Thoracic underreplication in Drosophila species estimates a minimum genome size and the dynamics of added DNA
Thoracic underreplication in Drosophila species estimates a minimum genome size and the dynamics of added DNA
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DOI：
10.1111/evo.14022
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发表时间：
2020-05-31
期刊：
影响因子：
3.3
通讯作者：
Johnston, John Spencer
中科院分区：
文献类型：
--
作者：
Hjelmen, Carl E.;Holmes, Valerie Renee;Johnston, John Spencer
果蝇胸部的许多细胞在复制过程中被发现停滞，这种现象被称为复制不足。与唾液细胞和滤泡细胞核中的复制不足不同，这种停滞发生在不到一个完整的复制轮中。这个停滞点允许精确估计早期复制的常染色质和晚期复制的异染色质区域，提供了一个强大的工具来研究整个基因组的结构变化的动态。我们测量了果蝇属132个物种的复制不足，并利用这些数据提出了一个模型，用于估计额外的DNA作为异染色质和常染色质积累的速率，并预测果蝇的最小基因组大小。根据比较系统发育的方法，异染色质的变化率显着不同的果蝇亚属。虽然这些亚属在核型上不同，但在染色体数目上没有差异，这表明其他结构变化可能影响异染色质的积累。对两种性别都进行了测量，从而使XY性染色体分化的假设路径的基因组大小和异染色质变化可视化。此外，这里提出的模型估计Sophophora的最小基因组大小非常接近迄今为止测量的最小昆虫基因组，在一个与果蝇有2亿多年差异的物种中。
Many cells in the thorax of Drosophila were found to stall during replication, a phenomenon known as underreplication. Unlike underreplication in nuclei of salivary and follicle cells, this stall occurs with less than one complete round of replication. This stall point allows precise estimations of early-replicating euchromatin and late-replicating heterochromatin regions, providing a powerful tool to investigate the dynamics of structural change across the genome. We measure underreplication in 132 species across the Drosophila genus and leverage these data to propose a model for estimating the rate at which additional DNA is accumulated as heterochromatin and euchromatin and also predict the minimum genome size for Drosophila. According to comparative phylogenetic approaches, the rates of change of heterochromatin differ strikingly between Drosophila subgenera. Although these subgenera differ in karyotype, there were no differences by chromosome number, suggesting other structural changes may influence accumulation of heterochromatin. Measurements were taken for both sexes, allowing the visualization of genome size and heterochromatin changes for the hypothetical path of XY sex chromosome differentiation. Additionally, the model presented here estimates a minimum genome size in Sophophora remarkably close to the smallest insect genome measured to date, in a species over 200 million years diverged from Drosophila.