Exome genotyping, linkage disequilibrium and population structure in loblolly pine Pinus taeda L.Reportar como inadecuado




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BMC Genomics

, 17:730

Plant genomics

Abstract

BackgroundLoblolly pine Pinus taeda L. is one of the most widely planted and commercially important forest tree species in the USA and worldwide, and is an object of intense genomic research. However, whole genome resequencing in loblolly pine is hampered by its large size and complexity and a lack of a good reference. As a valid and more feasible alternative, entire exome sequencing was hence employed to identify the gene-associated single nucleotide polymorphisms SNPs and to genotype the sampled trees.

ResultsThe exons were captured in the ADEPT2 association mapping population of 375 clonally-propagated loblolly pine trees using NimbleGen oligonucleotide hybridization probes, and then exome-enriched genomic DNA fragments were sequenced using the Illumina HiSeq 2500 platform. Oligonucleotide probes were designed based on 199,723 exons ≈49 Mbp partitioned from the loblolly pine reference genome PineRefSeq v. 1.01. The probes covered 90.2 % of the target regions. Capture efficiency was high; on average, 67 % of the sequence reads generated for each tree could be mapped to the capture target regions, and more than 70 % of the captured target bases had at least 10X sequencing depth per tree. A total of 972,720 high quality SNPs were identified after filtering. Among them, 53 % were located in coding regions CDS, 5 % in 5’ or 3’ untranslated regions UTRs and 42 % in non-target and non-coding regions, such as introns and adjacent intergenic regions collaterally captured. We found that linkage disequilibrium LD decayed very rapidly, with the correlation coefficient r between pairs of SNPs linked within single scaffolds decaying to half maximum r = 0.22 within 55 bp, to r = 0.1 within 192 bp, and to r = 0.05 within 451 bp. Population structure analysis using unlinked SNPs demonstrated the presence of two main distinct clusters representing western and eastern parts of the loblolly pine range included in our sample of trees.

ConclusionsThe obtained results demonstrated the efficiency of exome capture for genotyping species such as loblolly pine with a large and complex genome. The highly diverse genetic variation reported in this study will be a valuable resource for future genetic and genomic research in loblolly pine.

KeywordsLoblolly pine Exome sequence capture Target enrichment Genotyping by sequencing Linkage disequilibrium Population structure SNPs AbbreviationsCDSCoding sequence

ESTExpressed sequence tag

GBSGenotyping by sequencing

LDLinkage disequilibrium

SNPSingle nucleotide polymorphism

UTRUntranslated region

Electronic supplementary materialThe online version of this article doi:10.1186-s12864-016-3081-8 contains supplementary material, which is available to authorized users.

An erratum to this article is available at http:-dx.doi.org-10.1186-s12864-016-3220-2.

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Autor: Mengmeng Lu - Konstantin V. Krutovsky - C. Dana Nelson - Tomasz E. Koralewski - Thomas D. Byram - Carol A. Loopstra

Fuente: https://link.springer.com/







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