OMICS Approaches to Assess Dinoflagellate Responses to Chemical Stressors

Dinoflagellates are important primary producers known to biosynthesize metabolites of interest and toxins and form Harmful Algae Blooms (HABs). Water conditions such as nutrient availability, anthropogenic contaminants or pH impact dinoflagellate toxin productions, and HABs' formation remains unclear. In this review, we present the recent contributions of OMICs approaches to the investigation of dinoflagellate responses to water chemical stressors. Transcriptomic and proteomic studies highlight whole-cell strategies to cope with nutrient deficiencies. Metabolomic studies offer a great view of toxin, lipid and sugar productions under stressors. However, the confrontation of different OMICs studies is tedious, as approaches are conducted in different species. As for other model organisms, it would be interesting to use multi-OMIC approaches to build a complete view of dinoflagellate responses to chemical stressors. Overcoming the complex genome of dinoflagellates and increasing their genomic resources is therefore essential to push further. The combination of OMICs studies will provide a much-needed global view of molecular processes, which is essential to optimize the production of dinoflagellate metabolites of interest and identify markers of HABs' formation and toxin production events

Donskoy cats as a new model of oculocutaneous albinism with the identification of a splice-site variant in Hermansky-Pudlak Syndrome 5 gene

International audienceIn the feline Donskoy breed, a phenotype that breeders call "pink‐eye," with associated light‐brown skin, yellow irises and red‐eye effect, has been described. Genealogical data indicated an autosomal recessive inheritance pattern. A single candidate region was identified by genome‐wide association study and SNP‐based homozygosity mapping. Within that region, we further identified HPS5 (HPS5 Biogenesis Of Lysosomal Organelles Complex 2 Subunit 2 ) as a strong candidate gene, since HPS5 variants have been identified in humans and animals with Hermansky–Pudlak syndrome 5 or oculocutaneous albinism. A homozygous c.2571‐1G>A acceptor splice‐site variant located in intron 16 of HPS5 was identified in pink‐eye cats. Segregation of the variant was 100% consistent with the inheritance pattern. Genotyping of 170 cats from 19 breeds failed to identify a single carrier in non‐Donskoy cats. The c.2571‐1G>A variant leads to HPS5 exon‐16 splicing that is predicted to produce a 52 amino acids in‐frame deletion in the protein. These results support an association of the pink‐eye phenotype with the c.2571‐1G>A variant. The pink‐eye Donskoy cat extends the panel of reported HPS5 variants and offers an opportunity for in‐depth exploration of the phenotypic consequences of a new HPS5 variant

Targeted and non-targeted metabolomic analyses of Heterocapsa cf. bohaiensis under nickel and iron high concentration and its photophysiology

International audienceMicroalgae are able to adapt and to synthesize valuable compounds in response to abiotic stresses such as temperature, UV-radiation or metallic trace elements. We studied this faculty of adaptation by assessing the impact of high metal concentrations on Heterocapsa cf. bohaiensis, a newly isolated dinoflagellate from the New Caledonian coastal water rich in metals. We cultivated H. cf. bohaiensis in continuous culture mode using 10L photobioreactors and exposed the algae to high concentrations (10-3M) of nickel (Ni2+) and/or iron (Fe2+). We then followed its photosynthetic efficiency using Pulse Amplitude Modulated chlorophyll fluorometry and its metabolome with targeted (HPLC-UV-DAD, GC-MS) and non-targeted (LC-MS2 and NMR) approaches. The photosynthetic measurements indicate that H. cf. bohaiensis is tolerant to Ni2+ but sensitive to Fe2+ high concentrations. In presence of Fe2+, Fv/Fm and rETRm decreased from 0.62 to 0.47 and from 156 to 102, respectively. The JIP-tests (i.e. the fast chlorophyll fluorescence transient) suggest that the reduction of photosynthesis in response to Fe2+ is due to a disruption in the electron transport chain rather than a defect in the PSII light absorption and trapping which are on the contrary enhanced by Fe2+. The metabolomics analyses highlight the variation of the main dinoflagellate pigments, Chlorophyll c and a, peridinin, diadinoxanthin and diatoxanthin in response to time and metals and give a first glimpse on the complex metabolomic response to metal stress. These results bring new knowledge on this species and on the impact of nickel and iron on the microalgae photosynthetic pathway and metabolomic responses

