Unit on Chromosome Dynamics, Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America.
TriLab Bioinformatics Group, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
PLoS Genet. 2024 Jun 24;20(6):e1011329. doi: 10.1371/journal.pgen.1011329. eCollection 2024 Jun.
Precise regulation of chromosome dynamics in the germline is essential for reproductive success across species. Yet, the mechanisms underlying meiotic chromosomal events such as homolog pairing and chromosome segregation are not fully understood in many species. Here, we employ Oligopaint DNA FISH to investigate mechanisms of meiotic homolog pairing and chromosome segregation in the holocentric pantry moth, Plodia interpunctella, and compare our findings to new and previous studies in the silkworm moth, Bombyx mori, which diverged from P. interpunctella over 100 million years ago. We find that pairing in both Bombyx and Plodia spermatogenesis is initiated at gene-rich chromosome ends. Additionally, both species form rod shaped cruciform-like bivalents at metaphase I. However, unlike the telomere-oriented chromosome segregation mechanism observed in Bombyx, Plodia can orient bivalents in multiple different ways at metaphase I. Surprisingly, in both species we find that kinetochores consistently assemble at non-telomeric loci toward the center of chromosomes regardless of where chromosome centers are located in the bivalent. Additionally, sister kinetochores do not seem to be paired in these species. Instead, four distinct kinetochores are easily observed at metaphase I. Despite this, we find clear end-on microtubule attachments and not lateral microtubule attachments co-orienting these separated kinetochores. These findings challenge the classical view of segregation where paired, poleward-facing kinetochores are required for accurate homolog separation in meiosis I. Our studies here highlight the importance of exploring fundamental processes in non-model systems, as employing novel organisms can lead to the discovery of novel biology.
精确调控生殖细胞中染色体的动态变化对于物种的生殖成功至关重要。然而，在许多物种中，同源染色体配对和染色体分离等减数分裂染色体事件的机制尚未完全了解。在这里，我们使用寡核苷酸 DNA FISH 来研究全染色体 pantry 蛾 Plodia interpunctella 中的减数分裂同源染色体配对和染色体分离的机制，并将我们的发现与新的和以前在丝蛾 Bombyx mori 中的研究进行比较，Bombyx mori 与 P. interpunctella 分化超过 1 亿年。我们发现，Bombyx 和 Plodia 精子发生中的配对都是从富含基因的染色体末端开始的。此外，这两个物种在减数分裂 I 中期都形成棒状十字形二价体。然而，与在 Bombyx 中观察到的端粒定向染色体分离机制不同，Plodia 可以在减数分裂 I 中期以多种不同的方式定向二价体。令人惊讶的是，在这两个物种中，我们发现无论染色体中心位于二价体中的何处，动粒始终在染色体中心的非端粒区域组装。此外，在这些物种中，姐妹动粒似乎没有配对。相反，在减数分裂 I 中期很容易观察到四个不同的动粒。尽管如此，我们发现明显的端对端微管附着，而不是侧向微管附着，共同将这些分离的动粒定向。这些发现挑战了经典的分离观点，即配对的、朝向极点的动粒对于减数分裂 I 中同源染色体的准确分离是必需的。我们在这里的研究强调了在非模型系统中探索基本过程的重要性，因为采用新的生物体可以发现新的生物学。
