Biology subjects

Delage, L.

Publications and source records attributed to Delage, L..

8 recordsLinked to original sources

bioRxiv2026

The genome of the Delisea pulchra: a resource for the study of chemical host-microbe interactions in red algae

BackgroundRed macroalgae (Rhodophyta) are ecologically and economically important marine primary producers, yet genomic resources for most species remain scarce. Delisea pulchra, a temperate red alga known for its halogenated furanone-based chemical defenses, serves as a model for studying algal-microbe interactions, antifouling mechanisms, and disease dynamics. ResultsHere we present a high-quality genome assembly of this species. The nuclear genome comprises 134 Mbp across 271 contigs with an N50 of 1.47 Mbp and encodes 13,387 predicted protein-coding genes. Comparative genomics with other red algae revealed expansions in gene families involved in DNA methylation, and oxidative stress responses, including glutathione S-transferases and superoxide dismutases. Analysis of glycosyltransferases, sulfatases, and sulfurylases implicated in galactan biosynthesis suggests D. pulchra possesses a complex and potentially novel extracellular matrix. We also identified several vanadium haloperoxidases (vHPOs), heme-dependent haloperoxidases (hHPOs), and two type III polyketide synthase (PKS) genes unique to the D. pulchra, which together represent promising candidate genes for bromofuranone production. ConclusionThe D. pulchra genome provides a foundation for molecular investigations into defense, signaling, and host-microbe interactions. It has been deposited at the European Nucleotide Archive under accession number PRJEB101077. All datasets, annotations, and interactive tools for exploring the genome are also available through the Rhodoexplorer portal at https://rhodoexplorer.sb-roscoff.fr.

genomics↗

bioRxiv2026

The cuticle lamellae responsible for structural coloration in red algae display common features with the metazoan extracellular matrix

Structural coloration is a physical phenomenon observed in many living organisms, including seaweeds, via the formation of highly organized nanostructures. Although the deposition of multilayer thin-film in the extracellular matrix (ECM) is a widespread characterized system, enabling light interference, to date such lamellae have only been described in the cuticle of red algae belonging to the Gigartinaceae family within macroalgae. Here, we determine the composition of the multilayered cuticle components in the model species Chondrus crispus (Rhodophyta), using genomic, transcriptomic, proteomic, metabolomic and analytical profiling of carbohydrates. The complex structural assembly revealed common features with the ECM of animals. The carbohydrate fraction consists of a complex mixture of ECM carrageenans and glycosaminoglycan-like structures. A major von Willerbrand factor A domain (VWA) protein plays a critical role for the adhesion of macromolecules, including protein-protein interactions and to sulfated polysaccharides. We propose the name of Lamellae Cohesive Protein (LCP) regarding the alternate distribution of chemically distinct constituents within the cuticle. For the first time, we identified major proteins of the algal cuticle, providing a framework for addressing the evolutionary origins of the algal cuticle biosynthesis and raise important questions regarding its role, particularly across the life cycle marked by major structural ECM modifications.

biochemistry↗

bioRxiv2024

Evolutionary history of the main extracellular matrix polysaccharides in brown algae

Brown algae belong to the Stramenopiles phylum and are phylogenetically distant from plants and other multicellular organisms. This independent evolutionary history has shaped brown algae with numerous metabolic characteristics specific to this group, including the synthesis of peculiar polysaccharides contained in their extracellular matrix (ECM). Alginates and fucose-containing sulphated polysaccharides (FCSP), the latter including fucans, are the main components of ECMs. However, the metabolic pathways of these polysaccharides remain poorly described due to a lack of genomic data. An extensive genomic dataset has been recently released for brown algae and their close sister species. We performed an expert annotation of key genes involved in ECM-carbohydrate metabolisms, combined with comparative genomics, phylogenetics analyses, and protein modelling. Our analysis indicates that the gene families involved in both the synthesis and degradation of alginate were acquired by the common ancestor of brown algae and their closest sister species Schizocladia ischiensis, and subsequently expanded in brown algae. The pathway for the biosynthesis of fucans still remains biochemically unresolved and we identify the most likely fucosyltransferase genes that may harbour a fucan synthase activity in brown algae. Our analysis questions the possible occurrence of FCSPs outside brown algae, notably within their closest sister taxon.

evolutionary biology↗

bioRxiv2024

Evolutionary genomics of the emergence of brown algae as key components of coastal ecosystems

Brown seaweeds are keystone species of coastal ecosystems, often forming extensive underwater forests, that are under considerable threat from climate change. Despite their ecological and evolutionary importance, this phylogenetic group, which is very distantly related to animals and land plants, is still poorly characterised at the genome level. Here we analyse 60 new genomes that include species from all the major brown algal orders. Comparative analysis of these genomes indicated the occurrence of several major events coinciding approximately with the emergence of the brown algal lineage. These included marked gain of new orthologous gene families, enhanced protein domain rearrangement, horizontal gene transfer events and the acquisition of novel signalling molecules and metabolic pathways. The latter include enzymes implicated in processes emblematic of the brown algae such as biosynthesis of the alginate-based extracellular matrix, and halogen and phlorotannin biosynthesis. These early genomic innovations enabled the adaptation of brown algae to their intertidal habitats. The subsequent diversification of the brown algal orders tended to involve loss of gene families, and genomic features were identified that correlated with the emergence of differences in life cycle strategy, flagellar structure and halogen metabolism. Analysis of microevolutionary patterns within the genus Ectocarpus indicated that deep gene flow between species may be an important factor in genome evolution on more recent timescales. Finally, we show that integration of large viral genomes has had a significant impact on brown algal genome content and propose that this process has persisted throughout the evolutionary history of the lineage.

