthodox mitochondrial enzymes. [less ▲]

Detailed reference viewed: 62 (5 ULg)
Peer Reviewed
See detailIs the Mehler reaction the main photoprotective mechanism occurring in Symbiodinium in hospite?
Roberty, Stéphane ULg; Beraud, Eric; Ferrier-Pagès, Christine et al

Poster (2015, August)

The ecological success of reef-building corals throughout tropical oligotrophic waters relies on the symbiosis between cnidarians and photosynthetic dinoflagellates of the genus Symbiodinium. This ... [more ▼]

The ecological success of reef-building corals throughout tropical oligotrophic waters relies on the symbiosis between cnidarians and photosynthetic dinoflagellates of the genus Symbiodinium. This association allows the transfer of highly energetic compounds and an efficient recycling of growth-limiting nutrients. In the natural environment the holobiont have to cope with significant daily variations in light intensities that sometimes exceed Symbiodinium photosynthetic capacity. Fortunately, these organisms possess regulatory features that help to ensure that high light intensities can be endured without the accumulation of photodamage. Among them, it has been found recently that photoreduction of oxygen downstream PSI by the so-called Mehler reaction was the main alternative electron sink at the onset and steady state of photosynthesis in different cultured strains of Symbiodinium. In this study, we investigated the occurrence and the relative amplitude of this photoprotective mechanism in Symbiodinium cells living within the tropical coral Stylophora pistillata and the sea anemone Anemonia viridis. To this end, joint measurements of oxygen evolution, PSI and PSII activities were conducted. The impacts of CO2 limitation and CO2 fixation on the photoreduction of oxygen by PSI was also studied by using several inhibitors targeting the carbon concentrating mechanism and the Calvin-Benson-Bassham cycle. Conversely to cultured cells, these measurements revealed that the Symbiodinium located in S. pistillata, under control conditions, rely on other photoprotective mechanisms than the Mehler reaction to prevent over-excitation of the photosynthetic apparatus. However, we observed an increased O2 uptake capacity during photosynthesis when the efficiency of the carbon fixation was reduced in S. pistillata. [less ▲]

Detailed reference viewed: 53 (7 ULg)
Peer Reviewed
See detailCritical role of oxygen photoreduction downstream of PSI in Symbiodinium: photoprotection, energetic adjustement and ROS production
Roberty, Stéphane ULg; Bailleul, Benjamin; Berne, Nicolas ULg et al

Conference (2015, August)

The ecological success of symbiotic cnidarians (reef building-corals and sea anemones) relies on the symbiosis between cnidarians and photosynthetic dinoflagellates of the genus Symbiodinium ... [more ▼]

The ecological success of symbiotic cnidarians (reef building-corals and sea anemones) relies on the symbiosis between cnidarians and photosynthetic dinoflagellates of the genus Symbiodinium. Photosynthetic organisms have evolved various photoprotective and regulatory mechanisms to cope with changing and high light intensities, but the nature and relative amplitude of these mechanisms is still a matter of debate in Symbiodinium. Few studies showed that molecular oxygen (O2) can be an efficient electron sink during photosynthesis in Symbiodinium, with an O2 uptake capacity that could represent up to half the maximum O2 evolution. In addition, members of clade A Symbiodinium were proposed to possess enhanced capabilities for alternative photosynthetic electron flows. In this work, the amplitude of photosynthetic alternative electron flows to oxygen (chlororespiration, Mehler reaction, mitochondrial respiration) and PSI cyclic electron flow were investigated in Symbiodinium strains belonging to different Clades (A, B and F). Joint measurements of oxygen evolution, PSI and PSII activities allowed us to demonstrate that photoreduction of oxygen downstream PSI by the so-called Mehler reaction is the main alternative electron sink at the onset and steady state of photosynthesis in all strains1. This mechanism in Symbiodinium sustains significant photosynthetic electron flux under high light, thus acting as a photoprotective mechanism and modifying the ratio of ATP/NADPH to match the requirements of carbon reduction. At higher temperature (26 to 33°C), the amplitude of Mehler reaction was still significantly increased but the capacity of enzymes responsible for superoxide detoxification largely decreased. This imbalance generated twice more ROS than during the treatment at 26°C, suggesting that under conditions known to induce coral bleaching, the photoprotective role of Mehler reaction can no longer be maintained, at least at short term. [less ▲]

