
The inside of the algal cell also had surprises in store for the researchers. An S. nivaloides cell has only one chloroplast, whose thylakoids-the disk-shaped membranes where photosynthesis takes place-are not all oriented in the same direction as they are in most photosynthesising organisms. Instead, they fan out to receive light from every direction. Such an adaptation is eminently suited to life in the snow, where light is reflected and diffused as in a hall of mirrors. Mitochondria, the cell’s power plants, surround the chloroplast to receive and process the starch it synthesizes. Finally, the team focused on the red carotenoid pigments of S. nivaloides. These apparently do not shield the cell nucleus from UV radiation, as had been thought, but protect the algae from the harmful effects of free radicals within an environment bathed in intense light.
When the snow around it has melted, S. nivaloides is deposited in the soil, where it metamorphoses to adapt to this completely different environment. The scientists would now like to understand this transformation process, which has never been studied before. Here time is of the essence because the entire ecosystem built around S. nivaloides is threatened by climate change and decreased mountain snowfall.
1 The team’s members hail from the Cell & Plant Physiology Laboratory (LPCV) (CNRS/CEA/UGA/INRAE), the French National Centre for Meteorological Research (CNRM) (CNRS/Météo-France), the Modelling and Exploration of Materials (MEM) laboratory (CEA/UGA), the Institut de Biologie Structurale (CNRS/CEA/UGA), and the Lautaret Garden support and research unit (CNRS/UGA).
Adaptative traits of cysts of the snow alga Sanguina nivaloides unveiled by 3D subcellular imaging. E. Maréchal, et al . Nature Communications , 18 november 2023.
DOI: https://doi.org/10.1038/s41467’023 -43030-7