Yonghua Li-Beisson

• PhD HDR
• Researcher at Atomic Energy and Alternative Energies Commission

This book summarizes recent advances in understanding the functions of plant and algal lipids in photosynthesis, in development and signaling, and in industrial applications. As readers will discover, biochemistry, enzymology and analytical chemistry, as well as gene knock-out studies have all contributed to our rapidly increasing understanding of...

In photosynthetic organisms, light acts as an environmental signal to control their development and physiology, as well as energy source to drive the conversion of CO2 into carbohydrates used for growth or storage. The main storage carbohydrate in green algae is starch, which accumulates during the day and is broken down at night to meet cellular e...

The first step in chloroplast de novo fatty acid synthesis is catalysed by acetyl‐CoA carboxylase (ACCase). As the rate‐limiting step for this pathway, ACCase is subject to both positive and negative regulation. In this study, we identify a Chlamydomonas homologue of the plant carboxyltransferase interactor 1 (CrCTI1) and show that this protein int...

Nitrogen (N) scarcity frequently constrains global biomass productivity. N deficiency halts cell division, downregulates photosynthetic electron transfer, and enhances carbon storage. However, the molecular mechanism downregulating photosynthesis during N deficiency and its relationship with carbon storage are not fully understood. Proton Gradient...

Increasing CO 2 availability is a common practice at the industrial level to trigger biomass productivity in microalgae cultures. Still, the consequences of high CO 2 availability in microalgal cells exposed to relatively high light require further investigation. Here, the photosynthetic, physiologic, and metabolic responses of the green microalga...

Lipid droplets (LDs) are the major sites of lipid and energy homeostasis. However, few LD biogenesis proteins have been identified. Using model microalga Chlamydomonas, we show that ABHD1, an α/β-hydrolase domain-containing protein, is localized to the LD surface and stimulates LD formation through two actions: one enzymatic and one structural. The...

The cell wall of plants and algae is an important cell structure that protects cells from changes in the external physical and chemical environment. This extracellular matrix, composed of polysaccharides and glycoproteins, must be constantly remodeled throughout the life cycle. However, compared to matrix polysaccharides, little is known about the...

The committed step for de novo fatty acid (FA) synthesis is the ATP-dependent carboxylation of acetyl-coenzyme A catalysed by acetyl-CoA carboxylase (ACCase). In most plants, ACCase is a multi-subunit complex orthologous to prokaryotes. However, unlike prokaryotes, the plant and algal orthologues are comprised both catalytic and additional dedicate...

Due to low availability of CO2 in aquatic environment, microalgae have evolved a CO2 concentrating mechanism (CCM). It has long been thought that operation of CCM would suppress photorespiration by increasing the CO2 concentration at the Rubisco active site, but experimental evidence is scarce. To better explore the function of photorespiration in...

The first step in chloroplast de novo fatty acid synthesis is catalyzed by acetyl-CoA carboxylase (ACCase). As the rate-limiting step for this pathway, ACCase is subject to both positive and negative regulation. In this study, we identify a Chlamydomonas homolog of the plant carboxyltransferase interactor 1 (CrCTI1) and show that this protein, inte...

Fatty Acid Photodecarboxylase (FAP) has emerged as a promising catalyst for the biological production of long-chain hydrocarbons. We have recently shown that purified FAP or FAP-expressing bacteria can efficiently convert octanoic acid into heptane, thus extending the potential applications of FAP to medium-chain hydrocarbons (i.e., solvent- or ker...

Alka(e)nes are produced by many living organisms and exhibit diverse physiological roles, reflecting a high functional versatility. Alka(e)nes serve as waterproof wax in plants, communicating pheromones for insects, and microbial signaling molecules in some bacteria. Although alka(e)nes have been found in cyanobacteria and algal chloroplasts, their...

Microalgae contribute to about half of global net photosynthesis, which converts sunlight into the chemical energy (ATP and NADPH) used to transform CO2 into biomass. Alternative electron pathways of photosynthesis have been proposed to generate additional ATP that is required to sustain CO2 fixation. However, the relative importance of each altern...

Microalgae are emerging as a promising feedstock for bioplastics, with Chlorella vulgaris yielding significant amounts of starch. This polysaccharide is convertible into thermoplastic starch (TPS), a biodegradable plastic of industrial relevance. In this study, we developed a pilot-scale protocol for extracting and purifying starch from starch-enri...

