Biology subjects

Thurotte, A.

Publications and source records attributed to Thurotte, A..

4 recordsLinked to original sources

bioRxiv2026

Dim blue light drives reversible fucoxanthin derivative accumulation in the pelagophyte Pelagomonas calceolata

Pigment composition and regulation are critical for efficient photosynthesis in the ocean, where light intensity decreases and the spectrum narrows with depth. Fucoxanthin (Fx), the main carotenoid of several microalgal lineages, harvests the blue-green light prevailing in the deep euphotic zone. In pelagophytes, the acylated derivative 19'-butanoyloxyfucoxanthin (19'-BFx) is abundant, yet its function and regulation remain unclear. Here, we investigated how irradiance and spectral quality shape photoacclimation in Pelagomonas calceolata, an abundant and cosmopolitan low-light pelagophyte. Cultures were grown under blue or white light across 2-60 umol photons m^-2 s^-1. We analysed growth, PSII photophysiology, pigment composition, gene expression levels, and the impact of spectral shifts on the 19'-BFx/Fx ratio. Pelagomonas calceolata grew optimally under dim blue light and displayed low non-photochemical quenching (NPQ) under assay conditions. Transcriptomes revealed broad remodelling driven mainly by irradiance and modulated by light colour, including carotenoid-related processes. Dim blue light progressively increased the 19'-BFx/Fx ratio, whereas white light kept it low and reversed the response after a blue-to-white shift. These results identify reversible, spectrum-dependent 19'-BFx accumulation as a key component of photoacclimation in P. calceolata and separate irradiance-driven from spectrum-dependent cellular responses. This plasticity may explain the ecological success of P. calceolata in low-light oceans.

plant biology↗

bioRxiv2025

Genomics-based quantitative biogeography of marine plankton

Marine plankton are key drivers of ocean productivity and global carbon cycling, yet their quantitative biogeography remains poorly characterized. Environmental genomic datasets are inherently compositional, restricting analyses to relative abundances and limiting their integration into ecological and biogeochemical models. Here we combine DNA mass measurements, filtered seawater volumes, and metagenomic relative abundances to generate absolute estimates of cell concentrations and carbon biomass of plankton across the global ocean. Leveraging thousands of samples, this approach provides quantitative estimates for hundreds of eukaryotic and thousands of prokaryotic environmental genomes, unveiling ecological associations not captured by compositional data. Using the psbO marker gene, we reconstruct quantitative biogeographies of photosynthetic lineages and, through global-scale modeling, project their distributions to generate quantitative maps of phytoplankton communities across the worlds ocean. By bridging genomic data with biogeochemical metrics, this study provides novel resources for integrating plankton at genomic resolution into next-generation biogeochemical models.

genomics↗

bioRxiv2025

Effector Repertoire and Host Transcriptomic Responses in the Tripartite Interaction Between the bloom-forming diatom Coscinodiscus granii, the oomycete Lagenisma coscinodisci and Co-occurring Pedinellale Pteridomonas.

Parasitic interactions play a central role in shaping phytoplankton community dynamics. Diatoms are a major phytoplankton group for which many parasites have been describe including chytrids and oomycetes, yet host defense mechanisms remain poorly studied, limiting our understanding of the factors that constrain or promote infection events in natural environments. Major challenges in investigating diatom-parasite interactions include obtaining cultivable host-parasite pairs, maintain stable co-cultures with synchronized infection stages, and harvesting sufficient biomass for molecular analyses such as transcriptomics and metabolomics. To address these challenges, we focused on the bloom-forming diatom Coscinodiscus granii, a large species ({approx}200 {micro}m) to allow manual isolation of single cells. This diatom is naturally infected by Lagenisma coscinodisci, an abundant oomycete occasionally observed in temperate coastal environments. We assembled high-quality transcriptomes for both C. granii and L. coscinodisci, providing an important resource for future molecular studies. Transcriptome analyses revealed a sophisticated effector repertoire in L. coscinodisci, including canonical oomycete virulence factors such as Crinklers, RxLR effectors, cystatins, transposon-associated proteins, and components of the RNA interference machinery (Argonaute, Dicer, RdRP), as well as cyclophilins. In the differential gene expression analyses, C. granii exhibited a transcriptional response involving proteases and exosome-related pathways, suggesting a deeply conserved, defense mechanism. In parallel, we analysed the differential expression of the heterotrophic flagellate Pteridomonas sp., which consistently co-occurred in culture, and identified a distinct transcriptional profile characterized by the upregulation of motility-related genes, highlighting a striking mobility strategy. Owing to the exceptionally large host size and the availability of both transcriptomic and metabolomic data, this tripartite system provides a unique marine model for exploring oomycete-diatom interactions.

plant biology↗

bioRxiv2024

Nitrogen metabolism in the picoalgae Pelagomonas calceolata: disentangling cyanate lyase function under different nutrient conditions.

Cyanate (OCN-) is potentially an important organic nitrogen source in aquatic environments given the prevalence and activity of cyanate lyase genes in microalgae. However, the conditions under which these genes are expressed and the actual capacity of microalgae to assimilate cyanate remain underexplored. Here, we studied the nitrogen metabolism of the cosmopolitan picoalga Pelagomonas calceolata (Pelagophyceae, Stramenopiles) in environmental metatranscriptomes and transcriptomes from culture experiments under different nitrogen sources and concentrations. We observed that cyanate lyase is over-expressed in nitrate-poor oceanic regions, suggesting that cyanate is an important molecule contributing to the persistence of P. calceolata in oligotrophic environments. In the laboratory, we confirmed that this gene is over-expressed in low-nitrate medium together with several genes involved in nitrate recycling from endogenous molecules. Non-axenic cultures of P. calceolata were capable of growing on various nitrogen sources, including nitrate, urea and cyanate, but not ammonium. RNA sequencing of these cultures revealed that cyanate lyase was under-expressed in the presence of cyanate, indicating that this gene in not involved in the catabolism of extracellular cyanate to ammonia. Conversely, axenic P. calceolata cultures were not able to grow on cyanate, suggesting that the bacterial community consumes cyanate and provides an available form of nitrogen for growth of the alga. Based on environmental datasets and laboratory experiments, we propose that cyanate lyase is important in nitrate-poor environments to reduce the toxicity of intracellular cyanate produced by endogenous nitrogenous compound recycling, rather than being used to metabolise imported extracellular cyanate as an alternative nitrogen source.

genomics↗