Detailed reference viewed: 63 (8 ULg)
Full Text
Peer Reviewed
See detailEnergetic coupling between plastids and mitochondria drives CO assimilation in diatoms.
Bailleul, Benjamin; Berne, Nicolas ULg; Murik, Omer et al

in Nature (2015)

Diatoms are one of the most ecologically successful classes of photosynthetic marine eukaryotes in the contemporary oceans. Over the past 30 million years, they have helped to moderate Earth's climate by ... [more ▼]

Diatoms are one of the most ecologically successful classes of photosynthetic marine eukaryotes in the contemporary oceans. Over the past 30 million years, they have helped to moderate Earth's climate by absorbing carbon dioxide from the atmosphere, sequestering it via the biological carbon pump and ultimately burying organic carbon in the lithosphere. The proportion of planetary primary production by diatoms in the modern oceans is roughly equivalent to that of terrestrial rainforests. In photosynthesis, the efficient conversion of carbon dioxide into organic matter requires a tight control of the ATP/NADPH ratio which, in other photosynthetic organisms, relies principally on a range of plastid-localized ATP generating processes. Here we show that diatoms regulate ATP/NADPH through extensive energetic exchanges between plastids and mitochondria. This interaction comprises the re-routing of reducing power generated in the plastid towards mitochondria and the import of mitochondrial ATP into the plastid, and is mandatory for optimized carbon fixation and growth. We propose that the process may have contributed to the ecological success of diatoms in the ocean. [less ▲]

Detailed reference viewed: 33 (4 ULg)
Full Text
See detailPhotosynthetic electron Transfer and their regulation-Which recipe ?
Cardol, Pierre ULg

Conference (2015)

Detailed reference viewed: 18 (0 ULg)
See detailQuantitative Targeted Proteomics and Electrochromic Shift for Measuring Photosystem Content of Marine Phytoplankton
Malcolm, Christopher M.; Bailleul, Benjamin; Melanson, J.R. et al

Poster (2015)

Abundance and stoichiometry data for the photosystems, the intersystem electron transport complexes and the Calvin cycle enzymes are rich in information about light and nutrient acclimation. Quantifying ... [more ▼]

Abundance and stoichiometry data for the photosystems, the intersystem electron transport complexes and the Calvin cycle enzymes are rich in information about light and nutrient acclimation. Quantifying these complexes is essential for understanding limitations on and capacities for photosynthesis. Targeted quantitative immunodetections of conserved subunits (eg. PsbA for PSII; PsaC for PSI) are becoming an established method for absolute measurement of these complexes. An advantage of protein measurements is that they can be done with non-living flash-frozen samples and processed post-field. A pitfall of physical versus functional measures is that in some scenarios, such as during photoinhibition of photosystem II (PSII), physical and functional measures give different values, but such disparities are often meaningful, informing targeted studies of regulation, repair and enzyme kinetics. Electrochromic Shift (ECS) is an alternative, fast and noninvasive method which can be exploited to determine functional PSI:PSII ratios in living cells. The basis for ECS is that pigments in the photosynthetic membrane exhibit a shift in their absorption spectra when the electric component of the proton motive force is generated across the membrane in the light. Cross-validation of methods by independent measures builds confidence in results from both approaches and can be useful for ground truthing of underway or high-throughput optical measurements or functional measurements from bioassays. We present comparative data from immunoquantitation and ECS for an array of diatom taxa. The physical data fall within established ranges. The basis for similarities and disparities in the photosystem stoichiometries between the methods are discussed. [less ▲]

