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Abstract Detail

Recent Topics Posters

Scott , Alison Dawn [1], Baum, David A. [2].

Big trees and mysteries: Redwoods, an evolutionary history.

Coast redwoods (Sequoia sempervirens) are well-known for their great height (over 100m) and advanced age (over 2,000 years), but perhaps less so for being the only hexaploid conifer (2n=6x=66). Though these colossal ancient trees are limited to the foggy coastal forests of central and northern California and southwestern Oregon, the redwood fossil record suggests a broader historical range across the Northern hemisphere. S. sempervirens was confirmed as a hexaploid many decades ago. How, when, and where polyploidization took place remains a mystery, though putative genome donors and polyploidization mechanisms have been proposed, including hybridization with an extant conifer lineage. Sequoia is a monotypic genus. Its closest extant relatives are the giant sequoia, Sequoiadendron giganteum, of the Californian Sierra Nevada and the dawn redwood, Metasequoia glyptostroboides, endemic to China. Cumulatively, S. sempervirens, S. giganteum, and M. glyptostroboides are known as the redwood clade. Our project uses a combination of molecular sequence data and fossil foliage to shed light on the evolutionary history of this enigmatic lineage.  
Despite their limited modern-day distributions, the fossil record shows a variety of redwood-like lineages scattered across the Northern Hemisphere. Fossils from this group, which date back to the Jurassic, often include imprints of foliage, permitting the observation and measurement of epidermal morphological characters. As guard cell size is well-known to correlate with genome size, we can compare fossil redwood specimens to extant redwoods of known genome size, allowing the inference of ploidy across the historical range and over evolutionary time.  
Transcriptome sequencing of the redwood clade (S. sempervirens, S. giganteum, and M. glyptostroboides) yielded thousands of genes. A subset of genes were chosen for targeted sequencing of genomic DNA to isolate homeologs in S. sempervirens. Subsequent phylogenetic comparison among gene copies in S. sempervirens and its close relatives will reveal whether hybridization with an extant lineage contributed to polyploidy in the Sequoia lineage.

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1 - UW - Madison, Department Of Botany, Birge Hall, 430 Lincoln Drive, Madison, WI, 53706, USA
2 - University Of Wisconsin, Department Of Botany, Birge Hall, 430 Lincoln Drive, Madison, WI, 53706, USA


Presentation Type: Recent Topics Poster
Session: P
Location: /
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PRT016
Abstract ID:1254
Candidate for Awards:None

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