Monospecific renaming within the cyanobacterial genus Limnospira (Spirulina) and consequences for food authorization.

AIMS: The cyanobacterial genus, Limnospira (anc. Arthrospira Stizenberger ex Gomont 1892), commonly called "Spirulina", is widely used for commercial purposes because of its high protein content and beneficial probiotic metabolites. Thus, the taxonomy of this genus is important because of its consequences for food applications. METHODS AND RESULTS: We constructed a database with formation on all Limnospira strains plus new ones from 72 new French isolates. We used a polyphasic approach (phylogenetic, phylogenomic, presence or absence of coding DNA sequences, morphological, and ultrastructure analyses) to confirm that the species A. platensis belonged to the genus Limnospira (L. platensis Gomont comb. nov. Basionym. Arthrospira platensis Gomont 1892) and that the genus Limnospira was monospecific, only represented by L. platensis. CONCLUSIONS: This study highlighted the large intra-specific diversity of L. platensis, independent of the affiliations of the phylogenetic clades or geographical location of the habitats and the subsequent physiological and metabolic plasticity.

Correction to: Docking and in silico toxicity assessment of Arthrospira compounds as potential antiviral agents against SARS-CoV-2.

[This corrects the article DOI: 10.1007/s10811-021-02372-9.].

Docking and in silico toxicity assessment of Arthrospira compounds as potential antiviral agents against SARS-CoV-2.

A race is currently being launched as a result of the international health situation. This race aims to find, by various means, weapons to counter the Covid-19 pandemic now widespread on all continents. The aquatic world and in particular that of photosynthetic organisms is regularly highlighted but paradoxically little exploited in view of the tremendous possibilities it offers. Computational tools allow not only to clear the existence and activity of many molecules but also to model their relationships with receptors identified in potential hosts. On a routine basis, our laboratory carries out a research activity on functionalities of molecules derived from algae using in silico tools. We have implemented our skills in algae biology and in modeling, as tests in order to identify molecules expressed by the genus Arthrospira showing an antiviral potential and more particularly anti-SARS-CoV-2. Using consensus docking and redocking with Autodock Vina and SwissDock, we were able to identify several promising molecules from Arthrospira: phycocyanobilin, phycoerythrobilin, phycourobilin, and folic acid. These four compounds showed reliable binding energies comprised between - 6.95 and - 7.45 kcal.mol-1 in Autodock Vina and between - 9.285 and - 10.35 kcal.mol-1 with SwissDock. Toxicity prediction as well as current regulations provided promising arguments for the inclusion of these compounds in further studies to assess their ability to compete with the SARS-CoV-2/ACE2 complex both in vitro and in vivo. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10811-021-02372-9.

Chloroplast Dual Divergent Promoter Plasmid for Heterologous Protein Expression in Tetraselmis suecica (Chlorophyceae, Chlorodendrales).

The eukaryotic green microalga Tetraselmis suecica is commonly used for aquaculture purposes because of its high stress tolerance and ease of culture in a wide spectrum of environments; they are therefore suitable candidates for biotechnology applications. To date, no data are available regarding chloroplast transformation vectors based on specific endogenous promoters and homologous targeting regions. We report on the identification of Tetraselmis suecica genes encoding the ribulose bisphosphate carboxylase/oxygenase large subunit protein, the photosystem II D1 protein and the ATP synthase CF1-beta subunit protein together with their untranslated regions (5'UTR, 3'UTR). The full-length ORFs of the putative genes with their regulatory sequences were obtained. We were also able to identify the downstream 3' end of the large subunit ribosomal RNA gene (23S) along with the 5S RNA end-to-end with the psbA gene on the complementary strand. The intergenic region between these genes appears to be a good target site for the integration of target proteins. Moreover, we identified a back-to-back promoter region among the rbcL and atpB genes. To assess the bidirectionality activities of both promoters, a dual reporter vector was constructed for Tetraselmis suecica transformation containing the cat and TurboGFP genes driven by the 5'rbcL/5'atpB divergent promoter. The vector included the 23S-5S and psbA nucleotide sequences as flanking regions. These flanking regions provided suitable insertion sites within the chloroplast genome for cassette integration via homologous recombination. Simultaneous expression of the chloramphenicol-resistant conferring gene and the gene coding for TurboGFP driven by 5'rbcL/5'atpB showed a potent natural bidirectional promoter as a reliable genetic tool.

