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首页> 外文期刊>PLoS Genetics >The SNAP hypothesis: Chromosomal rearrangements could emerge from positive Selection during Niche Ada ptation
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The SNAP hypothesis: Chromosomal rearrangements could emerge from positive Selection during Niche Ada ptation

机译：快照假设：染色体重排可以从阳性<下划线> s 选举中出现<下划线> n iChe A DA <下划线> P Tation

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The relative linear order of most genes on bacterial chromosomes is not conserved over evolutionary timescales. One explanation is that selection is weak, allowing recombination to randomize gene order by genetic drift. However, most chromosomal rearrangements are deleterious to fitness. In contrast, we propose the hypothesis that rearrangements in gene order are more likely the result of selection during niche adaptation (SNAP). Partial chromosomal duplications occur very frequently by recombination between direct repeat sequences. Duplicated regions may contain tens to hundreds of genes and segregate quickly unless maintained by selection. Bacteria exposed to non-lethal selections (for example, a requirement to grow on a poor nutrient) can adapt by maintaining a duplication that includes a gene that improves relative fitness. Further improvements in fitness result from the loss or inactivation of non-selected genes within each copy of the duplication. When genes that are essential in single copy are lost from different copies of the duplication, segregation is prevented even if the original selection is lifted. Functional gene loss continues until a new genetic equilibrium is reached. The outcome is a rearranged gene order. Mathematical modelling shows that this process of positive selection to adapt to a new niche can rapidly drive rearrangements in gene order to fixation. Signature features (duplication formation and divergence) of the SNAP model were identified in natural isolates from multiple species showing that the initial two steps in the SNAP process can occur with a remarkably high frequency. Further bioinformatic and experimental analyses are required to test if and to which extend the SNAP process acts on bacterial genomes.
机译：细菌染色体上大多数基因的相对线性顺序在进化时间表上不保守。一种解释是选择弱，允许通过遗传漂移将基因级随机化。然而，大多数染色体重排都对健身有害。相比之下，我们提出了基因令重新排列的假设更可能在利基适应期间选择的结果（SNAP）。通过直接重复序列之间的重组发生部分染色体重复性。除非通过选择保持，否则重复的区域可以包含数十个基因和数百个基因和分离。暴露于非致命选择的细菌（例如，在较差的营养物上生长）可以通过维持包含改善相对适应性的基因的重复来适应。对健身的进一步改善是由于每份重复的每拷贝中未选择基因的损失或灭活。当单拷贝中必不可少的基因被从复制的不同副本中丢失时，即使原始选择被提升，也可以防止分离。功能基因损失持续，直至达到新的遗传平衡。结果是重新排列的基因令。数学建模表明，这种适应新的利基的阳性选择的过程可以快速地驱动基因顺序排列到固定。在来自多种物种的自然分离物中识别符号特征（重复的形成和分歧），从而显示快速的初始两个步骤可以以显着的高频发生。需要进一步的生物信息和实验分析来测试延伸延长捕获过程的作用对细菌基因组。

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