Microalgae are eukaryotic photosynthetic micro-organisms that convert CO2 into carbohydrates, lipids, and other valuable metabolites. They are considered promising chassis for the production of various bioproducts, including fatty acid–derived biofuels. However, algae-based biofuels are not yet commercially available, mainly because of their l...

In photosynthetic organisms light acts as an environmental signal to control their development and physiology, and as energy source to drive the conversion of CO2 into carbohydrates used for growth or storage. The main storage carbohydrate in green algae is starch, which accumulates during the day and is broken down at night to meet cellular energy...

Plants are a treasure trove of metabolic compounds. The chemical diversity of plant cells has developed and been maintained through evolution and metabolic regulation, and plays a crucial role in plant physiology, development, and adaption to changing environmental situations. Metabolomics, when combined with genomics and proteomics, has opened up...

In photosynthetic organisms light acts as an environmental signal to control their development and physiology, and as energy source to drive the conversion of CO 2 into carbohydrates used for growth or storage. The main storage carbohydrate in green algae is starch, which accumulates during the day and is broken down at night to meet cellular energ...

The cell wall of plants and algae is an important cell structure that protects cells from changes in the external physical and chemical environment. This extracellular matrix composed of polysaccharides and glycoproteins, is needed to be remodeled continuously throughout the life cycle. However, compared to matrix polysaccharides, little is known a...

Lipid droplets (LDs) are the major sites of lipid and energy homeostasis. However, few LD biogenesis proteins have been identified. Here, using Chlamydomonas as a model, we show that ABHD1, a member of the α/β hydrolase domain-containing protein family, is a novel type of LD-associated protein which stimulates LD formation through two distinct acti...

Alka(e)nes are produced by many living organisms and exhibit diverse physiological roles, reflecting a high functional versatility. Alka(e)nes serve as water proof wax in plants, communicating pheromones for insects, and microbial signaling molecules in some bacteria. Although alka(e)nes have been found in cyanobacteria and algal chloroplasts, a po...

Diatoms (Bacillariophyceae) accumulate neutral storage lipids in lipid droplets during stress conditions, which can be rapidly degraded and recycled when optimal conditions resume. Since nutrient and light availability fluctuate in marine environments, storage lipid turnover is essential for diatom dominance of marine ecosystems. Diatoms have garne...

On Earth, microalgae contribute to about half of global net photosynthesis. During photosynthesis, sunlight is converted into chemical energy (ATP and NADPH) used by metabolism to convert CO2 into biomass. Alternative electron pathways of photosynthesis have been proposed to generate additional ATP that is required for sustaining CO2 fixation, but...

Plant lipids are important as alternative sources of carbon and energy when sugars or starch are limited. Here, we applied combined heat and darkness or extended darkness to a panel of ∼ 300 Arabidopsis (Arabidopsis thaliana) accessions to study lipid remodeling under carbon starvation. Natural allelic variation at 3-KETOACYL-COENZYME A SYNTHASE4 (...

Genetic crossing is routinely applied to alter multigenic traits in the unicellular model green microalga Chlamydomonas reinhardtii (Chlamydomonas). However, efficient antibiotic resistance-based screening for the desired progenies is impossible through the conventional approach when two parental strains are harboring the same antibiotic marker. In...

Nitrogen (N) scarcity is a frequently encountered situation that constrains global biomass productivity. In response to N deficiency, cell division stops and photosynthetic electron transfer is downregulated, while carbon storage is enhanced. However, the molecular mechanism downregulating photosynthesis during N deficiency and its relationship wit...

SEALIVE and Nenu2PHAr European projects are both dedicated to produce biodegradable and biosourced plastics. Microalgae can provide material for the manufacture of plastics currently obtained from petrol or food crop. Starch is notably used as a natural biopolymer base to be integrated in plastics blends, and can also be degraded into monomeric glu...

In algae and land plants, transport of fatty acids (FAs) from their site of synthesis in the plastid stroma to the endoplasmic reticulum (ER) for assembly into acyl lipids is crucial for cellular lipid homeostasis, including the biosynthesis of triacylglycerol (TAG) for energy storage. In the unicellular green alga Chlamydomonas reinhardtii , under...

The nucleotides guanosine tetraphosphate and pentaphosphate (or (p)ppGpp) are implicated in the regulation of chloroplast function in plants. (p)ppGpp signalling is best understood in the model vascular plant Arabidopsis thaliana in which it acts to regulate plastid gene expression to influence photosynthesis, plant development and immunity. Howeve...

