芽殖酵母对环境胁迫适应的多效性结果
Pleiotropic consequences of adaptation across gradations of environmental stress in budding yeast
摘要：
对一种环境的适应往往会导致在其他条件下的适应性增加或减少。为了表征这些适应的后果如何依赖于环境之间的物理相似性，我们进化了180个酿酒酵母种群，它们在不同程度的盐，温度，pH值或葡萄糖消耗引起的应力下。我们测量适应每种环境的克隆的适应性如何取决于相应类型的压力的强度。我们发现，在特定类型和强度的压力下进化的克隆体往往会在其他类似强度的压力下获得适应性，并在物理上更不相似的环境中逐渐失去更多的适应性。这些健身权衡是不对称的：适应宽松的条件下产生的压力条件下的权衡较小，反之亦然。我们还发现，克隆体的适应度在类似的压力强度下高度相关，但这些相关性在更不相似的环境中衰减到零。为了解释这些结果，我们引入了多个环境中新突变的适应度效应的联合分布（JDFE）的概念，它描述了给定突变在某些条件下具有特定适应度效应的概率。我们发现，我们的观察结果是一致的JDFE是高度相关的物理相似的环境之间，并成为相关性和不对称的环境变得更加不同。JDFE提供了一个框架，用于量化条件之间的进化相似性，并形成了一个有用的基础，旨在预测波动环境中的进化结果的理论工作。
英文摘要：
Adaptation to one environment often results in fitness gains and losses in other conditions. To characterize how these consequences of adaptation depend on the physical similarity between environments, we evolved 180 populations of Saccharomyces cerevisiae at different degrees of stress induced by either salt, temperature, pH, or glucose depletion. We measure how the fitness of clones adapted to each environment depends on the intensity of the corresponding type of stress. We find that clones evolved in a given type and intensity of stress tend to gain fitness in other similar intensities of that stress, and lose progressively more fitness in more physically dissimilar environments. These fitness trade-offs are asymmetric: adaptation to permissive conditions incurred a smaller trade-off in stressful conditions than vice versa. We also find that fitnesses of clones are highly correlated across similar intensities of stress, but these correlations decay towards zero in more dissimilar environments. To interpret these results, we introduce the concept of a joint distribution of fitness effects of new mutations in multiple environments (the JDFE), which describes the probability that a given mutation has particular fitness effects in some set of conditions. We find that our observations are consistent with JDFEs that are highly correlated between physically similar environments, and that become less correlated and asymmetric as the environments become more dissimilar. The JDFE provides a framework for quantifying evolutionary similarity between conditions, and forms a useful basis for theoretical work aimed at predicting the outcomes of evolution in fluctuating environments.
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