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Intragenomic polymorphisms among high-copy loci: a genus-wide study of nuclear ribosomal DNA in Asclepias (Apocynaceae)

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Title Intragenomic polymorphisms among high-copy loci: a genus-wide study of nuclear ribosomal DNA in Asclepias (Apocynaceae)
Names Weitemier, Kevin (creator)
Straub, Shannon C. K. (creator)
Fishbein, Mark (creator)
Liston, Aaron (creator)
Date Issued 2015-01-06 (iso8601)
Note This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by PeerJ. The published article can be found at: https://peerj.com/.
Abstract Despite knowledge that concerted evolution of high-copy loci is often imperfect,
studies that investigate the extent of intragenomic polymorphisms and comparisons
across a large number of species are rarely made. We present a bioinformatic pipeline
for characterizing polymorphisms within an individual among copies of a high-copy
locus. Results are presented for nuclear ribosomal DNA (nrDNA) across the milkweed
genus, Asclepias. The 18S-26S portion of the nrDNA cistron of Asclepias syriaca
served as a reference for assembly of the region from 124 samples representing 90
species of Asclepias. Reads were mapped back to each individual’s consensus and at
each position reads differing from the consensus were tallied using a custom perl
script. Low frequency polymorphisms existed in all individuals (mean = 5.8%). Most
nrDNA positions (91%) were polymorphic in at least one individual, with polymorphic
sites being less frequent in subunit regions and loops. Highly polymorphic sites
existed in each individual, with highest abundance in the “noncoding” ITS regions.
Phylogenetic signal was present in the distribution of intragenomic polymorphisms
across the genus. Intragenomic polymorphisms in nrDNA are common in Asclepias,
being found at higher frequency than any other study to date. The high and variable
frequency of polymorphisms across species highlights concerns that phylogenetic
applications of nrDNA may be error-prone. The new analytical approach provided
here is applicable to other taxa and other high-copy regions characterized by low
coverage genome sequencing (genome skimming).
Genre Article
Access Condition http://creativecommons.org/licenses/by/3.0/us/
Topic Bioinformatics
Identifier Weitemier, K., Straub, S. C. K., Fishbein, M., & Liston, A. (2015). Intragenomic polymorphisms among high-copy loci: A genus-wide study of nuclear ribosomal DNA in Asclepias (Apocynaceae). PeerJ, 3, e718. doi:10.7717/peerj.718

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