Photosynthetic organisms have developed sophisticated strategies to fine-tune light energy conversion to meet the metabolic demand, thereby optimizing growth in fluctuating light environments. Although mechanisms such as energy dissipation, photosynthetic control, or the photosystem II (PSII) damage and repair have been widely studied, little is kn...

Global photosynthesis consumes ten times more CO2 than net anthropogenic emissions, and microalgae account for nearly half of this consumption¹. The high efficiency of algal photosynthesis relies on a mechanism concentrating CO2 (CCM) at the catalytic site of the carboxylating enzyme RuBisCO, which enhances CO2 fixation². Although many cellular com...

Microalgae accumulate high levels of oil under stress, but the underlying biosynthetic pathways are not fully understood. We sought to identify key regulators of lipid metabolism under stress conditions. We found that the Chlamydomonas reinhardtii gene encoding the MYB‐type transcription factor MYB1 is highly induced under stress conditions. Two my...

Long‐chain acyl‐CoA synthetases (LACSs) play many roles in mammals, yeasts and plants, but knowledge on their functions in microalgae remains fragmented. Here via genetic, biochemical and physiological analyses, we unraveled the function and roles of LACSs in the model microalga Chlamydomonas reinhardtii. In vitro assays on purified recombinant pro...

Subcellular compartmentalization confers evolutionary advantage to eukaryotic cells but entails the need for efficient interorganelle communication. Malate functions as redox carrier and metabolic intermediate. It can be shuttled across membranes through translocators. The interconversion of malate and oxaloacetate mediated by malate dehydrogenases...

Wildlife is chronically exposed to various sources of ionizing radiations, both environmental or anthropic, due to nuclear energy use, which can induce several defects in organisms. In invertebrates, reproduction, which directly impacts population dynamics, has been found to be the most radiosensitive endpoint. Understanding the underlying molecula...

Lipid droplets (LDs) are ubiquitous and specialized organelles in eukaryotic cells. Consisting of a triacylglycerol core surrounded by a monolayer of membrane lipids, LDs are decorated with proteins and have myriad functions, from carbon/energy storage to membrane lipid remodeling and signal transduction. The biogenesis and turnover of LDs are ther...

Microalgae represent a potential solution to reduce CO2 emission exploiting their photosynthetic activity. Here, the physiologic and metabolic responses at the base of CO2 assimilation were investigated in conditions of high or low CO2 availability in two of the most promising algae species for industrial cultivation, Chlorella sorokiniana and Chlo...

Fatty acid photodecarboxylase (FAP) is one of the few enzymes that require light for their catalytic cycle (photoenzymes). FAP was first identified in the microalga Chlorella variabilis NC64A, and belongs to an algae-specific subgroup of the glucose-methanol-choline oxidoreductase family. While the FAP from C. variabilis and its Chlamydomonas reinh...

Chloroplasts retain elements of a bacterial stress response pathway that is mediated by the signalling nucleotides guanosine penta‐ and tetraphosphate ((p)ppGpp). In the model flowering plant Arabidopsis, ppGpp acts as a potent regulator of plastid gene expression and influences photosynthesis, plant growth and development. However, little is known...

Global photosynthesis consumes ten times more CO 2 than net anthropogenic emissions, and microalgae account for nearly half of this consumption ¹ . The great efficiency of algal photosynthesis relies on a mechanism concentrating CO 2 (CCM) at the catalytic site of the carboxylating enzyme RuBisCO, thus enhancing CO 2 fixation ² . While many cellula...

Microalgae represent potential solutions to reduce the atmospheric CO 2 level through photosynthesis. To boost CO 2 fixation by microalgae it is essential to understand physiologic and metabolic responses at the base of CO 2 assimilation and carbon flow. In this work two Trebouxiophyceae species, Chlorella sorokiniana and Chlorella vulgaris , were...

The nucleotides guanosine tetraphosphate and pentaphosphate (or ppGpp) are implicated in the regulation of chloroplast function in plants. ppGpp signalling is best understood in the model vascular plant Arabidopsis thaliana where it acts to regulate plastid gene expression to influence photosynthesis, plant development and immunity. However, little...

[This corrects the article DOI: 10.3389/fpls.2020.01302.].

The unicellular industrial oleaginous microalgae Nannochloropsis spp. are model organisms for microalgal systems and synthetic biology. To facilitate community‐based annotation and mining of the rapidly accumulated functional genomics resources, we have initiated an international consortium and present a comprehensive, multi‐omics resource database...