What Is in Store for EPS Microalgae in the Next Decade?

Microalgae and their metabolites have been an El Dorado since the turn of the 21st century. Many scientific works and industrial exploitations have thus been set up. These developments have often highlighted the need to intensify the processes for biomass production in photo-autotrophy and exploit all the microalgae value including ExoPolySaccharides (EPS). Indeed, the bottlenecks limiting the development of low value products from microalgae are not only linked to biology but also to biological engineering problems including harvesting, recycling of culture media, photoproduction, and biorefinery. Even respecting the so-called "Biorefinery Concept", few applications had a chance to emerge and survive on the market. Thus, exploiting EPS from microalgae for industrial applications in some low-value markets such as food is probably not a mature proposition considering the competitiveness of polysaccharides from terrestrial plants, macroalgae, and bacteria. However, it does not imply drawing a line on their uses but rather "thinking them" differently. This review provides insights into microalgae, EPS, and their exploitation. Perspectives on issues affecting the future of EPS microalgae are also addressed with a critical point of view.

Marine algae as attractive source to skin care.

As the largest organ in the human body, the skin has multiple functions of which one of the most important is the protection against various harmful stressors. The keratinised stratified epidermis and an underlying thick layer of collagen-rich dermal connective tissues are important components of the skin. The environmental stressors such as ultraviolet radiation (UVR) and pollution increase the levels of reactive oxygen species (ROS), contributing to clinical manifestations such as wrinkle formation and skin aging. Skin aging is related to the reduction of collagen production and decrease of several enzymatic activities including matrix metalloproteinases (MMPs), which degrade collagen structure in the dermis; and tissue inhibitor of metalloproteinases (TIMPs), which inhibit the action of MMPs. In addition to alterations of DNA, signal transduction pathways, immunology, UVR, and pollution activate cell surface receptors of keratinocytes and fibroblasts in the skin. This action leads to a breakdown of collagen in the extracellular matrix and a shutdown of new collagen synthesis. Therefore, an efficient antioxidants strategy is of major importance in dermis and epidermis layers. Marine resources have been recognised for their biologically active substances. Among these, marine algae are rich-sources of metabolites, which can be used to fight against oxidative stress and hence skin aging. These metabolites include, among others, mycosporine-like amino acids (MAAs), polysaccharides, sulphated polysaccharides, glucosyl glycerols, pigments, and polyphenols. This paper reviews the role of oxidative processes in skin damage and the action of the compounds from algae on the physiological processes to maintain skin health.

Community analysis of pigment patterns from 37 microalgae strains reveals new carotenoids and porphyrins characteristic of distinct strains and taxonomic groups.

Phytoplankton, with an estimated 30 000 to 1 000 000 species clustered in 12 phyla, presents a high taxonomic and ecophysiological diversity, reflected by the complex distribution of pigments among the different algal classes. High performance liquid chromatography is the gold standard method for qualitative and quantitative analysis of phytoplankton pigments in seawater and culture samples, but only a few pigments can be used as robust chemotaxonomic markers. A major challenge is thus to identify new ones, characteristic of a strain, species, class or taxon that cannot be currently identified on the basis of its pigment signature. Using an optimized extraction process coupled to a HPLC de-replication strategy, we examined the pigment composition of 37 microalgae strains, representative of the broad taxonomic diversity of marine and freshwater species (excluding cyanobacteria). For each species, the major pigments already described were unambiguously identified. We also observed the presence of several minor unidentified pigments in each chromatogram. The global analysis of pigment compositions revealed a total of 124 pigments, including 98 pigments or derivatives unidentified using the standards. Absorption spectra indicated that 35 corresponded to chlorophyll/porphyrin derivatives, 57 to carotenoids and six to derivatives having both spectral signatures. Sixty-one of these unidentified or new carotenoids and porphyrin derivatives were characteristic of particular strains or species, indicating their possible use as highly specific chemotaxonomic markers capable of identifying one strain out of the 37 selected. We developed a graphical analysis using Gephi software to give a clear representation of pigment communities among the various phytoplankton strains, and to reveal strain-characteristic and shared pigments. This made it possible to reconstruct the taxonomic evolution of microalgae classes, on the basis of the conservation, loss, and/or appearance of pigments.

Transcription factors in microalgae: genome-wide prediction and comparative analysis.

