SNP discovery, gene diversity, and linkage disequilibrium in wild populations of Populus tremuloides
The use of single-nucleotide polymorphisms (SNPs) as molecular markers in plant studies has become increasingly common. With the development of these markers, there is an interest in determining levels of variation in natural populations. Here, we identify and characterize levels of SNPs in wild populations of aspen (Populus tremuloides Michx.). Four populations were sampled from Alberta and British Columbia in Western Canada. A total of 35 gene regions were selected for analysis. The loci selected are mainly involved in wood formation and include regions from genes for lignin biosynthesis, cellulose biosynthesis, and other cell wall compounds and a number of transcription factors. Other genes included those coding for growth hormones, disease resistance, and light responses. Primers were developed from conserved regions in multi-species EST alignments. Regions were PCR amplified, and products (approximately 500 to 1,000 bp) were assessed for levels of SNPs using Ecotilling. From a total of approximately 25 kb 462 SNPs were identified, over 18 SNPs/kb. Thus, SNPs are an abundant and potentially useful molecular marker in aspen. Gene diversity (heterozygosity) varied in the gene regions, with an overall average of HT = 0.18. Although gene diversity was considerable, genetic differentiation was low with the overall FST value being 0.004. A surrogate measure of linkage disequilibrium (LD) was calculated, and overall, the LD was shown to decay relatively rapidly with distance along the gene region. The results obtained from the wood formation genes in this study will enable further targeting of regions for association studies on lignin and cellulose variation in aspen and other Populus species.
KeywordsSNPs Populus tremuloides Gene diversity Wood formation Lignin Cellulose
- Ehlting J, Mattheus N, Aeschliman DS, Li EY, Hamberger B, Cullis IF, Zhuang J, Kaneda M, Mansfield SD, Samuels L, Ritland K, Ellis BE, Bohlmann J, Douglas CJ (2005) Global transcript profiling of primary stems from Arabidopsis thaliana identifies candidate genes for missing links in lignin biosynthesis and transcriptional regulators of fiber differentiation. Plant J 42:618–640PubMedCrossRefGoogle Scholar
- Excoffier LGL, Schneider S (2005) Arlequin ver. 3.0: an integrated software package for population genetics data analysis. Evolutionary Bioinformatics Online 1:47–50Google Scholar
- Gilchrist EJ, Haughn GW, Ying CC, Otto SP, Zhuang J, Cheung D, Hamberger B, Aboutorabi F, Kalynyak T, Johnson L, Bohlmann J, Ellis BE, Douglas CJ, Cronk QCB (2006) Use of Ecotilling as an efficient SNP discovery tool to survey genetic variation in wild populations of Populus trichocarpa. Mol Ecol 15:1367–1378PubMedCrossRefGoogle Scholar
- Ralph S, Chun HJ, Cooper D, Kirkpatrick R, Kolosova N, Gunter L, Tuskan G, Douglas C, Holt R, Jones S, Marra M, Bohlmann J (2008) Analysis of 4,664 high-quality sequence-finished poplar full-length cDNA clones and their utility for the discovery of genes responding to insect feeding. BMC Genomics 9:57PubMedCrossRefGoogle Scholar
- R Development Core Team (2008) R: A language and environment for statistical computing. R Foundation for Statistical Computing. http://www.R-project.org, Vienna, Austria.
- Rozen S, Skaletsky HJ (2000) Primer3 on the WWW for general users and for biologist programmers. In: Krawetz S, Misener S (eds) Bioinformatics methods and protocols: methods in molecular biology. Humana Press, Totowa, pp 365–386Google Scholar
- Sterky F, Regan S, Karlsson J, Hertzberg M, Rohde A, Holmberg A, Amini B, Bhalerao R, Larsson M, Villarroel R, Van Montagu M, Sandberg G, Olsson O, Teeri TT, Boerjan W, Gustafsson P, Uhlen M, Sundberg B, Lundeberg J (1998) Gene discovery in the wood-forming tissues of poplar: analysis of 5,692 expressed sequence tags. Proc Natl Acad Sci U S A 95:13330–13335PubMedCrossRefGoogle Scholar
- Tuskan G, DiFazio S, Jansson S, Bohlmann J, Grigoriev I, Hellsten U, Putnam N, Ralph S, Rombauts S, Salamov A, Schein J, Sterck L, Aerts A, Bhalerao RR, Bhalerao RP, Blaudez D, Boerjan W, Brun A, Brunner A, Busov V, Campbell M, Carlson J, Chalot M, Chapman J, Chen G-L, Cooper D, Coutinho P, Couturier J, Covert S, Cronk Q, Cunningham R, Davis J, Degroeve S, Déjardin A, dePamphilis C, Detter J, Dirks B, Dubchak I, Duplessis S, Ehlting J, Ellis B, Gendler K, Goodstein D, Gribskov M, Grimwood J, Groover A, Gunter L, Hamberger B, Heinze B, Helariutta Y, Henrissat B, Holligan D, Holt R, Huang W, Islam-Faridi N, Jones S, Jones-Rhoades M, Jorgensen R, Joshi C, Kangasjärvi J, Karlsson J, Kelleher C, Kirkpatrick R, Kirst M, Kohler A, Kalluri U, Larimer F, Leebens-Mack J, Leplé J, Locascio P, Luo Y, Lucas S, Martin F, Montanini B, Napoli C, Nelson DR, Nelson C, Nieminen K, Nilsson O, Peter G, Philippe R, Pilate G, Poliakov A, Razumovskaya J, Richardson P, Rinaldi C, Ritland K, Rouzé P, Ryaboy D, Schmutz J, Schrader J, Segerman B, Shin H, Siddiqui A, Sterky F, Terry A, Tsai C, Uberbacher E, Unneberg P, Vahala J, Wall K, Wessler S, Yang G, Yin T, Douglas C, Marra M, Sandberg G, Van de Peer Y, Rokhsar D (2006) The genome of black cottonwood, Populus trichocarpa (Torr. & Gray ex Brayshaw). Science 313:1596–1604PubMedCrossRefGoogle Scholar