Factors and processes shaping the temperature dependence of the point mutation rate

突变将变异引入生物体的基因组，因此是没有进化就不可能的过程。一个物种的突变率一直被认为是一个与环境无关的常数。然而，在最近的一项研究中，我们第一次能够全面地表明，环境温度实际上强烈地决定了突变率。存在一个最适温度，在此温度下突变率最低。任何方向的偏差都会导致速率增加。这些结果立即提出了几个重要的问题：观察到的最佳曲线背后的过程是什么？是什么过程驱动了突变率的变化？为什么突变率在两个极端温度下都增加？是什么决定了突变率在温标上的最佳位置？它是一个物种特有的常数，还是随着当地温度条件的变化而进化的？通过这个项目，我的目标是了解观察到的突变率对温度依赖性的因果过程，并探索其进化原因和后果。具体而言，将测试两种不同的假设：观察到的突变率增加到低于最佳温度是由于世代长度。氧化冷应激是导致低温下突变率增加的原因。这些假设进行了测试，通过实验解耦产生时间从温度。突变率的最适温度在不同的种群之间是不同的，这取决于它们在进化过程中所经历的气候，因此它是局部适应的。备选：突变率的最适温度是一个物种特异性常数。这一假设是测试在一个共同的花园设计，通过确定的温度依赖性的突变率的冷适应和温暖的适应人口。

Mutations introduce variation into the genomes of organisms and are thus the process without which evolution would not be possible. The mutation rate of a species has long been considered an environmentally independent constant. However, in a recent study, we were able to comprehensively show for the first time that environmental temperature actually strongly determines the mutation rate. There is an optimum temperature at which the mutation rate is lowest. Deviations in either direction cause the rate to increase. These results immediately raise several important questions: What are the processes behind the observed optimum curve? What processes drive the variation in mutation rate? Why does the mutation rate increase toward both extreme temperatures? What determines the position of the optimum of the mutation rate on the temperature scale? Is it a species-specific constant or does it evolve in response to local temperature conditions? With this project, I aim to understand the causal processes for the observed temperature dependence of the mutation rate and explore its evolutionary causes and consequences. Specifically, two different hypotheses will be tested: The observed increase in mutation rate to lower than optimal temperatures is due to generation length. Oxidative cold stress is responsible for the increase in mutation rate at lower temperatures. These hypotheses are tested by experimentally decoupling generation time from temperature. The thermal optimum of mutation rate differs between populations depending on the climate experienced in their evolution, thus it is locally adapted. Alternative: the thermal optimum of mutation rate is a species-specific constant. This hypothesis is tested in a common-garden design by determining the temperature dependence of the mutation rate of cold-adapted and warm-adapted populations.