iDAPT · iDAPT: ice Dependent Adaptations for Plant Terrestrialization

The evolution of a terrestrial flora from within a single fresh-water algal lineage (Streptophyta) represented a singularity in Earth’s history, giving rise to one of the most profound geobiological transitions in the history of the planet. Adaptations key for the transition from aquatic to terrestrial habitats included the ability to tolerate extremes in temperature, desiccation, and radiation; key stressors characteristic of the surfaces of glaciers, where Zygnematophycean ‘ice algae’, some of the closest living relatives to land plants, currently thrive. With this proposal, I hypothesise that glacier surfaces represent important intermediates between aquatic and terrestrial habitats, driving evolution of unique adaptations in ice algal lineages that represent exaptations of ancestral Streptophytes for the colonisation of land. To test my hypothesis, I will unite the disciplines of genomics, engineering, glaciology and biology to constrain ice algal cold-adaptation mechanisms to life in surface ice and provide unique insight into the aspects of Streptophyte biology that enabled the conquest of land. I will achieve this by i) sequencing the genomes of two ice environment specialists that dominate across the cryosphere, allowing identification of ice algal cold-adaptation mechanisms and homologs in extant basal land plant lineages; ii) develop a controlled environment microalgal assessment system, i.e. ‘photosynthetron’, optimised for deployment in surface ice environments in collaboration with a leading developer of high-throughput plant and algal phenotyping platforms; iii) deploy this across the cryosphere to validate cold-adaptation mechanisms identified from genome interrogation and significantly advance our understanding of how life excels within icy environments. Taken together, outcomes will significantly advance the emerging field of glacial microbiology and could represent a fundamental shift in the way we view processes of land plant terrestrialization.