Organisms cope with change by taking advantage of transcriptional regulators. However, when faced with rare environments, the evolution of transcriptional regulators and their promoters may be too slow. Here, we investigate whether the intrinsic instability of gene duplication and amplification provides a generic alternative to canonical gene regulation. Using real-time monitoring of gene-copy-number mutations in Escherichia coli, we show that gene duplications and amplifications enable adaptation to fluctuating environments by rapidly generating copy-number and, therefore, expression-level polymorphisms. This amplification-mediated gene expression tuning (AMGET) occurs on timescales that are similar to canonical gene regulation and can respond to rapid environmental changes. Mathematical modelling shows that amplifications also tune gene expression in stochastic environments in which transcription-factor-based schemes are hard to evolve or maintain. The fleeting nature of gene amplifications gives rise to a generic population-level mechanism that relies on genetic heterogeneity to rapidly tune the expression of any gene, without leaving any genomic signature.

生物利用转录调节因子来应对变化。但是，面对罕见的环境时，转录调节因子及其启动子的进化可能太慢。在这里，我们调查基因复制和扩增的内在不稳定性是否提供了规范基因调控的通用替代方法。使用大肠杆菌中基因拷贝数突变的实时监测，我们证明了基因复制和扩增能够通过快速生成拷贝数，进而实现表达水平的多态性来适应不断变化的环境。这种扩增介导的基因表达调节（AMGET）发生在类似于规范基因调节的时间尺度上，并且可以响应快速的环境变化。数学模型表明，扩增还可以在随机环境中调节基因表达，在这种环境中，基于转录因子的方案难以进化或维持。基因扩增的短暂本质产生了一种通用的种群水平机制，该机制依靠遗传异质性来快速调节任何基因的表达，而不会留下任何基因组特征。