Nature Communications (Nov 2023)

Adaptive traits of cysts of the snow alga Sanguina nivaloides unveiled by 3D subcellular imaging

  • Jade A. Ezzedine,
  • Clarisse Uwizeye,
  • Grégory Si Larbi,
  • Gaelle Villain,
  • Mathilde Louwagie,
  • Marion Schilling,
  • Pascal Hagenmuller,
  • Benoît Gallet,
  • Adeline Stewart,
  • Dimitris Petroutsos,
  • Fabienne Devime,
  • Pascal Salze,
  • Lucie Liger,
  • Juliette Jouhet,
  • Marie Dumont,
  • Stéphane Ravanel,
  • Alberto Amato,
  • Jean-Gabriel Valay,
  • Pierre-Henri Jouneau,
  • Denis Falconet,
  • Eric Maréchal

DOI
https://doi.org/10.1038/s41467-023-43030-7
Journal volume & issue
Vol. 14, no. 1
pp. 1 – 17

Abstract

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Abstract Sanguina nivaloides is the main alga forming red snowfields in high mountains and Polar Regions. It is non-cultivable. Analysis of environmental samples by X-ray tomography, focused-ion-beam scanning-electron-microscopy, physicochemical and physiological characterization reveal adaptive traits accounting for algal capacity to reside in snow. Cysts populate liquid water at the periphery of ice, are photosynthetically active, can survive for months, and are sensitive to freezing. They harbor a wrinkled plasma membrane expanding the interface with environment. Ionomic analysis supports a cell efflux of K+, and assimilation of phosphorus. Glycerolipidomic analysis confirms a phosphate limitation. The chloroplast contains thylakoids oriented in all directions, fixes carbon in a central pyrenoid and produces starch in peripheral protuberances. Analysis of cells kept in the dark shows that starch is a short-term carbon storage. The biogenesis of cytosolic droplets shows that they are loaded with triacylglycerol and carotenoids for long-term carbon storage and protection against oxidative stress.