Biology subjects

Herve, C.

Publications and source records attributed to Herve, C..

3 recordsLinked to original sources

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↗

bioRxiv2022

Taxonomic practice, creativity, and fashion: What's in a spider name?

Theres a secret pleasure in naming new species. Besides traditional etymologies recalling the sampling locality, habitat, or morphology of the species, etymologies may be tributes to some meaningful person (for example, the species collector, the authors husband or wife, or a celebrity), pop culture references, and even exercises of enigmatography. The possibility of choosing witty or even playful names for new species departs from the otherwise impersonal and old-fashioned writing style thats common in taxonomic papers; but, how has the descriptors choice for specific etymologies changed over the 300+ years since the introduction of the Linnaean binomial system of nomenclature? Using an unprecedented dataset of 48,464 etymologies (all valid species and subspecies of spiders described between 1757 and May 2020), we tested the hypothesis that species names given by taxonomists are deeply influenced by their cultural background. In particular, we asked whether naming practices change through space (continent in which the species was found) or have changed through time (year of description). We observed spatial and temporal differences in the way taxonomists name new species. In absolute terms, etymologies referring to morphology were the most frequently used. In relative terms, however, references to morphology peaked in 1850-1900 and then began to decline, with a parallel increase in etymologies dedicated to people and geography. Currently, these are the most widely used, with [~]38% of all etymologies of spider species described in the last ten years referring to geography, [~]25% to people, and [~]25% to morphology. Interestingly, there has been a dramatic increase in etymologies referring to pop culture and other cultural aspects in the last two decades, especially in Europe and the Americas. While such fashionable names often carry little or no biological information regarding the species itself, they help give visibility to the science of taxonomy, a discipline currently facing a profound crisis within academia. Taxonomy is among the most unchanged disciplines across the last centuries in terms of background, tools, rules, and writing style; but our analysis suggests that taxonomists remain deeply influenced by their living time and space.

scientific communication and education↗

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↗