Since the first great oxygenation event, photosynthetic microorganisms have continuously shaped the Earth’s atmosphere. Studying biological mechanisms involved in the interaction between microalgae and cyanobacteria with the Earth’s atmosphere requires the monitoring of gas exchange. Membrane inlet mass spectrometry (MIMS) has been developed in the...

Significance Intracellular lipid droplets (LDs) are formed under stress conditions in many organisms, including microalgae such as Chlamydomonas reinhardtii . When the stress is relieved, the cells degrade triacylglycerols (TAGs) stored in the LDs and resume growth. To decipher the mechanism of LD degradation, we screened for Chlamydomonas mutants...

Due to their sessile lifestyle, plants have evolved unique mechanisms to deal with environmental challenges. Under stress, plant lipids are important as alternative sources of carbon and energy when sugars or starch are limited. Here, we applied combined heat and darkness and extended darkness to a panel of ∼ 300 Arabidopsis accessions to study lip...

Fatty acid photodecarboxylase (FAP) is one of the three enzymes that require light for their catalytic cycle (photoenzymes). FAP has been first identified in the green microalga Chlorella variabilis NC64A and belongs an algae-specific subgroup of the glucose-methanol-choline oxidoreductase family. While the FAP from Chlorella and its Chlamydomonas...

The plant kingdom contains an abundance of structurally diverse fatty acids referred to as unusual fatty acids. Unusual fatty acids on plant surfaces can form polyesters that contribute to the function of cutin as a barrier for water loss and pathogen protection. Unusual fatty acids are also found as abundant components of seed oils of selected spe...

Microalgae are continuously shaping Earth’s atmosphere through oxygenic photosynthesis, and nowadays, half of the photosynthesis is attributed to microbial photosynthesis (Field et al., 1998; Behrenfeld et al., 2005). While algal photosynthesis contributes to offsetting the CO2 footprint, it also produces N2O, a potent greenhouse gas. In some ecolo...

Chloroplasts retain elements of a bacterial stress response pathway that is mediated by the signalling nucleotides guanosine penta-and tetraphosphate, or (p)ppGpp. In the model flowering plant Arabidopsis, ppGpp acts as a potent regulator of plastid gene expression and influences photosynthesis, plant growth and development. However, little is know...

Nitrous oxide (N 2 O), a potent greenhouse gas in the atmosphere, is produced mostly from aquatic ecosystems, to which algae substantially contribute. However, mechanisms of N 2 O production by pho-tosynthetic organisms are poorly described. Here we show that the green microalga Chlamydomonas reinhardtii reduces NO into N 2 O using the photosynthet...

Intracellular lipid droplets (LDs) are receiving increasing interest from the scientific community, notably because of their link with metabolic diseases (obesity, diabetes) and the production of lipid-derived biofuels in microorganisms. Understanding the biogenesis and fate of LDs upon energy mobilization is essential to monitor fat storage in adi...

Microalgae have emerged as a promising platform for production of carbon-and energy-rich molecules, notably starch and oil. Establishing an economically viable algal biotechnology sector requires a holistic understanding of algal photosynthesis, physiology, cell cycle and metabolism. Starch/oil productivity is a combined effect of their cellular co...

Use of microbes to produce liquid transportation fuels is not yet economically viable. A key point to reduce production costs is the design a cell factory that combines the continuous production of drop-in fuel molecules with the ability to recover products from the cell culture at low cost. Medium-chain hydrocarbons seem ideal targets because they...

The use of algal biomass for biofuel production requires improvements in both biomass productivity and its energy density. Green microalgae store starch and oil as two major forms of carbon reserves. Current strategies to increase the amount of carbon reserves often compromise algal growth. To better understand the cellular mechanisms connecting ce...

https://www.biorxiv.org/content/10.1101/745463v1 Nitrous oxide (N2O), a potent greenhouse gas in the atmosphere, is produced mostly from aquatic ecosystems, to which algae substantially contribute. However, mechanisms of N2O production by photosynthetic organisms are poorly described. Here, we show that the green microalga Chlamydomonas reinhardtii...

Chlorella vulgaris is a fast‐growing fresh‐water microalga cultivated at the industrial scale for applications ranging from food to biofuel production. To advance our understanding of its biology and to establish genetics tools for biotechnological manipulation, we sequenced the nuclear and organelle genomes of Chlorella vulgaris 211/11P by combini...

