EST databases as a source for molecular markers: lessons from Helianthus |
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Authors: | Pashley Catherine H Ellis Jennifer R McCauley David E Burke John M |
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Affiliation: | Department of Biological Sciences, Vanderbilt University, VU Station B 351634, Nashville, TN 37232, USA. |
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Abstract: | Expressed sequence tag (EST) databases represent a potentially valuable resource for the development of molecular markers for use in evolutionary studies. Because EST-derived markers come from transcribed regions of the genome, they are likely to be conserved across a broader taxonomic range than are other sorts of markers. This paper describes a case study in which the publicly available cultivated sunflower (Helianthus annuus) EST database was used to develop simple sequence repeat (SSR) markers for use in the genetic analysis of a rare sunflower species, Helianthus verticillatus, as well as the more widespread Helianthus angustifolius. EST-derived SSRs were found to be more than 3 times as transferable across species as compared with anonymous SSRs (73% vs. 21%, respectively). Moreover, EST-SSRs whose primers were located within protein-coding sequence were more readily transferable than those derived from untranslated regions, and the former loci were no less variable than the latter. The utility of existing EST databases as a means for facilitating population genetic analyses in plants was further explored by cross-referencing publicly available EST resources against available lists of rare or invasive flowering plant taxa. This survey revealed that more than one-third of all plant-derived EST collections of sufficient size could conceivably serve as a source of EST-SSRs for the analysis of rare, endangered, or invasive plant species worldwide. |
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