Detailed reference viewed: 58 (0 ULg)
Full Text
Peer Reviewed
See detailImbalance between oxygen photoreduction and antioxidant capacities in Symbiodinium cells exposed to combined heat and high light stress
Roberty, Stéphane ULg; Fransolet, David; Cardol, Pierre ULg et al

in Coral Reefs (2015), 34

During last decades coral reefs have been affected by several large-scale bleaching events and such phenomenon is expected to increase in frequency and severity in the future thus compromising their ... [more ▼]

During last decades coral reefs have been affected by several large-scale bleaching events and such phenomenon is expected to increase in frequency and severity in the future thus compromising their survival. High sea surface temperature accompanied by high levels of solar irradiance has been found to be responsible for the induction of an oxidative stress ultimately ending with the disruption of the symbiosis between cnidarians and Symbiodinium. Since two decades many studies have pointed out the water-water cycle as being one of the primary mediators of this phenomenon, but the impacts of environmental stress on the O2 reduction by PSI and the associated ROS-detoxifying enzymes remain to be determined. In this study, we analyzed the impacts of an acute thermal and light stress on the WWC in the model Symbiodinium strain A1. We observed that high light treatment at 26°C resulted in the up-regulation of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) activities and an increased production of Reactive Oxygen Species (ROS) with no significant change in O2-dependent electron transport. Under high light and at 33°C, O2-dependent electron transport was significantly increased relative to total electron transport. This increase was concomitant with a two-fold increase in ROS generation compared to the treatment at 26°C, while enzymes involved in the WWC were largely inactivated. These data show for the first time that combined heat and light stress inactivate antioxidant capacities of the WWC, and suggests that its photoprotective functions are overwhelmed under these conditions. This study also indicates that cnidarians may be more prone to bleach if they harbor Symbiodinium cells having a highly active Mehler-type electron transport, unless they are able to quickly up-regulate their antioxidant capacities. [less ▲]

Detailed reference viewed: 66 (25 ULg)
Full Text
See detailCritical role of oxygen photoreduction downstream of PSI in Symbiodinium: photoprotection, energetic adjustement and ROS production
Cardol, Pierre ULg

Conference (2015)

The ecological success of symbiotic cnidarians (reef corals and anemones) relies on the symbiosis between cnidarians and photosynthetic dinoflagellates of the genus Symbiodinium. Photosynthetic organisms ... [more ▼]

The ecological success of symbiotic cnidarians (reef corals and anemones) relies on the symbiosis between cnidarians and photosynthetic dinoflagellates of the genus Symbiodinium. Photosynthetic organisms have evolved various photoprotective and regulatory mechanisms to cope with changing and high light intensities, but the nature and relative amplitude of these mechanisms is still a matter of debate in Symbiodinium. Few studies showed that molecular oxygen (O2) can be an efficient electron sink during photosynthesis in Symbiodinium, with an O2 uptake capacity that could represent up to half the maximum O2 evolution. In addition, members of clade A Symbiodinium were proposed to possess enhanced capabilities for alternative photosynthetic electron flows. In this work, the amplitude of photosynthetic alternative electron flows to oxygen (chlororespiration, Mehler reaction, mitochondrial respiration) and PSI cyclic electron flow were investigated in Symbiodinium strains belonging to different Clades (A, B and F). Joint measurements of oxygen evolution, PSI and PSII activities allowed us to demonstrate that photoreduction of oxygen downstream PSI by the so-called Mehler reaction is the main alternative electron sink at the onset and steady state of photosynthesis in all strains1. This mechanism in Symbiodinium sustains significant photosynthetic electron flux under high light, thus acting as a photoprotective mechanism and modifying the ratio of ATP/NADPH to match the requirements of carbon reduction. At higher temperature (26 to 33°C), the amplitude of Mehler reaction was still significantly increased but the capacity of enzymes responsible for superoxide detoxification largely decreased. This imbalance generated twice more ROS than during the treatment at 26°C, suggesting that under environmental conditions leading to coral bleaching, the photoprotective role of Mehler reaction can no longer be maintained. [less ▲]

