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

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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.