%0 Journal Article %J Journal of Phycology %D 2019 %T Differential Influence of Life Cycle on Growth and Toxin Production of three Pseudo‐nitzschia species (Bacillariophyceae) %A Aurore Sauvey %A Pascal Claquin %A Bertrand Le Roy %A Le Gac, Mickael %A Juliette Fauchot %E Kroth, P. %B Journal of Phycology %V 55 %P 1126 - 1139 %8 Mar-10-2021 %G eng %U https://onlinelibrary.wiley.com/toc/15298817/55/5 %N 5 %! J. Phycol. %R 10.1111/jpy.v55.510.1111/jpy.12898 %0 Journal Article %J Journal of Phycology %D 2019 %T Differential Influence of Life Cycle on Growth and Toxin Production of three Pseudo-nitzschia Species (Bacillariophyceae) %A Aurore Sauvey %A Pascal Claquin %A Le Roy, Bertrand %A Le Gac, Mickael %A Juliette Fauchot %X We used a multistrain approach to study the intra- and interspecific variability of the growth rates of three Pseudo-nitzschia species – P. australis, P. fraudulenta, and P. pungens – and of their domoic acid (DA) production. We carried out mating and batch experiments to investigate the respective effects of strain age and cell size, and thus the influence of their life cycle on the physiology of these species. The cell size – life cycle relationship was characteristic of each species. The influence of age and cell size on the intraspecific variability of growth rates suggests that these characteristics should be considered cautiously for the strains used in physiological studies on Pseudo-nitzschia species. The results from all three species do not support the hypothesis of a decrease in DA production with time since isolation from natural populations. In P. australis, the cellular DA content was rather a function of cell size. More particularly, cells at the gametangia stage of their life cycle contained up to six times more DA than smaller or larger cells incapable of sexual reproduction. These findings reveal a link between P. australis life cycle and cell toxicity. This suggest that life cycle dynamics in Pseudo-nitzschia natural populations may influence bloom toxicity. © 2019 Phycological Society of America %B Journal of Phycology %V 55 %P 1126-1139 %G eng %U https://onlinelibrary.wiley.com/doi/abs/10.1111/jpy.12898 %R 10.1111/jpy.12898 %0 Journal Article %J Genome Biology and Evolution %D 2019 %T Inter- and Intra-Specific Transcriptional and Phenotypic Responses of Pseudo-nitzschia under Different Nutrient Conditions %A Lema, Kimberley A. %A Metegnier, G. %A Quéré, J. %A Latimier, Marie %A Agnès Youenou %A Lambert, Christophe %A Juliette Fauchot %A Le Gac, Mickael %A Costantini, M. %K analogs and derivatives %K Biological Evolution %K comparative study %K Diatom %K Diatoms %K Domoic acid %K evolution %K kainic acid %K Metabolism %K Multigene Family %K Nutrients %K Phenotype %K Physiology %X Untangling thefunctionalbasis of divergencebetweenclosely relatedspecies is a steptowardunderstanding speciesdynamicswithin communities at both the evolutionary and ecological scales. We investigated cellular (i.e., growth, domoic acid production, and nutrient consumption) and molecular (transcriptomic analyses) responses to varying nutrient concentrations across several strains belonging to three species of the toxic diatomgenus Pseudo-nitzschia. Threemain resultswere obtained. First, strains fromthe same species displayed similar transcriptomic, but not necessarily cellular, responses to the experimental conditions. It showed the importance of considering intraspecific diversity to investigate functional divergence between species. Second, a major exception to the first findingwas a strain recently isolated fromthe natural environment and displaying contrasting gene expression patterns related to cell motility and domoic acid production. This result illustrated the profound modifications thatmay occurwhen transferring a cell fromthe natural to the in vitro environment and asks for future studies to better understand the influence of culture duration and life cycleon expression patterns. Third, transcriptomic responsesweremore similarbetween the two speciesdisplaying similar ecology in situ, irrespective of the genetic distance. This was especially true formolecular responses related to TCA cycle, photosynthesis, and nitrogen metabolism. However, transcripts related to phosphate uptake were variable between species. It highlighted the importance of considering both overall genetic distance and ecological divergence to explain functional divergence between species. © The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. %B Genome Biology and Evolution %I Oxford University Press %V 11 %P 731-747 %G eng %U https://academic.oup.com/gbe/article/11/3/731/5332980 %R 10.1093/gbe/evz030 %0 Journal Article %J Harmful Algae %D 2017 %T Inter and intra-specific growth and domoic acid production in relation to nutrient ratios and concentrations in Pseudo-nitzschia: phosphate an important factor %A Lema, Kimberley A. %A Latimier, Marie %A Nézan, Elisabeth %A Juliette Fauchot %A Le Gac, Mickael %X

The factors responsible for inducing the synthesis of toxins and responses from toxic phytoplankton
blooms remain unclear. In this study we compare the influence of genotypic (at both the intra and
interspecific levels) and environmental factors (nutrient concentration and ratio) on growth (in terms of
cell densities) and domoic acid (DA) production in three Pseudo-nitzschia species: P. australis, P.pungens
and P.fradulenta. A strong phosphate effect was detected. More precisely, a low initial concentration in
phosphate, even at high initial nitrogen and silicate concentrations, induced the highest DA
concentrations and the lowest cell densities in all strains/species studied. In contrast, a low initial
concentration of nitrogen and silicate combined, with a higher phosphate concentration resulted in low
cell densities, but without high DA production. Inter-species effects were also observed in DA production,
where P. australis represented the most toxigenic species of all. Intra-specific variations were only
moderate, except for a recently isolated P. australis strain, suggesting the influence of time since isolation
on the physiology and DA production of Pseudo-nitzschia species. Overall, the lack of strong interaction
between environmental and genotypic factors showed that the various genotypes investigated did not
extensively diverge in their ability to respond (in terms of DA production and cell densities) to contrasting
nutrient supply.

%B Harmful Algae %V 64 %P 11-19 %G eng %U https://www.sciencedirect.com/science/article/pii/S1568988316303687 %R http://dx.doi.org/10.1016/j.hal.2017.03.001