Publications of Claire Remacle
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See detailCharacterization of the apx2 mutant in Chlamydomonas
Caccamo, Anna ULiege; Vega de Luna, Felix ULiege; Iacono, Fabrizio ULiege et al

Poster (2021, April 08)

One of the most common reactive oxygen species (ROS) produced in eukaryotic organisms during photosynthesis is hydrogen peroxide (H2O2) [1]. To evaluate the impact of H2O2-scavenging enzymes on algal ... [more ▼]

One of the most common reactive oxygen species (ROS) produced in eukaryotic organisms during photosynthesis is hydrogen peroxide (H2O2) [1]. To evaluate the impact of H2O2-scavenging enzymes on algal fitness, we selected a mutant deficient in ascorbate peroxidase 2 (APX2) in the green microalga Chlamydomonas reinhardtii. Ascorbate peroxidase (APX) uses ascorbate and H2O2 as substrates to form monodehydroascorbate (MDHA) and H2O. The enzyme, encoded by eight isoforms in Arabidopsis thaliana, has been already well-described in plants as one of the main actors involved in the Mehler reaction in which electrons obtained from H2O oxidation in photosystem II (PSII) are linearly transported to the acceptor side of photosystem I (PSI) where they are used to completely reduce the superoxide (O2-) to H2O [2]. In Chlamydomonas, four APX isoforms are present and APX2 is predicted to be targeted to the thylakoid membrane of the chloroplast using Target P [3]. In this study, we focus on the importance of APX2 in the Mehler reaction and during linear electron flow. To assess these two functionalities of APX2, we evaluated photosynthetic parameters under control light and high light in cells grown phototrophically. Therefore, we compared the quantum yield of PSII (φPSII) by monitoring in vivo chlorophyll a fluorescence, and the photooxidation and the re-reduction rate of the PSI of wild type (WT) and apx2 mutant cells. We found that the effects of the loss of APX2 are mainly seen in cells grown in control light. The apx2 mutant cells present a decreased rate of the relative electron transport (rETR) in phototrophic control light growth condition and the PSII efficiency resembles the one of WT under high light or H2O2 stress. We also observed a higher PSI photooxidation rate for the apx2 mutant compared to WT in cells grown in control light, suggesting an electron donor side limitation at the level of the PSI. Further, the lower re-reduction rate of the PSI in apx2 mutant compared to the WT after a short pulse of saturating light supports our observations. All in all, the APX2 enzyme seems to exert its function under unstressful physiological condition and could be involved in the early redox poise of photosynthesis. Funded by FNRS-FWO EOS Project 30829584 [1] Asada, Plant Physiol. 141, 391 – 396 (2006) [2] Dietz et al., J. Exp. Bot. 53, 1321 – 1329 (2002) [3] Emanuelsson et al., J. Mol. Biol. 300, 4, 1005 – 106 (2000) [less ▲]

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See detailFermentation pathways and their interactions with photosynthesis in the marine diatom T. pseudonana: proteomic and biophysics approaches
Gain, Gwenaëlle ULiege; Berne, Nicolas ULiege; Corato, Amélie ULiege et al

Conference (2021, April 08)

The glycolysis associated with mitochondrial oxidative phosphorylation is the process by which the vast majority of eukaryotes produces ATP from sugar. Under hypoxic or anoxic conditions, fermentation ... [more ▼]

The glycolysis associated with mitochondrial oxidative phosphorylation is the process by which the vast majority of eukaryotes produces ATP from sugar. Under hypoxic or anoxic conditions, fermentation pathways allow to maintain glycolytic activity by reducing alternative electron acceptors (other than O2) while generating various fermentation by-products. Anaerobic fermentation and photosynthesis coexist when organisms experience hypoxia or anoxia in their natural environment (e.g. marine sediments, eutrophic waters). In photosynthetic microeukaryotes, the detailed study of anaerobic metabolic pathways is limited to few freshwater model organisms such as Chlamydomonas reinhardtii (1). Based a previous genomic survey, Thalassiosira pseudonana, a centric marine diatom would contain a large variety of fermentation pathways (2). In our work, we studied the fermentation pathways and their interactions with photosynthesis in T. pseudonana. We first show that there are different waves of protein expression during the first 24 hours in anoxia in the dark. Several fermentative metabolites are also detected (H2, succinate), and our data suggest the existence of a bacterial fermentative pathway leading to butyrate production. The availability in photosynthetic electron acceptors is reduced but not null after 24h in anoxia. This suggests that at least one fermentative pathway is able to reoxidize photosynthetic electron acceptors, as it was previously shown for hydrogenase activity in C. reinhardtii (3). Finally, by comparing PSI and PSII activity, we evidence that a high and transient cyclic electron flow (CEF) around PSI is key to resume PSII electron transfer in anoxic condition. Overall, our results reveal regulatory mechanisms (CEF and fermentation pathways) that may help T. pseudonana cope with hypoxic or anoxic environments. References: (1) Muller, M. et al. (2012). Microbiol Mol Biol Rev, 76, 444-495 (2) Atteia et al. (2013). Biochim Biophys Acta - Bioenerg 1827: 210–223 (3) Godaux et al. (2013). Int. J. Hydrog. Energy, 38: 1826-1836 [less ▲]

