The evolutionary significance of genetic pleiotropy in species interactions

几乎所有的植物和动物都依赖其他物种来获取食物或吸引配偶。物种之间的这种有益的伙伴关系被称为互惠关系。尽管共生关系是生存和繁殖所必需的，但它们是有代价的：通常，形成共生关系会使个体无法抵御寄生虫和其他感染。本研究将探讨寄生虫何时以及如何影响共生关系的功能和进化。研究人员将在豆科植物（苜蓿、豌豆和豆类）中测试这些问题，这些植物依赖共生细菌提供关键的营养物质氮。在使用苜蓿及其近亲的一系列实验中，研究人员将确定寄生虫如何影响用于形成共生关系的植物基因的进化，并测试是否一些共生伙伴关系（即植物-细菌对）受寄生虫的影响比其他伙伴关系小。这项研究很重要，因为几乎所有的作物植物都依赖真菌或细菌作为营养物质，因此了解寄生虫何时以及如何危害这些互惠关系对于保护这些经济和生态上重要的伙伴关系至关重要。这个项目更广泛的影响包括培训初级科学家和两个新项目，向生物学本科学生教授数据分析——一项基本的科学技能。本研究的首要目标是验证遗传多效性——当同一基因影响多种性状时——是物种相互作用的一个广泛和进化上重要的特征这一中心假设。本项目将在紫花苜蓿属豆科植物和固氮细菌之间的共生模式中验证这一假设。许多参与细菌共生关系的植物基因都与对寄生根结线虫的抗性有关，这在两种相互作用之间产生了遗传权衡。本项目有三个目标：(1)通过比较多效性基因与共生和寄生特异性基因的种群基因组选择特征，检验多效性是否限制了相互作用下基因的进化。(2)整合种群基因组学和数量遗传学，通过检验多效性权衡与寄生是否在多株共生菌中持续存在，评估多效性是否依赖于环境。(3)通过比较6种紫花苜蓿细菌共生与抗寄生线虫的遗传权衡，确定多效性是否具有进化保守性。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。

Nearly all plants and animals rely on other species for food or to attract mates. These beneficial partnerships between species are known as mutualisms. Although mutualisms are necessary for survival and reproduction, they come at a cost: often, forming a mutualism leaves an individual defenseless against parasites and other infections. This research will investigate when and how parasites affect the function and evolution of mutualisms. The researchers will test these questions in legume plants (alfalfa, peas, and beans) that rely on mutualistic bacteria for a key nutrient, nitrogen. In a series of experiments using alfalfa and its relatives, the researchers will determine how parasites affect the evolution of plant genes used to form mutualisms, and test whether some mutualistic partnerships (i.e., plant-bacteria pairs) are less affected by parasites than others. This research is important because nearly all crop plants rely on fungi or bacteria for nutrients, so understanding when and how parasites jeopardize mutualisms like these is essential to protect these economically and ecologically significant partnerships. The broader impacts of this project include training junior scientists and two new programs to teach data analysis—an essential scientific skill—to undergraduate biology students.The overarching goal of this research is to test the central hypothesis that genetic pleiotropy—when the same gene influences multiple traits—is a widespread and evolutionarily significant feature of species interactions. This project will test this hypothesis in the model mutualism between legumes in the genus Medicago and nitrogen-fixing bacteria. Many plant genes involved in the bacterial mutualism are implicated in resistance to parasitic root-knot nematodes, creating a genetic tradeoff between the two interactions. This project has three objectives: (1) Test whether pleiotropy linking mutualism and parasitism constrains the evolution of genes underlying both interactions by comparing population genomic signatures of selection at pleiotropic genes to mutualism- and parasitism-specific genes. (2) Evaluate whether pleiotropy is context dependent by testing whether pleiotropic tradeoffs with parasitism persist across multiple strains of mutualistic bacteria, integrating population genomics and quantitative genetics. (3) Determine whether pleiotropy is evolutionarily conserved by comparing the genetic tradeoff between the bacterial mutualism and resistance to parasitic nematodes across six Medicago species.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.