Selection and establishment of charophyte algae model organisms (CharMod)

陆地植物的起源是单系的，很可能起源于大约5亿年前一种淡水轮藻对陆地栖息地的一次成功殖民。可以得出的结论是，与绿藻相比，轮藻的祖先必然携带着遗传编码的生化和分子适应机制，使它们能够适应陆地上遇到的极端环境。为了加深我们对进化的理解，并迎接维持和提高粮食产量的挑战，了解哪些特征使轮藻(链藻)能够进化为陆地植物，以适应可能发生的最剧烈的生境变化。一个主要原因是，到目前为止，很少有人关注轮藻具有环境适应能力的特征。因此，我们加入的项目CharMod寻求：(A)从轮藻亚科、鞘毛藻亚科和合欢藻亚科鉴定具有模式生物潜力的种质，代表与陆地植物关系最密切的纲。我们的目标是寻找基因组相对较小、能够在无菌条件下进行体外生命周期的快速生长生物，(B)在基因组和转录水平上建立选定材料的序列资源，(C)建立对这些藻类进行基因改造的工具，以及(D)开展渗透胁迫和激素信号的概念验证比较实验。预计通过提供强大的模式生物、相关的序列数据和实验工具，该项目将帮助越来越多的科学界开展导致现有轮藻祖先定居土地的分子适应研究。

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.