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See detailOccurrence, Evolution and Specificities of Iron-Sulfur Proteins and Maturation Factors in Chloroplasts from Algae
Przybyla-Toscano, Jonathan; Couturier, Jérémy; Remacle, Claire ULiege et al

in International Journal of Molecular Sciences (2021), 22(6), 3175

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See detailCharacterization of the apx2 mutant in Chlamydomonas
Caccamo, Anna ULiege; Larosa, Veronique; Messens, Joris et al

Poster (2021, February 16)

One of the most common reactive oxygen species (ROS) produced in eukaryotic organisms during photosynthesis is hydrogen peroxide (H2O2) [1]. To evaluate the impact of H2O2-scavenging enzymes on algal ... [more ▼]

One of the most common reactive oxygen species (ROS) produced in eukaryotic organisms during photosynthesis is hydrogen peroxide (H2O2) [1]. To evaluate the impact of H2O2-scavenging enzymes on algal fitness, we selected a mutant deficient in ascorbate peroxidase 2 (APX2) in the green microalga Chlamydomonas reinhardtii. Ascorbate peroxidase (APX) uses ascorbate and H2O2 as substrates to form monodehydroascorbate (MDHA) and H2O. The enzyme, encoded by eight isoforms in Arabidopsis thaliana, has been already well-described in plants as one of the main actors involved in the Mehler reaction in which electrons obtained from H2O oxidation in photosystem II (PSII) are linearly transported to the acceptor side of photosystem I (PSI) where they are used to completely reduce the superoxide (O2-) to H2O [2]. In Chlamydomonas, four APX isoforms are present and APX2 is predicted to be targeted to the thylakoid membrane of the chloroplast using Target P [3]. In this study, we focus on the importance of APX2 in the Mehler reaction and during linear electron flow. To assess these two functionalities of APX2, we evaluated photosynthetic parameters under control light and high light in cells grown phototrophically and mixotrophically. Therefore, we compared the quantum yield of PSII (φPSII) by monitoring in vivo chlorophyll a fluorescence, and the photooxidation and the re-reduction rate of the PSI of wild type (WT) and apx2 mutant cells. We found that the effects of the loss of APX2 are mainly seen in cells grown phototrophically in control light. The apx2 mutant cells present a decreased rate of the relative electron transport (rETR) in phototrophic control light growth condition and the PSII efficiency resembles the one of WT under high light or H2O2 stress. We also observed a higher PSI photooxidation rate for the apx2 mutant compared to WT in cells grown phototrophically in control light, suggesting an electron donor side limitation at the level of the PSI. Further, the lower re-reduction rate of the PSI in apx2 mutant compared to the WT after a short pulse of saturating light supports our observations. All in all, the APX2 enzyme seems to exert its function under unstressful physiological condition and could be involved in the early redox poise of photosynthesis. Funded by FNRS-FWO EOS Project 30829584 [1] Asada, Plant Physiol. 141, 391 – 396 (2006) [2] Dietz et al., J. Exp. Bot. 53, 1321 – 1329 (2002) [3] Emanuelsson et al., J. Mol. Biol. 300, 4, 1005 – 106 (2000) [less ▲]

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See detailMixotrophic growth of the extremophile Galdieria sulphuraria reveals the flexibility of its carbon assimilation metabolism
Curien, Gilles; Lyska, Dagmar; Guglielmino, Erika et al

in New Phytologist (2021), doi: 10.1111/NPH.17359

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See detailPolypeptide monomérique présentant une activité hydrogénase, en particulier polypeptide monomérique recombinant présentant une activité hydrogénase
Godaux, Damien ULiege; Lorge, Philippe ULiege; Ghysels, Bart ULiege et al