Targeted and non-targeted metabolomic analyses of Heterocapsa cf. bohaiensis under nickel and iron high concentration and its photophysiology

International audienceMicroalgae are able to adapt and to synthesize valuable compounds in response to abiotic stresses such as temperature, UV-radiation or metallic trace elements. We studied this faculty of adaptation by assessing the impact of high metal concentrations on Heterocapsa cf. bohaiensis, a newly isolated dinoflagellate from the New Caledonian coastal water rich in metals. We cultivated H. cf. bohaiensis in continuous culture mode using 10L photobioreactors and exposed the algae to high concentrations (10-3M) of nickel (Ni2+) and/or iron (Fe2+). We then followed its photosynthetic efficiency using Pulse Amplitude Modulated chlorophyll fluorometry and its metabolome with targeted (HPLC-UV-DAD, GC-MS) and non-targeted (LC-MS2 and NMR) approaches. The photosynthetic measurements indicate that H. cf. bohaiensis is tolerant to Ni2+ but sensitive to Fe2+ high concentrations. In presence of Fe2+, Fv/Fm and rETRm decreased from 0.62 to 0.47 and from 156 to 102, respectively. The JIP-tests (i.e. the fast chlorophyll fluorescence transient) suggest that the reduction of photosynthesis in response to Fe2+ is due to a disruption in the electron transport chain rather than a defect in the PSII light absorption and trapping which are on the contrary enhanced by Fe2+. The metabolomics analyses highlight the variation of the main dinoflagellate pigments, Chlorophyll c and a, peridinin, diadinoxanthin and diatoxanthin in response to time and metals and give a first glimpse on the complex metabolomic response to metal stress. These results bring new knowledge on this species and on the impact of nickel and iron on the microalgae photosynthetic pathway and metabolomic responses

Effect of nickel and Iron stress on photosynthesis and metabolite production of Heterocapsa cf. bohaiensis (dinoflagellate).

International audienceMicroalgae are well known to produce valuable compounds in response to abiotic stresses. Among these stresses, metals can influence the production of primary or specific metabolites related to reactive oxygen species formation (Barra et al. 2014; Chen et al. 2017; Paliwal et al. 2017). Heterocapsa cf. bohaiensis, a newly described dinoflagellate species with haemolytic activity, and associated with shrimp (Penaeus japonicas) and crab (Eriocheir sinensis) mortalities (Xiao et al. 2018; Zhang et al. 2019), has been recently isolated in New Caledonian iron and nickel-rich waters (Merrot et al. 2022; Pelletier 2006). To induce the metallic stress and the production of metabolites, we exposed H. cf. bohaiensis to high concentrations (10-3M) of nickel (Ni2+) and/or iron (Fe2+) and investigate its photosynthetic efficiency in continuous culture using Pulse Amplitude Modulated chlorophyll fluorescence. The results indicates that H. cf. bohaiensis is tolerant to Ni2+ but sensitive to Fe2+ high concentrations, without cell death. JIP-test suggest that the reduction of photosynthesis in response to Fe2+ is due to a disruption in the electron transport chain rather than a defect in the PSII light absorption and trapping which are enhanced by Fe2+(Adamski et al. 2011; Redillas et al. 2011; Strasser et al.). These results highlight the toxic mechanisms of Fe2+ in microalgae and help to understand the production of biomass under metallic stress. Studying this species in this particular environment will also bring knowledge in the field of aquaculture and ecotoxicology, owing to the transfer of metals in the food chain (bioaccumulation, biosorption) and to the possible production of toxins. This study will also provide some insights for potential valorisations in the biotechnology and/or cosmetics fields, through the analysis of primary (pigments, fatty acids / antioxidants) and specific metabolites, with interesting activities, produced under metal stress conditions