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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 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 detailA MAGIC design to study metal homeostasis in Chlamydomonas reinhardtii
Cardoso Esteves, Sara Marina ULiege; Iacono, Fabrizio ULiege; Jadoul, Alice ULiege et al

Poster (2020, November 17)

Natural trait variation is present across all domains of life. Individuals of the same species often present differences in response to environmental stress or adaptation. Some traits, such as biomass or ... [more ▼]

Natural trait variation is present across all domains of life. Individuals of the same species often present differences in response to environmental stress or adaptation. Some traits, such as biomass or High Value Molecule production, have economical interest in the industrial, pharmaceutical or agricultural sectors. Identifying the genetic variants affecting important biological processes is, therefore, fundamental. Chlamydomonas reinhardtii is the reference unicellular photosynthetic eukaryote model organism. C. reinhardtii is a haploid unicellular green alga capable of sexual reproduction, metabolize alternative carbon sources, growing in the dark and under nutrient deficiency. Furthermore, C. reinhardtii has very short generation interval, a high recombination rate and a relatively small genome, making it a suitable organism for a MAGIC design. In model organisms, genetic variation can be studied using Multiparent Advanced Generation Inter-Cross (MAGIC) designs. In these designs, lines of founders presenting phenotypic variation are intercrossed in a determined design where each founder line contributes equally. This process originates terminal lines where the initial variability is shuffled, forming a genetic mosaic of the founder lines. Three MAGIC designs, consisting of 8 initial founders intercrossed for 8 generations (F8) were made, and a total of 768 progenies were selected in order to study mineral nutrition. Metal homeostasis is assured by an intricate network of metal uptake, chelation, trafficking, and storage processes. Mixotrophy was used as control condition, and 10 conditions were tested: autotrophy, macronutrient deprivation (Ca, Mg, N, P, S), and micronutrient deprivation (Cu, Fe, Mn, Zn), in 96h assays. Here we present the preliminary results of a small subset. [less ▲]

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See detailIn vivo assessment of mitochondrial respiratory alternative oxidase activity and cyclic electron flow around photosystem I on small coral fragments
Vega de Luna, Felix ULiege; Córdoba-Granados, Juan José; Dang, Kieu-Van et al

in Scientific Reports (2020), 10(1), 17514

The mutualistic relationship existing between scleractinian corals and their photosynthetic endosymbionts involves a complex integration of the metabolic pathways within the holobiont. Respiration and ... [more ▼]

The mutualistic relationship existing between scleractinian corals and their photosynthetic endosymbionts involves a complex integration of the metabolic pathways within the holobiont. Respiration and photosynthesis are the most important of these processes and although they have been extensively studied, our understanding of their interactions and regulatory mechanisms is still limited. In this work we performed chlorophyll-a fluorescence, oxygen exchange and time-resolved absorption spectroscopy measurements on small and thin fragments (0.3 cm2) of the coral Stylophora pistillata. We showed that the capacity of mitochondrial alternative oxidase accounted for ca. 25% of total coral respiration, and that the high-light dependent oxygen uptake, commonly present in isolated Symbiodiniaceae, was negligible. The ratio between photosystem I (PSI) and photosystem II (PSII) active centers as well as their respective electron transport rates, indicated that PSI cyclic electron flow occurred in high light in S. pistillata and in some branching and lamellar coral species freshly collected in the field. Altogether, these results show the potential of applying advanced biophysical and spectroscopic methods on small coral fragments to understand the complex mechanisms of coral photosynthesis and respiration and their responses to environmental changes. [less ▲]

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See detailAn antioxidant function for dimethylsulfonopropionate (DMSP) and dimethylsulfoxide (DMSO) within three different phytoplankton groups
Gypens, Nathalie; Roberty, Stéphane ULiege; Borges, Alberto ULiege et al

Poster (2020, May 04)

Dimethylsulfonopropionate (DMSP) and dimethylsulfoxide (DMSO) are two compounds involved in the carbon and sulfur cycle and are the precursors of the climate cooling gas dimethylsulfide (DMS). Despite ... [more ▼]