Detailed reference viewed: 48 (5 ULg)
Full Text
Peer Reviewed
See detailInduction of Photosynthetic Carbon Fixation in Anoxia Relies on Hydrogenase Activity and Proton-Gradient Regulation-Like1-Mediated Cyclic Electron Flow in Chlamydomonas reinhardtii.
Godaux, Damien ULg; Bailleul, Benjamin ULg; Berne, Nicolas ULg et al

in Plant physiology (2015), 168(2), 648-58

The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the ... [more ▼]

The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF), we demonstrate the sequential contribution of these alternative electron flows (AEFs) in the reactivation of photosynthetic carbon fixation during a shift from dark anoxia to light. At light onset, hydrogenase activity sustains a linear electron flow from photosystem II, which is followed by a transient PSI-CEF in the wild type. By promoting ATP synthesis without net generation of photosynthetic reductants, the two AEF are critical for restoration of the capacity for carbon dioxide fixation in the light. Our data also suggest that the decrease in hydrogen evolution with time of illumination might be due to competition for reduced ferredoxins between ferredoxin-NADP(+) oxidoreductase and hydrogenases, rather than due to the sensitivity of hydrogenase activity to oxygen. Finally, the absence of the two alternative pathways in a double mutant pgrl1 hydrogenase maturation factor G-2 is detrimental for photosynthesis and growth and cannot be compensated by any other AEF or anoxic metabolic responses. This highlights the role of hydrogenase activity and PSI-CEF in the ecological success of microalgae in low-oxygen environments. [less ▲]

Detailed reference viewed: 38 (6 ULg)
Full Text
Peer Reviewed
See detailThe involvement of hydrogen-producing and ATP-dependent NADPH-consuming pathways in setting the redox poise in the chloroplast of Chlamydomonas reinhardtii in anoxia.
Clowez, Sophie; Godaux, Damien ULg; Cardol, Pierre ULg et al

in The Journal of biological chemistry (2015), 290(13), 8666-76

Photosynthetic microalgae are exposed to changing environmental conditions. In particular, microbes found in ponds or soils often face hypoxia or even anoxia, and this severely impacts their physiology ... [more ▼]

Photosynthetic microalgae are exposed to changing environmental conditions. In particular, microbes found in ponds or soils often face hypoxia or even anoxia, and this severely impacts their physiology. Chlamydomonas reinhardtii is one among such photosynthetic microorganisms recognized for its unusual wealth of fermentative pathways and the extensive remodeling of its metabolism upon the switch to anaerobic conditions. As regards the photosynthetic electron transfer, this remodeling encompasses a strong limitation of the electron flow downstream of photosystem I. Here, we further characterize the origin of this limitation. We show that it stems from the strong reducing pressure that builds up upon the onset of anoxia, and this pressure can be relieved either by the light-induced synthesis of ATP, which promotes the consumption of reducing equivalents, or by the progressive activation of the hydrogenase pathway, which provides an electron transfer pathway alternative to the CO2 fixation cycle. [less ▲]

Detailed reference viewed: 95 (2 ULg)
Full Text
Peer Reviewed
See detailIsolation of Chlamydomonas reinhardtii mutants with altered mitochondrial respiration by chlorophyll fluorescence measurement.
Massoz, Simon; Larosa, Véronique ULg; Horrion, Bastien et al

in Journal of biotechnology (2015)

The unicellular green alga Chlamydomonas reinhardtii is a model organism for studying energetic metabolism. Most mitochondrial respiratory-deficient mutants characterized to date have been isolated on the ... [more ▼]