BACKGROUND: Studying transcription factors, which are some of the key players in gene expression, is of outstanding interest for the investigation of the evolutionary history of organisms through lineage-specific features. In this study we performed the first genome-wide TF identification and comparison between haptophytes and other algal lineages. RESULTS: For TF identification and classification, we created a comprehensive pipeline using a combination of BLAST, HMMER and InterProScan software. The accuracy evaluation of the pipeline shows its applicability for every alga, plant and cyanobacterium, with very good PPV and sensitivity. This pipeline allowed us to identify and classified the transcription factor complement of the three haptophytes Tisochrysis lutea, Emiliania huxleyi and Pavlova sp.; the two stramenopiles Phaeodactylum tricornutum and Nannochloropsis gaditana; the chlorophyte Chlamydomonas reinhardtii and the rhodophyte Porphyridium purpureum. By using T. lutea and Porphyridium purpureum, this work extends the variety of species included in such comparative studies, allowing the detection and detailed study of lineage-specific features, such as the presence of TF families specific to the green lineage in Porphyridium purpureum, haptophytes and stramenopiles. Our comprehensive pipeline also allowed us to identify fungal and cyanobacterial TF families in the algal nuclear genomes. CONCLUSIONS: This study provides examples illustrating the complex evolutionary history of algae, some of which support the involvement of a green alga in haptophyte and stramenopile evolution.

UPLC-MSE profiling of Phytoplankton metabolites: application to the identification of pigments and structural analysis of metabolites in Porphyridium purpureum.

A fast and high-resolution UPLC-MSE analysis was used to identify phytoplankton pigments in an ethanol extract of Porphyridium purpureum (Pp) devoid of phycobiliproteins. In a first step, 22 standard pigments were analyzed by UPLC-MSE to build a database including retention time and accurate masses of parent and fragment ions. Using this database, seven pigments or derivatives previously reported in Pp were unequivocally identified: ß,ß-carotene, chlorophyll a, zeaxanthin, chlorophyllide a, pheophorbide a, pheophytin a, and cryptoxanthin. Minor amounts of Divinyl chlorophyll a, a chemotaxonomic pigment marker for prochlorophytes, were also unequivocally identified using the database. Additional analysis of ionization and fragmentation patterns indicated the presence of ions that could correspond to hydroxylated derivatives of chlorophyll a and pheophytin a, produced during the ethanolic extraction, as well as previously described galactosyldiacylglycerols, the thylakoid coenzyme plastoquinone, and gracilamide B, a molecule previously reported in the red seaweed Gracillaria asiatica. These data point to UPLC-MSE as an efficient technique to identify phytoplankton pigments for which standards are available, and demonstrate its major interest as a complementary method for the structural elucidation of ionizable marine molecules.

The use of fluorescent Nile red and BODIPY for lipid measurement in microalgae.

Microalgae are currently emerging as one of the most promising alternative sources for the next generation of food, feed, cosmetics and renewable energy in the form of biofuel. Microalgae constitute a diverse group of microorganisms with advantages like fast and efficient growth. In addition, they do not compete for arable land and offer very high lipid yield potential. Major challenges for the development of this resource are to select lipid-rich strains using high-throughput staining for neutral lipid content in microalgae species. For this purpose, the fluorescent dyes most commonly used to quantify lipids are Nile red and BODIPY 505/515. Their fluorescent staining for lipids offers a rapid and inexpensive analysis tool to measure neutral lipid content, avoiding time-consuming and costly gravimetric analysis. This review collates and presents recent advances in algal lipid staining and focuses on Nile red and BODIPY 505/515 staining characteristics. The available literature addresses the limitations of fluorescent dyes under certain conditions, such as spectral properties, dye concentrations, cell concentrations, temperature and incubation duration. Moreover, the overall conclusion of the present review study gives limitations on the use of fluorochrome for screening of lipid-rich microalgae species and suggests improved protocols for staining recalcitrant microalgae and recommendations for the staining quantification.

High-affinity nitrate/nitrite transporter genes (Nrt2) in Tisochrysis lutea: identification and expression analyses reveal some interesting specificities of Haptophyta microalgae.

