The ITS region of nuclear ribosomal DNA: A valuable source of evidence on angiosperm phylogeny

TitleThe ITS region of nuclear ribosomal DNA: A valuable source of evidence on angiosperm phylogeny
Publication TypeJournal Article
Year of Publication1995
AuthorsBaldwin BG, Sanderson MJ, Porter JM, Wojciechowski MF, Campbell CS, Donoghue MJ
JournalAnnals of the Missouri Botanical Garden
Volume82
Pagination247 - 277
ISSN00266493
KeywordsPLANT SCIENCES
Abstract

The internal transcribed spacer (ITS) region of 18S-26S nuclear ribosomal DNA (nrDNA) has proven to be a useful source of characters for phylogenetic studies in many angiosperm families. The two spacers of this region, ITS-1 and ITS-2 (each < 300 bp), can be readily amplified by PCR and sequenced using universal primers, even from DNAs of herbarium specimens. Despite high copy numbers of both spacers, the near uniformity of ITS paralogues, attributed to rapid concerted evolution, allows direct sequencing of pooled PCR products in many species. Divergent paralogues, where detected, require cloning, but may offer a means of obtaining multiple estimates of organismal relationships and of determining placement of the root in a phylogeny independent of outgroup considerations. In reported studies, variation between ITS sequences is mostly attributable to point mutations. A relatively minor proportion of sites is affected by insertions or deletions (indels) among sequences that are similar

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