Monocots are one of the most diverse groups of flowering plants, and tracing the evolution of their ancestral genome into modern species is essential for understanding their evolutionary success. Here, we report a high-quality assembly of the Acorus tatarinowii genome, a species that diverged early from all the other monocots. Genome-wide comparisons with a range of representative monocots characterized Acorus as a slowly evolved genome with one whole-genome duplication. Our inference of the ancestral monocot karyotypes provides new insights into the chromosomal evolutionary history assigned to modern species and reveals the probable molecular functions and processes related to the early adaptation of monocots to wetland or aquatic habitats (that is, low levels of inorganic phosphate, parallel leaf venation and ephemeral primary roots). The evolution of ancestral gene order in monocots is constrained by gene structural and functional features. The newly obtained Acorus genome offers crucial evidence for delineating the origin and diversification of monocots, including grasses.

单子叶植物是最多样化的开花植物群之一，追踪其祖先基因组向现代物种的进化对于了解它们的进化成功至关重要。在这里，我们报告了Acorus tatarinowii基因组的高质量组装，该物种很早就从所有其他单子叶植物中分化出来。与以Acorus为特征的一系列代表性单子叶植物进行全基因组比较作为一个缓慢进化的基因组，具有一个全基因组重复。我们对祖先单子叶植物核型的推断为现代物种的染色体进化史提供了新的见解，并揭示了与单子叶植物早期适应湿地或水生生境相关的可能的分子功能和过程（即低水平的无机磷酸盐，平行叶脉和短暂的初生根）。单子叶植物祖先基因顺序的进化受到基因结构和功能特征的限制。新获得的Acorus基因组为描绘包括草在内的单子叶植物的起源和多样化提供了重要证据。