Ions channels/transporters and chloroplast regulation.

2015

International audience; Ions play fundamental roles in all living cells and their gradients are often essential to fuel transports, to regulate enzyme activities and to transduce energy within and between cells. Their homeostasis is therefore an essential component of the cell metabolism. Ions must be imported from the extracellular matrix to their final subcellular compartments. Among them, the chloroplast is a particularly interesting example because there, ions not only modulate enzyme activities, but also mediate ATP synthesis and actively participate in the building of the photosynthetic structures by promoting membrane-membrane interaction. In this review, we first provide a comprehen…

The Water to Water Cycles in Microalgae.

2016

In oxygenic photosynthesis, light produces ATP plus NADPH via linear electron transfer, i.e. the in-series activity of the two photosystems: PSI and PSII. This process, however, is thought not to be sufficient to provide enough ATP per NADPH for carbon assimilation in the Calvin-Benson-Bassham cycle. Thus, it is assumed that additional ATP can be generated by alternative electron pathways. These circuits produce an electrochemical proton gradient without NADPH synthesis, and, although they often represent a small proportion of the linear electron flow, they could have a huge importance in optimizing CO2 assimilation. In Viridiplantae, there is a consensus that alternative electron flow comp…

A systems-wide understanding of photosynthetic acclimation in algae and higher plants

2017

The ability of phototrophs to colonise different environments relies on robust protection against oxidative stress, a critical requirement for the successful evolutionary transition from water to land. Photosynthetic organisms have developed numerous strategies to adapt their photosynthetic apparatus to changing light conditions in order to optimise their photosynthetic yield, which is crucial for life on Earth to exist. Photosynthetic acclimation is an excellent example of the complexity of biological systems, where highly diverse processes, ranging from electron excitation over protein protonation to enzymatic processes coupling ion gradients with biosynthetic activity, interact on drasti…

Membrane glycerolipid remodeling triggered by nitrogen and phosphorus starvation in Phaeodactylum tricornutum.

2014

International audience; Diatoms constitute a major phylum of phytoplankton biodiversity in ocean water and freshwater ecosystems. They are known to respond to some chemical variations of the environment by the accumulation of triacylglycerol, but the relative changes occurring in membrane glycerolipids have not yet been studied. Our goal was first to define a reference for the glycerolipidome of the marine model diatom Phaeodactylum tricornutum, a necessary prerequisite to characterize and dissect the lipid metabolic routes that are orchestrated and regulated to build up each subcellular membrane compartment. By combining multiple analytical techniques, we determined the glycerolipid profil…

Investigating mixotrophic metabolism in the model diatom Phaeodactylum tricornutum.

2017

Diatoms are prominent marine microalgae, interesting not only from an ecological point of view, but also for their possible use in biotechnology applications. They can be cultivated in phototrophic conditions, using sunlight as the sole energy source. Some diatoms, however, can also grow in a mixotrophic mode, wherein both light and external reduced carbon contribute to biomass accumulation. In this study, we investigated the consequences of mixotrophy on the growth and metabolism of the pennate diatom Phaeodactylum tricornutum , using glycerol as the source of reduced carbon. Transcriptomics, metabolomics, metabolic modelling and physiological data combine to indicate that glycerol affect…

Energetic coupling between plastids and mitochondria drives CO2 assimilation in diatoms.

2015

International audience; 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 prin…

Contributory presentations/posters

1999

Boosting Biomass Quantity and Quality by Improved Mixotrophic Culture of the Diatom Phaeodactylum tricornutum

2021

Diatoms are photoautotrophic unicellular algae and are among the most abundant, adaptable, and diverse marine phytoplankton. They are extremely interesting not only for their ecological role but also as potential feedstocks for sustainable biofuels and high-value commodities such as omega fatty acids, because of their capacity to accumulate lipids. However, the cultivation of microalgae on an industrial scale requires higher cell densities and lipid accumulation than those found in nature to make the process economically viable. One of the known ways to induce lipid accumulation in Phaeodactylum tricornutum is nitrogen deprivation, which comes at the expense of growth inhibition and lower c…

Supplementary Fig. 4 A Respiration and photosynthesis in P. tricornutum cells from Investigating mixotrophic metabolism in the model diatom Phaeodact…

2017

Direct assessment of oxygen consumption by a polarographic approach in both phototrophy (black bar) and mix-otrophy (red bar). B. Fluorescent based-assay to monitoring the changes in respiration using the Redox Dye A in presence of the selected compounds (see methods).

Supplementary Fig. 1 Quantitative analysis of P. tricornutum glycerolipids from Investigating mixotrophic metabolism in the model diatom Phaeodactylu…

2017

TAG profile in a total lipid extract from cells grown in replete conditions (A) and deplete conditions (B) in both mixotrophic and phototrophic mode. Glycerolipids are expressed in nmol / mg of dry cells. Each result is the average of two biological replicates ± SD. PHOT: light in N-replete condition; PHOTO-N: light in N-deplete condi-tion; MIX: light+glycerol in N-replete condition; MIX-N: light+glycerol in N-deplete condition.

Supplementary Fig. 2 Membrane lipid composition in P. tricornutum from Investigating mixotrophic metabolism in the model diatom Phaeodactylum tricorn…

2017

Lipid analysis of cells grow in N-replete conditions and N-deplete conditions in both mixotrophic and phototrophic mode. Each result is the average of two biological replicates ± SD. SQDG, sulfoquinovosyldiacylglycerol; DGDG, digalactosyldiacylglycerol; MGDG, monogalactosyldiacylglycerol; PC, phosphatidylcholine; PHOT: light in N-replete condition; PHOTO-N: light in N-deplete condition; MIX: light+glycerol in N-replete condition; MIX-N: light+glycerol in N-deplete condition.

Supplementary Fig. 3 Quantification of intracellular pyruvate by a fluorescence-based method from Investigating mixotrophic metabolism in the model d…

2017

A. Pyruvate standard curve. B. Quantification of intracellular pyruvate in cells grown in phototrophy (PHOT) and mixotrophy (MIX).

Supplementary Fig. 5 Screening of mixotrophic efficiency by biolog and redox dye assay in P. tricornutum from Investigating mixotrophic metabolism in…

2017

A. OD750 nm changes (relative to phototrophic growth) of P. tricornutum cells grown for 6 days in BiologTM plates P1 and PM2A that contains 190 carbon compounds (see methods). Each data point represents a different com-pound. B. Growth profile of P. tricornutum on few selected compounds (at 20 mM) and a phototrophic control in 100 mL flasks. C. Areas under the growth curves of Supplementary Fig. 5B normalized to the area of the curve of phototrophic growth.