CAREER: Host-Parasite Coevolutionary Dynamics: Testing key hypotheses in host mating system evolution

繁殖是最基本的生物过程。它影响DNA如何从一代遗传到下一代。生物体实际上有许多不同的繁殖方式。目前还不清楚为什么最常见的是父母双方（双亲生殖）的遗传贡献，而不是一个（单亲生殖）。双亲生殖的一个重要后果是它产生了更多的遗传变异的后代。然而，为什么这是一个优势，目前还不清楚。一种可能性是，基因变异的后代更有可能逃脱寄生虫和疾病的感染，这些疾病已经适应了父母的基因构成。另一种说法是，遗传变异更普遍地有助于适应不断变化的环境。这个项目使用秀丽隐杆线虫，这种线虫可以单代或双代繁殖，以及它的细菌寄生虫粘质沙雷氏菌，来实验验证这些想法。该项目还将有助于在多个层面上对学生进行教学和培训，为他们提供以动手方式学习科学方法的机会。它将整合本科教学实验室的研究与教育，并将包括开发和实施新的教学实验课程。它还将培养研究生。最后，它将包括一个推广项目，将假设检验科学带到一个社区，那里有许多来自科学领域代表性不足群体的幼儿。在进化生物学中，双亲本生殖是如何以及为什么在自然界中得以维持的问题在很大程度上仍然是一个谜。目前，关于异交的进化和维持，红皇后假说（RQH）是得到最充分支持的假说。RQH的核心预测是，由共同进化的寄生虫施加的负频率依赖选择倾向于通过异交而不是自交受精在宿主种群中繁殖。尽管越来越多的研究表明，共同进化的寄生虫更倾向于宿主异交而不是宿主自交受精，但共同进化的寄生虫施加的选择模式，以及总体上，异交宿主与其各自的寄生虫之间的共同进化动力学尚不清楚。在这里，RQH的基本预测将在可能是目前唯一能够允许进行此类测试的实验系统中进行全面测试。具体来说，寄主秀丽隐杆线虫和寄主粘质沙雷氏菌种群将通过实验进化，以确定共同进化的寄主是否对异种杂交的进化和维持是必要的，或者是否只需要动态变化的环境。在此之后，宿主和寄生虫的表型和潜在的遗传变化，以及由拮抗共同进化产生的选择模式（或模式），将通过表型分析、下一代测序、通过转化进行的功能基因测试和随后的实验进化来确定。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Reproduction is the most essential biological process. It influences how DNA is inherited from one generation to the next. Organisms actually have many different ways of reproducing. It is unclear why the most common should involve genetic contributions from two parents (bi-parental reproduction) as opposed to one (uni-parental reproduction). One important consequence of bi-parental reproduction is that it produces more genetically variable offspring. Why this is an advantage, however, is unclear. One possibility is that genetically variable offspring are more likely to escape infection from parasites and diseases that have adapted to the parents' genetic make-up. Another is that the genetic variability is helpful more generally for adaptation to changing environments. This project uses the nematode worm Caenorhabditis elegans, which can reproduce either uni- or bi-parentally, along with its bacterial parasite, Serratia marcescens, to experimentally test these ideas. The project will also contribute to teaching and training students at many levels, providing opportunities for them to learn scientific methods in a hands-on fashion. It will integrate research with education in undergraduate teaching labs and will include developing and implementing new teaching laboratory classes. It will also train graduate students. Finally, it will include an outreach program that will bring hypothesis testing science to a neighborhood with many young children from underrepresented groups in science. The questions of both how and why bi-parental reproduction is maintained in nature largely remain a mystery in evolutionary biology. Currently, the Red Queen hypothesis (RQH) is the most well supported hypothesis regarding the evolution and maintenance of outcrossing. The central prediction of the RQH is that negative frequency-dependent selection, imposed by coevolving parasites, favors reproduction via outcrossing over self-fertilization in host populations. Although a rapidly growing number of studies demonstrate the ability of coevolving parasites to favor host outcrossing over host self-fertilization, the mode of selection imposed by coevolving parasites, and in general, the coevolutionary dynamics between outcrossing hosts and their respective parasites remain unclear. Here, the fundamental predictions of the RQH will be comprehensively tested in perhaps the only experimental system currently capable of permitting such a test. Specifically, the host, Caenorhabditis elegans, and parasite, Serratia marcescens, populations will be experimentally evolved to determine if coevolving parasites are necessary for the evolution and maintenance of outcrossing, or if only a dynamic changing environment is required. After which, the phenotypic and underlying genetic changes in the hosts and parasites, as well as the mode (or modes) of selection that result from antagonistic coevolution, will be determined through a combination of phenotypic assays, next-generation sequencing, functional genetic testing via transformation, and subsequent experimental evolution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.