Chromosome rearrangements are arguably the most dramatic type of mutations, often leading to rapid evolution and speciation. However, chromosome dynamics have only been studied at the sequence level in a small number of model systems. In insects, Diptera and Lepidoptera have conserved genome structure at the scale of whole chromosomes or chromosome arms. Whether this reflects the diversity of insect genome evolution is questionable given that many species exhibit rapid karyotype evolution. Here, we investigate chromosome evolution in aphids – an important group of hemipteran plant pests – using newly generated chromosome-scale genome assemblies of the green peach aphid (Myzus persicae) and the pea aphid (Acyrthosiphon pisum), and a previously published assembly of the corn-leaf aphid (Rhopalosiphum maidis). We find that aphid autosomes have undergone dramatic reorganisation over the last 30 million years, to the extent that chromosome homology cannot be determined between aphids from the tribes Macrosiphini (M. persicae and A. pisum) and Aphidini (R. maidis). In contrast, gene content of the aphid sex (X) chromosome remained unchanged despite rapid sequence evolution, low gene expression and high transposable element load. To test whether rapid evolution of genome structure is a hallmark of Hemiptera, we compared our aphid assemblies to chromosome-scale assemblies of two blood-feeding Hemiptera (Rhodnius prolixus and Triatoma rubrofasciata). Despite being more diverged, the blood-feeding hemipterans have conserved synteny. The exceptional rate of structural evolution of aphid autosomes renders them an important emerging model system for studying the role of large-scale genome rearrangements in evolution.

中文翻译：

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蚜虫的染色体规模基因组组装揭示了常染色体的广泛重排和 X 染色体的长期保守。

染色体重排可以说是最引人注目的突变类型，通常会导致快速进化和物种形成。然而，染色体动力学仅在少数模型系统的序列水平上进行了研究。在昆虫中，双翅目和鳞翅目在整个染色体或染色体臂的尺度上具有保守的基因组结构。鉴于许多物种表现出快速的核型进化，这是否反映了昆虫基因组进化的多样性值得怀疑。在这里，我们利用新生成的绿桃蚜 ( Myzus persicae ) 和豌豆蚜 ( Acyrthosiphon pisum ) 的染色体级基因组组装，以及之前发表的玉米叶蚜（Rhopalosiphummaidis）。我们发现，在过去的 3000 万年里，蚜虫常染色体经历了巨大的重组，以至于无法确定来自 Macrosiphini（M. persicae和A. pisum）部落和 Aphidini（R. maidis）部落的蚜虫之间的染色体同源性。相比之下，尽管序列进化快速、基因表达量低和转座元件负载高，但蚜虫性（X）染色体的基因内容保持不变。为了测试基因组结构的快速进化是否是半翅目的标志，我们将我们的蚜虫组装体与两种吸血半翅目（Rhodnius prolixus和Triatoma rubrofasciata）的染色体规模组装进行了比较。尽管更加分化，吸血半翅目动物仍保持同线性。蚜虫常染色体异常的结构进化速度使其成为研究大规模基因组重排在进化中的作用的重要新兴模型系统。