title: Target Enrichment Improves Mapping of Complex Traits by Deep Sequencing.
abstract: Complex traits such as crop performance and human diseases are controlled by multiple genetic loci, many of which have small effects and often go undetected by traditional quantitative trait locus (QTL) mapping. Recently, bulked segregant analysis with large F2 pools and genome-level markers (named extreme-QTL or X-QTL mapping) has been used to identify many QTL. To estimate parameters impacting QTL detection for X-QTL mapping, we simulated the effects of population size, marker density, and sequencing depth of markers on QTL detectability for traits with differing heritabilities. These simulations indicate that a high (>90%) chance of detecting QTL with at least 5% effect requires 5000× sequencing depth for a trait with heritability of 0.4-0.7. For most eukaryotic organisms, whole-genome sequencing at this depth is not economically feasible. Therefore, we tested and confirmed the feasibility of applying deep sequencing of target-enriched markers for X-QTL mapping. We used two traits in Arabidopsis thaliana with different heritabilities: seed size (H(2) = 0.61) and seedling greening in response to salt (H(2) = 0.94). We used a modified G test to identify QTL regions and developed a model-based statistical framework to resolve individual peaks by incorporating recombination rates. Multiple QTL were identified for both traits, including previously undiscovered QTL. We call our method target-enriched X-QTL (TEX-QTL) mapping; this mapping approach is not limited by the genome size or the availability of recombinant inbred populations and should be applicable to many organisms and traits.
authors.affiliation: Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305.
authors.forename: Jue
authors.initials: J
authors.lastname: Fan
authors.affiliation: Department of Biology, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, Florida 32611.
authors.forename: Bernard A
authors.initials: BA
authors.lastname: Hauser
authors.affiliation: Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305 srhee@carnegiescience.edu.
authors.forename: Seung Y
authors.initials: SY
authors.lastname: Rhee
mesh_terms: D000465:Algorithms; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D002874:Chromosome Mapping; D005819:Genetic Markers; D059014:High-Throughput Nucleotide Sequencing; D040582:Inheritance Patterns; D008957:Models, Genetic; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci; D019655:Quantitative Trait, Heritable; D012372:ROC Curve; D055049:Salt Tolerance / Q000235:genetics; D012639:Seeds
chemical_list: D005819:Genetic Markers
keywords: Arabidopsis thaliana; bulked segregant analysis; salt tolerance; seed size; target-enriched extreme quantitative trait locus mapping