Department of Biology, Stanford University, Stanford, United States.
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States.
Elife. 2023 Oct 20;12:e92899. doi: 10.7554/eLife.92899.
Adaptation is driven by the selection for beneficial mutations that provide a fitness advantage in the specific environment in which a population is evolving. However, environments are rarely constant or predictable. When an organism well adapted to one environment finds itself in another, pleiotropic effects of mutations that made it well adapted to its former environment will affect its success. To better understand such pleiotropic effects, we evolved both haploid and diploid barcoded budding yeast populations in multiple environments, isolated adaptive clones, and then determined the fitness effects of adaptive mutations in 'non-home' environments in which they were not selected. We find that pleiotropy is common, with most adaptive evolved lineages showing fitness effects in non-home environments. Consistent with other studies, we find that these pleiotropic effects are unpredictable: they are beneficial in some environments and deleterious in others. However, we do find that lineages with adaptive mutations in the same genes tend to show similar pleiotropic effects. We also find that ploidy influences the observed adaptive mutational spectra in a condition-specific fashion. In some conditions, haploids and diploids are selected with adaptive mutations in identical genes, while in others they accumulate mutations in almost completely disjoint sets of genes.
适应是由有益突变的选择驱动的，这些突变在种群进化的特定环境中提供了适应优势。然而，环境很少是恒定或可预测的。当一个适应于一种环境的生物发现自己处于另一种环境中时，使其适应前一种环境的突变的多效性效应将影响其成功。为了更好地理解这种多效性效应，我们在多个环境中进化了单倍体和二倍体带条码的出芽酵母种群，分离了适应性克隆，然后确定了它们在未选择的“非原生”环境中的适应性突变的适应度效应。我们发现多效性很常见，大多数适应性进化的谱系在非原生环境中表现出适应度效应。与其他研究一致，我们发现这些多效性效应是不可预测的：它们在某些环境中是有益的，而在其他环境中则是有害的。然而，我们确实发现，具有相同基因中的适应性突变的谱系往往表现出相似的多效性效应。我们还发现，ploidy 以特定条件的方式影响观察到的适应性突变谱。在某些条件下，单倍体和二倍体以相同基因中的适应性突变被选择，而在其他条件下，它们积累的突变几乎完全是不相交的基因集。