Patent (2020)

Processus d’obtention (production recombinante chez E. coli et purification par chromatographie d’affinité) de la sous-unité catalytique d’une hydrogénase pentamérique, cette sous-unité présentant une ... [more ▼]

Processus d’obtention (production recombinante chez E. coli et purification par chromatographie d’affinité) de la sous-unité catalytique d’une hydrogénase pentamérique, cette sous-unité présentant une activité hydrogénase. [less ▲]

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See detailAssembly of Mitochondrial Complex I Requires the Low-Complexity Protein AMC1 in Chlamydomonas reinhardtii
Subrahmanian, N; Castonguay, AD; Remacle, Claire ULiege et al

in Genetics (2020), 214(4), 895-911

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See detailIsolation and Characterization of Two Microalgal Isolates from Vietnam with Potential for Food, Feed, and Biodiesel Production
Luu Thao Nguyen, ULiege; Alsafra, Zouheir ULiege; Corato, Amélie ULiege et al

in Energies (2020), 13

Microalgae are promising feedstock for the production of biodiesel and diverse medium- and high-value products such as pigments and polyunsaturated fatty acids. The importance of strain selection adapted ... [more ▼]

Microalgae are promising feedstock for the production of biodiesel and diverse medium- and high-value products such as pigments and polyunsaturated fatty acids. The importance of strain selection adapted to specific environments is important for economical purposes. We characterize here two microalgal strains, isolated from wastewater of shrimp cultivation ponds in Vietnam. Based on the 18S rDNA-ITS region, one strain belongs to the Eustigmatophyceae class and is identical to the Nannochloropsis salina isolate D12 (JX185299.1), while the other is a Chlorophyceae belonging to the Desmodesmus genus, which possesses a S516 group I intron in its 18S rDNA gene. The N. salina strain is a marine and oleaginous microalga (40% of dry weight (DW) at stationary phase) whole oil is rich in saturated fatty acids (around 45% of C16:0) suitable for biodiesel and contains a few percent of eicosapentaenoic acid (C20:5). The Desmodesmus isolate can assimilate acetate and ammonium and is rich in lutein. Its oil contains around 40%–50% α-linolenic acid (C18:3), an essential fatty acid. Since they tolerate various salinities (10% to 35‰), both strains are thus interesting for biodiesel or aquaculture valorization in coastal and tropical climate where water, nutrient, and salinity availability vary greatly depending on the season. [less ▲]

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See detailA novel culture medium for freshwater diatoms promotes efficient photoautotrophic batch production of biomass, fucoxanthin, and eicosapentaenoic acid
Gerin, Stéphanie ULiege; Delhez, Thomas; Corato, Amélie ULiege et al

in Journal of Applied Phycology (2020), 32

Diatoms have recently emerged as new promising sources of fucoxanthin and eicosapentaenoic acid (EPA). Most applied studies in this area have focused on marine diatoms whereas the characterization of ... [more ▼]

Diatoms have recently emerged as new promising sources of fucoxanthin and eicosapentaenoic acid (EPA). Most applied studies in this area have focused on marine diatoms whereas the characterization of freshwater diatom metabolism has been restricted to ecophysiological studies. Here, we describe a novel culture medium for freshwater diatoms, the FDMed medium, and we demonstrate that it supports high biomass, fucoxanthin, and EPA production yields in photoautotrophic batch cultures of Sellaphora minima and Nitzschia palea. Growth was monitored for 21 days, fucoxanthin and EPA concentrations were assayed all along cultivation processes, and results were compared to those obtained for two other media (WC and Modified COMBO(MCOMBO)). The FDMed medium was found to increase biomass yields comparatively to MCOMBO medium (5–7-fold higher algal concentration at the stationary phase in S. minima and N. palea, respectively) while WC medium enables nearly no growth. The evolution of nitrate, silicate, and phosphate concentrations in culture media indicated a much better balance of macroelements in the FDMed medium. Fucoxanthin contents within the biomass remained very stable in the FDMed mediumcompared to the other media, in which it gradually decreases, and the best results (around 7.5 mg g-1 dry weight ) were obtained forS. minima in the FDMed medium. EPA could only be measured in the FDMed medium and the highest content (14.0 mg EPAg-1dry weight) was recorded in N. palea. This work demonstrates the great industrial potential of freshwater diatoms and provides an efficient culture medium for those organisms. [less ▲]

