Data from: Evolution of long centromeres in fire ants

Background: Centromeres are essential for accurate chromosome segregation, yet sequence conservation is low even among closely related species. Centromere drive predicts rapid turnover because some centromeric sequences may compete better than others during female meiosis. In addition to sequence composition, longer centromeres may have a transmission advantage. Results: We report the first observations of extremely long centromeres, covering on average 34 % of the chromosomes, in the red imported fire ant Solenopsis invicta. By comparison, cytological examination of Solenopsis geminata revealed typical small centromeric constrictions. Bioinformatics and molecular analyses identified CenSol, the major centromeric satellite DNA repeat. We found that CenSol sequences are very similar between the two species but the CenSol copy number in S. invicta is much greater than that in S. geminata. In addition, centromere expansion in S. invicta is not correlated with the duplication of CenH3. Comparative analyses revealed that several closely related fire ant species also possess long centromeres. Conclusions: Our results are consistent with a model of simple runaway centromere expansion due to centromere drive. We suggest expanded centromeres may be more prevalent in hymenopteran insects, which use haplodiploid sex determination, than previously considered.

背景：着丝粒（centromere）对于染色体的精准分离至关重要，但即便在近缘物种之间，其序列保守性也极低。着丝粒驱动假说预测着丝粒会发生快速周转，这是因为在雌性减数分裂过程中，部分着丝粒序列相较于其他序列更具竞争优势。除序列组成外，更长的着丝粒可能还拥有更高的传递优势。
结果：本研究首次在红火蚁（Solenopsis invicta）中观察到极长的着丝粒，其平均覆盖34%的染色体区域。相比之下，对热带火蚁（Solenopsis geminata）的细胞学检测显示其着丝粒为典型的小型缢痕结构。通过生物信息学与分子分析，我们鉴定出了主要的着丝粒卫星DNA重复序列CenSol。研究发现，两个物种的CenSol序列相似度极高，但红火蚁中CenSol的拷贝数远高于热带火蚁。此外，红火蚁的着丝粒扩张与CenH3的复制并无关联。比较分析显示，多种近缘火蚁物种同样拥有长着丝粒。
结论：本研究结果与着丝粒驱动引发的简单失控性着丝粒扩张模型相符。我们提出，采用单倍二倍性性别决定机制的膜翅目昆虫中，扩张型着丝粒的分布频率可能比此前认知的更高。