Microalgae have a diversity of industrial applications such as feed, food ingredients, depuration processes and energy. However, microalgal production costs could be substantially improved by controlling nutrient intake. Accordingly, a better understanding of microalgal nitrogen metabolism is essential. Using in silico analysis from transcriptomic data concerning the microalgae Tisochrysis lutea, four genes encoding putative high-affinity nitrate/nitrite transporters (TlNrt2) were identified. Unlike most of the land plants and microalgae, cloning of genomic sequences and their alignment with complementary DNA (cDNA) sequences did not reveal the presence of introns in all TlNrt2 genes. The deduced TlNRT2 protein sequences showed similarities to NRT2 proteins of other phyla such as land plants and green algae. However, some interesting specificities only known among Haptophyta were also revealed, especially an additional sequence of 100 amino acids forming an atypical extracellular loop located between transmembrane domains 9 and 10 and the function of which remains to be elucidated. Analyses of individual TlNrt2 gene expression with different nitrogen sources and concentrations were performed. TlNrt2.1 and TlNrt2.3 were strongly induced by low NO3 (-) concentration and repressed by NH4 (+) substrate and were classified as inducible genes. TlNrt2.2 was characterized by a constitutive pattern whatever the substrate. Finally, TlNrt2.4 displayed an atypical response that was not reported earlier in literature. Interestingly, expression of TlNrt2.4 was rather related to internal nitrogen quota level than external nitrogen concentration. This first study on nitrogen metabolism of T. lutea opens avenues for future investigations on the function of these genes and their implication for industrial applications.

Microwave-assisted extraction of phycobiliproteins from Porphyridium purpureum.

In the present study, microwave-assisted extraction was first employed to extract the phycobiliproteins of Porphyridium purpureum (Pp). Freeze-dried Pp cells were subjected to microwave-assisted extraction (MAE) to extract phycoerythin (PE), phycocyanin (PC), and allophycocyanin (APC). MAE combined reproducibility and high extraction yields and allowed a 180- to 1,080-fold reduction of the extraction time compared to a conventional soaking process. The maximal PE extraction yield was obtained after 10-s MAE at 40 °C, and PE was thermally damaged at temperatures higher than 40 °C. In contrast, a flash irradiation for 10 s at 100 °C was the best process to efficiently extract PC and APC, as it combined a high temperature necessary to extract them from the thylakoid membrane to a short exposure to thermal denaturation. The extraction order of the three phycobiliproteins was coherent with the structure of Pp phycobilisomes. Moreover, the absorption and fluorescence properties of MAE extracted phycobiliproteins were stable for several months after the microwave treatment. Scanning electron microscopy indicated that MAE at 100 °C induced major changes in the Pp cell morphology, including fusion of the exopolysaccharidic cell walls and cytoplasmic membranes of adjacent cells. As a conclusion, MAE is a fast and high yield process efficient to extract and pre-purify phycobiliproteins, even from microalgae containing a thick exopolysaccharidic cell wall.

Comparative transcriptome of wild type and selected strains of the microalgae Tisochrysis lutea provides insights into the genetic basis, lipid metabolism and the life cycle.

The applied exploitation of microalgae cultures has to date almost exclusively involved the use of wild type strains, deposited over decades in dedicated culture collections. Concomitantly, the concept of improving algae with selection programs for particular specific purposes is slowly emerging. Studying since a decade an economically and ecologically important haptophyte Tisochrysis lutea (Tiso), we took advantage of the availability of wild type (Tiso-Wt) and selected (Tiso-S2M2) strains to conduct a molecular variations study. This endeavour presented substantial challenges: the genome assembly was not yet available, the life cycle unknown and genetic diversity of Tiso-Wt poorly documented. This study brings the first molecular data in order to set up a selection strategy for that microalgae. Following high-throughput Illumina sequencing, transcriptomes of Tiso-Wt and Tiso-S2M2 were de novo assembled and annotated. Genetic diversity between both strains was analyzed and revealed a clear conservation, while a comparison of transcriptomes allowed identification of polymorphisms resulting from the selection program. Of 34,374 transcripts, 291 were differentially expressed and 165 contained positional polymorphisms (SNP, Indel). We focused on lipid over-accumulation of the Tiso-S2M2 strain and 8 candidate genes were identified by combining analysis of positional polymorphism, differential expression levels, selection signature and by study of putative gene function. Moreover, genetic analysis also suggests the existence of a sexual cycle and genetic recombination in Tisochrysis lutea.

Antiproliferative activity of Cyanophora paradoxa pigments in melanoma, breast and lung cancer cells.