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See detailH2O2 signalling from mitochondria and chloroplast to the nucleus in the green microalga Chlamydomonas: in vivo and in vitro approaches
Caccamo, Anna ULiege; Vertommen, Didier; Pyr dit Ruys, Sébastien et al

Poster (2019, December 07)

Reactive oxygen species (ROS) are mainly produced in the mitochondrial (Larosa and Remacle, 2018) and in the photosynthetic electron transport chains (Pospíšil, 2009). Historically, ROS were only ... [more ▼]

Reactive oxygen species (ROS) are mainly produced in the mitochondrial (Larosa and Remacle, 2018) and in the photosynthetic electron transport chains (Pospíšil, 2009). Historically, ROS were only considered as toxic molecules for cells, leading to oxidation of proteins, lipids and DNA. Nowadays, the ROS-molecule H2O2 is increasingly being recognized as a signaling molecule due to the fact that it is relatively stable compared to the other ROS-molecules and H2O2 can potentially travel across membranes (Mittler, 2017). H2O2 signals via rapid reactions with protein cysteine sulfurs, which results in an altered protein structure and function (Pedre et al., 2018). Such cysteine modifications are known as S-sulfenylations (-SOH). So far, hundreds of sulfenylated proteins have been identified in the model plant Arabidopsis thaliana (Waszczak et al., 2014; Akter et al., 2015). In this project we want to (i) identify C. reinhardtii crucial redox enzymes which effect the phenotype under H2O2-stress inducing conditions; (ii) trap and identify sulfenylated proteins involved in the redox signaling, using dimedone-based carbon nucleophiles and mass spectrometry; (iii) in vitro characterize the oxidation kinetics and the oxidation induced structural changes on one of the identified redox-sensing proteins. This work is supported by the Fonds Wetenschappelijk Onderzoek – Vlaanderen (FWO) and the Fonds de la Recherche Scientifique – FNRS under EOS Project No. 30829584. REFERENCES 1.Akter S. et al., (2015) DYn-2 Based identification of Arabidopsis sulfenomes. Mol. Cell Proteomics 14:1183–1200 2.Larosa V. and Remacle C. (2018) Insight the respiratory chain and oxidative stress. Bioscience Rep. 38 BSR20171492 3.Mittler R. (2017) ROS are Good. Trends Plant Sci. 22:11-19 4.Pedre B. et al., (2018) Structural snapshots of OxyR reveal the peroxidatic mechanism of H2O2 sensing. Proc. Natl. Acad. Sci. 115:E11623-E11632 5.Pospíšil P. (2009) Production of reactive oxygen species by photosystem II as a response to light and temperature stress. Biochim Biophys Acta 10:1151-1160 6.Waszczak C. et al., (2014) Sulfenome mining in Arabidopsis thaliana. Proc. Natl. Acad. Sci. 111:11545-11550 [less ▲]

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See detailISOLATION AND CHARACTERIZATION OF A DESMODESMUS SPECIES FROM VIETNAM WITH POTENTIAL FOR THE PRODUCTION OF ANIMAL FEEDSTOCKS AND NUTRACEUTICALS
Luu Thao Nguyen, ULiege; Remacle, Claire ULiege; Eppe, Gauthier ULiege et al

Poster (2019, December 03)

In this work, a microalgal strain (NL3) was isolated using waste water sampled from shrimp cultivation ponds in the central province of Ninh Thuan, Vietnam. The 18S rDNA-ITS region (3492 bp) was sequenced ... [more ▼]

In this work, a microalgal strain (NL3) was isolated using waste water sampled from shrimp cultivation ponds in the central province of Ninh Thuan, Vietnam. The 18S rDNA-ITS region (3492 bp) was sequenced and used for the phylogenetic identification. As a result, the isolate was identified as Desmodesmus sp. NL3, genus Desmodesmus, family Scenedesmaceae. Desmodesmus sp. NL3 is considered as potential production of biomass with the highest biomass obtained at stationary phase of 1.54 ± 0.06 g L-1. Salinity tolerance experiments (10, 20, 30 and 35‰) were conducted. Desmodesmus sp. NL3 was proved to be highly tolerant to the all the salinities tested. The biomass and protein contents were high and did not vary much among those treatments. FAME analyses of the control and salinity treatments showed that fatty acid chain lengths were of C16 – C18 in which C18:2 and C18:3 were dominant. Therefore, this resulted in the high accumulation of PUFA ranging from 65.80% TFA to 71.53% TFA. Of the four salinity treatments, the highest FAME content of 15.59 %DW was recorded in salinity of 35‰. In terms of pigment, HPLC – DAD was employed for the study and the results reported a high accumulation of lutein which was 4.01, 7.00, 5.67 and 2.24 mg/g DW in 10, 20, 30 and 35‰, respectively. [less ▲]

