Selection and establishment of charophyte algae model organisms (CharMod)

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Land plants are monophyletic in origin, most probably deriving from a single successful colonization of the terrestrial habitat by a freshwater charophyte alga ca. 500 million years ago. It can be concluded that the charophyte ancestors of land plants, in contrast to the green algae, must necessarily have carried genetically encoded biochemical and molecular adaptive mechanisms enabling them to adapt to the environmental extremes encountered on land.To deepen our evolutionary understanding, and to meet the challenge of maintaining and improving food production, it is essential to learn which traits enabled charophyte (streptophyte) algae to evolve to land plants, adapting to one of the most drastic habitat changes conceivable.One main reason that - so far - only little attention has been paid to traits enabling environmental resilience in charophyte algae is the lack of well established model organisms.Hence, our joined project CharMod therefore seeks: (a) to identify accessions with model organism potential from Charophyceae, Coleochaetophyceae and Zygnematophyceae, representing the classes most closely related to land plants. We aim to identify fast growing organisms with relatively small genomes, capable to perform their life cycle in vitro under axenic conditions, (b) to establish sequence resources on genomic and transcriptomic level for selected accessions, (c) to establish tools to genetically modify these algae, and (d) to carry out proof of concept comparative experiments on osmotic stress and hormonal signaling.It is expected that by providing robust model organisms, related sequence data and experimental tools, this project will help a growing scientific community to perform research on the molecular adaptations having led to the colonization of land by the ancestors of extant charophyte algae.