The unicellular green alga Chlamydomonas reinhardtii is a model organism for studying energetic metabolism. Most mitochondrial respiratory-deficient mutants characterized to date have been isolated on the basis of their reduced ability to grow in heterotrophic conditions. Mitochondrial deficiencies are usually partly compensated by adjustment of photosynthetic activity and more particularly by transition to state 2. In this work, we explored the opportunity to select mutants impaired in respiration and/or altered in dark metabolism by measuring maximum photosynthetic efficiency by chlorophyll fluorescence analyses (FV/FM). Out of about 2900 hygromycin-resistant insertional mutants generated from wild type or from a mutant strain deficient in state transitions (stt7 strain), 22 were found to grow slowly in heterotrophic conditions and 8 of them also showed a lower FV/FM value. Several disrupted coding sequences were identified, including genes coding for three different subunits of respiratory-chain complex I (NUO9, NUOA9, NUOP4) or for isocitrate lyase (ICL1). Overall, the comparison of respiratory mutants obtained in wild-type or stt7 genetic backgrounds indicated that the FV/FM value can be used to isolate mutants severely impaired in dark metabolism. [less ▲]

Detailed reference viewed: 41 (18 ULg)
Full Text
Peer Reviewed
See detailPSI Mehler reaction is the main alternative photosynthetic electron pathway in Symbiodinium sp., symbiotic dinoflagellates of cnidarians
Roberty, Stéphane ULg; Bailleul, Benjamin ULg; Berne, Nicolas et al

in New Phytologist (2014), 204(1), 81-91

• Photosynthetic organisms have evolved various photoprotective and regulatory mechanisms to cope with changing and high light intensities. The nature and relative amplitude of these mechanisms is matter ... [more ▼]

• Photosynthetic organisms have evolved various photoprotective and regulatory mechanisms to cope with changing and high light intensities. The nature and relative amplitude of these mechanisms is matter of debate in dinoflagellates that live in symbiosis with cnidarians. In this work, the amplitude of photosynthetic alternative electron flows to oxygen (chlororespiration, Mehler reaction, mitochondrial respiration) and PSI cyclic electron flow were investigated in Symbiodinium clades A1, B1 and F1. • Cultured Symbiodinium strains were maintained semi-continuously under identical environmental conditions. Joint measurements of oxygen evolution, fluorescence emission, and absorption changes at specific wavelengths were used to evaluate PSI and PSII electron transfer rates (ETR). • A light-dependent and O2-dependent ETR was observed in all strains. This ETR involved PSII and PSI and was insensitive to addition of mitochondrial and carbon fixation inhibitors. • These results demonstrate that photoreduction of oxygen downstream of PSI by the so-called Mehler reaction is the main alternative electron sink at the onset and steady state of photosynthesis in all strains. This mechanism in Symbiodinium sustains significant levels of photosynthetic electron flux under high light, thus acting as a photoprotective mechanism and increasing the ATP/NADPH ratio by the electron transfer chain. [less ▲]

Detailed reference viewed: 138 (35 ULg)
Full Text
See detailTranscriptomics and Proteomics of a Secondary Green Alga.
Perez, Emilie ULg; Lapaille, Marie; Degand, Hervé et al

Poster (2014, August)

Euglena gracilis is a secondary green alga related to trypanosomes that derives from a secondary endosymbiosis between a phagotrophic ancestor and a prasinophycean green alga. Our general objective is to ... [more ▼]

