Biology subjects

Corellou, F.

Publications and source records attributed to Corellou, F..

3 recordsLinked to original sources

bioRxiv2026

Unveiling the Epigenomic Control of Temperature Acclimation in Marine Phytoplankton through Multiomics Integration

Temperature plays a central role in marine phytoplankton biogeographical dynamics, physiology and gene expression. Nonetheless, the transcriptional regulatory mechanisms controlling temperature acclimation in marine phytoplankton are yet to be characterized. Ostreococcus tauri was chosen as a model species for green marine phytoplankton due to its cellular and genomic simplicity, as well as its evolutionary position within the green lineage. In this study, epigenomic and transcriptomic data were integrated to characterize changes induced by temperature in the trimethylation of histone 3 at lysines 27 and 4 (H3K27me3 and H3K4me3) epigenetic marks established by the Polycomb (PcG) and Trithorax group (TrxG) complexes, respectively. H3K27me3 was found to be a repressive mark responding to temperature, showing predominantly significant increased levels at high temperatures. While H3K4me3 was associated with active transcription, presenting less evident variations in cultures acclimated to different temperatures. H3K27me3 was found only marginally associated with transposable elements, being mostly involved in the repression of specific biological processes, such as gene expression control by transcription factors, meiosis, motors proteins and cytoskeletal structures. No significant conservation was found between the H3K27me3 gene targets in the model plant Arabidopsis thaliana and Ostreococcus tauri. Nonetheless, transcriptions factors belonging to the MADS-box, WRKY and AP2 families were consistently repressed by H3K27me3 in both species, unveiling that, although the specific downstream targets of this epigenetic mark have diversified during evolution, its role in modulating higher order regulatory nodes remains evolutionary conserved.

plant biology↗

bioRxiv2023

SPHINGOLIPIDS AND DELTA8-SPHINGOLIPID DESATURASE FROM THE PICOALGA O. TAURI AND INVOLVEMENT IN TEMPERATURE ACCLIMATION

Sphingolipids are crucial components of cell membranes. Sphingolipid {Delta}8-unsaturation is more specific to plants and is involved in the regulation of stress responses. The structure and functions of sphingolipids in microalgae are still poorly understood. Ostreococus tauri is a minimal microalga at the base of the green lineage, and is therefore a key organism for understanding lipid evolution. The present work reports the characterisation as well as the temperature regulation of sphingolipids and {Delta}8-sphingolipid desaturase from O. tauri. Complex sphingolipids are glycosylceramides with unique glycosyl moieties encompassing hexuronic acid residues, reminiscent of bacterial glucuronosylceramides, with up to three additional hexose residues. In contrast, the ceramide backbones show limited variety, with dihydroxylated C18/C18:1E{Delta}8 sphingoid bases and C16:0 fatty-acyl chain being the main compounds. The sphingolipid {Delta}8-desaturase from O. tauri, although phylogenetically related to plant homologues has a substrate preference similar to the diatom homologue. Both sphingolipid {Delta}8-desaturase transcripts and sphingolipid {Delta}8-unsaturation are regulated in a temperature- dependent manner being higher at 14{degrees}C than 24{degrees}C. Overexpressing the sphingolipid {Delta}8- desaturase in O. tauri at 24{degrees}C results in higher sphingolipid unsaturation and impairs the increase in cell size, structure and chlorophyll. In particular, the cell-size defect is not detected in cells acclimated to 14{degrees}C and is furthermore suppressed upon transfer from 24{degrees}C to 14{degrees}C. Our work provides the first functional evidence for the involvement of sphingolipid {Delta}8-unsaturation for temperature acclimation in microalgae, suggesting that this function is an ancestral feature in the green lineage.

biochemistry↗

bioRxiv2020

Plastidic Δ6 Fatty-Acid Desaturases With Distinctive Substrate Specificity Regulate The Pool Of C18-PUFAs In The Ancestral Picoalga Ostreococcus tauri

Eukaryotic {Delta}6-desaturases are microsomal enzymes which balance the synthesis of {omega}-3 and {omega}-6 C18-polyunsaturated-fatty-acids (PUFA) accordingly to their specificity. In several microalgae, including O. tauri, plastidic C18-PUFA are specifically regulated by environmental cues suggesting an autonomous control of {Delta}6-desaturation of plastidic PUFA. Sequence retrieval from O. tauri desaturases, highlighted two putative {Delta}6/{Delta}8-desaturases sequences clustering, with other microalgal homologs, apart from other characterized {Delta}-6 desaturases. Their overexpression in heterologous hosts, including N. benthamiana and Synechocystis, unveiled their {Delta}6-desaturation activity and plastid localization. O. tauri lines overexpressing these {Delta}6-desaturases no longer adjusted their plastidic C18-PUFA amount under phosphate starvation but didnt show any obvious physiological alterations. Detailed lipid analyses from the various overexpressing hosts, unravelled that the substrate features involved in the {Delta}6-desaturase specificity importantly involved the lipid head-group and likely the non-substrate acyl-chain, in addition to the overall preference for the {omega}-class of the substrate acyl-chain. The most active desaturase displayed a broad range substrate specificity for plastidic lipids and a preference for {omega}-3 substrates, while the other was selective for {omega}-6 substrates, phosphatidylglycerol and 16:4-galactolipid species specific to the native host. The distribution of plastidial {Delta}6-desaturase products in eukaryotic hosts suggested the occurrence of C18-PUFA export from the plastid. One sentence summaryOsteococcus tauri plastidic lipid C18-PUFA remodelling involves two plastid-located cytochrome-b5 fused {Delta}6-desaturases with distinct preferences for both head-group and acyl-chain.

biochemistry↗