Conserved Environmental Programs of Streptophyte Cells

A single monophylum accounts for our entire macroflora: the embryophytes, thus referred to as land plants. Emerging from streptophyte algae, the embryophyte lineage successfully established itself and massively radiated on land. What allowed for this singular success story? One of the features strictly required and particularly prominent in land plants is the ability to adjust their growth and physiology according to environmental cues specifically encountered in terrestrial habitats. Land plant physiology is plastic. This plasticity hinges on a flow of information from sensing cues to adjusting internal programs. Here, my team and I will study the evolution of this flow of information to establish what defines this program. In the last decade, research into early plant evolution has moved from a clarification of who the closest relatives of land plants are to an understanding of which genes are shared across 600 million years of streptophyte evolution. Key genes for stress response previously thought specific to land plants are in fact active in their algal relatives. Now, with first genetic tools for these algae at hand we can establish how evolution has assembled these ancient genes into functional molecular programs that underpin decisive traits inherent to streptophyte cells. These traits concertedly act in a single cell. Sub-functionalization of these genes has yielded a flow of form and function in land plants, obscuring their core functions. We will combine genetics and high-throughput assessment of a unicellular alga and cell suspension cultures in land plants to study the core gene network hierarchy for acclimation to environmental perturbation. Using network analyses for data integration that build on genetic manipulation, time-course phopshpoproteomics and transcriptomic data, we will uncover decisive shared hubs and highlight their conserved and divergent interactions. Our work will establish the shared genetic architecture of the streptophyte program.