Collaborative Research: Genetic and Physiological Mechanisms of Local Climatic Adaptation in a Widespread Perennial Plant Species

一些植物物种能够在各种气候条件下茁壮成长，但人们对这种情况发生的机制知之甚少。描述当地气候适应的遗传和生理基础对于评估包括作物在内的植物物种能否以及如何在环境变化时期持续存在尤为重要。利用广泛适应的物种白三叶草，该项目研究了使这种植物在明尼苏达州北部和佛罗里达州中部截然不同的气候中茁壮成长的因素。含氰化合物的产生似乎在这一过程中发挥了作用，特别是对高温和干旱的适应。这些化合物也在一些重要的作物物种中被发现，它们对干旱适应的重要性将首次被详细研究。气候耐受性的自然遗传和生理变异的其他方面将通过实地试验进行评估。该项目将为一项正在进行的、非常成功的探究式教育推广计划提供课堂材料和课程活动，该计划由首席研究员开发，已经吸引了全国8000多名学生和100多名教师。学生们对当地的三叶草种群进行取样和分析，并将数据提供给一个在线数据库，在那里他们可以将观察结果与其他气候的班级进行比较。为本科生提供科学培训，包括少数民族背景的本科生，以及两名研究生和两名博士后。对当地环境的适应在植物物种在环境变化中生存和持续的能力中起着关键作用，然而这一过程背后的遗传和生理机制在很大程度上是未知的。通过对适合度性状的QTL定位、对两种具有良好特征的生化多态性的候选基因分析以及对其适合度影响的生理评估，以白三叶草（Trifolium repens）为研究系统，解决了以下问题：1)当地气候适应的遗传结构是什么？具体来说，它在多大程度上是通过个体基因的替代等位基因的适应性权衡（拮抗多效性）产生的，还是通过个体基因在一种环境中提供适应性利益而在另一种环境中选择性中性的位点组合（条件中性）产生的？2)产氰苷在非生物胁迫适应中的生理机制是什么？3)基因拷贝数变异（CNVs）在局部适应中的作用是什么？本研究将严格测试3000种植物（包括许多作物）中发现的氰苷在非生物胁迫适应中的功能。CNVs在许多分类群的基因组中都很丰富，该项目将直接评估它们在当地气候适应中的作用，这是以前没有做过的。该项目还将通过一个正在进行的、非常成功的基于三叶草氰化氢的推广项目，让全国的高中学生和教师参与到实践中来，以探究为基础的学习，并将为本科生、研究生和博士后提供培训。

Some plant species are able to thrive across a wide range of climates, and the mechanisms by which this occurs are poorly understood. Characterizing the genetic and physiological basis of local climatic adaptation is especially critical for assessing whether and how plant species, including crops, can persist through periods of environmental change. Using the widely-adapted species white clover, this project examines the factors that allow this plant to thrive in climates as dramatically different as northern Minnesota and central Florida. The production of cyanide-containing compounds appears to play a role in this process, particularly for adaptation to heat and drought. These compounds are also found in several important crop species, and their importance for drought adaptation will be examined in detail for the first time. Other aspects of natural genetic and physiological variation in climate tolerance will be assessed through field experiments. The project will provide classroom materials and curricular activities for an ongoing and highly successful inquiry-based educational outreach program developed by the principle investigator, which has already engaged more than 8000 students and 100 teachers nationwide. Students sample and analyze their local clover populations and contribute data to an online database, where they can compare observations with classes from other climates. Scientific training will be provided to undergraduates, including those from minority backgrounds, as well as two graduate students and two postdoctoral associates.Adaptation to local environments plays a key role in the ability of plant species to survive and persist through environmental change, yet the genetic and physiological mechanisms that underlie this process are largely unknown. Through work that integrates QTL mapping of fitness traits, candidate gene analyses of two well-characterized biochemical polymorphisms, and physiological assessments of their fitness impacts, the following questions are addressed, using white clover (Trifolium repens) as a study system: 1) What is the genetic architecture of local climatic adaptation? Specifically, to what extent does it arise through fitness tradeoffs for alternate alleles of individual genes (antagonistic pleiotropy), or through combinations of loci where individual genes provide a fitness benefit in one environment and are selectively neutral in others (conditional neutrality)? 2) What are the physiological mechanisms by which cyanogenic glycosides function in abiotic stress adaptation? 3) What is the role of gene copy number variation (CNVs) in local adaptation? This work will rigorously test the function of cyanogenic glycosides, which are found in 3,000 plant species including many crops, in abiotic stress adaptation. CNVs are abundant in the genomes of many taxa, and the project will directly assess their role in local climatic adaptation, which has not previously been done. The project will also engage high school students and teachers nationwide in hands-on, inquiry-based learning through an ongoing and highly successful outreach program based on clover cyanogenesis, and it will provide training for undergraduates, graduate students and postdoctoral associates.