Genome of the glacier alga Ancylonema and its insights into the evolution of streptophyte life on ice and land
Genome of the glacier alga Ancylonema and its insights into the evolution of streptophyte life on ice and land
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DOI：
10.1101/2023.10.20.563300
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发表时间：
2023-10
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影响因子：
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通讯作者：
Alexander M. C. Bowles;T. Williams;P. Donoghue;Douglas A. Campbell;Christopher J. Williamson
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作者：
Alexander M. C. Bowles;T. Williams;P. Donoghue;Douglas A. Campbell;Christopher J. Williamson
当代冰川和冰盖是链藻冰藻群落的家园，它们必须在光合作用和生长要求与对极端温度、干燥和紫外线辐射的耐受性之间取得平衡。这些同样的环境挑战被假设为低温纪链藻类祖先(7.2亿-6.35亿年前)陆地植物进化的驱动力。在这里，我们对冰川藻类AncyLonema Nordenskiöldii的超基因组组装基因组(MAG)进行测序、组装和分析，以研究它对冰中生命的适应，以及这是否代表了低温水生植物剥离的遗迹。系统发育分析证实，冰川藻类位于陆地植物Zygnematophyceae的姊妹谱系中。MAG的特征是涉及高辐射和紫外线耐受性的基因的扩展，而特定谱系的多样化导致了冰川藻类的新的筛选色素作用。我们没有发现支持一个共同的基因组基础的假说，以适应冰川和登陆链藻。比较基因组学分析表明，Zygnematophyceae祖先的还原基因组进化与其还原形态进化相关。这第一个冰川藻类基因组规模的数据支持线虫特有的冰冻圈适应，并揭示了陆地植物和Zygnematophyceae的基因组进化。
Contemporary glaciers and ice sheets are home to communities of streptophyte glacier algae that must balance their requirements for photosynthesis and growth with tolerance of extremes in temperature, desiccation and UV radiation. These same environmental challenges have been hypothesized as the driving force behind the evolution of land plants from streptophyte algal ancestors in the Cryogenian (720–635 million years ago). Here, we sequence, assemble and analyze the metagenome-assembled genome (MAG) of the glacier alga Ancylonema nordenskiöldii to investigate its adaptations to life in ice, and whether this represents a vestige of Cryogenian anydrophyte exaptations. Phylogenetic analysis confirms the placement of glacier algae within the sister lineage to land plants, Zygnematophyceae. The MAG is characterized by an expansion of genes involved in high irradiance and UV light tolerance, whilst lineage-specific diversification led to the novel screening pigmentation of glacier algae. We found no support for the hypothesis of a common genomic basis for adaptations to ice and to land in streptophytes. Comparative genomic analysis revealed that reductive genome evolution in the ancestor of Zygnematophyceae correlates with their reductive morphological evolution. This first genome-scale data for glacier algae supports an Ancylonema-specific adaptation to the cryosphere, as well as shedding light on the genome evolution of land plants and Zygnematophyceae.