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See detailHeterotrophic growth of microalgae
Carone, Michele ULiege; Corato, Amélie ULiege; Dauvrin, Thomas ULiege et al

in Rampelotto, Pabulo H; Hallman, A (Eds.) Heterotrophic growth of microalgae (2019)

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See detailH2O2 signaling from mitochondria and chloroplast to the nucleus in the green microalga Chlamydomonas: in vivo and in vitro approaches
Caccamo, Anna ULiege; Nguyen, Ho Thuy Dung; Vertommen, Didier et al

Poster (2019, September 17)

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See detailDefining H2O2 signaling from chloroplast and mitochondria to the nucleus in Chlamydomonas reinhardtii
Caccamo, Anna ULiege; Larosa, Véronique ULiege; Messens, Joris et al

Poster (2019, July 11)

Reactive oxygen species (ROS) are mainly produced in the mitochondrial (Larosa and Remacle, 2018) and in the photosynthetic electron transport chains (Pospíšil, 2009). Historically, ROS were only ... [more ▼]

Reactive oxygen species (ROS) are mainly produced in the mitochondrial (Larosa and Remacle, 2018) and in the photosynthetic electron transport chains (Pospíšil, 2009). Historically, ROS were only considered as toxic molecules for cells, leading to oxidation of proteins, lipids and DNA. Nowadays, the ROS-molecule H2O2 is increasingly being recognized as a signaling molecule due to the fact that it is relatively stable compared to the other ROS-molecules and H2O2 can potentially travel across membranes (Mittler, 2017). H2O2 signals via rapid reactions with protein cysteine sulfurs, which results in an altered protein structure and function (Pedre et al., 2018). Such cysteine modifications are known as S-sulfenylations (-SOH). So far, hundreds of sulfenylated proteins have been identified in the model plant Arabidopsis thaliana (Waszczak et al., 2014; Akter et al., 2015). In this project we want to (i) identify C. reinhardtii crucial redox enzymes which effect the phenotype under H2O2-stress inducing conditions; (ii) trap and identify sulfenylated proteins involved in the redox signaling, using dimedone-based carbon nucleophiles and mass spectrometry; (iii) in vitro characterize the oxidation kinetics and the oxidation induced structural changes on one of the identified redox-sensing proteins. [less ▲]

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See detailCharacterization of the GPR1/FUN34/YaaH protein family in the green microalga Chlamydomonas suggests their role as intracellular membrane acetate channels
Durante, Lorenzo ULiege; Hübner, Wolfgang; Lauersen, Kyle J et al

in Plant Direct (2019), 3(6),

The unicellular green microalga Chlamydomonas reinhardtii is a powerful photosynthetic model organism which is capable of heterotrophic growth on acetate as a sole carbon source. This capacity has enabled ... [more ▼]

The unicellular green microalga Chlamydomonas reinhardtii is a powerful photosynthetic model organism which is capable of heterotrophic growth on acetate as a sole carbon source. This capacity has enabled its use for investigations of perturbations in photosynthetic machinery as mutants can be recovered heterotrophically. Fixation of acetate into cellular carbon metabolism occurs first by its conversion into acetyl‐CoA by a respective synthase and the generation of succinate by the glyoxylate cycle. These metabolic steps have been recently determined to largely occur in the peroxisomes of this alga; however, little is known about the trafficking and import of acetate or its subcellular compartmentalization. Recently, the genes of five proteins belonging to the GPR1/FUN34/YaaH (GFY) superfamily were observed to exhibit increased expression in C. reinhardtii upon acetate addition, however, no further characterization has been reported. Here, we provide several lines of evidence to implicate CrGFY1–5 as channels which share structural homology with bacterial succinate‐acetate channels and specifically localize to microbodies, which are surprisingly distinct from the glyoxylate cycle‐containing peroxisomes. We demonstrate structural models, gene expression profiling, and in vivo fluorescence localization of all five isoforms in the algal cell to further support this role. [less ▲]

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