A New model System to Test the Adaptive Significance of Recombination

植物和动物的繁殖可以在有或没有基因重组的情况下发生，但大多数多细胞生物在产生后代时利用基因重组。相比之下，许多农业上重要的作物，如坚果树、果树、葡萄、浆果等，都是无性系繁殖的，即没有基因重组。绕过正常的有性繁殖重组模式的代价是什么？这项拟议的研究创建了一个新的模型系统，允许对目前大多数关于基因重组的适应性意义的理论进行真正明确的测试。该模型系统将被用来检验这样的假设，即新的有益突变以远高于克隆群体的速度并入重组群体。由于人类活动引起的环境快速变化，例如全球变暖、栖息地碎片化、外来物种的引入和疾病生物的引入，快速适应进化的能力变得越来越重要。常见的果蝇(果蝇)被用作模型系统，因为它的培养成本低，世代时间短，并且可以获得许多对这些多世代实验的操作至关重要的遗传工具。使用我们实验室最近开发的一项新的克隆生成器技术，我们将试验性地将新的有益突变引入基因重组水平较低和较高水平的人群。接下来，我们将测量这些有益突变积累的可能性，并将其与实验控制的基因重组水平联系起来。目前的理论预测，基因重组将极大地增强种群纳入新的有益突变和清除有害突变的能力。这些实验的结果将有助于我们对动植物育种计划、长期和短期进化的基本了解，并有助于我们预测不同生命形式适应人类引发的环境变化的能力。

Rice9806917 Reproduction in plants and animals can occur with or without genetic recombination, yet most multicellular organisms utilize genetic recombination when producing offspring. In contrast, many agriculturally important crops such as nut trees, fruit trees, grapes, berries, etc. are propagated clonally, i.e., without genetic recombination. What are the costs of bypassing the normal recombining mode of sexual reproduction? The proposed research creates a new model system that permits a truly definitive test of most of the current theories concerning the adaptive significance of genetic recombination. The model system will be used to test the hypothesis that new beneficial mutations are incorporated into recombining populations at a far greater rate than clonal populations. The capacity for rapid adaptive evolution is becoming increasingly important owing to the rapid environmental change induced by human activities, e.g. global warming, habitat fragmentation, introduction of exotic species and disease organisms. The common fruit fly (Drosophila melanogaster) is used as a model system owing to its inexpensive culturing, short generation time, and availability of numerous genetic tools which are critical for the operation of these multi-generation experiments. Using a new clone-generator technology recently developed in our laboratory, we will experimentally introduce new beneficial mutations into populations with low vs. high levels of genetic recombination. Next we will measure the probability of accumulation of these beneficial mutations and relate this to the experimentally controlled level of genetic recombination. Current theory predicts that genetic recombination will greatly enhance the capacity of the populations to incorporate new beneficial mutations, and to purge deleterious mutations. Results from these experiments will contribute to our basic understanding of plant and animal breeding programs, long and short-term evolution, and will help us to predict the capacity of different life forms to adapt to human-induced environmental change.