Euglena gracilis is a secondary green alga related to trypanosomes that derives from a secondary endosymbiosis between a phagotrophic ancestor and a prasinophycean green alga. Our general objective is to study the metabolic interactions established between the secondary plastid and the mitochondrion after the endosymbiotic event and to determine the phylogenetic origin of the genes encoding the proteins involved in the energetic pathways. As a first step, we analysed the subunit composition of the mitochondrial respiratory chain, both in silico and by targeted proteomics, to assess the extent of its similitude with the respiratory chain of Trypanosomatidae. We have shown that Euglena shares many additional subunits with trypanosomes, which suggests that these subunits are not especially associated to a parasitic lifestyle. As a second step, we sequenced the total transcriptome of Euglena and determined the phylogenetic origin of each predicted transcript using a database of about 1000 complete proteomes representing the diversity of life. These analyses confirmed that Euglena recruited its genes from a very diverse set of sources. As a third step, we performed a high-throughput analysis of the mitochondrial proteome of Euglena. Our MS/MS experiments, taking advantage of the availability of our transcriptome, mostly recovered mitochondrial proteins, which indicates that our mitochondrial extracts were quite pure. The identified proteins encompassed about 15 different mitochondrial pathways. We are now in the process of comparing the expression levels of both the transcripts and the corresponding proteins across a range of culture conditions selected to differently stimulate the mitochondrion and the plastid. [less ▲]

Detailed reference viewed: 90 (24 ULg)
Full Text
Peer Reviewed
See detailA forward genetic screen to identify hydrogenase-deficient mutants in the unicellular green alga Chlamydomonas reinhardtii
Emonds-Alt, Barbara ULg; Godaux, Damien ULg; Cardol, Pierre ULg et al

Poster (2014, June 15)

The ability of the unicellular green alga Chlamydomonas reinhardtii to evolve molecular hydrogen (H2) is due to the presence of oxygen-sensitive Fe-hydrogenases (HydA1/2), expressed in anoxic conditions ... [more ▼]

The ability of the unicellular green alga Chlamydomonas reinhardtii to evolve molecular hydrogen (H2) is due to the presence of oxygen-sensitive Fe-hydrogenases (HydA1/2), expressed in anoxic conditions that drive the photosynthetic electron flow to reduce protons into H2. In order to identify new players involved in H2 photoproduction in Chlamydomonas, an insertion mutant library was generated using cassettes conferring resistance to hygromycin or paromomycin. Hydrogenase activity is physiologically relevant during a transition from dark anoxia to light. In dark anoxic conditions, the cellular redox poise is high and the photosynthetic electron transport chain is fully reduced. Upon illumination, hydrogenase activity allows the reoxidation of photosynthetic intersystem electron carriers until oxic conditions and carbon fixation ability are restored. We thus designed an in vivo fluorescence imaging screen based on the different kinetics of photosynthesis induction between wild type and hydrogenase-deficient mutants [1]. At this stage, three putative hydrogenase mutants have been identified on 10,000 transformants. Molecular characterization of the insertion site of the resistance cassette by TAIL-PCR and genetic analyses of the linkage between the antibiotic resistance and the fluorescence phenotype showed that one mutant was untagged with the resistance while two tagged mutants were deficient for the HydG assembly factor. [less ▲]

Detailed reference viewed: 62 (13 ULg)
Full Text
See detailMitochondrial Proteomics of a Secondary Green Alga.
Perez, Emilie ULg; Degand, Hervé; Morsomme, Pierre et al

Poster (2014, May 06)

Euglena gracilis is an alga that derives from a secondary endosymbiosis with a green alga. Our general objective is to study the interactions established between the chloroplast and the mitochondrion ... [more ▼]

Euglena gracilis is an alga that derives from a secondary endosymbiosis with a green alga. Our general objective is to study the interactions established between the chloroplast and the mitochondrion during the endosymbiosic event and to determine the phylogenetic origin of the genes encoding the proteins involved in these interactions. As a first step, we performed a high-throughput analysis of the mitochondrial proteome of Euglena gracilis. Our MS/MS experiments mostly recover mitochondrial proteins representing 15 mitochondrial pathways, which indicates that our mitochondrial extracts are relatively pure, but the phylogenetic origins of the corresponding genes are surprisingly diverse. [less ▲]

Detailed reference viewed: 23 (4 ULg)