Dimethylsulfonopropionate (DMSP) and dimethylsulfoxide (DMSO) are two compounds involved in the carbon and sulfur cycle and are the precursors of the climate cooling gas dimethylsulfide (DMS). Despite decades of research, their role as osmoregulator, cryoprotector or antioxidant within the phytoplankton cells remains uncertain in some part. Since the antioxidant cascade system from the DMSP reported by Sunda & al. (2002), more investigation need to be conducted to confirm or accurate these interactions. This study aims to improve the knowledge about DMSP and DMSO and their hypothetic role of antioxidant on three different classes of phytoplankton (Dinophyceae – Prymnesiophyceae – diatom) and one diatom no-DMSP producer Chaetoceros sp. as negative control. Laboratory cultures were submitted to three oxidative stress to produce Reactive Oxygen Species (ROS) with (1) increasing light intensity from 100 to 600 and up to 1200 µmole/m²s for a global and natural oxidative stress; (2) using the menadone bisulfite (MSB) to generate ·O2 and (3) using 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) to inhibit the photosystem II (PSII). The PSII activity, the Chlorophyll a concentration (Chl a), the lipidic peroxidation (LOP), the ROS production and the pigment variation were analysed after 6h of incubation and related to the evolution of the DMSP and DMSO concentrations to better understand the cellular oxidative stress and its impact on the phytoplankton cell and DMSP and DMSO production. [less ▲]

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See detailDifferent levels of energetic coupling between photosynthesis and respiration do not determine the occurrence of adaptive responses of Symbiodiniaceae to global warming
Pierangelini, Mattia ULiege; Thiry, Marc ULiege; Cardol, Pierre ULiege

in New Phytologist (2020)

Disentangling the metabolic functioning of corals' endosymbionts (Symbiodiniaceae) is relevant to understanding the response of coral reefs to warming oceans. In this work, we first question whether there ... [more ▼]

Disentangling the metabolic functioning of corals' endosymbionts (Symbiodiniaceae) is relevant to understanding the response of coral reefs to warming oceans. In this work, we first question whether there is an energetic coupling between photosynthesis and respiration in Symbiodiniaceae (Symbiodinium, Durusdinium and Effrenium), and second, how different levels of energetic coupling will affect their adaptive responses to global warming. Coupling between photosynthesis and respiration was established by determining the variation of metabolic rates during thermal response curves, and how inhibition of respiration affects photosynthesis. Adaptive (irreversible) responses were studied by exposing two Symbiodinium species with different levels of photosynthesis–respiration interaction to high temperature conditions (32°C) for 1 yr. We found that some Symbiodiniaceae have a high level of energetic coupling; that is, photosynthesis and respiration have the same temperature dependency, and photosynthesis is negatively affected when respiration is inhibited. Conversely, photosynthesis and respiration are not coupled in other species. In any case, prolonged exposure to high temperature caused adjustments in both photosynthesis and respiration, but these changes were fully reversible. We conclude that energetic coupling between photosynthesis and respiration exhibits wide variation amongst Symbiodiniaceae and does not determine the occurrence of adaptive responses in Symbiodiniaceae to temperature increase. [less ▲]

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See detailAlternative Photosynthetic Electron Transfers and Bleaching Phenotypes Upon Acute Heat Stress in Symbiodinium and Breviolum spp. (Symbiodiniaceae) in Culture
Dang, Thi Kieu Van ULiege; Pierangelini, Mattia ULiege; Roberty, Stéphane ULiege et al

in Frontiers in Marine Science (2019)

The breakdown of the symbiosis between cnidarians and Symbiodiniaceae often occurs upon periods of elevated sea surface temperature and gives rise to bleaching events that affect coral reefs worldwide. In ... [more ▼]

The breakdown of the symbiosis between cnidarians and Symbiodiniaceae often occurs upon periods of elevated sea surface temperature and gives rise to bleaching events that affect coral reefs worldwide. In this respect, an impairment of photosynthesis would be responsible for light-dependent generation of toxic reactive oxygen species putatively contributing to death of symbionts and/or host cells. In some Symbiodiniaceae species, alternative photosynthetic electron flows (AEF) have been documented to occur upon a shift to high temperature, possibly contributing to photoprotection and to the balance of energetic ratio between photoproduced ATP and NADPH. By using a combination of in vivo spectrofluorimetric and oximetric techniques, we studied the capacity for electron rerouting toward oxygen and cyclic electron flow (CEF) around photosystem I in eight Symbiodiniaceae in culture belonging to Symbiodinium and Breviolum genera upon an acute shift from 25 to 33°C. CEF capacity was determined as the kinetic of PSI primary donor P700 re-reduction in the presence of DCMU, a PSII inhibitor. An active oxygen uptake in light was estimated by comparing net oxygen evolution and relative electron transport rate of PSII at different light intensities. Among strains that showed elevated capacity for both AEF, some were thermotolerant while others were thermosensitive. Conversely, in some thermotolerant strains, capacities for these AEF were low upon acute heat stress. A principal component analysis of these results indicates that the long-term heat tolerant/bleached phenotype of cultured Symbiodinium and Breviolum spp. is not correlated with a capacity for different AEF across isolates during early onset of acute heat stress. [less ▲]

