Recurrent losses and rapid evolution of the condensin II complex in insects

Condensins play a crucial role in the organization of genetic material by compacting and disentangling chromosomes. Based on studies in a few model organisms, the condensin I and condensin II complexes are considered to have distinct functions, with the condensin II complex playing a role in meiosis and somatic pairing of homologous chromosomes in Drosophila. Intriguingly, the Cap-G2 subunit of condensin II is absent in Drosophila melanogaster, and this loss may be related to the high levels of chromosome pairing seen in flies. Here, we find that all three non-SMC subunits of condensin II (Cap-G2, Cap-D3, and Cap-H2) have been repeatedly and independently lost in taxa representing multiple insect orders, with some taxa lacking all three. We also find that all non-Dipteran insects display near-uniform low pairing levels regardless of their condensin II complex composition, suggesting that some key aspects of genome organization are robust to condensin II subunit losses. Finally, we obser...

凝缩蛋白（Condensins）通过压缩并解缠染色体，在遗传物质的组织过程中发挥关键作用。基于针对少数模式生物的研究，凝缩蛋白I（condensin I）与凝缩蛋白II（condensin II）复合物被认为具有截然不同的功能，其中凝缩蛋白II复合物在果蝇（Drosophila）中参与减数分裂（meiosis）以及同源染色体的体细胞配对过程。值得注意的是，黑腹果蝇（Drosophila melanogaster）中缺乏凝缩蛋白II的Cap-G2亚基，这一缺失可能与该物种染色体的高配对水平相关。本研究发现，代表多个昆虫目的类群中，凝缩蛋白II的三个非SMC亚基（non-SMC subunits，即Cap-G2、Cap-D3与Cap-H2）均经历了多次独立的丢失事件，部分类群甚至完全缺失这三个亚基。研究同时发现，所有非双翅目（non-Dipteran）昆虫的染色体配对水平均普遍偏低，且与其凝缩蛋白II复合物的组成无关，这表明基因组组织的某些关键特征对凝缩蛋白II亚基的缺失具有鲁棒性。最后，我们观测到……