CAREER: Tempo, Contingency, and Gene Flow in the Coevolution of a Model Microbial Mutualism

互利主义-两个生物体之间的有益互动-在自然界中很常见，并深刻地塑造了我们星球上的生命。 互利共生的微生物对人类健康很重要，因为生活在我们体内和体表的微生物很重要。它们影响人类福祉，例如，因为与高产作物植物相关的微生物的作用。这些例子证明了微生物互利共生对人类繁荣的根本重要性。 令人惊讶的是，很少有人知道这种互惠是如何产生的，或者在他们的形成中很重要的条件。这个项目将研究互惠关系是如何在基因水平上形成和建立的。它将探讨环境因素如何影响这些新的互惠关系的演变和稳定性。 从这项工作的见解可能是相关的生物多样性保护工作和管理入侵物种的环境变化。 该项目还将促进旨在改善研究生、本科生、高中和社区学院转学生的STEM教育实践和STEM准备的举措的增长和发展，这些举措建立在首席研究员现有的努力基础上，以改善密西西比州的STEM成功前景。首席研究员创建了一种基于两种模式微生物之间的碳和氮交换的新互惠关系，芽殖酵母酿酒酵母和绿色衣藻莱茵衣藻，这是一个具有前所未有的实验和遗传易处理性的系统。 利用这个系统，该项目将阐明新生的互利关系如何在遗传水平上得到巩固，并调查（1）碳和氮营养物质的可用性，（2）历史偶然性（即，（3）基因流动/迁移（适应不同当地环境条件的群落之间）。 这项工作将实验测试汤普森的地理镶嵌理论的共同进化的基本思想，并解决几个问题，包括：（一）如何做环境条件和/或物种间的依赖程度（专性或兼性）影响共同进化的轨迹和适应性遗传变化的分布在合作伙伴之间？ (ii)先前的互惠进化历史在多大程度上引导或限制了随后进化适应的可能性？ (iii)与没有基因流动的情况相比，在不同条件下进化的伴侣的基因混合如何影响随后的共同进化结果？ 该项目的一个组成部分包括努力：（1）加强进化和基因组学的本科生和研究生教育，（2）提高社区大学转学生的学术准备和成功，（3）促进低收入高中生对STEM的兴趣和大学准备，该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值进行评估来支持和更广泛的影响审查标准。

Mutualisms - beneficial interactions between two organisms - are common in nature and have profoundly shaped life on our planet. Mutualistic microbes are important to human health because of the importance of microbes that live in and on our bodies. They impact human welfare, for example because of the role of microbes associated with high-yielding crop plants. These examples demonstrate the fundamental importance of microbial mutualisms to human flourishing. Surprisingly, very little is understood about how such mutualisms are born, or the conditions that are important in their formation. This project will investigate how mutualistic relationships form and become established at the genetic level. It will explore how environmental factors impact the evolution and stability of these new mutualisms. Insights from this work may be relevant for biodiversity conservation efforts and for the management of invasive species in light of environmental change. This project will also facilitate the growth and development of initiatives aimed at improving STEM education practices and STEM preparedness of graduate, undergraduate, high school, and community college transfer students, that build upon the Principal Investigator's existing efforts to improve the STEM success landscape in Mississippi.The Principal Investigator created a new mutualism based on carbon and nitrogen exchange between two model microbes, the budding yeast Saccharomyces cerevisiae and the green alga Chlamydomonas reinhardtii, a system with an unprecedented degree of experimental and genetic tractability. Using this system, this project will elucidate how nascent mutualistic relationships are consolidated at the genetic level and investigate the impact of (1) carbon and nitrogen nutrient availability, (2) historical contingency (i.e., prior evolutionary history), and (3) gene flow/migration (between communities adapted to different local environmental conditions) on the coevolution of mutualism. This work will experimentally test ideas underlying Thompson's Geographic Mosaic Theory of Coevolution, and address several questions, including: (i) how do environmental conditions and/or the degree of interspecies dependency (obligate or facultative) influence coevolutionary trajectories and the distribution of adaptive genetic changes among partners? (ii) To what degree does prior mutualistic evolutionary history canalize or limit the possibilities for subsequent evolutionary adaptation? (iii) How does genetic mixing of partners that have evolved under different sets of conditions influence subsequent coevolutionary outcomes compared to cases where there is no gene flow? An integral part of this project includes efforts to: (1) enhance undergraduate and graduate education in evolution and genomics, (2) improve academic preparedness and success of community college transfer students, and (3) catalyze STEM interest and college readiness among low-income high school students, notably from the Mississippi Delta.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.