Biology subjects

Scornet, D.

Publications and source records attributed to Scornet, D..

5 recordsLinked to original sources

bioRxiv2026

Comparison of the performance of sporophytes derived from narrow and wide genetic crosses between strains of the cultivated kelp Saccharina latissima

Seaweed mariculture allows sustainable production of large quantities of biomass for multiple downstream applications but the genotypes cultivated by this industry need to be improved to increase efficiency and cost-effectiveness. It is important that the genetic improvement of cultivated strains does not lead to the introduction of foreign genetic material into wild seaweed populations, which are already under threat from global heating. To circumvent this problem, efforts are being made to develop breeding approaches based on the use of locally-resourced genetic material. The aim of this study was to evaluate the potential effectiveness of this 'local' breeding strategy compared to a classical breeding approach based on wide genetic crosses. Analyses of growth rates and cell wall composition of F1 hybrids derived from either intra- or inter-population crosses between Saccharina latissima strains from two localities, southern Brittany, France and the Faroe Islands, did not identify any clear advantage of inter- compared to intra-population crosses. Breeding based on locally-resourced strains would therefore appear to be a valid approach for current strain selection programs. The study also established a large collection of gametophyte strains from multiple sites for future breeding programs and showed that these strains retained the capacity to become fertile after more than ten years in culture.

genetics↗

bioRxiv2023

THE RHODOEXPLORER PLATFORM FOR RED ALGAL GENOMICS AND WHOLE GENOME ASSEMBLIES FOR SEVERAL GRACILARIA SPECIES

Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales are highly diverse and widely distributed order whose species can serve as ecosystem engineers in intertidal habitats, including several notorious introduced species. The genus Gracilaria is cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole genome assemblies for two species (G. chilensis and G. gracilis), a draft genome assembly of G. caudata, and genome annotation of the previously published G. vermiculophylla genome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.

genomics↗

bioRxiv2022

The baseless mutant links protein phosphatase 2A with basal cell identity in the brown alga Ectocarpus

The first mitotic division of the initial cell is a key event in all multicellular organisms and is usually concomitant with the establishment of major developmental axes and cell fates. The brown alga Ectocarpus has a haploid-diploid life cycle that involves the development of two multicellular and independent generations, the sporophyte and the gametophyte. Each generation deploys a distinct developmental program autonomously from an initial cell, whose first cell division sets up the future body pattern. Here, we show that mutations in the BASELESS (BAS) gene result in multiple cellular defects during the first division of the initial cell and subsequently failure to produce basal structures (rhizoids and prostrate filaments) during both generations of the life cycle. Cloning-by-sequencing revealed that BAS encodes a type B" regulatory subunit of protein phosphatase 2A, and transcriptomic analysis of early developmental stages uncovered potential effector genes involved in setting up basal cell fate in this organism. The bas mutant phenotype is very similar to that observed in the distag (dis) mutants, which lack a functional TBCCd1 protein, at both the cellular and morphological levels. The high level of similarity of the dis and bas mutant phenotypes indicate that TBCCd1 and PP2A are two critical components of the cellular machinery that regulates the division of the initial cell and mediates the establishment of basal cell fate in the developing thallus.

developmental biology↗

bioRxiv2020

Histone modifications during the life cycle of the brown alga Ectocarpus

BackgroundBrown algae evolved complex multicellularity independently of the animal and land plant lineages and are the third most developmentally complex phylogenetic group on the planet. An understanding of developmental processes in this group is expected to provide important insights into the evolutionary events necessary for the emergence of complex multicellularity. Here we have focused on mechanisms of epigenetic regulation involving post-translational modifications (PTMs) of histone proteins. ResultsA total of 47 histone PTMs were identified, including a novel mark H2AZR38me1, but Ectocarpus lacks both H3K27me3 and the major polycomb complexes. ChIP-seq identified PTMs associated with transcription start sites (TSSs) and gene bodies of active genes, and with transposons. H3K79me2 exhibited an unusual pattern, often marking large genomic regions spanning several genes. TSSs of closely spaced divergently transcribed gene pairs shared a common nucleosome depleted region and exhibited shared histone PTM peaks. Overall, patterns of histone PTMs were stable through the life cycle. Analysis of histone PTMs at generation-biased genes identified a correlation between the presence of specific chromatin marks and the level of gene expression. ConclusionsThe overview of histone PTMs in the brown algae presented here will provide a foundation for future studies aimed at understanding the role of chromatin modifications in the regulation of brown algal genomes.

genomics↗

bioRxiv2018

Convergent recruitment of life cycle regulators to direct sporophyte development in two eukaryotic supergroups

Three amino acid loop extension homeodomain transcription factors (TALE HD TFs) act as life cycle regulators in green algae and land plants. In mosses these regulators are required for the deployment of the sporophyte developmental program. We demonstrate that mutations in either of two TALE HD TF genes, OUROBOROS or SAMSARA, in the brown alga Ectocarpus result in conversion of the sporophyte generation into a gametophyte. The OUROBOROS and SAMSARA proteins heterodimerise in a similar manner to TALE HD TF life cycle regulators in the green lineage. These observations demonstrate that TALE-HD-TF-based life cycle regulation systems have an extremely ancient origin, and that these systems have been independently recruited to regulate sporophyte developmental programs in at least two different complex multicellular eukaryotic supergroups, Archaeplastida and Chromalveolata.

plant biology↗