The glaucophyte Cyanophora paradoxa (Cp) was chemically investigated to identify pigments efficiently inhibiting malignant melanoma, mammary carcinoma and lung adenocarcinoma cells growth. Cp water and ethanol extracts significantly inhibited the growth of the three cancer cell lines in vitro, at 100 µg · mL(-1). Flash chromatography of the Cp ethanol extract, devoid of c-phycocyanin and allophycocyanin, enabled the collection of eight fractions, four of which strongly inhibited cancer cells growth at 100 µg · mL(-1). Particularly, two fractions inhibited more than 90% of the melanoma cells growth, one inducing apoptosis in the three cancer cells lines. The detailed analysis of Cp pigment composition resulted in the discrimination of 17 molecules, ten of which were unequivocally identified by high resolution mass spectrometry. Pheophorbide a, ß-cryptoxanthin and zeaxanthin were the three main pigments or derivatives responsible for the strong cytotoxicity of Cp fractions in cancer cells. These data point to Cyanophora paradoxa as a new microalgal source to purify potent anticancer pigments, and demonstrate for the first time the strong antiproliferative activity of zeaxanthin and ß-cryptoxanthin in melanoma cells.

The potential of microalgae for the production of bioactive molecules of pharmaceutical interest.

Through the photosynthetic activity, microalgae process more than 25% of annual inorganic carbon dissolved in oceans into carbohydrates that ultimately, serve to feed the other levels of the trophic networks. Besides, microalgae synthesize bioactive molecules such as pigments and lipids that exhibit health properties. In addition, abiotic stresses, such as high irradiance, nutrient starvation, UV irradiation, trigger metabolic reorientations ending with the production of other bioactive compounds such as ω-3 fatty acids or carotenoids. Traditionally, these compounds are acquired through the dietary alimentation. The increasing, and often unsatisfied, demand for compounds from natural sources, combined with the decrease of the halieutic resources, forces the search for alternative resources for these bioactive components. Microalgae possess this strong potential. For instance, the diatom Odontella aurita is already commercialized as dietary complement and compete with fish oil for human nutrition. In this contribution, the microalga world is briefly presented. Then, the different types of biologically active molecules identified in microalgae are presented together with their potential use. Due to space limitation, only the biological activities of lipids and pigments are described in details. The contribution ends with a description of the possibilities to play with the environmental constrains to increase the productivity of biologically active molecules by microalgae and by a description of the progresses made in the field of alga culturing.

Selection and optimisation of a method for efficient metabolites extraction from microalgae.

Over the last decade, the use of microalgae for biofuel production and carbon dioxide sequestration has become a challenge worldwide. Processing costs are still too high for these methods to be profitable though, leading to a need to find high value by-products to optimise the added value of this biomass. For high-throughput screening of such metabolites, it is essential to reach the inner content of the cell. This paper presents research and development of a technique enabling a high extraction yield of any metabolite, taking into account the difficulty of extracting bound and or inaccessible molecules with a wide variety of polarities. To this end, several disruption techniques were tested at laboratory scale on two biological models: Porphyridium purpureum and Phaeodactylum tricornutum. A mixer mill gave the best results, offering access to a broad diversity of metabolites from microalgae for high-throughput screening.

Enhancement of neutral lipid productivity in the microalga Isochrysis affinis Galbana (T-Iso) by a mutation-selection procedure.

Microalgae offer a high potential for energetic lipid storage as well as high growth rates. They are therefore considered promising candidates for biofuel production, with the selection of high lipid-producing strains a major objective in projects on the development of this technology. We developed a mutation-selection method aimed at increasing microalgae neutral lipid productivity. A two step method, based on UVc irradiation followed by flow cytometry selection, was applied to a set of strains that had an initial high lipid content and improvement was assessed by means of Nile-red fluorescence measurements. The method was first tested on Isochrysis affinis galbana (T-Iso). Following a first round of mutation-selection, the total fatty acid content had not increased significantly, being 262 ± 21 mgTFA (gC)-1 for the wild type (WT) and 269 ± 49 mgTFA (gC)-1 for the selected population (S1M1). Conversely, fatty acid distribution among the lipid classes was affected by the process, resulting in a 20% increase for the fatty acids in the neutral lipids and a 40% decrease in the phospholipids. After a second mutation-selection step (S2M2), the total fatty acid content reached 409 ± 64 mgTFA (gC)-1 with a fatty acid distribution similar to the S1M1 population. Growth rate remained unaffected by the process, resulting in a 80% increase for neutral lipid productivity.

