What is the relative importance of evolutionary factors that maintain genetic variation within populations and species? Two evolutionary mechanisms contribute to trait variation in populations, although their relative importance remains unclear. Recurring deleterious variants provide a continual influx of harmful alleles which are gradually removed by purifying selection. In addition, balancing selection can maintain polymorphisms due to advantageous phenotypes. Understanding the importance of these alternatives has important implications for the genetics of human health and variation in the organisms around us. These questions will be addressed using a cloned quantitative trait locus (QTL) within a well-characterized pathway in the model plant Boechera stricta. This system provides known molecular mechanisms, and fitness can be measured in undisturbed populations and undisturbed habitats, enabling tests of evolutionary hypotheses in historically relevant environments. These analyses combine genetic variation in biochemical and regulatory function, measurements of resistance traits and fitness in nature, and the geography and history of functional alleles. Such experiments to understand the evolutionary significance of complex trait variation must confront the limitations of the QTL program: the large-effect alleles that can be discovered may be unrepresentative of the genes that matter for evolution. This proposed research moves beyond this limitation. Beginning with a large-effect polymorphism that influences defensive chemistry and individual fitness in nature, multiple, small-effect functional allelic differences have been identified. The proposed experiments will quantify precisely the allelic effects on defensive chemistry and gene expression, and will measure the consequences of this variation in nature in order to understand variation of natural selection in space and time. These approaches can elucidate the relative importance of evolutionary factors that maintain genetic variation for ecologically important traits.

Public Health Relevance

These proposed experiments examine genetic variation for complex traits, which are fundamental for human health and for organisms in their environments. Analyses will examine the evolutionary forces that influence genetic variation in populations. This research is focused on genes that synthesize glucosinolates, which are present in human diets and have well documented effects on resistance to cancer.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM086496-07
Application #
9096168
Study Section
Genetic Variation and Evolution Study Section (GVE)
Program Officer
Janes, Daniel E
Project Start
2008-09-30
Project End
2018-06-30
Budget Start
2016-07-01
Budget End
2017-06-30
Support Year
7
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Duke University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
Wagner, Maggie R; Lundberg, Derek S; Del Rio, Tijana G et al. (2016) Host genotype and age shape the leaf and root microbiomes of a wild perennial plant. Nat Commun 7:12151
Manzaneda, Antonio J; Rey, Pedro J; Anderson, Jill T et al. (2015) Natural variation, differentiation, and genetic trade-offs of ecophysiological traits in response to water limitation in Brachypodium distachyon and its descendent allotetraploid B. hybridum (Poaceae). Evolution 69:2689-704
Anderson, Jill T; Perera, Nadeesha; Chowdhury, Bashira et al. (2015) Microgeographic Patterns of Genetic Divergence and Adaptation across Environmental Gradients in Boechera stricta (Brassicaceae). Am Nat 186 Suppl 1:S60-73
Olson-Manning, Carrie F; Strock, Christopher F; Mitchell-Olds, Thomas (2015) Flux Control in a Defense Pathway in Arabidopsis thaliana Is Robust to Environmental Perturbations and Controls Variation in Adaptive Traits. G3 (Bethesda) 5:2421-7
Wagner, Maggie R; Lundberg, Derek S; Coleman-Derr, Devin et al. (2014) Natural soil microbes alter flowering phenology and the intensity of selection on flowering time in a wild Arabidopsis relative. Ecol Lett 17:717-26
Lee, Cheng-Ruei; Anderson, Jill T; Mitchell-Olds, Thomas (2014) Unifying genetic canalization, genetic constraint, and genotype-by-environment interaction: QTL by genomic background by environment interaction of flowering time in Boechera stricta. PLoS Genet 10:e1004727
Anderson, J T; Wagner, M R; Rushworth, C A et al. (2014) The evolution of quantitative traits in complex environments. Heredity (Edinb) 112:4-12
Anderson, Jill T; Lee, Cheng-Ruei; Mitchell-Olds, Thomas (2014) Strong selection genome-wide enhances fitness trade-offs across environments and episodes of selection. Evolution 68:16-31
Heo, Jae-Yun; Feng, Dongsheng; Niu, Xiaomu et al. (2014) Identification of quantitative trait loci and a candidate locus for freezing tolerance in controlled and outdoor environments in the overwintering crucifer Boechera stricta. Plant Cell Environ 37:2459-69
Mitchell-Olds, Thomas (2013) Selection on QTL and complex traits in complex environments. Mol Ecol 22:3427-9

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