多样性生成逆转录元件在切换环境中的进化优势
Evolutionary Advantage of Diversity-Generating Retroelements in Switching Environments
AI总结：
研究揭示了多样性生成逆转录元件在环境切换条件下通过进化优势维持其超突变机制的机制。
摘要：
多样性生成逆转录元件（DGRs）在噬菌体和细菌中通过随机的逆转录转录作用，在特定基因组区域中产生快速且定向的变异。它们通过将模板区域（TR）随机逆转录到可变区域（VR）来运作，该区域通常编码配体结合蛋白。尽管它们普遍存在，但维持此类超突变系统的进化条件仍不明确。在这里，我们介绍了一个双时间尺度框架，将快速的VR多样化与缓慢的TR进化分开，使DGR控制的位点动态能够从TR设计的角度进行解析。我们量化了在存在环境切换的情况下，DGR多样化机制所提供的适应性优势，相对于标准突变。我们的框架解释了在人类肠道Bacteroides中观察到的DGR活动模式，并阐明了何时持续激活DGR在进化上是被青睐的。
英文摘要：
Diversity-Generating Retroelements (DGRs) create rapid, targeted variation within specific genomic regions in phages and bacteria. They operate through stochastic retro-transcription of a template region (TR) into a variable region (VR), which typically encodes ligand-binding proteins. Despite their prevalence, the evolutionary conditions that maintain such hypermutating systems remain unclear. Here we introduce a two-timescale framework separating fast VR diversification from slow TR evolution, allowing the dynamics of DGR-controlled loci to be analytically understood from the TR design point of view. We quantity the fitness gain provided by the diversification mechanism of DGR in the presence of environmental switching with respect to standard mutagenesis. Our framework accounts for observed patterns of DGR activity in human-gut \textit{Bacteroides} and clarifies when constitutive DGR activation is evolutionarily favored.
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