Out of the Water: Algae and Mosses Adapt to Living on Land

The move out of the water was an evolutionary milestone of early land plants. Streptophyte algae and bryophytes belong to these early settlers and are ideal models that range in complexity from filaments to multicellular 3-D bodies. They adapted on different hierarchical levels (tissues, cells, interfaces, cell wall) and life cycles (vegetative organs, rigid spores). In-depth understanding of the different life forms from organ to micro to nano level and their in-situ reactions upon desiccation are missing, although necessary to understand adaptations under changing environments. Three flagship species groups will be investigated during realistic desiccation scenarios: 1) streptophyte algae with different abilities to tolerate desiccation like Klebsormidium sp. and Zygnema circumcarinatum (Zygnematopyhceae), 2) the liverwort Riccia fluitans (Ricciaceae) with terrestrial as well as water-prone representatives and 3) the moss Physcomitrium patens (Funariaceae). Our integrative approach is combining cell biological, biochemical and biophysical methods to study the properties and rearrangements of cells in early land plants. The data will be used to develop a predictive biophysical model for cellular reactions to dehydration/desiccation scenarios. In-situ analysis of cell walls and surfaces of the flagship species under desiccation will give insights into adaptations in different life cycles as well as remodeling and microstructural changes upon drying. We will gain a better view on the properties of distinct layers from the cortical cytoplasm, the plasma membrane, the cell wall and the cuticle and by finite element models on the role of cell-shape, cell wall thickness and mechanical properties on buckling and wrinkling of the cells. With innovative multidisciplinary approaches we will tackle a common research question from various angles. We will gather essential information on adaptation to desiccation and climate change in algae and mosses. These early land plants are leading the way as they managed to move out of the water to thrive in a changing environment. We will learn from evolution for the present and future.