The evolution of the molecular adaptation mechanisms in more than 1.8 billion years diverging snow algae

Dr. Tim Rieseberg

University of Salzburg

Snow and glacier ice algae are widespread around the globe and include phylogenetically diverse organisms from different kingdoms, 1.8 billion years divergent from each other. Despite their biodiversity and evolutionary distance, the strong physics of snow and ice habitats at elevated altitudes forces photosynthetic organisms to cope with the strong oxidative stressors (strong light intensity, UV, temperature stressors) of their environment in similar ways. Molecular tools that enable a photosynthetic lifestyle under the harsh conditions found on glaciers are still elusive. Evolutionary distant microalgae from Dinophytes to Zygnematophyceae were subjected to combined highlight and UV stress at low temperatures in a phytotron simulation device and the following glacial stress scenario were simulated: Snow coverage (low PAR, no UV, control), melted snow with full sunshine (high PAR +UVA and UVB, stress treatment), overcast weather (low PAR, no UV, recovery). To understand the genetic stress response to combined high light and UVA/B radiation at low temperatures, as well as its evolutionary conservation and divergence, time-resolved RNAseq samples for transcriptome analysis from three species were taken, and morphological changes upon stress exposure and recovery analyzed.