Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education & State Key Laboratory of Hydraulics & Mountain River Engineering, College of Life Sciences, Sichuan University, Chengdu, China.
State Key Laboratory of Grassland Agro-Ecosystem, Institute of Innovation Ecology, Lanzhou University, Lanzhou, China.
Nat Plants. 2020 Mar;6(3):215-222. doi: 10.1038/s41477-020-0594-6. Epub 2020 Feb 24.
Angiosperms represent one of the most spectacular terrestrial radiations on the planet, but their early diversification and phylogenetic relationships remain uncertain. A key reason for this impasse is the paucity of complete genomes representing early-diverging angiosperms. Here, we present high-quality, chromosomal-level genome assemblies of two aquatic species-prickly waterlily (Euryale ferox; Nymphaeales) and the rigid hornwort (Ceratophyllum demersum; Ceratophyllales)-and expand the genomic representation for key sectors of the angiosperm tree of life. We identify multiple independent polyploidization events in each of the five major clades (that is, Nymphaeales, magnoliids, monocots, Ceratophyllales and eudicots). Furthermore, our phylogenomic analyses, which spanned multiple datasets and diverse methods, confirm that Amborella and Nymphaeales are successively sister to all other angiosperms. Furthermore, these genomes help to elucidate relationships among the major subclades within Mesangiospermae, which contain about 350,000 species. In particular, the species-poor lineage Ceratophyllales is supported as sister to eudicots, and monocots and magnoliids are placed as successively sister to Ceratophyllales and eudicots. Finally, our analyses indicate that incomplete lineage sorting may account for the incongruent phylogenetic placement of magnoliids between nuclear and plastid genomes.
被子植物是地球上最壮观的陆地辐射之一，但它们的早期多样化和系统发育关系仍不确定。造成这种僵局的一个关键原因是缺乏代表早期分化的被子植物的完整基因组。在这里，我们呈现了两种水生物种——芡（Euryale ferox；睡莲目）和硬角苔（Ceratophyllum demersum；金鱼藻目）的高质量、染色体水平的基因组组装，并扩展了被子植物生命之树关键分支的基因组代表性。我们在每个五个主要分支（即睡莲目、木兰类植物、单子叶植物、金鱼藻目和真双子叶植物）中都鉴定到了多个独立的多倍化事件。此外，我们的系统发育基因组学分析，涵盖了多个数据集和多种方法，证实了 Amborella 和睡莲目依次是所有其他被子植物的姐妹群。此外，这些基因组有助于阐明 Mesangiospermae 中的主要亚分支之间的关系，其中包含约 35 万种物种。特别是，物种较少的金鱼藻目被支持为真双子叶植物的姐妹群，单子叶植物和木兰类植物依次被支持为金鱼藻目和真双子叶植物的姐妹群。最后，我们的分析表明，不完全谱系分选可能是木兰类植物在核基因组和质体基因组之间的不一致系统发育位置的原因。