genomics↗

bioRxiv2023

Hyperaccumulation of Vanadium in animals: two sponges compete with urochordates

Vanadium (V) is the second most abundant transition metal in the oceans. Nevertheless, its concentration in organisms is generally low despite its involvement in various physiological or enzymatic functions. Because exposure to high concentrations was shown to be harmful for various organisms including animals, the unexpected very high concentrations found in urochordates and annelids yielded additional studies to decipher their biological meaning. Here we report cases of V hyperaccumulators in a distinct animal phylum (Porifera): the two homoscleromorph sponge species Oscarella lobularis and Oscarella tuberculata (up to 30 mg/g dw). These high concentrations overpass those reported previously in urochordates and annelids and are not found in the 5 other sponge species studied here. In both Oscarella species, vanadium is mainly accumulated in the 100 m surface tissues, and in particular in mesohylar cells, as vanadyl (+4) before being partly reduced to V (+3) in the deeper tissues. Genomic surveys failed to find any previously described gene implicated in vanadium metabolism, suggesting that V hyperaccumulation emerged convergently in this lineage. This feature may be of interest for developing bioremediation strategies in marine ecosystems or bioinspired processes to recycle this critical metal. SynopsisThis study reports extremely high concentrations of vanadium in two sponges. This unusual bioaccumulation of reduced V (+3) in mesohylar cells relies on unknown molecular mechanisms.

ecology↗

bioRxiv2022

AuCoMe: inferring and comparing metabolisms across heterogeneous sets of annotated genomes

Comparative analysis of Genome-Scale Metabolic Networks (GSMNs) may yield important information on the biology, evolution, and adaptation of species. However, it is impeded by the high heterogeneity of the quality and completeness of structural and functional genome annotations, which may bias the results of such comparisons. To address this issue, we developed AuCoMe - a pipeline to automatically reconstruct homogeneous GSMNs from a heterogeneous set of annotated genomes without discarding available manual annotations. We tested AuCoMe with three datasets, one bacterial, one fungal, and one algal, and demonstrated that it successfully reduces technical biases while capturing the metabolic specificities of each organism. Our results also point out shared metabolic traits and divergence points among evolutionarily distant species, such as algae, underlining the potential of AuCoMe to accelerate the broad exploration of metabolic evolution across the tree of life.

systems biology↗

bioRxiv2018

Inferring biochemical reactions and metabolite structures to cope with metabolic pathway drift

Inferring genome-scale metabolic networks in emerging model organisms is challenging because of incomplete biochemical knowledge and incomplete conservation of biochemical pathways during evolution. This limits the possibility to automatically transfer knowledge from well-established model organisms. Therefore, specific bioinformatic tools are necessary to infer new biochemical reactions and new metabolic structures that can be checked experimentally. Using an integrative approach combining both genomic and metabolomic data in the red algal model Chondrus crispus, we show that, even metabolic pathways considered as conserved, like sterol or mycosporine-like amino acids (MAA) synthesis pathways, undergo substantial turnover. This phenomenon, which we formally define as \"metabolic pathway drift\", is consistent with findings from other areas of evolutionary biology, indicating that a given phenotype can be conserved even if the underlying molecular mechanisms are changing. We present a proof of concept with a new methodological approach to formalize the logical reasoning necessary to infer new reactions and new molecular structures, based on previous biochemical knowledge. We use this approach to infer previously unknown reactions in the sterol and MAA pathways.\n\nAuthor summaryGenome-scale metabolic models describe our current understanding of all metabolic pathways occuring in a given organism. For emerging model species, where few biochemical data are available about really occurring enzymatic activities, such metabolic models are mainly based on transferring knowledge from other more studied species, based on the assumption that the same genes have the same function in the compared species. However, integration of metabolomic data into genome-scale metabolic models leads to situations where gaps in pathways cannot be filled by known enzymatic reactions from existing databases. This is due to structural variation in metabolic pathways accross evolutionary time. In such cases, it is necessary to use complementary approaches to infer new reactions and new metabolic intermediates using logical reasoning, based on available partial biochemical knowledge. Here we present a proof of concept that this is feasible and leads to hypotheses that are precise enough to be a starting point for new experimental work.

systems biology↗

bioRxiv2018

The genome of Ectocarpus subulatus highlights unique mechanisms for stress tolerance in brown algae

Brown algae are multicellular photosynthetic stramenopiles that colonize marine rocky shores worldwide. Ectocarpus sp. Ec32 has been established as a genomic model for brown algae. Here we present the genome and metabolic network of the closely related species, Ectocarpus subulatus Kutzing, which is characterized by high abiotic stress tolerance. Since their separation, both strains show new traces of viral sequences and the activity of large retrotransposons, which may also be related to the expansion of a family of chlorophyll-binding proteins. Further features suspected to contribute to stress tolerance include an expanded family of heat shock proteins, the reduction of genes involved in the production of halogenated defence compounds, and the presence of fewer cell wall polysaccharide-modifying enzymes. Overall, E. subulatus has mainly lost members of gene families down-regulated in low salinities, and conserved those that were up-regulated in the same condition. However, 96% of genes that differed between the two examined Ectocarpus species, as well as all genes under positive selection, were found to encode proteins of unknown function. This underlines the uniqueness of brown algal stress tolerance mechanisms as well as the significance of establishing E. subulatus as a comparative model for future functional studies.

genomics↗