Scott, Alison , Stenz, Noah , Baum, David A. .
Trees on trees: Resolving the hexaploid origin of coast redwood (Sequoia sempervirens) with phylotranscriptomics.
Coast redwood (Sequoia sempervirens) stands out as not only one of the tallest, longest-lived trees, but as the only hexaploid conifer. Despite its charisma, the polyploid origin of coast redwood has long been a mystery. As whole genome duplication is rare in gymnosperms, a better understanding of the causes of polyploidy in Sequoia may clarify why polyploidy has played a relatively minimal role in gymnosperm evolution. Based on historical range overlap and morphological similarities, close relatives giant sequoia (Sequoiadendron giganteum) and dawn redwood (Metasequoia glyptostroboides) have both been considered potential genome donor lineages to coast redwood. Different polyploidization mechanisms have also been considered, including autopolyploidy, allopolyploidy, and autoallopolyploidy. We sequenced de novo transcriptomes from coast redwood, giant sequoia, and dawn redwood, and estimated phylogenetic trees based on single- and multi-copy genes. Bayesian concordance analysis of low-copy genes indicate giant sequoia is the closest relative of coast redwood. Gene trees with multiple homeologs inferred for hexaploid coast redwood consistently support monophyly of those homeologs. These data suggest coast redwood is an autopolyploid, or that if hybridization did occur it involved species more closely related to coast redwood than either Sequoiadendron or Metasequoia. Our data also indicate a more recent polyploidization than the Sequoia fossil record suggests.
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1 - University of Wisconsin - Madison, Department of Botany, 430 Lincoln Drive, Madison, WI, 53706, USA
2 - University of Wisconsin - Madison, Botany, 430 Lincoln Dr., Madison, WI - Wisconsin, 53706, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Salon 9/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 3:45 PM
Candidate for Awards:Margaret Menzel Award