Algal lipid metabolism fascinates both scientists and entrepreneurs due to the large diversity of fatty acyl structures that algae produce. Algae have therefore long been studied as sources of genes for novel fatty acids; and, due to their superior biomass productivity, algae are also considered a potential feedstock for biofuels. However, a major...

Endoplasmic reticulum (ER) stress is caused by the stress-induced accumulation of unfolded proteins in the ER. Here, we identified proteins and lipids that function downstream of the ER stress sensor INOSITOL-REQUIRING ENZYME1 (CrIRE1) that contributes to ER stress tolerance in Chlamydomonas (Chlamydomonas reinhardtii). Treatment with the ER stress...

Degradation of the storage compound triacylglycerol (TAG) is a crucial process in response to environmental stimuli. In microalgae, this process is important for re-growth when conditions become favorable after cells have experienced stresses. Mobilization of TAG is initiated by actions of lipases causing the release of glycerol and free fatty acid...

Chlamydomonas reinhardtii represents an ideal model microbial system to decipher starch metabolism. In this green algae, in cells growing in photosynthetic conditions, starch mainly accumulates as a sheath surrounding the pyrenoid while in cells subjected to a nutrient starvation, numerous starch granules are filling up the plastid stroma. The mech...

Nitrogen (N) starvation-induced triacylglycerol (TAG) synthesis and its complex relationship with starch metabolism in algal cells has been intensively studied; however, few studies have examined the interaction between amino acid metabolism and TAG biosynthesis. Here, via a forward genetic screen for TAG homeostasis, we isolated a Chlamydomonas mu...

Microalgae constitute a highly diverse group of eukaryotic and photosynthetic microorganisms that have developed extremely efficient systems for harvesting and transforming solar energy into energy-rich molecules such as lipids. Although microalgae are considered to be one of the most promising platforms for the sustainable production of liquid oil...

We found that Chlamydomonas reinhardtii, a model microalga, produces triacylglycerols (TAGs) when the cell pellet is left overnight after centrifugation. The centrifuged cells produce three times more TAGs than those cultured in a nitrogen (N) depletion condition in the first 24 h. The chloroplast membranes of the centrifuged cells are largely disr...

Plants and algae must tightly coordinate photosynthetic electron transport and metabolic activities 30given that they often face fluctuating light and nutrient conditions. The exchange of metabolites and 31signaling molecules between organelles is thought to be central to this regulation but evidence for this 32is still fragmentary. Here we show th...

Phosphate starvation-mediated induction of the HAD-type phosphatases PPsPase1 (AT1G73010) and PECP1 (AT1G17710) has been reported in Arabidopsis. However, little is known about their in vivo function or impact on plant responses to nutrient deficiency. The preferences of PPsPase1 and PECP1 for different substrates have been studied in vitro but req...

Lipid degradation processes are important in microalgae because survival and growth of microalgal cells under fluctuating environmental conditions require permanent remodeling or turnover of membrane lipids as well as rapid mobilization of storage lipids. Lipid catabolism comprises two major spatially and temporarily separated steps, namely lipolys...

Chlamydomonas reinhardtii is frequently used as a model organism to study fundamental processes in photosynthesis, metabolism, and flagellar biology. Versatile tool boxes have been developed for this alga ( Fuhrmann et al., 1999 ; Schroda et al., 2000 ; Schroda, 2006). Among them, forward genetic approach has been intensively used, mostly because o...

The MEX1 locus of Chlamydomonas reinhardtii was identified in a genetic screen as a factor that affects starch metabolism. Mutation of MEX1 causes a slow-down in the mobilization of storage polysaccharide. Cosegregation and functional complementation analyses were used to assess the involvement of the Mex1 protein in starch degradation. Heterologou...

In plants, de novo synthesis of fatty acids (FAs) occurs in plastids, whereas assembly and modification of acyl lipids is accomplished in the endoplasmic reticulum (ER) and plastids as well as in mitochondria. Subsequently, lipophilic compounds are distributed within the cell and delivered to their destination site. Thus, constant acyl-exchanges be...

Algal enzyme driven by blue light Microalgae make hydrocarbons. In searching for the enzyme responsible, Sorigué et al. found a glucose-methanolcholine oxidoreductase (see the Perspective by Scrutton). Expression of the enzyme in Escherichia coli showed that hydrocarbon production requires visible light. In fact, the enzyme requires a constant inpu...