CE34 - Contaminants, écosystèmes et santé

Deciphering the molecular mechanisms underlying the tolerance and accumulation of metals in a metal-hypertolerant green microalga of the Coelastrella genus – DemoniaCo

Conventional cell biology and plant physiology approaches are used to study metal tolerance in Coelastrella.

Our first results describe the physiological responses of Coelastrella in a synthetic medium containing U. Taken together, our data indicate that Coelastrella is a U-tolerant, hyperaccumulative green microalga capable of depolluting contaminated natural waters with complex metal speciation, while accumulating valuable compounds (lipids).

Cell imaging experiments are underway to localize and quantify the U accumulated in the alga. The molecular responses of Coelastrella to U are currently being analyzed.

Camille Beaulier, Marie Dannay, Fabienne Devime, Célia Baggio, Nabila El Sakkout, Camille Raillon, Olivier Courson, Jacques Bourguignon, Claude Alban, Stéphane Ravanel. Characterization of a uranium-tolerant green microalga of the genus Coelastrella with high potential for the remediation of metal-polluted waters. doi.org/10.1101/2023.06.29.546994

Submission summary

Pollution of terrestrial and aquatic ecosystems by trace metal elements, also referred to as heavy metals, is a major and ever-growing threat to environmental and human health. A better understanding of the effects of toxic elements on land plants and microalgae is critical to develop approaches for treating contaminated environments using phyto- and phycoremediation processes The identification and characterization of organisms that tolerate and accumulate metals are essential to reach these objectives. Indeed, these organisms evolved sophisticated molecular mechanisms to cope with toxic elements. Deciphering these strategies may indicate how plants/algae might behave in contamination scenario and could provide clues for new biotechnological applications for the capture of metals.
We isolated a metal-hypertolerant unicellular photosynthetic microalga from an environment contaminated with uranium, a chemotoxic radionuclide. This green microalga was identified by 18S rDNA sequencing as a Coelastrella species, hereafter designated Cos. Because it is able to live in culture media contaminated with high concentrations of uranium or silver, we assume that Cos has evolved unique molecular mechanisms to survive in environments polluted by toxic elements. In support of our hypothesis, it is known that some metal-tolerant land plants and microalgae have established efficient strategies to cope with metals (e.g. cellular uptake and efflux, compartmentalization, detoxification by chelators). The key genetic loci that explain the unique metal-tolerance and accumulation properties have been identified only in some land plants, for example in the zinc and cadmium hypertolerant Arabidopsis halleri species. These findings were essential to better understand metal homeostasis in both tolerant and non-tolerant species. In addition, they were the basis for new strategies to improve the phytoextraction properties of fast-growing, high-biomass but non-tolerant plant species. In green microalgae, however, the genes involved in metal tolerance and accumulation have never been identified. The objective of the DemoniaCo project is to fill this gap and unravel the molecular mechanisms involved in the tolerance and accumulation of toxic metals in Coelastrella sp. To this aim, we will use a combination of cell physiology and systems-based approaches, including a thorough analysis of the toxicological outcomes of metals on the transcriptome, proteome, ionome, and metabolome of the alga. This unprecedented multiscale and integrative strategy will provide new insights into the fundamental and applied biology of a metal-hypertolerant green microalga. Besides the identification of the gene network enabling Cos to tolerate uranium and silver, the expected results of the project include the characterization of Cos tolerance to a variety of toxic elements, the characterization of metal uptake and subcellular distribution in algal cells, the behaviour of the microalga in natural metal-contaminated waters to estimate its performance for phycoremediation, and the investigation of the potential of Cos as an oleaginous model species for the production of lipids for biofuel applications.

Project coordinator

Monsieur Stéphane Ravanel (LABORATOIRE DE PHYSIOLOGIE CELLULAIRE ET VEGETALE)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

LPCV LABORATOIRE DE PHYSIOLOGIE CELLULAIRE ET VEGETALE
BFP Biologie du Fruit et Pathologie

Help of the ANR 428,009 euros
Beginning and duration of the scientific project: December 2021 - 48 Months

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