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See detailDesigning an Open-hardware Remotely Controllable Phototurbidostat for Studying Algal Growth
Gervasi, Alain ULiege; Cardol, Pierre ULiege; Meyer, Patrick ULiege

in 3rd International Conference on Computational Biology and Bioinformatics (2019, October)

Keeping an algal culture at a constant turbidity requires expensive and complex devices. We designed a low-cost, user friendly but also highly configurable phototurbidostat using 3D-printing, open-source ... [more ▼]

Keeping an algal culture at a constant turbidity requires expensive and complex devices. We designed a low-cost, user friendly but also highly configurable phototurbidostat using 3D-printing, open-source software and electronics. The device is able to monitor in real time a culture in photobioreactor, and dynamically adjust the conditions to maintain the turbidity at a desired value. It can accommodate to a large set of volumes or laboratory equipments with little effort thanks to its modular and scalable design. Each module (such as light, pumps or sensors) are autonomous and controllable via Wi-Fi. Furthermore, our phototurbidostat is fully open-source and can be remotely controlled by a smartphone or a computer via a web-based graphical user interface. Finally, the device can be reproduced easily for a cost ranging between 1/20th and 1/50th of the price of a classical commercial device [less ▲]

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See detailGenetic Mapping of Quantitative Trait Loci (QTLs) involved in photosynthesis in Chlamydomonas reinhardtii
Iacono, Fabrizio ULiege; Cardoso Esteves, Sara Marina ULiege; Houet, Rebecca ULiege et al

Poster (2019, July 21)

Multi-Parent Advanced Generation Inter-Cross (MAGIC) populations have been developed for several model organisms proving to be a powerful mapping resource in quantitative genetics. Chlamydomonas ... [more ▼]

Multi-Parent Advanced Generation Inter-Cross (MAGIC) populations have been developed for several model organisms proving to be a powerful mapping resource in quantitative genetics. Chlamydomonas reinhardtii is a unicellular haploid green alga studied for decades as model organism to understand the nature and dynamics of photosynthesis. The genome of this species has been previously shown to harbor extensive genetic variation; a precious source of information to dissect the polygenic nature of quantitative traits. Here, we use eight divergent founder strains of C. reinhardtii to develop a MAGIC population constituted of about one thousand Advanced Inter-Crossed Lines (AILs). Once created, the MAGIC population will be employed to map quantitative trait loci (QTLs) correlated to photosynthesis and growth. [less ▲]

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See detailPhotosynthetic capacity of the endosymbiotic dinoflagellate Cladocopium sp. is preserved during digestion of its jellyfish host Mastigias papua by the anemone Entacmaea medusivora
Vega de Luna, Felix ULiege; Dang, Thi Kieu Van ULiege; Cardol, Mila et al

in FEMS microbiology ecology (2019), 95(10),

The sea anemone Entacmaea medusivora (Actiniaria, Anthozoa) commonly feeds on the golden jellyfish Mastigias papua (Rhizostomeae, Scyphozoa) which harbours an endosymbiotic dinoflagellate of the genus ... [more ▼]

The sea anemone Entacmaea medusivora (Actiniaria, Anthozoa) commonly feeds on the golden jellyfish Mastigias papua (Rhizostomeae, Scyphozoa) which harbours an endosymbiotic dinoflagellate of the genus Cladocopium (Symbiodiniaceae). In this study, we monitored the photosynthetic activity of the endosymbiotic microalgae while their host jellyfish were ingested and digested by starved medusivorous anemones. By analyzing the photosynthetic yield of photosystem II, we observed that Cladocopium cells remain photosynthetically competent during the whole digestion process, thus confirming the exceptional resistance of Symbiodiniaceae to digestive enzymes. In the gastric cavity of E. medusivora, Cladocopium cells release oxygen, which could broadly stimulate the gastric microbiotic flora of the sea anemone. Ultimately, E. medusivora is not able to retain Cladocopium cells more than few days and physiologically-unaltered cells are therefore expelled in faecal pellets. The potential contribution of E. medusivora to maintain a reservoir of Cladocopium symbionts and its role in the life cycle of M. papua is discussed. © FEMS 2019. [less ▲]

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