Integrative taxonomy of the Pavlovophyceae (Haptophyta): a reassessment.

The Pavlovophyceae (Haptophyta) contains four genera (Pavlova, Diacronema, Exanthemachrysis and Rebecca) and only thirteen characterised species, several of which are important in ecological and economic contexts. We have constructed molecular phylogenies inferred from sequencing of ribosomal gene markers with comprehensive coverage of the described diversity, using type strains when available, together with additional cultured strains. The morphology and ultrastructure of 12 of the described species was also re-examined and the pigment signatures of many culture strains were determined. The molecular analysis revealed that sequences of all described species differed, although those of Pavlova gyrans and P. pinguis were nearly identical, these potentially forming a single cryptic species complex. Four well-delineated genetic clades were identified, one of which included species of both Pavlova and Diacronema. Unique combinations of morphological/ultrastructural characters were identified for each of these clades. The ancestral pigment signature of the Pavlovophyceae consisted of a basic set of pigments plus MV chl cPAV, the latter being entirely absent in the Pavlova + Diacronema clade and supplemented by DV chl cPAV in part of the Exanthemachrysis clade. Based on this combination of characters, we propose a taxonomic revision of the class, with transfer of several Pavlova species to an emended Diacronema genus. The evolution of the class is discussed in the context of the phylogenetic reconstruction presented.

Antiproliferative activity of violaxanthin isolated from bioguided fractionation of Dunaliella tertiolecta extracts.

Dunaliella tertiolecta (DT) was chemically investigated to isolate molecules inhibiting cancer cell proliferation and inducing apoptosis in vitro. The potency to inhibit cell growth was used for the bio-guided fractionation and isolation of active compounds using chromatographic techniques. The DT dichloromethane extract exhibited a strong anti-proliferative activity on MCF-7 and LNCaP cells, and was further fractionated and sub-fractionated by RP-HPLC. High resolution mass spectrometry and spectrophotometric analysis unequivocally identified violaxanthin as the most antiproliferative molecule present in DT DCM extract. Violaxanthin purified from DT induced MCF-7 dose-dependent growth inhibition in continuous and discontinuous treatments, at concentrations as low as 0.1 µg·mL⁻¹ (0.17 µM). Phosphatidylserine exposure, typical of early apoptosis, was observed after 48 h treatment at 8 µg·mL⁻¹ (13.3 µM) but no DNA fragmentation, characteristic of late apoptosis steps, could be detected even after 72 h treatment at 40 µg·mL⁻¹ (66.7 µM). Taken together, our results demonstrate the strong antiproliferative activity of violaxanthin on one human mammary cancer cell line, and suggest that studying the pharmacology of violaxanthin and pharmacomodulated derivatives on cancer cells may allow potent antiproliferative drugs to be obtained.

N-glycans of Phaeodactylum tricornutum diatom and functional characterization of its N-acetylglucosaminyltransferase I enzyme.

N-glycosylation, a major co- and post-translational event in the synthesis of proteins in eukaryotes, is unknown in aquatic photosynthetic microalgae. In this paper, we describe the N-glycosylation pathway in the diatom Phaeodactylum tricornutum. Bio-informatic analysis of its genome revealed the presence of a complete set of sequences potentially encoding for proteins involved in the synthesis of the lipid-linked Glc(3)Man(9)GlcNAc(2)-PP-dolichol N-glycan, some subunits of the oligosaccharyltransferase complex, as well as endoplasmic reticulum glucosidases and chaperones required for protein quality control and, finally, the α-mannosidase I involved in the trimming of the N-glycan precursor into Man-5 N-glycan. Moreover, one N-acetylglucosaminyltransferase I, a Golgi glycosyltransferase that initiates the synthesis of complex type N-glycans, was predicted in the P. tricornutum genome. We demonstrated that this gene encodes for an active N-acetylglucosaminyltransferase I, which is able to restore complex type N-glycans maturation in the Chinese hamster ovary Lec1 mutant, defective in its endogeneous N-acetylglucosaminyltransferase I. Consistent with these data, the structural analyses of N-linked glycans demonstrated that P. tricornutum proteins carry mainly high mannose type N-glycans ranging from Man-5 to Man-9. Although representing a minor glycan population, paucimannose N-glycans were also detected, suggesting the occurrence of an N-acetylglucosaminyltransferase I-dependent maturation of N-glycans in this diatom.